Pulmonary stenosis is a congenital heart defect, most commonly diagnosed in neonates and children, in which narrowing of the pulmonary valve or outflow tract obstructs blood flow from the right ventricle to the pulmonary artery, leading to right ventricular pressure overload.

Pulmonary Stenosis in Children

Valvular PS accounts for 7.5–12% of all congenital heart disease (CHD), making it the 2nd most common CHD ^[1]^[2]
Incidence: 0.6–0.8 per 1,000 live births ^[1]
Male-to-female ratio approximately 1:1 (no significant sex predilection for isolated valvular PS)
Frequently under-reported because mild PS is often asymptomatic and therefore not picked up ^[1] — many children with mild PS are only detected incidentally during routine examinations or echocardiography for other reasons
In Hong Kong, where universal neonatal screening and paediatric cardiac services are well-established, mild PS may still be missed if there is no audible murmur at the well-baby check
Critical PS (neonatal presentation) represents the severe end of the spectrum, accounting for a small but clinically important subset

Risk Factors and Associations

Factor	Detail
Noonan syndrome	Associated with thick and dysplastic pulmonary valve leaflets ^[1]; autosomal dominant RASopathy (RAS-MAPK pathway); classic facies, short stature, cryptorchidism, bleeding diathesis
Congenital rubella syndrome	Associated with peripheral pulmonary arterial stenosis (PPS) ^[2]
Alagille syndrome	Bile duct paucity + PPS (JAG1/NOTCH2 mutations) ^[2]
Williams syndrome	Supravalvular aortic stenosis classically, but also PPS ^[2]; elastin gene deletion (7q11.23)
Tetralogy of Fallot (TOF)	Infundibular PS is a cardinal feature ^[3]
LEOPARD syndrome	Mnemonic: Lentigo, ECG abnormalities, Ocular hypertelorism, Pulmonary stenosis, Abnormal genitalia, Retarded growth, Deafness ^[4]
Familial/sporadic	Most isolated valvular PS is sporadic; rare familial clustering

High Yield Association

If you see PS + Noonan syndrome on an exam, think dysplastic valve → poor response to balloon valvuloplasty → will need surgical valvotomy. This is a classic exam discriminator.

Anatomy and Function

Aetiology and Classification

PS is classified by the anatomical level of obstruction:

Pathophysiology

The fundamental haemodynamic consequence of PS is RV pressure overload ^[1]. Let us trace through the pathophysiology systematically from first principles:

1. Obstruction → Increased RV Systolic Pressure

The narrowed RVOT creates resistance to forward flow
To maintain cardiac output through the stenotic orifice, the RV must generate higher systolic pressures
By the Bernoulli principle, the pressure gradient across the stenosis (ΔP) is proportional to the square of flow velocity: ΔP = 4v² (simplified Bernoulli equation used in Doppler echocardiography)
In severe PS, RV systolic pressure may even exceed that of the LV ^[1]

2. RV Hypertrophy (RVH)

RVH develops as a compensatory response to chronic pressure overload ^[1]
The RV myocardium thickens (concentric hypertrophy) to normalise wall stress (Laplace's law: wall stress = Pressure × Radius / 2 × Wall thickness)
The hypertrophied RV is stiffer (reduced compliance) → impaired diastolic filling

3. Elevated RV End-Diastolic Pressure (RVEDP) → Right Atrial Hypertrophy (RAH)

↑RVEDP → back-pressure transmitted to the RA ^[1]
RA dilates and hypertrophies to overcome the increased downstream pressure
This is reflected on ECG as right atrial enlargement (P pulmonale: tall, peaked P waves > 2.5 mm in lead II)

4. Post-Stenotic Dilation of the Pulmonary Trunk

Post-stenotic dilation of the MPA occurs due to turbulent blood flow ^[1] distal to the stenotic valve
The jet of blood through the narrow orifice impacts the wall of the MPA, causing localised dilation (a "Venturi effect" analogy — though more accurately, it is turbulence-related wall stress)
This post-stenotic dilation is visible on CXR as a prominent pulmonary knob ^[1]
Crucially, post-stenotic dilation is NOT present in infundibular or supravalvular PS ^[1] — because the valve itself is normal and the turbulence pattern is different

5. Critical PS: Cyanosis Pathway

Critical PS occurs when there is a pinhole opening of the pulmonary valve ^[1]:

In critical PS with PFO or ASD: ↑↑↑RA pressure → right-to-left shunting via PFO or ASD → cyanosis ^[1]
In critical PS without PFO/ASD: duct-dependent pulmonary circulation occurs ^[1] — the PDA is the sole source of pulmonary blood flow. When the duct closes (typically within hours to days of birth), the infant develops profound hypoxaemia and cardiovascular collapse

