Aortic Stenosis
Aortic stenosis is the narrowing of the aortic valve opening that obstructs left ventricular outflow, leading to increased afterload, concentric hypertrophy, and eventually heart failure.
Aortic Stenosis
Aortic stenosis (AS) is the pathological narrowing or obstruction of the aortic valve orifice, resulting in impedance to left ventricular outflow during systole. The name itself is informative: "aortic" = pertaining to the aorta/aortic valve; "stenosis" (Greek stenōsis) = narrowing. This creates a fixed obstruction that the left ventricle must overcome with every heartbeat, leading to a progressive pressure-overload state.
The obstruction can occur at three anatomical levels:
- Valvular (most common by far): the valve leaflets themselves are thickened, calcified, or fused
- Subvalvular: a fibrous membrane or muscular ridge below the valve (includes hypertrophic obstructive cardiomyopathy, HOCM)
- Supravalvular: narrowing of the ascending aorta above the valve (e.g., Williams syndrome)
For the purposes of these notes, we focus on valvular aortic stenosis unless otherwise specified.
2. Epidemiology
- > 5% of people aged > 75 years have aortic valve disease [3]
- > 1 in 20 people in the elderly population have aortic valve disease [3]
- Prevalence approximately 14% in those > 75 years old (including aortic sclerosis and stenosis) [3]
- The prevalence is rising globally because populations are ageing — AS is fundamentally a disease of wear-and-tear in most patients
- Degenerative calcific AS: typically presents in the 7th–9th decade; slightly more common in females at the oldest ages [2]
- Bicuspid aortic valve AS: typically presents in the 6th–7th decade; more common in males (bicuspid AV occurs in 1–2% of the population, M > F ~3:1) [2]
- Rheumatic AS: presents earlier (3rd–5th decade), more common in developing countries and regions where rheumatic heart disease remains prevalent
- Hong Kong has an ageing population with increasing life expectancy (~85 years), so degenerative calcific AS is increasingly common
- Rheumatic heart disease has declined substantially but is still seen in older patients and immigrants from mainland China and Southeast Asia
- Bicuspid aortic valve remains a significant cause in middle-aged patients presenting to cardiac surgery units in Hong Kong
- AS is one of the most common reasons for cardiac surgery referral at centres such as Queen Mary Hospital and Grantham Hospital
The risk factors for degenerative calcific AS overlap considerably with atherosclerotic risk factors, because the disease process shares similar pathological mechanisms (endothelial injury, lipid infiltration, inflammation, calcification):
| Risk Factor | Mechanism |
|---|---|
| Advanced age | Cumulative mechanical stress and endothelial injury over decades |
| Hypertension | Increased mechanical shear stress on valve leaflets |
| Hyperlipidaemia / Hypercholesterolaemia | Lipid infiltration into valve leaflets → inflammatory cascade → calcification |
| Diabetes mellitus | Accelerated vascular and valvular calcification |
| Smoking | Endothelial injury, oxidative stress |
| Chronic kidney disease / ESRD | Disordered calcium-phosphate metabolism → accelerated calcification |
| Male sex | Higher prevalence of bicuspid AV; earlier presentation |
| Bicuspid aortic valve | Abnormal haemodynamic stress on two leaflets instead of three → premature degeneration |
| Hyperuricaemia | Associated with calcific valve disease (mentioned in senior notes) [1] |
| Paget's disease of bone | Altered calcium metabolism |
| Previous rheumatic fever | Commissural fusion |
Atherosclerosis ≠ AS, but they share risk factors
Although degenerative AS shares risk factors with atherosclerosis, statins have NOT been shown to slow the progression of established AS in randomised controlled trials (SEAS, SALTIRE, ASTRONOMER trials). This is because by the time AS is established, the dominant process is osteoblastic calcification, not lipid accumulation. However, lipid-lowering in early aortic sclerosis may have some benefit — this remains under investigation.
4. Anatomy and Function of the Aortic Valve
The aortic valve sits at the junction between the left ventricular outflow tract (LVOT) and the ascending aorta. It is a semilunar valve with three cusps (leaflets):
- Right coronary cusp (gives rise to the right coronary artery ostium)
- Left coronary cusp (gives rise to the left coronary artery ostium)
- Non-coronary cusp (posterior, no coronary artery)
Each cusp is a crescent-shaped ("semilunar" = half-moon) pocket of tissue. Behind each cusp is a small dilation of the aortic root called the sinus of Valsalva.
- Normal aortic valve area (AVA): 3.0–4.0 cm²
- The valve opens during systole to allow unimpeded ejection of blood from the LV into the aorta
- The valve closes during diastole, preventing backflow, and the coronary arteries fill during diastole (this is crucial for understanding why AS causes angina)
- Valve leaflets are composed of three layers:
- Ventricularis (facing LV): rich in elastin — allows flexibility
- Spongiosa (middle): glycosaminoglycans — acts as shock absorber
- Fibrosa (facing aorta): dense collagen — provides structural strength
- Normally avascular in adults; neovascularity develops in diseased valves
- Contains valve interstitial cells (VICs) that can undergo osteoblastic differentiation in disease
The aortic valve annulus is in close anatomical proximity to the:
- Bundle of His and left bundle branch — which traverse the membranous interventricular septum just below the aortic valve
- This explains why calcification of AS can extend into the conduction system, causing heart block (particularly LBBB or complete heart block) [1][2]
- This also explains why aortic valve replacement (AVR) can cause post-operative conduction abnormalities
5. Etiology
The three main causes of aortic stenosis are: [3][4]
| Age Group | Most Common Cause | Key Features |
|---|---|---|
| < 60 years | Congenital (bicuspid/unicuspid aortic valve) | Abnormal valve architecture → turbulent flow → premature calcification; bicuspid AV in 1–2% of population [2] |
| 60–75 years | Calcified bicuspid aortic valve | Usually male; bicuspid valve degenerates 10–20 years earlier than a tricuspid valve [2] |
| > 75 years | Degenerative calcification (senile/calcific AS) | Most common overall; associated with atherosclerotic risk factors [2] |
Additionally:
- Rheumatic heart disease — commissural fusion ± calcification; nearly always associated with mitral valve involvement (~95%) [2][3]
- Other rare causes: [1]
- Infective endocarditis (vegetations causing obstruction or destruction)
- Hyperuricaemia (crystal deposition)
- Williams syndrome — supravalvular AS (deletion of elastin gene on chromosome 7; "elfin facies," hypercalcaemia, developmental delay)
- Paget's disease of bone
- Radiation-induced valvular disease
- Systemic lupus erythematosus (Libman-Sacks endocarditis)
- Ochronosis (alkaptonuria)
Detailed Pathophysiology by Etiology
This is essentially a disease of "active biology, not passive wear-and-tear":
-
Initiation phase (similar to atherosclerosis):
- Endothelial injury from mechanical stress (especially on the aortic side of leaflets where shear stress is highest)
- Lipid infiltration (LDL, Lp(a)) into the fibrosa layer
- Oxidation of lipids → recruitment of macrophages and T-lymphocytes
- Inflammatory cytokine release (TNF-α, IL-1β, IL-6, TGF-β)
-
Propagation phase (diverges from atherosclerosis):
- Valve interstitial cells (VICs) undergo osteoblastic differentiation (phenotypic switch)
- Active bone formation within the valve leaflets — with hydroxyapatite deposition, bone morphogenetic proteins (BMP-2, BMP-4), and Runx2 transcription factor expression
- This is why established AS does not respond to statins — it's an osteoblastic process, not just lipid accumulation
-
End result:
- Progressive thickening, stiffening, and calcification of leaflets
- Reduced leaflet mobility → progressive narrowing of orifice
- Aortic sclerosis (thickening without obstruction) → Aortic stenosis (thickening with obstruction)
- Congenital malformation where the aortic valve has only two cusps instead of three
- Occurs in ~1–2% of the population; most common congenital cardiac malformation
- The two cusps experience abnormal and asymmetric mechanical stress → accelerated degeneration and calcification
- Typically presents with significant AS 10–20 years earlier than degenerative calcific AS
- Associated conditions:
- Coarctation of the aorta (important to check!)
- Ascending aortic aneurysm/dilatation (bicuspid aortopathy — due to intrinsic connective tissue abnormality of the aortic wall, NOT just haemodynamic effects)
- Turner syndrome (45,XO) — associated with both bicuspid AV and coarctation
- VSD (less common association)
- Caused by Group A Streptococcal pharyngitis → molecular mimicry → autoimmune valvulitis
- Commissural fusion is the hallmark → leads to a "fish-mouth" or "buttonhole" orifice
- Almost always involves the mitral valve as well (~95% co-involvement) [2]
- More common in developing countries; in Hong Kong, seen in older patients or immigrants
- Can cause mixed AS/AR (combined stenosis and regurgitation)
- Rare; causes severe obstruction even in infancy/childhood
- Often presents with critical AS in neonates
Exam Pearl
If you see AS in a patient < 60 years → think bicuspid aortic valve first. If AS is associated with mitral valve disease → think rheumatic heart disease. If AS is in a patient > 75 years → think degenerative calcific AS.
6. Pathophysiology
This section is crucial — understanding the pathophysiology of AS explains virtually every clinical feature, investigation finding, and management decision. Let's build it from first principles.
The stenotic aortic valve creates a pressure gradient between the LV and the aorta during systole. The LV must generate much higher pressures than normal to push blood through the narrowed orifice.
Gorlin formula [1]: This formula relates the pressure gradient across the valve to the valve area, heart rate, and cardiac output. In simple terms:
- Smaller valve area → higher pressure gradient for the same cardiac output
- Higher cardiac output (e.g., exercise) → higher pressure gradient for the same valve area
According to the Law of Laplace: Wall stress = (Pressure × Radius) / (2 × Wall thickness)
When LV pressure increases chronically:
- The LV responds by increasing wall thickness (concentric hypertrophy) to normalise wall stress
- This is an adaptive mechanism initially — it allows the LV to generate the high pressures needed without excessive oxygen consumption
- The apex beat remains sustained and heaving but is NOT displaced (because the LV cavity does not dilate — this is concentric, not eccentric, hypertrophy)
Cardiac output is initially maintained at the cost of a steadily increasing aortic valve pressure gradient [2]
6.3 Consequences of Concentric LVH
The hypertrophied LV becomes thick and stiff (reduced compliance). This has several critical consequences:
- The stiff, hypertrophied LV does not relax properly during diastole
- Higher filling pressures are needed to fill the LV adequately
- The left atrium hypertrophies to generate the extra "kick" needed (atrial contraction contributes up to 40% of LV filling in severe AS, compared to ~20% normally)
- This generates an S4 gallop (sound of blood hitting a stiff ventricle during atrial contraction)
- Loss of atrial contraction (e.g., onset of atrial fibrillation) can cause acute haemodynamic deterioration because the LV is so dependent on the atrial kick
Why AF is Dangerous in AS
Patients with severe AS tolerate AF very poorly. The loss of atrial kick means the stiff LV is underfilled → dramatic drop in cardiac output → acute pulmonary oedema or syncope. This is a medical emergency. Never forget to check the rhythm in any AS patient who acutely deteriorates.
Angina occurs because of a supply-demand mismatch: [2]
Increased demand:
- Increased LV muscle mass requires more oxygen [2]
- Increased wall stress (elevated intracavitary pressures) increases myocardial oxygen consumption
Decreased supply:
- Increased LV diastolic pressure impedes coronary flow into the myocardium [2]
- Coronary arteries fill during diastole; elevated LV diastolic pressure means the transmural pressure gradient driving coronary flow is reduced
- Subendocardial ischaemia occurs first (subendocardium is most vulnerable to ischaemia because it is furthest from the epicardial coronary arteries and is most compressed during systole)
- 50% of patients with AS have coexistent coronary artery disease [2] — this compounds the ischaemia
This is why angina in AS occurs even without coronary artery disease.
Exertional syncope occurs because of inability to increase cardiac output + decreased SVR due to peripheral vasodilation → sudden decrease in BP leading to syncope [2]
Let's unpack this:
- During exercise, skeletal muscle arterioles dilate → systemic vascular resistance (SVR) drops
- Normally, the heart compensates by increasing cardiac output
- In severe AS, the cardiac output is fixed — the stenotic valve is the bottleneck and cannot accommodate increased flow
- The result: a fall in systemic BP → cerebral hypoperfusion → syncope
- Additional mechanism: exercise may trigger ventricular arrhythmias in the hypertrophied, ischaemic LV → another cause of syncope/sudden death
Decompensation occurs due to chronic LV pressure overload → rapid deterioration with LV failure (dilated LV) → pulmonary oedema [2]
Eventually, the compensatory mechanisms fail:
- The LV can no longer maintain adequate wall thickness relative to the pressure load
- LV wall stress rises → the LV begins to dilate (transition from concentric hypertrophy to eccentric hypertrophy/dilatation)
- LVEF falls → forward cardiac output drops
- LV end-diastolic pressure rises further → transmitted back to LA → pulmonary veins → pulmonary oedema
- If pulmonary hypertension develops → right heart failure (peripheral oedema, ascites, JVP elevation)
This is one of the most important concepts in AS:
Natural History of AS: [4]
- The classic symptoms are: SOB (dyspnoea), LOC (syncope), chest pain (angina) [4]
- If symptoms appear: average survival is only 2–5 years [4]
- Without intervention, once symptomatic: [4]
- Angina → mean survival ~5 years
- Syncope → mean survival ~3 years
- Heart failure → mean survival ~2 years
The disease progresses slowly during the asymptomatic phase, but once symptoms appear, there is a dramatic increase in mortality [4].
- Average aortic valve area decreases by ~0.1 cm²/year
- Average peak gradient increases by ~7 mmHg/year
- Average jet velocity increases by ~0.3 m/s/year
Clinical Pearl: Sudden Death in AS
Sudden cardiac death occurs in ~1% of asymptomatic patients per year, but in up to 15–20% of symptomatic patients. The mechanisms include ventricular arrhythmias (from LVH and ischaemia), complete heart block, and acute haemodynamic collapse. This is why symptomatic AS is an urgent indication for intervention.
7. Classification of Aortic Stenosis
| Level | Examples |
|---|---|
| Supravalvular | Williams syndrome, post-surgical (e.g., supra-aortic ridge), familial supravalvular AS |
| Valvular (most common) | Degenerative calcific, bicuspid AV, rheumatic |
| Subvalvular | Discrete fibromuscular membrane, HOCM (dynamic LVOT obstruction), tunnel-type subaortic stenosis |
| Parameter | Mild | Moderate | Severe |
|---|---|---|---|
| Aortic valve area (AVA) | > 1.5 cm² | 1.0–1.5 cm² | < 1.0 cm² (or < 0.6 cm²/m² indexed) |
| Mean pressure gradient | < 20 mmHg | 20–40 mmHg | > 40 mmHg |
| Peak aortic jet velocity (Vmax) | < 3.0 m/s | 3.0–4.0 m/s | > 4.0 m/s |
| Velocity ratio (LVOT/AV) | > 0.50 | 0.25–0.50 | < 0.25 |
Poor prognostic factors include: heavy calcification, jet velocity > 4 m/s [2]
Low-Flow, Low-Gradient Severe AS
A common exam pitfall: A patient with a severely calcified, immobile aortic valve but a low gradient ( < 40 mmHg) and low AVA ( < 1.0 cm²). This can occur in two scenarios:
-
Classical low-flow, low-gradient AS (LVEF < 50%): The LV is too weak to generate a high gradient. Use dobutamine stress echo — if AVA remains < 1.0 cm² with increasing flow, it is "true severe AS." If AVA increases to > 1.0 cm², it is "pseudo-severe AS."
-
Paradoxical low-flow, low-gradient AS (LVEF ≥ 50%): Small, hypertrophied LV with a low stroke volume index ( < 35 mL/m²) despite preserved EF. Seen in elderly hypertensive women. Genuinely severe AS but generates low gradients. Use CT calcium scoring to confirm.
Both are genuinely severe and carry a poor prognosis. Do not be falsely reassured by a low gradient!
| Category | Description |
|---|---|
| Asymptomatic | No symptoms at rest or with exertion; managed with surveillance |
| Symptomatic | Angina, syncope, or heart failure symptoms; indication for intervention |
8. Clinical Features
The classic triad of symptoms in AS (mnemonic: "ASH" — Angina, Syncope, Heart failure; or think "SAD" — Syncope, Angina, Dyspnoea):
| Symptom | Pathophysiological Basis | Details |
|---|---|---|
| Angina on exertion [1] | Supply-demand mismatch: ↑O₂ demand (LVH, ↑wall stress) + ↓O₂ supply (↑LVEDP impedes coronary flow + possible coexistent CAD in 50%) | Occurs in ~35% of patients with severe AS; may occur even without epicardial CAD |
| Syncope on exertion [1] | Fixed CO cannot increase with exercise + peripheral vasodilation → ↓cerebral perfusion; also ventricular arrhythmias from ischaemic/hypertrophied myocardium | Occurs in ~15% of patients; exertional syncope is a red flag for severe AS |
| Heart failure symptoms (SOBOE → orthopnoea → PND) [1] | LV decompensation → ↑LVEDP → ↑LA pressure → pulmonary congestion → dyspnoea | Dyspnoea is the most common presenting symptom (~50%); worst prognosis of the triad |
| Reduced exercise tolerance | Fixed cardiac output limits ability to increase flow during exertion; may also be due to diastolic dysfunction | May be subtle and insidious, especially in the elderly who reduce activity subconsciously |
| Palpitations | LVH predisposes to atrial and ventricular arrhythmias; loss of atrial kick in AF causes acute deterioration | AF, PVCs, and VT all more common |
'Masking' of Symptoms in the Elderly
Elderly patients often subconsciously reduce their physical activity to avoid symptoms. They may deny symptoms because they attribute their limitations to "just getting old." Always perform a careful functional assessment and consider exercise testing in seemingly asymptomatic patients with severe AS.
| Complication | Mechanism |
|---|---|
| LV failure [1] | Progressive pressure overload → decompensation → LV dilatation → ↓EF |
| Arrhythmias [1] | LVH → myocardial fibrosis → re-entrant circuits → AF, VT, VF |
| Heart block [1] | Calcification extends into the conduction system (bundle of His, left bundle branch lie adjacent to the aortic valve annulus) |
| Heyde's syndrome → iron deficiency anaemia [1] | High shear stress across the stenotic aortic valve → mechanical degradation of large vWF multimers → acquired type IIA von Willebrand disease → GI bleeding from angiodysplasia (Heyde's syndrome) [1][5] |
| Infective endocarditis | Turbulent flow across abnormal valve → endothelial damage → nidus for infection |
| Calcified emboli | Severe calcific AS → calcified debris embolisation → stroke or peripheral embolism |
| Sudden cardiac death | Ventricular arrhythmias (VT/VF) in ischaemic, hypertrophied myocardium; acute haemodynamic collapse |
8.3 Signs
Let's go through the signs systematically, connecting each to the underlying pathophysiology:
- Patient may appear well (if compensated) or in heart failure (if decompensated)
- Look for signs of heart failure: elevated JVP, peripheral oedema, tachypnoea
- Malar flush may be present if pulmonary hypertension has developed (similar to mitral stenosis)
- Low-volume, slow-rising pulse (pulsus parvus et tardus — "parvus" = small, "tardus" = slow) [1][2]
- Why? The stenotic valve limits the rate and volume of blood ejection into the aorta → the arterial pulse rises slowly and reaches a lower peak
- Best felt at the carotid artery (brachial/radial pulses may be unreliable in elderly with stiff arteries)
- Narrow pulse pressure [1]
- Why? Reduced stroke volume means lower systolic pressure; diastolic pressure is maintained or slightly elevated → narrow pulse pressure
Caution in the Elderly
In elderly patients with stiff, non-compliant arteries (arteriosclerosis), the classic slow-rising pulse may be masked. The stiff arteries transmit the pressure wave more rapidly, making the pulse feel more normal or even bounding despite severe AS. Do not rely on pulse character alone — always get an echocardiogram.
- Typically low systolic BP with narrow pulse pressure
- However, AS and systemic hypertension frequently coexist, especially in the elderly
- Normal unless right heart failure has developed secondary to pulmonary hypertension
- May show a prominent 'a' wave if RV hypertrophy/reduced compliance develops
| Finding | Pathophysiological Basis |
|---|---|
| Sustained, heaving apex beat [1][2] | Concentric LVH → sustained powerful contraction (heaving = pressure overload); apex is NOT displaced unless decompensation with LV dilatation has occurred |
| Systolic thrill at aortic area (right 2nd intercostal space) [1][2] | Palpable vibration from turbulent flow through the stenotic valve; a thrill indicates at least moderate-to-severe AS |
| Thrill may also be felt in the suprasternal notch and over the carotids | Turbulence transmitted along the aorta and great vessels |
This is high-yield and frequently examined:
| Finding | Pathophysiological Basis |
|---|---|
| Ejection systolic murmur (ESM) | Turbulent flow through the stenotic valve during systole; crescendo-decrescendo ("diamond-shaped") pattern because flow velocity increases then decreases during systole |
| Best heard at aortic area (right 2nd ICS, parasternal) | Closest surface landmark to the aortic valve |
| ± Radiates to bilateral carotids (neck) | Turbulent flow transmitted along the direction of blood flow in the aorta and carotid arteries |
| Harsh quality, described as "saw cutting wood" [2] | High-velocity turbulent jet through a rigid, calcified orifice |
| Soft or absent A2 (aortic component of S2) [1][2] | Calcified, immobile valve leaflets cannot "snap" shut properly; in severe AS, A2 may be inaudible |
| Reverse (paradoxical) splitting of S2 [1] | Prolonged LV ejection time (because it takes longer to empty through a stenotic valve) → A2 is delayed beyond P2; normally A2 precedes P2, but in AS the order is reversed |
| S4 (fourth heart sound) [1][2] | Atrial contraction against a stiff, non-compliant, hypertrophied LV → audible "thump" just before S1 |
| Late systolic peaking of a long murmur [1] | In severe AS, peak flow velocity occurs later in systole → the peak of the crescendo-decrescendo murmur shifts later; an early-peaking murmur suggests milder AS |
| S3 (third heart sound) | If present, indicates LV systolic dysfunction/decompensation (dilated LV with high filling pressures); ominous sign |
Severity assessment by auscultation:
| Feature | Mild AS | Severe AS |
|---|---|---|
| Murmur peaking | Early systolic peaking | Late systolic peaking |
| Murmur duration | Short | Long |
| A2 | Normal | Soft or absent |
| S4 | Absent | Present |
| Systolic thrill | Absent | Present |
| S2 splitting | Normal | Paradoxical (reversed) |
-
Gallavardin phenomenon [1]: In elderly patients with heavily calcified AS, the murmur may be best heard at the apex and may have a more musical quality, mimicking mitral regurgitation. This occurs because the high-frequency components of the AS murmur are selectively transmitted to the apex. Don't be fooled — listen at both the aortic area and apex, and check for radiation to the neck (AS) vs. axilla (MR).
-
Pulmonary hypertension signs [1]: If long-standing AS has caused LV failure → pulmonary hypertension → loud P2, right heart failure signs
-
Pulmonary congestion signs [1]: Bilateral basal crackles on lung auscultation if decompensated
Signs of Severity — Summary
The following signs point to severe AS [1][2]:
- Low-volume, slow-rising pulse
- Narrow pulse pressure
- Heaving, sustained apex (undisplaced)
- Palpable systolic thrill
- Soft/absent A2
- Reversed (paradoxical) splitting of S2
- S4
- Late systolic peaking of a long, harsh ESM
- Pulmonary hypertension / pulmonary congestion
For completeness of the clinical picture before diagnosis:
| Investigation | Expected Findings | Rationale |
|---|---|---|
| ECG | LVH (Sokolow-Lyon or Cornell criteria), LV strain pattern (ST depression + T inversion in lateral leads), left axis deviation, conduction block (LBBB, 1st/2nd/3rd degree AV block) [1] | LVH from pressure overload; conduction block from calcification into septum |
| CXR | Cardiomegaly (if decompensated), pulmonary oedema, prominent pulmonary arteries, post-stenotic dilatation of ascending aorta, ± aortic valve calcification [1] | Heart size may be normal in compensated AS (concentric LVH does not enlarge the cardiac silhouette); calcification may be visible on lateral CXR |
| Echocardiography | Valve morphology, AVA, gradients, jet velocity, LVEF, LV wall thickness, associated lesions | Gold standard for diagnosis and severity assessment |
| Coronary angiogram | Assess for coexistent CAD | Required pre-operatively in most patients ≥ 40 years (50% have coexistent CAD) |
| Exercise testing | Not required if symptomatic [1]; can unmask symptoms in "asymptomatic" patients | Contraindicated in symptomatic severe AS (risk of syncope, arrhythmia, death) |
Exercise Testing in AS
Exercise testing is NOT required if the patient is symptomatic [1]. It is contraindicated in symptomatic severe AS because of the risk of fatal arrhythmia or haemodynamic collapse. It is only used in asymptomatic patients with severe AS to unmask symptoms or assess haemodynamic response, and must be done under close supervision.
10. Additional Important Concepts
Heyde's syndrome = GI bleeding from angiodysplasia in the presence of aortic stenosis [1][5]
Mechanism:
- Blood passes through the severely stenotic aortic valve at high velocity and high shear stress
- This mechanically unfolds and cleaves large von Willebrand factor (vWF) multimers (the ADAMTS-13 metalloprotease is more effective under high shear)
- Large vWF multimers are essential for platelet adhesion at sites of vascular injury
- Their loss creates an acquired type IIA von Willebrand disease
- Patients become prone to mucocutaneous bleeding, particularly from angiodysplastic lesions (which are common in the elderly, especially in the right colon/caecum)
- This manifests as iron deficiency anaemia from chronic GI blood loss
- Correction of the AS (e.g., AVR) normalises vWF multimers and resolves the bleeding tendency
This is a beautiful example of how haemodynamics affect haemostasis!
Observed in mixed aortic valve lesions (combined AS + AR) — a pulse with two systolic peaks. The first peak is due to rapid ejection (percussion wave) and the second is due to reflected wave (tidal wave). This occurs when there is both a stenotic component (slow rise) and a regurgitant component (increased stroke volume from regurgitation).
| Pathophysiology | Clinical Feature |
|---|---|
| Fixed LVOT obstruction → ↑LV pressure | Pressure-overloaded LV → concentric LVH |
| Concentric LVH → stiff LV | S4 gallop, diastolic dysfunction |
| Stiff LV → dependent on atrial kick | AF causes acute deterioration |
| ↑LV mass + ↑wall stress + ↑LVEDP → ischaemia | Angina (even without CAD) |
| Fixed CO + exercise-induced vasodilation | Exertional syncope |
| LV decompensation → ↑LVEDP → pulmonary congestion | Dyspnoea, orthopnoea, PND, pulmonary oedema |
| Slow ejection through stenotic valve | Slow-rising, low-volume pulse; narrow pulse pressure |
| Prolonged LV ejection time | Paradoxical splitting of S2; late-peaking ESM |
| Calcified, immobile leaflets | Soft/absent A2; systolic thrill |
| Calcification → conduction system | LBBB, heart block |
| High shear stress → vWF degradation | Heyde's syndrome (GI bleeding) |
| LVH → fibrosis → arrhythmogenic substrate | AF, VT, VF, sudden cardiac death |
High Yield Summary
Aortic Stenosis — Key Points:
-
Most common valvular heart disease requiring intervention in the developed world; prevalence > 5% in those > 75 years
-
Three main aetiologies: degenerative calcific (elderly), bicuspid AV (middle-aged), rheumatic (associated with MV disease)
-
Pathophysiology: Fixed LVOT obstruction → concentric LVH → diastolic dysfunction → eventual decompensation with LV dilatation and failure
-
Classic triad of symptoms (SAD): Syncope, Angina, Dyspnoea — once symptomatic, prognosis is 2–5 years without intervention
-
Key signs of severity: Slow-rising pulse, narrow pulse pressure, heaving undisplaced apex, systolic thrill, soft/absent A2, reversed S2 splitting, S4, late-peaking long ESM
-
Angina mechanism: Supply-demand mismatch (↑demand from LVH; ↓supply from elevated LVEDP compressing coronary perfusion)
-
Syncope mechanism: Fixed CO + exercise-induced vasodilation → cerebral hypoperfusion; also ventricular arrhythmias
-
Heyde's syndrome: High shear → acquired type IIA vWD → GI bleeding from angiodysplasia
-
Heart block: Calcification extends from aortic annulus into adjacent conduction tissue (His bundle, left bundle branch)
-
Exercise testing is contraindicated in symptomatic severe AS
-
Once symptomatic: Angina ~5 yr survival, Syncope ~3 yr, Heart failure ~2 yr without intervention
Active Recall - Aortic Stenosis (Definition to Clinical Features)
[1] Senior notes: Maksim Medicine Notes.pdf (p35, p37 — Valvular heart disease, terminologies, indications for valve replacement) [2] Senior notes: Ryan Ho Cardiology.pdf (p158–160 — Aortic Stenosis, Aortic Regurgitation) [3] Lecture slides: Cardiac Surgery Tutorial_Prof. D Chan.pdf (p48–49 — epidemiology, causes of AS) [4] Lecture slides: Cardiac Surgery Tutorial_Prof. D Chan.pdf (p50–51 — natural history of AS, symptom onset and survival) [5] Senior notes: Maksim Surgery Notes.pdf (p97 — Angiodysplasia, Heyde's syndrome) [6] Senior notes: Ryan Ho Fundamentals.pdf (p210, p215, p281 — syncope, heart failure, lower GI bleeding/angiodysplasia)
Differential Diagnosis of Aortic Stenosis
The differential diagnosis of aortic stenosis is best approached by thinking about what clinical features you are actually trying to differentiate. In practice, a patient suspected of AS will present with one or more of three things: (1) a systolic murmur, (2) symptoms of angina/syncope/dyspnoea, or (3) signs of LV outflow obstruction on examination. We need to consider mimics for each of these.