This links to the lecture concept: "Cardiac origins of central cyanosis — systemic venous blood bypassing the lung (right-to-left shunts) and reduced pulmonary flow (pulmonary outflow obstruction, pulmonary atresia)" ^[5]

Severity	Peak Systolic Gradient (Doppler)	RV Pressure	Haemodynamic Consequence
Trivial/Mild	< 36 mmHg	< 50% systemic	Usually none; well-compensated
Moderate	36–64 mmHg	50–75% systemic	Progressive RVH; usually asymptomatic
Severe	> 64 mmHg	> 75% systemic (may exceed LV)	Significant RVH; risk of RV failure; exercise limitation
Critical	Near-atretic valve	Suprasystemic	Duct-dependent ± cyanosis; neonatal emergency

Why > 60 mmHg is the Threshold for Intervention

A gradient > 60 mmHg corresponds to RV pressure approaching systemic levels. At this point, the RV is chronically working against near-systemic afterload, risking irreversible RV dysfunction, arrhythmias, and exercise intolerance. This is why balloon pulmonary valvuloplasty (BPV) is indicated when gradient > 60 mmHg ^[1].

Clinical Features

Symptom	Pathophysiological Basis
Usually asymptomatic in the majority (even with moderate/severe PS) ^[1]	The RV compensates well with hypertrophy; the low-resistance pulmonary bed means even moderate obstruction may be well-tolerated for years
Cyanosis in critical PS ^[1]	Right-to-left shunting at atrial level (via PFO/ASD) when RA pressure exceeds LA pressure; or duct-dependent pulmonary flow with inadequate PDA flow
Exertional dyspnoea / exercise intolerance	In severe PS, the RV cannot augment cardiac output during exercise because the fixed stenosis limits forward flow; exercise → ↑HR → shorter diastolic filling → ↓stroke volume
Fatigue and failure to thrive	Chronically reduced cardiac output in severe PS; increased metabolic demands of a hypertrophied RV
Syncope / pre-syncope on exertion	In severe PS, exercise-induced ↓cardiac output → cerebral hypoperfusion; also possible exertional right-to-left shunting if PFO present
Peripheral oedema, hepatomegaly, ascites (rare, late)	RV failure → elevated systemic venous pressure → third-space fluid accumulation (same mechanism as adult right heart failure)
Rapid clinical deterioration after ductal closure in critical PS	Duct-dependent pulmonary circulation ^[1] — once PDA closes, there is no pathway for blood to reach the lungs → profound hypoxaemia, metabolic acidosis, shock

Critical PS is a Neonatal Emergency

Critical PS presenting in the first days of life must be immediately recognised. If the duct closes, these neonates deteriorate rapidly with severe cyanosis, metabolic acidosis, and circulatory collapse. Urgent PGE₁ (prostaglandin E₁ / alprostadil) infusion is life-saving ^[1] — it reopens and maintains the ductus arteriosus, restoring pulmonary blood flow until definitive intervention.

Signs

The clinical signs of PS are elegantly related to the severity and level of obstruction:

1. Ejection Click (EC)

Present in valvular PS; absent in infundibular/supravalvular/peripheral PS ^[1]^[2]
Heard best at the upper left sternal border (ULSB/LUSB) in early systole
Mechanism: The domed, fused valve cusps suddenly halt at their maximal excursion during RV ejection, producing a brief high-frequency sound
Timing clue: The EC becomes softer with inspiration in PS (because increased venous return partially opens the valve during diastole, so there is less abrupt excursion in systole) — opposite to aortic EC which does not vary with respiration
In severe PS, the EC may merge with S1 and become inaudible

2. Ejection Systolic Murmur (ESM)

ESM at the left upper sternal border (LUSB) ^[1]
Crescendo-decrescendo ("diamond-shaped") murmur caused by turbulent flow across the stenotic orifice
Radiates to the back (left infraclavicular area) and to the lung fields
Severity correlation:
- Mild PS: short, early-peaking ESM
- Severe PS: longer, later-peaking ESM (delayed peak because it takes longer for the RV to generate enough pressure to push blood through the tight stenosis)
- In Tet spells (TOF context): increasing obstruction → decreasing murmur ^[3] — because less blood flows across the RVOT; more is shunted right-to-left through the VSD