Let's work through this systematically.
1. Differential Diagnosis of the Ejection Systolic Murmur at the Aortic Area
This is the most common clinical scenario — you hear an ESM at the right upper sternal border and need to decide: is this truly AS, or something else? The senior notes specifically highlight three important differentials [2]:
Aortic sclerosis: normal volume pulse, normal/wide pulse pressure, intact S2 and no LVH [2]
| Feature | Aortic Stenosis | Aortic Sclerosis |
|---|---|---|
| Definition | Thickening + calcification of leaflets with obstruction (gradient present) | Thickening + calcification of leaflets without obstruction (no significant gradient) |
| Pulse | Slow-rising, low volume | Normal volume and character |
| Pulse pressure | Narrow | Normal or wide |
| S2 (A2) | Soft or absent | Intact, normal A2 |
| LVH | Present (ECG/echo) | Absent |
| Murmur | Loud, late-peaking, radiates to neck | Soft, early-peaking, may not radiate to neck |
| Echocardiography | AVA < 1.5 cm², significant gradient | Thickened leaflets but AVA > 1.5 cm², gradient < 20 mmHg |
Why does this matter? Aortic sclerosis is extremely common in the elderly (~25% of those > 65 years). It produces a soft ESM but no haemodynamic obstruction. However, aortic sclerosis is a marker of cardiovascular risk — these patients have a ~50% increased risk of cardiovascular events, even though the valve itself is not causing symptoms. It is also a precursor lesion that may progress to AS over years/decades. Think of it like fatty streaks in atherosclerosis — not yet causing obstruction, but a warning sign.
Exam Trap: Aortic Sclerosis vs Stenosis
The key differentiators are the pulse character and S2. In aortic sclerosis, pulse volume is normal and A2 is preserved. In aortic stenosis, the pulse is slow-rising and A2 is diminished or absent. If the question gives you "ESM in an elderly patient with normal pulse and normal S2" — think sclerosis, not stenosis.
HOCM: jerky pulse, normal S2, murmur increases on standing [2]
HOCM produces a dynamic LVOT obstruction (as opposed to the fixed obstruction in valvular AS). The asymmetrically hypertrophied interventricular septum bulges into the LVOT, and during systole, the anterior mitral valve leaflet is pulled towards the septum by the Venturi effect (systolic anterior motion, SAM), worsening the obstruction.
| Feature | Aortic Stenosis | HOCM |
|---|---|---|
| Type of obstruction | Fixed, valvular | Dynamic, subvalvular |
| Pulse | Slow-rising, low volume (parvus et tardus) | Jerky, bifid (rapid upstroke then obstruction) |
| S2 | Soft/absent A2 | Normal S2 |
| Murmur location | Aortic area, radiates to neck | Left lower sternal border, does NOT typically radiate to neck |
| Response to Valsalva / standing | Murmur decreases (↓venous return → ↓flow → less turbulence) | Murmur increases (↓venous return → ↓LV cavity size → septum and MV leaflet closer → ↑obstruction) |
| Response to squatting | Murmur increases (↑venous return → ↑flow → more turbulence) | Murmur decreases (↑venous return → ↑LV cavity size → less obstruction) |
| Family history | Absent (unless bicuspid AV) | Often positive (autosomal dominant, sarcomeric gene mutations) |
| Age | Typically elderly (degenerative) | Typically younger; can present at any age |
| Echo | Calcified valve, restricted opening | Asymmetric septal hypertrophy (ASH), SAM of MV |
Why does the pulse differ? In AS, the fixed obstruction slows ejection from the start → slow-rising pulse. In HOCM, the initial ejection is unobstructed (rapid upstroke) but then the dynamic obstruction kicks in mid-systole (SAM of MV) → sudden deceleration → "jerky" or bifid pulse.
Why does the murmur response to manoeuvres differ? This is one of the most commonly tested concepts:
- Manoeuvres that decrease LV preload (Valsalva strain phase, standing) → smaller LV cavity → septum and MV leaflet are closer together → MORE obstruction in HOCM → louder murmur. In AS, less blood flows through the fixed stenosis → quieter murmur.
- Manoeuvres that increase LV preload (squatting, leg elevation) → larger LV cavity → septum and MV leaflet are further apart → LESS obstruction in HOCM → quieter murmur. In AS, more blood flows through → louder murmur.
MR: pansystolic murmur best heard at apex with radiation to axilla [2]
| Feature | Aortic Stenosis | Mitral Regurgitation |
|---|---|---|
| Murmur character | Ejection systolic (crescendo-decrescendo, diamond-shaped) | Pansystolic (plateau-shaped, same intensity throughout systole) |
| Timing | Begins after S1, ends before S2 | Begins with S1, extends through S2 |
| Best heard | Aortic area (R 2nd ICS) | Apex |
| Radiation | Neck (carotids) | Axilla |
| S1 | Normal | Soft (most reliable differentiator — in MR, the mitral valve doesn't close properly → soft S1) [2] |
| S2 | Soft/absent A2 | Usually normal |
| Pulse | Slow-rising, low volume | Normal or hyperdynamic |
Why can this be confusing? Because of the Gallavardin phenomenon [1] — in elderly patients with heavily calcified AS, the high-frequency components of the AS murmur are selectively transmitted to the apex, where they sound more musical and may mimic MR. The key differentiator is S1: in MR, S1 is soft; in AS with Gallavardin phenomenon, S1 is normal. Also, true MR radiates to the axilla, while AS radiates to the neck.
| Condition | Key Differentiating Features |
|---|---|
| Pulmonic stenosis | Best heard at left 2nd ICS (pulmonary area), not right; radiates to left shoulder, not neck; may have ejection click; associated with right-sided signs (RV heave, raised JVP) [7] |
| Flow murmur (innocent/physiological) | Common in high-output states (pregnancy, anaemia, thyrotoxicosis, fever); soft, early-peaking; no thrill; normal S2; no LVH; disappears when the underlying condition resolves |
| Atrial septal defect (ASD) | ESM at pulmonary area due to relative pulmonic stenosis from ↑flow across pulmonary valve; fixed splitting of S2 is the hallmark (pathognomonic) |
| Aortic regurgitation with flow murmur | Severe AR causes ↑stroke volume → ejection flow murmur across the aortic valve; but the dominant murmur is the early diastolic murmur of AR; collapsing pulse, wide pulse pressure distinguish this [1] |
| Carotid artery atherosclerosis (carotid bruit) | Can radiate from neck and be confused with AS murmur radiating to neck; a true carotid bruit is best heard directly over the carotid, usually unilateral, and does not have a precordial component; AS murmur radiates bilaterally [2] |
Carotid Bruit vs AS Murmur Radiation
A carotid bruit from carotid artery atherosclerosis may be unilateral and is heard directly over the carotid, whereas aortic stenosis murmur radiates bilaterally to the neck from the precordium [2]. Always auscultate the precordium first — if the murmur is loudest at the aortic area and fades towards the neck, it is radiation from AS. If it is loudest at the neck and doesn't have a clear precordial origin, consider carotid bruit.
2. Differential Diagnosis by Presenting Symptom
Because AS often presents with one of its three cardinal symptoms rather than a murmur discovered incidentally, you must also consider the broad differentials for each symptom and explain why AS is considered.
The differential for exertional chest pain mimicking AS-related angina:
| Diagnosis | Key Differentiating Features | Why It Mimics/Differs from AS |
|---|---|---|
| Coronary artery disease (stable angina) [8] | Atherosclerotic risk factors; typical angina relieved by rest/nitrates; normal pulse character; no ESM | Fixed epicardial coronary stenosis → supply-demand mismatch with exertion. 50% of AS patients have coexistent CAD, so both may coexist [2] |
| HOCM | Younger patient; family history of sudden death; jerky pulse; ESM at LLSB louder with Valsalva | Dynamic LVOT obstruction → similar supply-demand mismatch |
| Severe pulmonary hypertension | RV heave; loud P2; signs of right HF; TR murmur | RV pressure overload → RV ischaemia → angina equivalent |
| Aortic regurgitation [1] | Collapsing pulse; wide pulse pressure; EDM; displaced thrusting apex | Chest pain in AR is due to ↓diastolic BP (↓coronary perfusion) + ↑LV mass; tends to be worse at night (↓HR → longer diastole → more regurgitation) |
| Severe anaemia | Pallor; tachycardia; flow murmur; low Hb | ↓O₂ carrying capacity → myocardial ischaemia at lower workload |
The differential for exertional syncope — this is a critical "red flag" scenario [6]:
| Diagnosis | Key Features | Mechanism |
|---|---|---|
| Aortic stenosis | ESM, slow-rising pulse, elderly | Fixed CO + exercise vasodilation → ↓cerebral perfusion |
| HOCM | Jerky pulse, young athlete, FHx sudden death | Dynamic LVOT obstruction worsens with exercise (↑contractility, ↓preload) |
| Pulmonary hypertension / massive PE | RV signs, hypoxia, risk factors for PE | RVOT obstruction → ↓LV filling → ↓CO |
| Arrhythmias (VT, VF, complete heart block) | Palpitations, known structural heart disease | ↓CO from arrhythmia → cerebral hypoperfusion |
| Anomalous coronary artery origin | Young patient, exertional syncope/sudden death | Coronary artery compressed between aorta and PA during exercise |
Causes of exercise-related syncope: (1) LVOT obstruction — AS, HCMP; (2) RVOT obstruction — pulmonary HTN; (3) Cardiomyopathy — DCMP, HCMP, ARVD; (4) Coronary artery disease — atherosclerotic, anomalous origin; (5) Arrhythmogenic — VT, SVT, WPWS, LQTS [6]
| Diagnosis | Key Features | Why It Mimics/Differs from AS |
|---|---|---|
| Ischaemic cardiomyopathy | History of MI; regional wall motion abnormality on echo; dilated LV | Systolic dysfunction from myocardial scar |
| Dilated cardiomyopathy | Displaced, diffuse apex; S3; global hypokinesis on echo | Volume overload → eccentric hypertrophy (vs. pressure overload in AS) |
| Hypertensive heart disease | Longstanding HTN; concentric LVH; diastolic dysfunction | Similar pathophysiology (pressure overload) but no valve obstruction |
| Mitral stenosis | Opening snap + mid-diastolic rumble; small pulse; AF; mitral facies | LA obstruction → pulmonary congestion → dyspnoea |
| Aortic regurgitation [1] | Collapsing pulse; EDM; displaced apex | Volume overload → LV dilatation → eventual failure |
| Restrictive/infiltrative cardiomyopathy (e.g., amyloid) | Diastolic dysfunction; low-voltage ECG; ± "sparkling" myocardium on echo | Important: cardiac amyloidosis can cause both diastolic dysfunction AND aortic valve thickening, mimicking degenerative AS. Increasingly recognised as an underdiagnosed cause of "AS" in the elderly |
Cardiac Amyloidosis Masquerading as AS
Transthyretin cardiac amyloidosis (ATTR-CM) is increasingly recognised in elderly patients who also have degenerative AS. Up to 10-15% of patients undergoing TAVI for "severe AS" may have coexistent cardiac amyloidosis. Suspect it when: LVH seems out of proportion to the degree of AS, low-voltage ECG despite thick walls (voltage-mass mismatch), or diastolic dysfunction is disproportionately severe. Bone scintigraphy (⁹⁹ᵐTc-PYP or DPD scan) is the non-invasive diagnostic test of choice.
When you have confirmed LVOT obstruction, you must determine where the obstruction is:
| Level | Condition | Key Differentiating Features |
|---|---|---|
| Supravalvular | Williams syndrome [1] | Elfin facies, hypercalcaemia, developmental delay, supravalvular narrowing on echo; BP higher in right arm than left (jet directed preferentially into brachiocephalic artery) |
| Post-surgical supravalvular ridge | History of previous cardiac surgery | |
| Valvular | Degenerative, bicuspid, rheumatic | Most common; ejection click may be present in bicuspid (before it calcifies); echo shows valve-level obstruction |
| Subvalvular (fixed) | Discrete subaortic membrane | Usually younger patients; no ejection click; progressive AR (jet trauma to aortic valve); echo shows membrane below valve |
| Subvalvular (dynamic) | HOCM | Jerky pulse; murmur varies with manoeuvres; SAM on echo; often familial [2] |
| Condition | Murmur Type | Best Heard | Radiation | Pulse | A2 | Key Manoeuvre |
|---|---|---|---|---|---|---|
| Aortic stenosis | ESM (crescendo-decrescendo) | R 2nd ICS | Bilateral neck | Slow-rising, low volume | Soft/absent | Louder with squatting |
| Aortic sclerosis | ESM (early-peaking, soft) | R 2nd ICS | ± Neck | Normal | Normal | — |
| HOCM | ESM | LLSB | Does not radiate to neck | Jerky | Normal | Louder with Valsalva/standing |
| MR | PSM (plateau) | Apex | Axilla | Normal/hyperdynamic | Normal | — |
| Pulmonic stenosis | ESM + ejection click | L 2nd ICS | Left shoulder | Normal | Normal (P2 may be soft) | — |
| Flow murmur | ESM (soft, early) | LUSB/pulmonary | None | Normal/hyperdynamic | Normal | Disappears with resolution of high-output state |
| Carotid bruit | Continuous or systolic | Over carotid | — | Normal | Normal | Unilateral, no precordial component |
High Yield Summary — Differential Diagnosis of Aortic Stenosis
-
Three most important DDx of ESM at aortic area: aortic sclerosis (normal pulse, normal A2, no LVH), HOCM (jerky pulse, normal S2, louder with Valsalva/standing), MR (pansystolic, apex, radiates to axilla, soft S1)
-
Gallavardin phenomenon can make AS sound like MR at the apex — differentiate by S1 (soft in MR, normal in AS) and radiation (axilla in MR, neck in AS)
-
Carotid bruit vs AS radiation: carotid bruit is usually unilateral, heard directly over carotid, no precordial component; AS radiates bilaterally from aortic area
-
Response to manoeuvres: AS murmur decreases with Valsalva/standing (↓flow); HOCM murmur increases (↓LV cavity → ↑obstruction). This is the opposite.