3. Second Heart Sound (S2) — Specifically P2

P2 (pulmonary valve closure sound) is generated by the snap-closure of the pulmonary valve leaflets
Severe PS: delayed, soft, or absent P2 ^[1]
- Delayed: Because RV ejection time is prolonged (it takes longer to empty through a narrow orifice) → P2 occurs later → wide splitting of S2
- Soft/absent: Because the stiff, stenotic valve leaflets cannot close with the normal snap; also, the pressure gradient means the valve closes more gently
Single S2 suggests severe PS or pulmonary atresia (no P2 at all) ^[1]

4. Systolic Thrill

Palpable thrill at LUSB and suprasternal notch in severe PS ^[1]
A thrill is simply a murmur you can feel — Grade ≥ 4/6 murmur
Suprasternal pulsation/thrill ^[1] reflects turbulent flow transmitted to the great vessels

Sign	Pathophysiological Basis
RV impulse (parasternal heave) ^[1]	RV hypertrophy from chronic pressure overload; the thickened RV pushes anteriorly against the chest wall
Suprasternal thrill ^[1]	Turbulent flow in the MPA transmitted to the suprasternal notch
Hepatomegaly (in RV failure)	Elevated RA pressure → hepatic venous congestion → hepatomegaly

Sign	Pathophysiological Basis
Cyanosis (critical PS only) ^[1]	Right-to-left shunting at atrial level
Clubbing (in chronic cyanotic PS)	Chronic hypoxaemia → platelet microthrombi releasing PDGF/VEGF in nail bed capillaries → soft tissue hypertrophy
JVP elevation with prominent 'a' wave (older children)	The RA contracts forcefully against a stiff, hypertrophied RV → large 'a' wave
Failure to thrive	Chronic low cardiac output state

Feature	Mild PS	Severe PS	Critical PS (neonate)
Cyanosis	Absent	Usually absent (unless PFO)	Present
Ejection click	Present	May be absent (merged with S1)	Variable
ESM at LUSB	Present, short	Present, long, loud, late-peaking	May be soft (low flow)
P2	Normal	Delayed/soft/absent	Absent
RV heave	Absent	Present	Variable
Thrill	Absent	Present (LUSB, suprasternal)	Variable
S2 splitting	Normal/mildly wide	Widely split, fixed	Single S2

Distinguishing Valvular from Non-Valvular PS at the Bedside

Three key clinical clues:

Ejection click → present ONLY in valvular PS
Post-stenotic dilation on CXR → present ONLY in valvular PS
Soft/absent P2 → present in valvular PS (abnormal valve closure) but NOT in infundibular/peripheral PS (where the valve itself is normal)

If the question describes PS without an ejection click and without post-stenotic dilation on CXR, think infundibular or peripheral PS.

Investigations (Overview — Detailed in Diagnosis Section)

While the full diagnostic algorithm will be covered later, the investigation findings are tightly linked to pathophysiology and are worth summarising here:

Finding	Explanation
Prominent pulmonary knob (post-stenotic dilation) ^[1]	Turbulent jet distal to the stenotic valve dilates the MPA — ONLY in valvular PS
Normal heart size ^[1]	RV pressure overload causes concentric hypertrophy (thicker wall, same chamber size) — unlike volume overload which causes dilation
Normal pulmonary vascular markings ^[1]	In mild-moderate PS, pulmonary blood flow is maintained. In critical PS, markings may be oligaemic (reduced)
Oligaemic lung fields (critical PS)	Severely reduced pulmonary blood flow

Finding	Explanation
Normal in mild PS ^[1]	Minimal haemodynamic burden
Right axis deviation (RAD) ^[1]	RVH shifts the mean QRS axis rightward
RA enlargement (P pulmonale) ^[1]	Tall, peaked P waves in lead II ( > 2.5 mm) from RA hypertrophy
RV hypertrophy ^[1]	Tall R waves in V1 (right precordial leads), deep S waves in V5–V6; may show RV strain pattern (ST depression, T-wave inversion in V1–V3) in severe PS

Paediatric ECG note: Normal ECG values change with age. RV dominance is normal in neonates (right axis, dominant R in V1). RAD and RVH must be interpreted against age-appropriate norms. By 6 months, the LV normally becomes dominant — persistence of RV dominance beyond this age suggests pathological RVH.

Finding	Explanation
Incomplete opening of PV cusps (doming) ^[1]	Fused commissures prevent full leaflet excursion
Post-stenotic dilation of MPA ^[1]	Turbulence-related dilation
Turbulent flow in pulmonary trunk ^[1]	Colour-flow Doppler shows aliasing (mosaic pattern) across the stenotic valve
Estimation of systolic pressure gradient across PV ^[1]	Continuous-wave (CW) Doppler measures peak velocity → ΔP = 4v² (modified Bernoulli)
RVH, RV function assessment	M-mode and 2D assessment of RV wall thickness and function
Presence of PFO/ASD and shunt direction	Critical for assessing cyanosis pathway
Dysplastic vs. typical valve morphology	Guides management (balloon vs. surgery)

High Yield Summary

Pulmonary Stenosis — Key Points for Exams:

Most common type: Valvular PS (~90%); 2nd most common CHD overall (7.5–12%)
Pathophysiology: RV pressure overload → RVH → ↑RVEDP → RAH; post-stenotic MPA dilation (valvular PS only)
Critical PS: Duct-dependent pulmonary circulation ± R-to-L shunt at atrial level → cyanosis → needs urgent PGE₁
Noonan syndrome: Dysplastic valve → poor response to balloon → needs surgical valvotomy
Ejection click: ONLY in valvular PS (fused, domed valve); absent in infundibular, supravalvular, peripheral PS
Severity by murmur: Longer, later-peaking ESM = more severe; delayed/soft/absent P2 = more severe
CXR clue: Prominent pulmonary knob (post-stenotic dilation) with normal heart size — classic of valvular PS
Intervention threshold: Gradient > 60 mmHg → balloon pulmonary valvuloplasty
Peripheral PS associations: Rubella, Alagille, Williams, TOF
Infundibular PS: Usually not isolated — think TOF, double-chambered RV, VSD

Active Recall - Pulmonary Stenosis: Definition to Clinical Features

Differential Diagnosis of Pulmonary Stenosis

When you encounter a child with a suspected RVOT obstruction — whether presenting as an ejection systolic murmur at the LUSB, neonatal cyanosis, or an incidental echocardiographic finding — you need a systematic framework to distinguish true pulmonary stenosis from its mimics. The differential depends heavily on the clinical presentation scenario: (A) the child with an ESM at the LUSB, (B) the cyanotic neonate, or (C) the child with RV hypertrophy on ECG/echo.

Let us work through this from first principles, always asking "what else could produce this clinical picture?"

A. Differential of an ESM at the Left Upper Sternal Border (LUSB)

This is the most common clinical scenario leading to consideration of PS. The LUSB (also called the "pulmonary area") is where flow across the pulmonary valve and RVOT is best auscultated. But several conditions produce murmurs heard here.

Feature	Detail
Physiological peripheral PS of the newborn	Very common in neonates; caused by the relatively small calibre and acute angulation of branch PAs relative to the MPA at birth. Produces a soft, short systolic murmur radiating to both axillae and the back. Resolves by 3–6 months as the branch PAs grow. Distinguished from pathological PPS by its transient nature and absence of RVH or post-stenotic dilation on echo.
Still's murmur	The most common innocent murmur in children (age 2–7 years). Musical, vibratory, low-pitched systolic murmur best heard at the LLSB to apex (not LUSB). Should not be confused with PS — location and quality differ.
Pulmonary flow murmur of childhood	Soft, blowing ESM at the LUSB in thin or high-cardiac-output children (fever, anaemia, anxiety). No thrill, no click, normal S2 splitting, normal ECG and CXR. Disappears when output normalises.

Key discriminator: Innocent murmurs are ≤ Grade 2/6, have no thrill, no click, normal S2, normal ECG, and normal CXR. If any of these are abnormal, the murmur is likely pathological.

TOF is a critical differential, particularly in the cyanotic infant with an ESM at the LUSB ^[3]^[9]:

TOF involves: pulmonary stenosis (usually infundibular), RVH, overriding aorta, VSD ^[3]
The ESM in TOF is due to the PS component, just as in isolated PS
The main haemodynamic determinant in TOF is the degree of RVOT obstruction ^[3]
Key differences from isolated PS:
- TOF has a VSD → right-to-left shunting at ventricular level → cyanosis occurs without needing a PFO/ASD
- Fallot's/Tet spells ^[3]: Transient near-occlusion of the RVOT with profound cyanosis; during a spell, the ESM paradoxically softens or disappears (less flow across RVOT) ^[3] — in isolated PS, the murmur does not behave this way
- CXR shows boot-shaped heart (coeur en sabot) ^[9] due to RVH + small PA segment and uplifted apex — in isolated valvular PS, the PA segment is prominent (post-stenotic dilation), which is the opposite
- Fallot's sign: squatting relieves cyanosis ^[3] by increasing SVR (reducing R-to-L shunt) and increasing venous return (increasing pulmonary flow)