-
Exertional syncope DDx: AS, HOCM, pulmonary HTN, arrhythmias, anomalous coronary arteries
-
Don't miss cardiac amyloidosis in elderly patients with apparent AS — suspect if LVH disproportionate to AS severity, low-voltage ECG, severe diastolic dysfunction
-
Always consider coexistent CAD — 50% of AS patients have significant coronary artery disease
Active Recall - Differential Diagnosis of Aortic Stenosis
References
[1] Senior notes: Maksim Medicine Notes.pdf (p5, p35, p37 — Valvular heart disease, chest pain DDx, terminologies including Gallavardin phenomenon) [2] Senior notes: Ryan Ho Cardiology.pdf (p158 — AS differentials: aortic sclerosis, HOCM, MR; Gallavardin phenomenon; carotid bruit vs AS) [6] Senior notes: Ryan Ho Fundamentals.pdf (p210 — causes of exercise-related syncope including LVOT obstruction) [7] Senior notes: Ryan Ho Fundamentals.pdf (p39 — systolic and diastolic murmur diagram, locations and radiation) [8] Senior notes: Ryan Ho Fundamentals.pdf (p199–203 — approach to chest pain, angina pectoris, AS as cause of increased demand)
Diagnosis of Aortic Stenosis: Criteria, Algorithm and Investigations
The diagnosis of aortic stenosis is fundamentally a two-step process:
- Detection: Suspecting AS based on clinical features (murmur, symptoms, or incidental finding)
- Confirmation and severity grading: Using echocardiography as the gold standard, supplemented by other investigations to assess consequences, plan management, and exclude coexistent disease
There is no single "diagnostic criterion" for AS the way you have Jones criteria for rheumatic fever or Duke criteria for endocarditis. Instead, the diagnosis rests on echocardiographic haemodynamic parameters that define both the presence and severity of obstruction. Let me walk you through each investigation modality, what you're looking for, and why.
2. Echocardiographic Diagnostic Criteria for Severity
Echocardiography is the cornerstone investigation — it simultaneously confirms the diagnosis, grades severity, identifies the aetiology, assesses LV function, and detects associated lesions [1][2].
| Parameter | Normal | Aortic Sclerosis | Mild AS | Moderate AS | Severe AS |
|---|---|---|---|---|---|
| Peak aortic jet velocity (Vmax) | < 2.0 m/s | ≤ 2.5 m/s (thickened, no obstruction) | 2.0–2.9 m/s | 3.0–3.9 m/s | ≥ 4.0 m/s [2] |
| Mean transvalvular pressure gradient | < 5 mmHg | < 10 mmHg | < 20 mmHg | 20–39 mmHg | ≥ 40 mmHg [2] |
| Aortic valve area (AVA) | 3.0–4.0 cm² | > 1.5 cm² | > 1.5 cm² | 1.0–1.5 cm² | ≤ 1.0 cm² [2] |
| Indexed AVA (AVAi) | — | — | > 0.85 cm²/m² | 0.60–0.85 cm²/m² | ≤ 0.6 cm²/m² |
| Velocity ratio (LVOT VTI / AV VTI) | > 0.50 | > 0.50 | > 0.50 | 0.25–0.50 | < 0.25 |
Diagnosis of severe AS is defined by transvalvular velocity ≥ 4 m/s, transvalvular pressure gradient ≥ 40 mmHg, aortic valve area ≤ 1 cm² [2]
How are these measured?
-
Peak jet velocity (Vmax): Measured using continuous-wave (CW) Doppler across the aortic valve. The Doppler beam measures the maximum velocity of blood flowing through the stenotic orifice. Higher velocity = more severe stenosis (blood must accelerate more to squeeze through a smaller opening — think of a garden hose: squeeze the nozzle, water comes out faster).
-
Mean pressure gradient: Calculated from the Doppler velocity profile using the modified Bernoulli equation:
ΔP = 4V²
where ΔP is the instantaneous pressure gradient (mmHg) and V is the instantaneous velocity (m/s). The mean gradient is the time-averaged integral of all instantaneous gradients across systole. This equation derives from fluid dynamics — the kinetic energy of flowing blood is converted from pressure energy as it accelerates through the stenosis.
-
Aortic valve area (AVA): Calculated using the continuity equation, which is based on conservation of mass (what goes in must come out):
AVA = (LVOT area × LVOT VTI) / AV VTI
where LVOT = left ventricular outflow tract, VTI = velocity-time integral (a measure of flow). The LVOT area is calculated from the LVOT diameter (measured in parasternal long-axis view): LVOT area = π × (d/2)². This gives a flow-independent estimate of valve area.
Why Do We Need Both Gradient AND Valve Area?
The pressure gradient is flow-dependent — it depends on how much blood is flowing across the valve. A patient with a truly severe stenosis (small AVA) but very poor LV function (low stroke volume) may generate only a low gradient because there isn't enough blood flow to create a large pressure drop. Conversely, a patient with a mildly stenotic valve but very high cardiac output (e.g., anaemia, pregnancy) may have a deceptively high gradient. The AVA, calculated via the continuity equation, is relatively flow-independent and gives a more reliable estimate of anatomical severity. You need both to avoid being fooled.
This concept is frequently tested and is explained thoroughly in the senior notes [2]:
The criteria for transvalvular pressure gradient only apply with sufficient stroke volume [2]
In decreased stroke volume (whether or not LVEF is reduced): [2]
- Transvalvular gradient and flow is reduced due to decreased blood flow
- Decreased valvular opening force → limited opening of valve that is not severely diseased → underestimation of aortic valvular area may wrongly classify a patient to have severe AS, i.e. pseudo-severe AS where valvular surgery may not reverse the underlying condition [2]
- However, decreased stroke volume can also be due to progressive LV failure from AS or other pathologies and does NOT rule out co-existence of significant AS [2]
There are four haemodynamic patterns of severe AS [2]:
| Pattern | AVA | Mean Gradient | Stroke Volume Index | LVEF | Approach |
|---|---|---|---|---|---|
| High-gradient severe AS (≥ 50%) [2] | ≤ 1.0 cm² | ≥ 40 mmHg | Variable | Variable | Diagnosis is straightforward — meets all criteria |
| Classical low-flow, low-gradient (LFLG) AS [2] | ≤ 1.0 cm² | < 40 mmHg | ≤ 35 mL/m² BSA [2] | Usually < 50% | Low dose dobutamine stress echo to differentiate true vs pseudo-severe AS [2] |
| Paradoxical LFLG AS [2] | ≤ 1.0 cm² | < 40 mmHg | ≤ 35 mL/m² | ≥ 50% (preserved) [2] | CT calcium scoring; often elderly hypertensive women with small, thick-walled LV |
| Normal flow, low-gradient AS [2] | ≤ 1.0 cm² | < 40 mmHg | > 35 mL/m² | ≥ 50% | Likely measurement error or truly moderate AS; reassess carefully |
Dobutamine Stress Echocardiography (DSE) — How it works and what it tells you:
In LFLG AS, a low dose dobutamine stress study may be indicated to trigger increased stroke volume → allow reassessment of aortic valve area under a high-flow state [2]
Dobutamine is a β₁-agonist → increases myocardial contractility → increases stroke volume → increases flow across the aortic valve. Under these conditions:
| Outcome | AVA Response | Gradient Response | Interpretation |
|---|---|---|---|
| True severe AS | AVA remains ≤ 1.0 cm² (valve is anatomically fixed) | Gradient rises significantly (≥ 40 mmHg) because ↑flow across a truly stenotic valve | Genuinely severe — benefit from intervention |
| Pseudo-severe AS | AVA increases to > 1.0 cm² (valve opens more with ↑force) | Gradient may increase modestly | Not truly severe — the valve was not opening fully due to low flow, not intrinsic stenosis; intervention may not help |
| No flow reserve | AVA unchanged, gradient unchanged | Neither parameter changes | Very poor LV function with no contractile reserve; extremely high operative risk; very poor prognosis regardless |
CT Calcium Scoring for Paradoxical LFLG AS: In paradoxical LFLG AS (preserved LVEF but low flow), dobutamine stress echo is less useful because the LV function is already preserved. Instead, non-contrast CT calcium scoring of the aortic valve provides a flow-independent assessment of disease burden:
- Male: AV calcium score ≥ 1200 Agatston units (AU) → confirms severe AS
- Female: AV calcium score ≥ 800 AU → confirms severe AS
- (The threshold is lower in women because female aortic valves are smaller and the same calcium burden produces more stenosis)
Exam Pearl: Low-Gradient Severe AS
This is a frequent exam pitfall. Remember: a low gradient does NOT exclude severe AS. Always check the stroke volume index. If SVI ≤ 35 mL/m², the gradient may be falsely low despite genuine severe stenosis. Order dobutamine stress echo (if LVEF < 50%) or CT calcium scoring (if LVEF ≥ 50%) to confirm.
3. Complete Investigation Workup
3.1 Baseline Investigations
ECG findings: LVH, LV strain, left axis deviation, conduction block (LBBB) [1]
| Finding | Interpretation / Pathophysiology |
|---|---|
| LVH voltage criteria (Sokolow-Lyon: S in V1 + R in V5 or V6 ≥ 35 mm; or Cornell: R in aVL + S in V3 > 28 mm in males / > 20 mm in females) | Increased LV muscle mass from concentric hypertrophy → larger electrical vector → taller QRS voltages |
| LV "strain" pattern: downsloping ST depression + asymmetric T-wave inversion in lateral leads (I, aVL, V5, V6) [2] | Subendocardial ischaemia from ↑wall stress and ↓coronary perfusion; repolarisation abnormality secondary to LVH. The ST depression is "downsloping" (not horizontal or upsloping), which distinguishes it from ischaemic ST changes |
| Left axis deviation (LAD) | LVH shifts the mean QRS axis leftward (more LV mass pulling the vector leftward) |
| Conduction abnormalities: LBBB, 1st/2nd/3rd degree AV block | Calcification extends from the aortic valve annulus into the adjacent conduction tissue — the bundle of His and left bundle branch lie immediately beneath the aortic valve. Progressive calcification → conduction delay or block |
| Left atrial enlargement (P mitrale: bifid P wave in lead II > 120 ms, or negative component of P wave in V1 > 1 mm deep and > 40 ms) | LA hypertrophies to overcome the stiff LV (increased LV filling pressures require greater atrial contraction force) |
| Atrial fibrillation | May develop due to LA dilatation/pressure overload; loss of atrial kick is poorly tolerated in AS |
Important
The ECG is neither sensitive nor specific for diagnosing AS — up to 15-20% of patients with severe AS may have a normal ECG (especially elderly women with smaller body habitus). The ECG helps assess consequences (LVH, conduction disease) but cannot confirm or exclude the diagnosis. Always get an echocardiogram.
CXR findings: cardiomegaly, pulmonary oedema, prominent pulmonary arteries [1]
| Finding | Interpretation / Pathophysiology |
|---|---|
| Normal heart size (compensated AS) | Concentric LVH increases wall thickness but does NOT dilate the LV cavity → cardiothoracic ratio may be normal. This is a key point — a normal-sized heart on CXR does NOT exclude severe AS |
| Cardiomegaly (decompensated AS) | LV dilatation occurs only in the decompensated phase when the LV fails and transitions from concentric to eccentric hypertrophy |
| Pulmonary oedema / upper lobe venous distension | Elevated LV filling pressures → transmitted to LA → pulmonary veins → pulmonary congestion. Look for the ABCDE pattern: Alveolar oedema (bat-wing), Kerley B lines, Cardiomegaly, upper lobe Diversion, pleural Effusion |
| Prominent pulmonary arteries | Indicates secondary pulmonary hypertension from chronic LV failure |
| Post-stenotic dilatation of ascending aorta | The high-velocity jet through the stenotic valve impacts the wall of the ascending aorta → localised dilatation just above the valve. This is distinct from generalised aortic dilatation and is a clue to AS even on plain CXR |
| Aortic valve calcification | Dense calcification of the aortic valve may be visible, especially on a lateral CXR. Heavy calcification correlates with severity |
Blood tests are not used to diagnose AS itself but to assess consequences, comorbidities, and fitness for intervention:
| Test | Rationale |
|---|---|
| Full blood count (CBC) | Anaemia (worsens angina by ↓O₂ supply; may be from Heyde's syndrome — iron deficiency from GI angiodysplasia bleeding); polycythaemia (uncommon) |
| Renal function tests (RFT) | Baseline before contrast studies (angiography) and surgery; renal impairment may result from low cardiac output |
| Liver function tests (LFT) | If right heart failure develops → hepatic congestion → raised transaminases/bilirubin |
| BNP / NT-proBNP | Elevated in heart failure; useful for prognostication; rising levels in asymptomatic severe AS may prompt earlier intervention. BNP > 400 pg/mL suggests heart failure [9] |
| Iron studies | If anaemia detected → investigate for iron deficiency (Heyde's syndrome) |
| Coagulation screen | Baseline for surgery; also assess for acquired vWD in Heyde's syndrome (↓ristocetin cofactor activity, ↓large vWF multimers) |
| Lipid profile, HbA1c, thyroid function | Assess cardiovascular risk factors and comorbidities that may accelerate progression or affect perioperative risk |
| Blood culture | If infective endocarditis is suspected (fever, new/changing murmur, embolic phenomena) |
ECHO [1] — this is the single most important investigation and is both diagnostic and prognostic.
Transthoracic echocardiography (TTE) provides:
| Assessment | What You're Looking For | Why It Matters |
|---|---|---|
| Valve morphology | Number of cusps (tricuspid vs bicuspid vs unicuspid); degree of calcification; leaflet thickening; commissural fusion (rheumatic); restricted leaflet motion | Determines aetiology; degree of calcification correlates with severity and prognosis. Heavy calcification is a poor prognostic factor [2] |
| Valve haemodynamics | Peak jet velocity, mean gradient, AVA (all described above) | Grades severity |
| LV geometry and function | Concentric LVH (wall thickness, LV mass index); LV cavity dimensions; LVEF (systolic function); diastolic function (E/A ratio, E/e' ratio, deceleration time) | Concentric LVH without dilatation = compensated; dilatation + ↓EF = decompensated. LVEF is a key determinant for intervention timing |
| Other valve lesions | Concomitant MR, AR, MS (especially if rheumatic) | Affects surgical planning (may need combined valve surgery) |
| Aortic root and ascending aorta | Aortic root dimensions; post-stenotic dilatation; bicuspid aortopathy | Ascending aortic dilatation ≥ 45 mm in bicuspid AV or ≥ 50 mm otherwise may require concomitant aortic surgery |
| Pulmonary artery systolic pressure | Estimate from TR jet velocity: PASP = 4V² + estimated RAP | Elevated PASP indicates secondary pulmonary hypertension from LV failure |
| Associated findings | Regional wall motion abnormalities (coexistent CAD); pericardial effusion; vegetations (IE) | 50% of AS patients have coexistent CAD [2] |
Transesophageal echocardiography (TOE/TEE): Not routinely needed but useful when:
- TTE image quality is poor (e.g., obesity, COPD)
- Infective endocarditis is suspected (better sensitivity for vegetations, abscesses)
- Intraoperative guidance during valve surgery or TAVI
- Better planimetric measurement of AVA in selected cases
Exercise testing: not required if symptomatic [1]
This is a critically important point with specific rules:
| Scenario | Role of Exercise Testing | Rationale |
|---|---|---|
| Symptomatic severe AS | CONTRAINDICATED | Risk of haemodynamic collapse, fatal arrhythmia, sudden death. The diagnosis is already clear — proceed to intervention |
| Asymptomatic severe AS | Useful and recommended (under careful supervision) | Many patients subconsciously limit activity and deny symptoms. A supervised exercise test can unmask symptoms (dyspnoea, chest pain, dizziness, syncope) or reveal objective abnormalities (↓BP response, ST changes, arrhythmias) that would change management |
| Asymptomatic moderate AS with equivocal symptoms | Useful | Helps determine functional capacity and risk |
Abnormal exercise test findings that suggest occult symptoms or high risk:
- Development of symptoms (dyspnoea, angina, pre-syncope/syncope)
- Fall in systolic BP (or failure to rise appropriately with exercise) → indicates inability to increase CO
- ST-segment depression → myocardial ischaemia
- Ventricular arrhythmias → substrate from LVH/ischaemia
- Inability to achieve predicted workload
Coronary angiogram [1]
| Indication | Rationale |
|---|---|
| Pre-operative assessment before AVR in patients aged ≥ 40 years (or younger if risk factors present) | 50% of AS patients have significant coronary artery disease [2]. Coexistent CAD must be identified to plan concomitant CABG at the time of valve surgery |
| Suspected CAD contributing to symptoms | Angina in AS may be entirely from the valve or from coexistent CAD — must distinguish to plan optimal treatment |
Alternative: CT coronary angiography — increasingly used as a less invasive alternative, especially in lower-risk patients or those with a lower pre-test probability of CAD. However, heavy aortic valve calcification can cause artefact that makes coronary assessment difficult.
During catheterisation, haemodynamic assessment can also be performed:
- Direct measurement of transvalvular pressure gradient (pull-back gradient across the aortic valve)
- Calculation of AVA using the Gorlin formula: AVA = CO / (44.3 × SEP × HR × √ΔP), where SEP = systolic ejection period, HR = heart rate, ΔP = mean gradient. This is the gold standard for AVA calculation but is rarely needed now that echo provides reliable non-invasive estimates.
Gorlin Formula
The Gorlin formula [1] estimates aortic valve area from catheter-measured flow and pressure data. It is named after Richard Gorlin (1926–1997). While historically important and still the gold standard, it has been largely supplanted by echocardiographic continuity equation in routine practice. You should know what it is conceptually but don't need to memorise the full formula — just know it relates AVA to cardiac output, heart rate, and pressure gradient.
3.5 Advanced Imaging
| Application | Purpose |
|---|---|
| Aortic valve calcium scoring | Non-contrast CT; quantifies calcium burden (Agatston units); essential for confirming severity in paradoxical LFLG AS (male ≥ 1200 AU, female ≥ 800 AU); flow-independent assessment |
| Aortic annular sizing for TAVI | CT is the gold standard for annular measurements to select the correct TAVI prosthesis size; measures annular perimeter, area, diameters; also assesses aortic root anatomy, coronary height, and iliofemoral access route |
| Ascending aorta assessment | Dimensions of ascending aorta (important for bicuspid aortopathy — may need concomitant aortic surgery if ≥ 45 mm) |
| CT coronary angiography | Non-invasive assessment of coronary arteries (alternative to invasive angiography in selected patients) |
| Application | Purpose |
|---|---|
| LV volumes and function | Most accurate modality for LV volumes and EF (gold standard) — useful when echo windows are poor |
| Myocardial fibrosis assessment | Late gadolinium enhancement (LGE) detects replacement fibrosis; T1 mapping detects diffuse interstitial fibrosis. Fibrosis burden correlates with prognosis and may help identify patients who would benefit from earlier intervention, even if asymptomatic |
| Concomitant cardiomyopathy | Helps identify coexistent cardiac amyloidosis (characteristic pattern of diffuse subendocardial or transmural LGE), hypertrophic cardiomyopathy, or other infiltrative diseases |
- Used to screen for transthyretin cardiac amyloidosis (ATTR-CM) in elderly patients with AS
- Uptake grade ≥ 2 with absent monoclonal protein → diagnostic for ATTR-CM without biopsy
- Important because 10–15% of elderly patients with severe AS may have coexistent ATTR-CM, which alters prognosis and management
A. TAVI Assessment Panel
For patients being considered for transcatheter aortic valve implantation (TAVI), a comprehensive multi-modality assessment is required:
| Investigation | Purpose |
|---|---|
| CT aortogram with TAVI protocol | Annular sizing, coronary ostia height, aortic root anatomy, ascending aorta, iliofemoral access assessment (diameter, calcification, tortuosity) |
| Pulmonary function tests | Baseline respiratory function; frailty assessment |
| Carotid duplex ultrasound | Screen for carotid stenosis (risk of peri-procedural stroke) |
| Dental assessment | Exclude dental sepsis (risk of prosthetic valve endocarditis) |
| Frailty scoring | Gait speed, grip strength, STS score, EuroSCORE II → determine risk profile and suitability for TAVI vs SAVR |
EOAI: [3]
- Red area = prosthesis is too small for the patient [3]
- Patient remains in aortic stenosis or pathology not completely corrected [3]
After aortic valve replacement (whether surgical AVR or TAVI), it is essential to assess whether the prosthesis is functioning adequately. The effective orifice area index (EOAI) is the prosthetic valve effective orifice area indexed to body surface area (BSA):
- EOAI = EOA / BSA
- Patient-prosthesis mismatch (PPM) occurs when the prosthetic valve orifice area is too small relative to the patient's body size:
- Moderate PPM: EOAI 0.65–0.85 cm²/m²
- Severe PPM: EOAI < 0.65 cm²/m²
- Severe PPM means the patient effectively remains in aortic stenosis despite having had valve replacement — the prosthesis creates its own residual obstruction
- This is associated with higher post-operative gradients, worse LV regression, increased mortality
- Prevention: careful pre-operative annular sizing and prosthesis selection; consider aortic root enlargement if the annulus is too small for an adequate prosthesis
| Investigation | Key Findings in AS | Clinical Utility |
|---|---|---|
| ECG [1] | LVH + strain; LAD; LBBB/AV block; LAE; AF | Assess LV consequences and conduction disease |
| CXR [1] | Normal (compensated) or cardiomegaly + pulmonary oedema (decompensated); post-stenotic aortic dilatation; valve calcification | Baseline; assess decompensation |
| Echocardiography (TTE) [1][2] | Valve morphology, Vmax, mean gradient, AVA, LVEF, LV dimensions, diastolic function, PASP | Gold standard for diagnosis and severity grading |
| Exercise testing [1] | Unmask symptoms, ↓BP response, ST changes, arrhythmias | Only in asymptomatic severe AS; contraindicated if symptomatic |
| Coronary angiogram [1][2] | Identify coexistent CAD | Pre-operative; 50% have significant CAD |
| Dobutamine stress echo [2] | True vs pseudo-severe in classical LFLG AS | Discordant AVA and gradient with low LVEF |
| CT calcium scoring | AV calcium Agatston score | Paradoxical LFLG AS confirmation |
| CT aortogram / TAVI protocol | Annular sizing, access route, coronary height | Pre-TAVI planning |
| Cardiac MRI | LV volumes, EF, fibrosis (LGE, T1 mapping) | When echo is inadequate; fibrosis assessment |
| BNP / NT-proBNP [9] | Elevated in decompensation | Prognostication; trigger for closer follow-up |
High Yield Summary — Diagnosis of Aortic Stenosis
-
Echocardiography is the gold standard for diagnosing and grading AS severity
-
Severe AS criteria: Vmax ≥ 4.0 m/s, mean gradient ≥ 40 mmHg, AVA ≤ 1.0 cm² — you need concordance among these
-
Low gradient does NOT exclude severe AS: Always check stroke volume index. Classical LFLG (low EF) → dobutamine stress echo. Paradoxical LFLG (preserved EF) → CT calcium scoring (M ≥ 1200, F ≥ 800 AU)
-
Dobutamine stress echo differentiates true severe AS (AVA stays ≤ 1.0, gradient rises) from pseudo-severe AS (AVA increases > 1.0) and identifies patients with no flow reserve (very poor prognosis)
-
Exercise testing is CONTRAINDICATED in symptomatic AS but useful to unmask symptoms in asymptomatic severe AS
-
Coronary angiography is required pre-operatively in most patients — 50% have coexistent CAD
-
ECG findings: LVH + strain, LAD, LBBB/heart block (calcification into conduction system)
-
CXR may be NORMAL in compensated AS — concentric LVH does not enlarge the cardiac silhouette
-
Patient-prosthesis mismatch: EOAI must be adequate after valve replacement; if too small, patient remains in AS
Active Recall - Diagnosis of Aortic Stenosis
References
[1] Senior notes: Maksim Medicine Notes.pdf (p35 — Valvular heart disease investigations: ECG, CXR, ECHO, coronary angiogram, exercise testing) [2] Senior notes: Ryan Ho Cardiology.pdf (p158–159 — AS investigations, classification by transvalvular gradient, LFLG AS, dobutamine stress echo, echo criteria) [3] Lecture slides: Cardiac Surgery Tutorial_Prof. D Chan.pdf (p60 — EOAI and patient-prosthesis mismatch) [9] Senior notes: Maksim Medicine Notes.pdf (p18 — BNP/NT-proBNP in heart failure diagnosis)
Management of Aortic Stenosis
Before diving into specific treatments, let's establish the guiding principles that govern every management decision in AS. If you understand these, the algorithm becomes intuitive rather than memorised.
Principle 1: There is no effective medical therapy that slows the progression of AS or improves survival.
Unlike coronary artery disease or heart failure with reduced EF, where we have a rich pharmacological armamentarium (ACEIs, beta-blockers, statins), there is no drug that reverses or halts the calcification process in established AS. Statins were trialled extensively (SEAS, SALTIRE, ASTRONOMER) and failed — because established AS is driven by osteoblastic calcification, not lipid accumulation.
No medication [3] — this is the stark reality. The only definitive treatment is mechanical relief of the obstruction by valve replacement.
Principle 2: The decision to intervene hinges on the presence of symptoms or LV dysfunction.
Indication of surgery: Severe valve problem with: Symptom or Ventricular dysfunction [3]
This is the central decision point. Why? Because:
- During the asymptomatic phase, the risk of sudden death (~1%/year) is lower than the procedural risk of valve replacement
- Once symptoms appear, the prognosis deteriorates catastrophically (2–5 year survival without intervention) [4], making the procedural risk clearly worthwhile
- LV dysfunction (LVEF < 50%) in the absence of symptoms indicates that the myocardium is failing under the pressure load — waiting for symptoms at this point risks irreversible myocardial damage
Principle 3: Preload is critical — drugs that reduce preload are dangerous.
Conservative if mild, asymptomatic… avoid drugs that decrease preload: LV output is dependent on adequate preload (with markedly increased afterload) [2]
Why? In severe AS, the LV faces a massive fixed afterload (the stenotic valve). The only way the LV can maintain cardiac output is through:
- Vigorous contraction (maintained by the compensatory LVH)
- Adequate preload (stretching the LV during diastole via the Frank-Starling mechanism)
If you reduce preload (with diuretics, nitrates, vasodilators), the LV cannot fill adequately → cardiac output drops precipitously → hypotension → syncope → cardiac arrest. This is why these drugs are used with extreme caution or avoided entirely in severe AS.
Principle 4: The choice between SAVR and TAVI depends on surgical risk, anatomy, and patient preference.
This is the modern management frontier — matching the right procedure to the right patient.
2. Medical Management (Conservative)
Medical therapy in AS is purely palliative or preventive — it does NOT change the natural history.
Conservative if mild, asymptomatic (only 20% will progress over 20 years) [2]
- Mild AS: No intervention needed; surveillance only
- Moderate AS: Surveillance with serial echocardiography
- Severe asymptomatic AS with preserved LV function and no exercise-induced abnormalities: Watchful waiting with regular surveillance (but threshold for intervention is getting lower with improving procedural outcomes)
- Patients unfit for any intervention: Palliative medical therapy only
Statin therapy to treat hypercholesterolaemia (progression associated with atherosclerotic risk factors) [2]
| Measure | Rationale |
|---|---|
| Control hypertension | Reduces additional LV afterload; use ACEIs/ARBs cautiously at low doses with careful monitoring; avoid aggressive vasodilation |
| Statin therapy | For hyperlipidaemia management and cardiovascular risk reduction; does NOT slow AS progression once established, but still indicated for overall CV risk [2] |
| Diabetes management | Reduces cardiovascular risk |
| Smoking cessation | General cardiovascular health |
| Weight management and exercise | Gentle exercise is safe in compensated asymptomatic AS; avoid strenuous isometric exercise |
Avoid drugs that decrease preload: LV output dependent on adequate preload (with markedly increased afterload) [2]
| Drug Class | Why Dangerous in Severe AS | Notes |
|---|---|---|
| Diuretics [2] | Reduce preload → ↓LV filling → ↓CO → hypotension, syncope | May be cautiously used in small doses if patient has overt pulmonary oedema (decompensated AS), but must be done carefully with close haemodynamic monitoring |
| Vasodilators (including nitrates) [2] | Reduce afterload AND preload → in a system where afterload is fixed by the valve, the only effect is ↓preload → ↓CO → catastrophic hypotension | GTN spray/sublingual nitrate can cause profound hypotension in severe AS. Avoid as anti-anginal |
| Beta-blockers (high dose) | In severe AS with borderline LV function, negative inotropy may precipitate decompensation | Low-dose beta-blockers may be used cautiously for rate control in AF, but avoid high doses |
| ACEIs/ARBs (high dose) | Reduce afterload → similar mechanism to vasodilators; however, low-dose ACEI/ARB is increasingly considered safe and possibly beneficial for coexisting hypertension | Start low, go slow; monitor BP closely |
The Nitrate Trap
A classic exam scenario: an elderly patient with severe AS presents with chest pain. The junior doctor gives sublingual GTN for presumed angina. The patient becomes profoundly hypotensive and loses consciousness. Why? Nitrates cause venodilation (↓preload) and mild arterial vasodilation (↓afterload). In severe AS, the fixed valvular obstruction means the LV cannot increase stroke volume to compensate for ↓preload → acute ↓CO → syncope. Never give nitrates for angina in severe AS unless you are in a monitored setting with vasopressor backup.
When a patient with severe AS presents with acute heart failure while awaiting definitive intervention:
| Agent | Role | Mechanism | Caution |
|---|---|---|---|
| IV frusemide | Reduce pulmonary congestion | Loop diuretic → ↓preload → ↓pulmonary oedema | Use smallest effective dose; over-diuresis → ↓CO |
| Dobutamine | Inotropic support if cardiogenic shock | β₁-agonist → ↑contractility → ↑CO | Does not address the obstruction; temporising measure only |
| Nitroprusside (ICU setting only) | Careful afterload reduction if severe HF | Direct vasodilator → ↓afterload | Requires invasive BP monitoring; risk of catastrophic hypotension |
| IABP (intra-aortic balloon pump) | Mechanical circulatory support | Augments diastolic coronary perfusion; reduces afterload during systole | Bridge to definitive intervention |
3. Definitive Treatment: Valve Replacement
Most of the aortic valve disease — very difficult to repair [3]
Unlike mitral valve disease where repair is often preferred over replacement, the aortic valve is rarely repairable because:
- Calcification destroys the leaflet tissue → nothing healthy to reconstruct
- The tri-leaflet geometry is difficult to restore
- Repair durability for AS is poor compared to replacement
Therefore, the definitive treatment is aortic valve replacement (AVR), either surgical or transcatheter.
3.1 Indications for Intervention
General indications for valvular replacement: [1]
- Symptomatic (heart failure) despite optimal medical therapy
- Asymptomatic, but severe disease defined by:
- Severe stenosis/regurgitation by ECHO criteria
- LV dilatation: LV end-systolic diameter
- LV systolic dysfunction: Impaired LVEF < 50%
- Complications, e.g. new-onset AF, pulmonary HT
- Infective endocarditis despite optimal medical therapy
Surgical AV replacement: more aggressive than MV due to markedly increased complication rate [2]
| Indication | Class | Explanation |
|---|---|---|
| Symptomatic severe high-gradient AS | Class I (must do) | Symptoms = angina, syncope, or HF; once present, median survival is 2–5 years without intervention [4] |
| Symptomatic severe LFLG AS with LVEF < 50%, confirmed true severe by dobutamine stress echo [2] | Class I | True severe AS despite low gradient; LV failure is FROM the AS; relieving obstruction allows LV recovery |
| Symptomatic paradoxical LFLG AS with LVEF ≥ 50%, confirmed by CT calcium scoring [2] | Class IIa | Genuinely severe AS despite seemingly preserved function; low flow from restrictive physiology |
| Asymptomatic severe AS with LVEF < 50% (without another cause for ↓EF) [2] | Class I | LV is failing silently from pressure overload; waiting for symptoms risks irreversible damage |
| Asymptomatic very severe AS (Vmax ≥ 5.0 m/s) [2] | Class IIa | Very high-risk lesion with high event rate even without symptoms (~5%/year sudden death risk) |
| Asymptomatic severe AS with abnormal exercise test (↓BP, symptoms) [2] | Class IIa | Unmasked symptoms on exercise = effectively symptomatic |
| During concomitant cardiac surgery (e.g., CABG, other valve surgery) [2] | Class I/IIa | Opportunity to address severe AS during an already planned open-heart procedure; avoids second operation |
| Asymptomatic severe AS with rapid progression (↑Vmax ≥ 0.3 m/s/year) | Class IIa | Markers of imminent symptom onset |
| Asymptomatic severe AS with elevated BNP (consistently > 3× age/sex-corrected normal) | Class IIa | Neurohormonal activation suggests subclinical decompensation |
| Asymptomatic severe AS with severe valve calcification + Vmax progression ≥ 0.3 m/s/year | Class IIa | Combined risk factors predict rapid transition to symptomatic disease |
Key Concept: Why Is Intervention for AS More Aggressive Than for MR/MS?
Surgical AV replacement is more aggressive than MV due to markedly increased complication rate [2]. This means we intervene EARLIER in AS than in many other valve diseases because:
- The mortality once symptomatic is catastrophic (worse than colon cancer)
- Sudden death is a real risk even in the asymptomatic phase (≈1%/year)
- Once the LV decompensates, the operative risk rises dramatically and LV recovery may be incomplete
- AVR has excellent outcomes when performed before irreversible myocardial damage
3.2 Surgical Aortic Valve Replacement (SAVR)
SAVR has been the gold standard for over 50 years and remains the reference treatment for many patients.
| Aspect | Details |
|---|---|
| Access | Median sternotomy (traditional, full access); mini-sternotomy (upper hemisternotomy — less trauma, faster recovery); right anterior thoracotomy (minimally invasive) |
| Cardiopulmonary bypass (CPB) | Required — the heart must be arrested to operate on the aortic valve. Blood is diverted through the heart-lung machine, which oxygenates and circulates it while the heart is stopped with cardioplegia |
| Procedure | Aortotomy → excision of diseased native valve and annular debridement → sizing of annulus → implantation of prosthetic valve → closure of aortotomy → weaning from CPB |
The choice of type of prosthetic heart valve should be a shared decision-making process that accounts for the patient's values and preferences and includes discussion of the indications for and risks of anticoagulant therapy and the potential need for and risk associated with reintervention [3]
| Type | Examples | Advantages | Disadvantages | Typical Indication |
|---|---|---|---|---|
| Mechanical valve | St. Jude (bileaflet tilting disc), Medtronic Hall, Starr-Edwards (ball-and-cage, historical) | Extremely durable (last 20–30+ years); low structural failure rate | Requires lifelong anticoagulation (warfarin, INR 2.5–3.5) → risk of bleeding; audible click; teratogenic (warfarin in pregnancy) | Younger patients (< 50–60 years) who can tolerate lifelong anticoagulation; want to avoid reoperation |
| Bioprosthetic (tissue) valve | Porcine (e.g., Hancock, Carpentier-Edwards), bovine pericardial (e.g., Edwards Perimount), homograft (human cadaveric) | No need for long-term anticoagulation (only 3–6 months warfarin or antiplatelet); lower thromboembolic risk | Limited durability (10–20 years) → structural valve degeneration → may need reoperation or valve-in-valve TAVI | Older patients (> 60–65 years) who are expected to outlive the valve OR who cannot tolerate anticoagulation; women of childbearing age (avoid warfarin) |
How to decide: The "55–65 zone"
- < 50 years: Generally mechanical (longer durability needed; lower reoperation risk; can tolerate warfarin)
- 50–65 years: Shared decision-making; increasingly bioprosthetic with the advent of valve-in-valve TAVI as a fallback for future degeneration
- > 65 years: Generally bioprosthetic (expected lifespan matches valve durability; avoid anticoagulation risks in elderly)
Patient preferences after understanding risk and benefits [3] — the patient MUST be part of this conversation. Some younger patients prefer a bioprosthesis to avoid warfarin (lifestyle factors, contact sports, pregnancy planning), accepting the risk of future reintervention.
| Scenario | Approach |
|---|---|
| Concomitant coronary artery disease | Combined AVR + CABG in a single operation; mortality slightly higher than isolated AVR (~3–5% vs 1–3%) but avoids a second procedure |
| Bicuspid AV with ascending aortic dilatation | AVR + ascending aortic replacement (Bentall procedure or separate supracoronary graft) if ascending aorta ≥ 45 mm (≥ 50 mm for tricuspid AV) |
| Small aortic root | Risk of patient-prosthesis mismatch (PPM) → prosthesis is too small for the patient → patient remains in aortic stenosis or pathology not completely corrected [3]. Solutions: aortic root enlargement (Nicks, Manouguian, or Konno procedures) or use of stentless/sutureless valve; or TAVI with supra-annular positioning |
| Outcome | Details |
|---|---|
| Operative mortality | Isolated SAVR: 1–3%; AVR + CABG: 3–5% |
| Long-term survival | Excellent if performed before irreversible LV damage; 10-year survival ~60–70% |
| Complications | See below in complications section; key ones: heart block (3rd degree AV block due to calcification of upper IV septal tissue or post-AVR) [2], stroke, bleeding, wound infection, prosthetic valve endocarditis, structural valve degeneration (bioprosthetic), thromboembolism (mechanical) |
3.3 Transcatheter Aortic Valve Implantation (TAVI / TAVR)
TAVI is the transformative innovation of the last two decades. The name tells you what it is: "trans" = across, "catheter" = tube-based delivery system; the valve is implanted via a catheter without open-heart surgery.
A bioprosthetic valve mounted on a collapsible stent frame is delivered via a catheter (usually through the femoral artery — "transfemoral" approach) and deployed within the diseased native aortic valve without excising it. The native calcified leaflets are pushed aside by the expanding stent frame, and the new valve sits inside the old one.
| Route | Description | When Used |
|---|---|---|
| Transfemoral (TF) | Through femoral artery → retrograde up aorta to aortic valve | Default route; least invasive; best outcomes |
| Transapical (TA) | Through small left thoracotomy → direct puncture of LV apex | When iliofemoral arteries are too small, calcified, or tortuous for transfemoral access |
| Transaortic (TAo) | Through mini-sternotomy → direct puncture of ascending aorta | Alternative when TF not feasible |
| Subclavian/axillary | Through subclavian/axillary artery | Alternative when TF not feasible |
| Transcaval | Through IVC → puncture into aorta | Rare; investigational |
TAVI for patients with high surgical risk and post-TAVI survival > 12 months [2]
| Risk Category | Recommended Approach | Rationale |
|---|---|---|
| Low surgical risk (STS/EuroSCORE II < 4%) | Surgical AVR [2] — but TAVI is now increasingly accepted based on PARTNER 3 and Evolut Low Risk trials | SAVR has the longest track record; TAVI durability data beyond 10 years is limited |
| Intermediate surgical risk (STS 4–8%) | TAVI or SAVR — shared decision-making; TAVI increasingly preferred especially if transfemoral access is feasible | PARTNER 2 and SURTAVI trials showed non-inferiority of TAVI |
| High surgical risk (STS > 8%) | TAVI preferred [2] | Lower procedural risk than SAVR; comparable or superior outcomes |
| Prohibitive surgical risk / inoperable | TAVI if expected survival > 12 months | Only option for definitive treatment; better than medical therapy alone |
| Extreme frailty / expected survival < 12 months | Palliative medical care | Futility of intervention; TAVI will not improve quality or quantity of life |
Use STS score / EuroSCORE to stratify risk [2]
Age-based guidance (simplified, 2021 ESC):
- < 75 years: Favour SAVR (unless high/prohibitive risk)
- ≥ 75 years: Favour TAVI (especially if transfemoral access feasible)
- This is a simplification — the Heart Team (cardiologist + cardiac surgeon + anaesthetist + geriatrician) should make individualised decisions
| Complication | Mechanism | Incidence |
|---|---|---|
| Vascular access complications | Large-bore catheter through iliofemoral arteries → dissection, perforation, pseudoaneurysm | 5–15% (decreasing with newer lower-profile devices) |
| Conduction disturbances / need for permanent pacemaker | TAVI stent frame exerts radial force on the LVOT and interventricular septum → compression of the bundle of His/left bundle branch | 10–25% (higher with self-expanding valves like CoreValve; lower with balloon-expandable like SAPIEN) |
| Paravalvular leak (PVL) | Unlike SAVR where the native valve is excised and the prosthesis is sewn to the annulus, in TAVI the native calcified leaflets remain → gaps between stent frame and irregular native annulus | More common than SAVR; mild PVL usually tolerated; moderate/severe PVL associated with worse outcomes |
| Stroke | Manipulation of catheters across calcified aortic arch → embolisation of debris | 2–4%; cerebral embolic protection devices reduce this |
| Coronary obstruction | Displaced native calcified leaflets obstruct coronary ostia | Rare (< 1%) but catastrophic; more common with low coronary heights and bulky calcification |
| Valve thrombosis | Thrombus formation on bioprosthetic leaflets | Clinical: rare; subclinical (on CT): more common; uncertain clinical significance; usually responds to anticoagulation |
| Annular rupture | Over-sizing of prosthesis relative to annulus | Very rare; lethal if uncontained |
TAVI may induce MI → PCI beforehand [2] — this refers to the risk that coronary obstruction during TAVI can cause acute MI, and that significant coexistent CAD should ideally be treated with PCI before or at the time of TAVI.
| Feature | SAVR | TAVI |
|---|---|---|
| Approach | Open heart surgery (sternotomy + CPB) | Catheter-based (usually transfemoral) |
| Native valve | Excised | Left in situ (pushed aside) |
| Paravalvular leak | Very low (valve sewn to annulus) | Higher (native valve creates irregular surface) |
| Pacemaker need | 3–5% | 10–25% |
| Stroke | Lower with newer TAVI devices | Historically higher but now comparable |
| Recovery time | 1–2 weeks in hospital; 6–12 weeks full recovery | 1–3 days; rapid mobilisation |
| Durability | Well-established (mechanical > 20 years; bioprosthetic 10–20 years) | Limited long-term data (5–10 year data encouraging) |
| Valve-in-valve option | Need redo surgery (higher risk) | TAVI valve-in-valve for degenerated bioprosthetic (either surgical bioprosthesis or prior TAVI) — this is changing the landscape of valve selection |
Percutaneous aortic balloon dilatation: poor results with up to 50% recurrence within 6 months → usually only as bridge to surgery if severe symptoms [2]
| Aspect | Details |
|---|---|
| Procedure | Balloon catheter advanced retrogradely across the aortic valve → inflation → fractures calcific deposits → ↑valve area |
| Results | Modest and temporary improvement in gradient and symptoms |
| Restenosis rate | ≈50% within 6 months — the fractured calcium re-accumulates rapidly |
| Indications | (1) Bridge to SAVR or TAVI in haemodynamically unstable patients; (2) Palliative in patients unfit for any definitive intervention; (3) Diagnostic — to assess whether symptoms improve with relief of obstruction (especially in LFLG AS to determine if LV dysfunction is reversible) |
| NOT a definitive treatment | Does NOT improve long-term survival; only buys time |
For patients who do not yet meet intervention criteria, structured surveillance is essential:
| Severity | Echo Interval | Clinical Review |
|---|---|---|
| Mild AS (Vmax 2.0–2.9 m/s) | Every 3–5 years | Annual clinical review; patient education to report symptoms |
| Moderate AS (Vmax 3.0–3.9 m/s) | Every 1–2 years | 6-monthly clinical review |
| Severe AS (Vmax ≥ 4.0 m/s), asymptomatic | Every 6–12 months | Every 6 months; consider exercise testing to unmask symptoms |
| Very severe AS (Vmax ≥ 5.0 m/s) | Every 6 months | Consider early intervention even if asymptomatic |
| Population | Considerations |
|---|---|
| Elderly (> 80 years) | TAVI preferred if transfemoral access feasible; frailty assessment critical; avoid futile intervention if life expectancy < 12 months |
| Bicuspid AV | SAVR preferred (TAVI outcomes in bicuspid AV are less predictable due to asymmetric calcification and elliptical annulus, though newer-generation TAVI devices are improving); assess ascending aorta for concomitant aortopathy |
| Concomitant CAD | SAVR + CABG if surgical; PCI before TAVI if transcatheter approach chosen [2] |
| Pregnancy | Severe AS + pregnancy is high-risk; ideally intervene before pregnancy; if symptomatic during pregnancy, balloon valvuloplasty can be performed as a bridge |
| Concurrent severe AR + AS (mixed disease) | SAVR required; TAVI relies on the native stenotic valve to anchor the prosthesis — in pure AR without calcific stenosis, transcatheter AVR CANNOT be done (relies on stenotic AV to hold prosthetic valve in place) [2] |
| Infective endocarditis | Infective endocarditis despite optimal medical therapy is an indication for surgery [1]; SAVR with thorough debridement; TAVI generally contraindicated in active IE |
| Aspect | Mechanical Valve | Bioprosthetic Valve (SAVR or TAVI) |
|---|---|---|
| Anticoagulation | Lifelong warfarin (INR 2.5–3.5 for aortic position); avoid DOACs (RE-ALIGN trial showed harm with dabigatran in mechanical valves) | Warfarin for 3–6 months post-SAVR (INR 2.0–3.0), then switch to aspirin alone; or aspirin + clopidogrel for 3–6 months post-TAVI, then aspirin alone |
| Endocarditis prophylaxis | Lifelong antibiotic prophylaxis for dental/surgical procedures (prosthetic valve is high-risk for IE) | Same as mechanical |
| Surveillance echo | Annual TTE to assess prosthetic valve function (gradient, regurgitation, LV recovery) | Annual TTE; watch for structural valve degeneration (increasing gradient, new regurgitation) especially after 5–10 years |
| LV recovery | Expect LVH regression over 6–18 months if intervention was timely; incomplete regression if delayed | Same |
| Activity | No contact sports (risk of bleeding with warfarin; risk of valve damage) | Generally unrestricted after recovery |
High Yield Summary — Management of Aortic Stenosis
-
No medication can halt or reverse AS progression — definitive treatment is valve replacement
-
Indication for intervention: severe AS with symptoms OR ventricular dysfunction — this is the cardinal rule
-
Avoid preload-reducing drugs in severe AS (diuretics, nitrates, vasodilators) — the LV depends on adequate preload to maintain output against the fixed obstruction
-
SAVR = gold standard, especially for low/intermediate risk and younger patients; choose mechanical (lifelong warfarin) vs bioprosthetic (limited durability) based on age, lifestyle, and shared decision-making
-
TAVI = preferred for high/prohibitive surgical risk, elderly (≥ 75 years), transfemoral access feasible; higher pacemaker rates and paravalvular leak than SAVR
-
Balloon valvuloplasty: poor results, 50% recurrence within 6 months — bridge to definitive therapy only
-
Most aortic valves cannot be repaired — unlike mitral valve, replacement is almost always necessary
-
Patient-prosthesis mismatch: prosthesis too small → patient remains in AS; prevent by careful sizing
-
TAVI cannot be done for pure AR — relies on the calcified stenotic native valve to anchor the prosthesis
-
Valve choice is a shared decision-making process accounting for patient values and preferences
Active Recall - Management of Aortic Stenosis
References
[1] Senior notes: Maksim Medicine Notes.pdf (p35, p37 — Valvular heart disease management, general indications for valvular replacement) [2] Senior notes: Ryan Ho Cardiology.pdf (p159 — AS treatment approach: conservative, SAVR, TAVI, balloon dilatation, indications; p161 — AR management and TAVI limitation for pure AR) [3] Lecture slides: Cardiac Surgery Tutorial_Prof. D Chan.pdf (p36 — treatment principles: no medication, indication of surgery; p56 — aortic valve not repairable; p60 — EOAI and patient-prosthesis mismatch; p70 — shared decision-making for prosthetic valve choice) [4] Lecture slides: Cardiac Surgery Tutorial_Prof. D Chan.pdf (p51 — natural history: average survival 2–5 years once symptomatic)
Complications of Aortic Stenosis
Complications of AS can be divided into two broad categories: (A) complications of the disease itself (untreated AS) and (B) complications related to treatment (post-AVR/TAVI). Both are high-yield for exams. Let's work through each systematically, always linking back to pathophysiology so you understand why each complication occurs rather than simply memorising a list.
A. Complications of the Disease (Untreated or Progressive AS)
LV failure [1]
Pathophysiology (from first principles):
- Chronic pressure overload → compensatory concentric LVH → initially maintains cardiac output
- Over time, the compensatory mechanisms become maladaptive:
- Myocardial fibrosis develops (replacement fibrosis from chronic subendocardial ischaemia + diffuse interstitial fibrosis from excessive collagen deposition)
- LV compliance worsens progressively → diastolic dysfunction worsens
- Eventually the LV "gives up" — wall stress overwhelms the hypertrophied muscle → the LV begins to dilate (transition from concentric to eccentric hypertrophy)
- LVEF drops → forward cardiac output falls
- LVEDP rises → transmitted retrograde to LA → pulmonary veins → pulmonary oedema
Decompensation due to chronic LV pressure overload → rapid deterioration with LV failure (dilated LV) → pulmonary oedema [2]
Clinical manifestations:
- Acute pulmonary oedema: sudden-onset dyspnoea, orthopnoea, PND, pink frothy sputum, bilateral crackles
- Chronic heart failure: progressive exercise intolerance, ankle swelling (if biventricular failure), fatigue
- Cardiogenic shock in extreme cases: hypotension, cold peripheries, oliguria, confusion
Why is this the deadliest complication? Once heart failure symptoms develop, the median survival is only ≈2 years without intervention [4]. The decompensation is rapid because the hypertrophied LV has very little reserve — it has been running at maximum capacity for years to maintain output against the obstruction, and once it begins to fail, there is a precipitous downward spiral.
Key point about reversibility: If AVR is performed before extensive irreversible myocardial fibrosis develops, LV function can recover significantly. This is why we intervene as soon as LV dysfunction is detected (LVEF < 50%), even in asymptomatic patients. If intervention is delayed too long, the fibrosis becomes irreversible and LV recovery after AVR is incomplete — the patient has "missed the window."
The Decompensation Cascade
Once LV failure begins in AS, it creates a vicious cycle: ↓CO → ↓coronary perfusion → more ischaemia → further ↓contractility → further ↓CO. Additionally, ↑LVEDP → pulmonary congestion → hypoxaemia → further ischaemia. Without relief of the obstruction (AVR), this cycle is self-perpetuating and fatal.
Arrhythmias [1]
Pathophysiology: The hypertrophied, fibrosed, ischaemic LV creates an ideal substrate for both atrial and ventricular arrhythmias:
| Arrhythmia | Mechanism | Clinical Significance |
|---|---|---|
| Atrial fibrillation (AF) | LA hypertrophy and dilatation (from trying to fill the stiff LV) → structural and electrical remodelling of the atria → triggers AF | Devastating in AS — loss of atrial kick (which contributes up to 40% of LV filling in the stiff ventricle) causes acute haemodynamic deterioration: ↓CO → pulmonary oedema → cardiogenic shock. New-onset AF in severe AS is a complication that can itself trigger intervention [1] |
| Ventricular tachycardia (VT) | LVH → subendocardial ischaemia → myocardial fibrosis → re-entrant circuits within the heterogeneous myocardium (areas of fibrosis interspersed with viable myocardium create the substrate for re-entry) | Can cause syncope or degenerate into VF → sudden cardiac death |
| Ventricular fibrillation (VF) | Triggered by VT degeneration, acute ischaemia, or electrolyte abnormalities in the context of LVH | Leading mechanism of sudden cardiac death in AS |
| Premature ventricular complexes (PVCs) | Increased automaticity in ischaemic/hypertrophied myocardium | Common; may be a marker of higher arrhythmic risk |
Sudden cardiac death due to ventricular arrhythmias [2]
Sudden cardiac death (SCD):
- Occurs in approximately 1% per year of asymptomatic patients with severe AS
- Much higher in symptomatic patients (15–20% of deaths)
- Mechanisms: VT/VF (most common), complete heart block, acute haemodynamic collapse
- This is the reason we cannot be entirely reassured by the asymptomatic state — a small but real risk of SCD exists, and this risk is part of the argument for earlier intervention in "very severe" AS (Vmax ≥ 5.0 m/s)
Coronary artery disease (85% of cardiac arrest causes), structural heart disease including AS (10%) [10]
Heart block (calcified conduction system) [1]
3rd degree heart block due to calcification of upper interventricular septal tissue or post-AVR [2]
Pathophysiology (anatomical basis): This is one of the most elegant anatomy-pathology correlations in cardiology. Let's trace the anatomy:
- The aortic valve annulus sits directly above the membranous interventricular septum
- The bundle of His penetrates through the membranous septum, just below the non-coronary cusp and the right coronary cusp of the aortic valve
- The left bundle branch runs along the left side of the interventricular septum, immediately beneath the aortic valve
When heavy calcification of the aortic valve extends inferiorly into the septum:
- It infiltrates and destroys the bundle of His → complete (3rd degree) heart block
- It damages the left bundle branch → left bundle branch block (LBBB)
- Less commonly, it can affect the right bundle branch or cause fascicular blocks
| Conduction Abnormality | Mechanism | Clinical Significance |
|---|---|---|
| LBBB | Calcification extends into the left bundle branch on the LV septal surface | Most common conduction abnormality in AS; may also occur post-AVR/TAVI (mechanical trauma during prosthesis deployment) |
| 1st degree AV block | Partial impairment of AV conduction through calcified tissue near the AV node/His bundle | Prolonged PR interval; usually asymptomatic; marker of advancing disease |
| 2nd degree AV block (Mobitz type II) | Intermittent block at or below the His bundle | More concerning; risk of progression to complete heart block |
| 3rd degree (complete) heart block | Complete destruction of the His bundle by calcification | Requires permanent pacemaker implantation; presents with syncope, presyncope, or sudden death if ventricular escape rhythm is unreliable |
Why is this also a post-procedural complication?
- Post-SAVR: Surgical debridement of calcified annular tissue can mechanically damage the conduction system; occurs in 3–5% of SAVR cases
- Post-TAVI: The stent frame of the TAVI prosthesis exerts radial force on the LVOT and septum, directly compressing the His bundle and left bundle branch; pacemaker requirement is 10–25% (higher with self-expanding valves that exert continuous radial force, like CoreValve/Evolut; lower with balloon-expandable valves like Edwards SAPIEN)
Heyde's syndrome → iron deficiency anaemia [1]
Heyde's syndrome: GI bleed from angiodysplasia in the presence of AS (increased shear stress across aortic valve → vWF degradation, i.e. acquired type IIA vWD) [1][5]
Detailed pathophysiology:
Key points about Heyde's syndrome:
- First described by Edward Heyde in 1958 — noted an association between calcific AS and GI bleeding
- The pathophysiological link was not understood until the discovery of acquired vWD in AS patients
- Angiodysplasia (also called arteriovenous malformations) are degenerative vascular lesions common in the elderly, especially in the right colon (caecum and ascending colon) [5]
- These lesions are fragile and bleed easily, but in patients with normal vWF, bleeding is usually minor and self-limiting
- In AS patients with acquired vWD, the impaired platelet adhesion means bleeding is prolonged and recurrent
- Correction of AS (AVR) normalises the vWF multimer profile and resolves the bleeding tendency — this is one of the most satisfying demonstrations of cause-and-effect in medicine
Clinical presentation:
- Recurrent painless lower GI bleeding (haematochezia)
- Chronic iron deficiency anaemia: fatigue, pallor, dyspnoea (which may be confounded with AS-related dyspnoea)
- May present as occult blood loss with unexplained anaemia
Investigation:
- Colonoscopy: cherry red spots (angiodysplastic lesions) [5]
- Blood: iron studies showing iron deficiency pattern (↓ferritin, ↓iron, ↑TIBC, ↓transferrin saturation)
- Haemostasis: ↓ristocetin cofactor activity, ↓large vWF multimers on multimer gel electrophoresis (confirms acquired type IIA vWD)
- Mesenteric angiogram if colonoscopy inconclusive: "mother-in-law phenomenon" — early filling, delayed emptying [5]
Pathophysiology:
- Turbulent, high-velocity flow across the stenotic aortic valve causes endothelial damage on the valve leaflets
- Damaged endothelium exposes subendothelial collagen → platelet and fibrin deposition → formation of non-bacterial thrombotic endocarditis (NBTE) — a sterile nidus
- During bacteraemia (e.g., from dental procedures, skin infections, IV drug use), bacteria adhere to this nidus → colonisation → vegetation formation → infective endocarditis (IE)
- Bicuspid aortic valves are at particularly high risk due to more turbulent flow
Clinical significance:
- IE on a stenotic or bicuspid aortic valve can cause acute deterioration:
- Valve destruction → acute severe AR → acute pulmonary oedema
- Abscess formation → extension into conduction system → heart block
- Septic emboli → stroke, splenic infarcts, mycotic aneurysms, Janeway lesions, Osler's nodes
- Infective endocarditis despite optimal medical therapy is an indication for urgent valve replacement [1]
- Post-AVR, both mechanical and bioprosthetic valves carry a lifelong risk of prosthetic valve endocarditis (PVE) — hence the need for endocarditis prophylaxis before dental and certain surgical procedures
Calcified emboli in severe calcific AS [2]
Pathophysiology:
- In severely calcified aortic valves, fragments of calcium can break off during valve movement or during catheter manipulation
- These calcified emboli travel via the arterial circulation to end-organs:
- Brain: stroke or TIA (presenting as acute focal neurological deficit)
- Retina: retinal artery occlusion (sudden painless monocular vision loss; fundoscopy may show Hollenhorst plaques — refractile cholesterol/calcium crystals at retinal arteriolar bifurcations)
- Kidneys: renal infarction
- Peripheral arteries: acute limb ischaemia, blue toe syndrome
- This complication is relatively uncommon but is an important consideration in any patient with severe calcific AS who develops acute embolic events
Pathophysiology:
- Long-standing LV failure from AS → chronically elevated LA pressure → transmitted to pulmonary veins → pulmonary venous hypertension (passive, post-capillary)
- Over time, chronic pulmonary venous congestion triggers reactive pulmonary arteriolar vasoconstriction and remodelling → mixed pre- and post-capillary pulmonary hypertension
- Progressive pulmonary hypertension → increased RV afterload → RV hypertrophy → eventually RV failure
- RV failure manifests as: elevated JVP, peripheral oedema, hepatomegaly (pulsatile liver if TR develops), ascites, functional tricuspid regurgitation
This represents the end-stage of the AS disease process — the pressure overload has cascaded from LV → LA → pulmonary vasculature → RV. By this point, operative risk is significantly higher and outcomes are worse.
Sudden cardiac death due to ventricular arrhythmias [2]
Mechanisms:
- Ventricular arrhythmias (VT/VF): the most common mechanism. The hypertrophied, ischaemic, fibrosed myocardium is a perfect substrate for re-entrant tachyarrhythmias
- Complete heart block: calcification destroys the conduction system → asystole or very slow ventricular escape rhythm → inadequate cardiac output
- Acute haemodynamic collapse: during exercise, the combination of fixed cardiac output and peripheral vasodilation → catastrophic drop in cerebral perfusion → cardiac arrest
- Coronary ischaemia: acute subendocardial infarction in the context of severe LVH → triggers VF
Epidemiology:
- ~1% per year in asymptomatic severe AS (lower than the procedural risk of AVR, which is why we generally observe asymptomatic patients unless very severe)
- Much higher once symptomatic — particularly with exertional syncope, which may be a "warning" near-miss for SCD
- If symptoms appear: average survival 2–5 years [4] — sudden death contributes significantly to this mortality
B. Complications Related to Treatment (Post-Intervention)
3rd degree heart block due to calcification of upper IV septal tissue or post-AVR [2]
| Setting | Mechanism | Incidence | Management |
|---|---|---|---|
| Post-SAVR | Surgical trauma during debridement of calcified annulus damages adjacent His bundle/LBB | LBBB: ~5–10%; Complete heart block needing PPM: 3–5% | Temporary pacing wires placed intraoperatively; if conduction does not recover within 5–7 days → permanent pacemaker |
| Post-TAVI | Radial force of stent frame compresses LVOT septum and conduction tissue; deeper implantation → higher risk | LBBB: 15–30%; PPM: 10–25% (self-expanding > balloon-expandable) | Monitoring with temporary pacing; many resolve spontaneously; if persistent → permanent pacemaker |
| Setting | Mechanism | Clinical Significance |
|---|---|---|
| Post-SAVR | Incomplete seating of prosthesis against annulus; suture dehiscence; annular calcification preventing full apposition | Rare (< 2%); if significant → haemolysis, HF; may require redo surgery |
| Post-TAVI | Native calcified leaflets remain in situ → irregular surface → gaps between stent frame and native annulus | More common than SAVR; mild PVL: usually tolerated; moderate/severe PVL: associated with ↑mortality → may need post-dilatation or valve-in-valve |
Prosthesis is too small for the patient → patient remains in aortic stenosis or pathology not completely corrected [3]
Pathophysiology:
- If the effective orifice area index (EOAI) of the prosthetic valve is too small relative to the patient's body surface area, a residual gradient persists across the prosthesis
- Severe PPM (EOAI < 0.65 cm²/m²) → patient effectively remains in aortic stenosis despite having had valve replacement
- Consequences: persistent LVH, impaired LV regression, higher long-term mortality, persistent symptoms
Prevention:
- Careful pre-operative annular sizing (CT measurements)
- Choose appropriate prosthesis size
- Consider aortic root enlargement procedures (Nicks, Manouguian) if the annulus is too small to accommodate an adequately sized prosthesis
- Stentless valves or sutureless valves may provide larger effective orifice area
| Aspect | Details |
|---|---|
| Mechanism | Progressive calcification, fibrosis, and leaflet tearing of the bioprosthetic tissue (porcine or bovine pericardium) over years → stenosis, regurgitation, or both |
| Timeline | Usually occurs after 10–15 years (earlier in younger patients — perhaps due to more vigorous immune response and calcium metabolism; and in patients on dialysis) |
| Presentation | Gradually increasing gradient on surveillance echo; new murmur; recurrence of symptoms |
| Management | Redo surgical AVR (higher risk than primary operation) OR valve-in-valve TAVI (lower risk; a new TAVI prosthesis is deployed inside the degenerated bioprosthesis — this is a major advantage of choosing a bioprosthetic valve initially) |
| Aspect | Mechanical Valve | Bioprosthetic Valve |
|---|---|---|
| Mechanism | Blood contact with artificial material → thrombus formation on valve surfaces or within hinge mechanism | Subclinical leaflet thrombosis — discovered incidentally on CT as hypoattenuating leaflet thickening (HALT) with reduced leaflet motion (RELM) |
| Risk factors | Subtherapeutic INR (most common trigger); hypercoagulable states | Inadequate early anticoagulation/antiplatelet therapy; low cardiac output states |
| Presentation | Acute: cardiogenic shock, embolic stroke. Chronic: gradually increasing gradient | Often subclinical; may cause gradually increasing gradient; clinical significance debated |
| Management | Thrombolysis (if non-obstructive or too sick for surgery) or emergency redo surgery (if obstructive with haemodynamic instability) | Therapeutic anticoagulation (warfarin) usually resolves subclinical thrombosis |
| Timing | Early PVE (< 12 months post-op) | Late PVE (> 12 months post-op) |
|---|---|---|
| Organisms | Nosocomial: S. aureus, coagulase-negative staphylococci, Gram-negative rods, fungi | Community-acquired: similar to native valve IE — Streptococcus, Enterococcus, S. aureus |
| Mechanism | Contamination during surgery or perioperative bacteraemia → seeding of prosthetic material | Bacteraemia from remote infection → adherence to prosthetic valve |
| Outcome | Higher mortality (20–40%); often requires urgent redo surgery | Better prognosis; medical therapy may suffice if no complications |
| Setting | Mechanism | Incidence |
|---|---|---|
| Mechanical valve | Thrombus on valve → embolisation to cerebral arteries | Without anticoagulation: 4%/year; with warfarin: 1–2%/year |
| TAVI | Catheter manipulation across calcified aortic arch dislodges debris → cerebral embolisation; valve thrombosis | 2–4% at 30 days; cerebral embolic protection devices may reduce this |
| Post-SAVR | Air embolism, particulate embolism during surgery; AF-related thromboembolism | 1–2% perioperatively |
| Context | Mechanism |
|---|---|
| Warfarin-related (mechanical valve) | Lifelong anticoagulation carries ongoing bleeding risk; GI bleeding, intracranial haemorrhage, epistaxis; INR must be monitored closely |
| DAPT-related (post-TAVI) | Aspirin + clopidogrel for 3–6 months → bleeding risk, especially in elderly with comorbidities |
| Acquired vWD resolution post-AVR | Interestingly, Heyde's syndrome bleeding resolves after AVR as vWF multimers normalise — this is a complication that is cured by treatment |
Pathophysiology:
- Blood flowing through or around the prosthetic valve may be subjected to high shear stress → mechanical fragmentation of red blood cells → intravascular haemolysis
- More common with paravalvular leaks (turbulent, high-velocity jets through the gap between prosthesis and annulus)
- More common with mechanical valves than bioprosthetic
Clinical features:
- Anaemia (often progressive)
- Jaundice (unconjugated hyperbilirubinaemia)
- Dark urine (haemoglobinuria)
- Raised LDH, reticulocyte count; low haptoglobin
- Blood film: schistocytes (fragmented RBCs), polychromasia
| Category | Complication | Mechanism | Key Clinical Feature |
|---|---|---|---|
| Disease | LV failure [1] | Chronic pressure overload → decompensation → dilatation | Dyspnoea, pulmonary oedema; median survival ≈2 years |
| Disease | Arrhythmias [1] | LVH + fibrosis + ischaemia → re-entrant substrate | AF (acute deterioration), VT/VF (sudden death) |
| Disease | Heart block [1] | Calcification of conduction system [1] | LBBB, complete heart block → syncope, pacemaker needed |
| Disease | Heyde's syndrome [1] | High shear → acquired vWD → GI bleeding [1][5] | Iron deficiency anaemia, recurrent GI bleed |
| Disease | Infective endocarditis | Endothelial damage → nidus → bacterial colonisation | Fever, new murmur, embolic phenomena |
| Disease | Calcified emboli [2] | Calcium fragments embolise | Stroke, TIA, peripheral ischaemia |
| Disease | Pulmonary HTN / RHF | LV failure → LA pressure → pulmonary vasoconstriction | Raised JVP, oedema, hepatomegaly |
| Disease | Sudden cardiac death [2] | VT/VF, complete heart block, acute haemodynamic collapse | Cardiac arrest |
| Treatment | Heart block post-AVR/TAVI [2] | Surgical/mechanical trauma to His bundle/LBB | PPM in 3–5% post-SAVR, 10–25% post-TAVI |
| Treatment | Paravalvular leak | Incomplete prosthesis-annulus apposition | Haemolysis, HF; more common post-TAVI |
| Treatment | Patient-prosthesis mismatch [3] | Prosthesis too small for patient | Residual AS; persistent symptoms |
| Treatment | Structural valve degeneration | Bioprosthetic calcification/fibrosis over time | Recurrent AS/AR after 10–15 years |
| Treatment | Prosthetic valve thrombosis | Thrombus on prosthetic surfaces | Increasing gradient; embolic events |
| Treatment | Prosthetic valve endocarditis | Infection of prosthetic material | Fever, new murmur; high mortality |
| Treatment | Stroke/thromboembolism | Embolisation from valve/catheter manipulation | Acute neurological deficit |
| Treatment | Haemolysis | Shear fragmentation of RBCs by prosthesis/PVL | Anaemia, jaundice, dark urine, schistocytes |
High Yield Summary — Complications of Aortic Stenosis
-
LV failure is the most feared complication — median survival ≈2 years without AVR; results from chronic pressure overload → decompensation → dilatation → pulmonary oedema
-
Arrhythmias (especially AF and VT/VF) arise from the ischaemic, fibrosed, hypertrophied myocardium; AF is especially devastating because loss of atrial kick causes acute haemodynamic collapse in the stiff LV
-
Heart block occurs because the conduction system (His bundle, left bundle branch) lies immediately below the aortic valve annulus; calcification extends into these structures. Also occurs post-SAVR and post-TAVI (10–25% PPM rate with TAVI)
-
Heyde's syndrome = acquired type IIA vWD from high shear stress → GI bleeding from angiodysplasia → iron deficiency anaemia; resolves after AVR
-
Sudden cardiac death occurs in ≈1%/year of asymptomatic and 15–20% of symptomatic patients; mechanism: VT/VF, complete heart block, or acute haemodynamic collapse
-
Post-intervention complications: heart block (most common), paravalvular leak (more in TAVI), patient-prosthesis mismatch (prosthesis too small), structural valve degeneration (bioprosthetic after 10–15 years), prosthetic valve endocarditis, thromboembolism, haemolysis
-
Calcified emboli can cause stroke, TIA, or peripheral ischaemia in severe calcific AS
Active Recall - Complications of Aortic Stenosis
References
[1] Senior notes: Maksim Medicine Notes.pdf (p35, p37 — Complications of AS: LV failure, arrhythmias, heart block, Heyde's syndrome, general indications for valve replacement including IE) [2] Senior notes: Ryan Ho Cardiology.pdf (p158 — Complications: sudden cardiac death, 3rd degree heart block, calcified emboli) [3] Lecture slides: Cardiac Surgery Tutorial_Prof. D Chan.pdf (p60 — EOAI and patient-prosthesis mismatch) [4] Lecture slides: Cardiac Surgery Tutorial_Prof. D Chan.pdf (p51 — natural history: average survival 2–5 years once symptomatic) [5] Senior notes: Maksim Surgery Notes.pdf (p97 — Angiodysplasia, Heyde's syndrome, investigations and management) [10] Senior notes: Ryan Ho Critical Care.pdf (p28 — Cardiac arrest causes: structural heart disease including AS)
Ischaemic Heart Disease
Ischaemic heart disease is a condition in which inadequate blood supply to the myocardium, usually due to coronary artery atherosclerosis, results in myocardial ischaemia or infarction.
Aortic Regurgitation
Aortic regurgitation is the backflow of blood from the aorta into the left ventricle during diastole due to incompetent closure of the aortic valve, leading to left ventricular volume overload.