TOF vs. Isolated Severe PS — Exam Favourite

Feature	Isolated Valvular PS	TOF
VSD	Absent	Present (large, non-restrictive)
Cyanosis mechanism	R-to-L at atrial level (needs PFO/ASD)	R-to-L at ventricular level (through VSD)
PA segment on CXR	Prominent (post-stenotic dilation) ^[1]	Small/absent ^[9]
Heart shape on CXR	Normal	Boot-shaped ^[9]
Tet spells	No	Yes ^[3]
Ejection click	Present (valvular)	Usually absent (infundibular PS)

B. Differential of the Cyanotic Neonate with Reduced Pulmonary Blood Flow

When critical PS presents as neonatal cyanosis, the differential includes all causes of cardiac cyanosis with reduced pulmonary flow ^[5]:

"Cardiac origins of central cyanosis — systemic venous blood bypassing the lung (right-to-left shunts) and reduced pulmonary flow (pulmonary outflow obstruction, pulmonary atresia)" ^[5]

If the presenting finding is RVH rather than a murmur, the differential broadens:

Condition	Mechanism of RVH	Key Distinguishing Feature
Valvular PS	RV pressure overload ^[1]	Ejection click, post-stenotic PA dilation on CXR, ESM at LUSB
Infundibular PS	RV pressure overload	No ejection click, no post-stenotic dilation; a/w VSD, TOF ^[2]
Peripheral PPS	RV pressure overload	A/w rubella, Alagille, Williams; bilateral murmurs radiating to axillae ^[2]
Pulmonary hypertension	↑PVR → RV pressure overload	Loud P2 (not soft!); causes include chronic lung disease, PPHN in neonates, Eisenmenger ^[11]
Large ASD	RV volume overload	Fixed split S2; pulmonary plethora; RA/RV dilation rather than hypertrophy
TOF	RV pressure overload from RVOT obstruction + VSD	Boot-shaped heart; VSD; cyanosis from ventricular-level shunting ^[3]
Cor pulmonale	Chronic lung disease → ↑PVR → RV failure	History of chronic respiratory disease; dilated PAs with peripheral pruning on CXR ^[11]
Normal neonatal RV dominance	Fetal physiology (RV is the dominant ventricle in utero)	Resolves by ~6 months; no pathological features

Loud P2 vs. Soft P2 — The Critical Differentiator

A common exam mistake is confusing PS with pulmonary hypertension. Both cause RVH and may present with exertional symptoms. However:

PS → soft/delayed/absent P2 (the stiff, stenotic valve closes poorly)
Pulmonary hypertension → loud, palpable P2 (the valve snaps shut forcefully against high PA pressure)

If you hear a loud P2, think pulmonary hypertension — NOT PS. This single finding can pivot your entire differential.

When PS is found in a syndromic child, the associated syndrome helps confirm the diagnosis and predict valve morphology:

Syndrome	Type of PS	Associated Cardiac Lesions	Key Dysmorphic Features
Noonan syndrome ^[1]^[12]	Valvular PS with thick dysplastic cusps; peripheral branch PA stenosis	ASD, hypertrophic cardiomyopathy	Turner-like features, ptosis, downslanting palpebral fissures, low-set ears, hypertelorism, shield chest, cryptorchidism ^[12]
Williams syndrome ^[12]	Peripheral branch PA stenosis	Supravalvular AS, systemic/renal/coronary arterial stenosis	Elfin facies, full cheeks, flat nasal bridge, long philtrum, prominent lips, hypercalcaemia, intellectual disability ^[12]
Congenital rubella syndrome ^[2]	Peripheral PA stenosis	PDA	Sensorineural deafness, cataracts, microcephaly, "blueberry muffin" rash
Alagille syndrome ^[2]	Peripheral PA stenosis	—	Bile duct paucity (cholestasis), butterfly vertebrae, posterior embryotoxon (eye), characteristic facies (broad forehead, deep-set eyes, pointed chin)
DiGeorge syndrome (22q11.2 deletion) ^[12]	Not classical PS, but conotruncal anomalies	Interrupted aortic arch, truncus arteriosus, TOF, VSD	Abnormal facies, thymic hypo/aplasia, cleft palate, hypocalcaemia ^[12]
LEOPARD syndrome ^[4]	Valvular PS	Hypertrophic cardiomyopathy	Lentigines, ECG abnormalities, ocular hypertelorism, pulmonary stenosis, abnormal genitalia, retarded growth, deafness

Differential	Shared Feature with PS	Key Distinguishing Feature
Innocent pulmonary flow murmur	ESM at LUSB	≤ Grade 2, no click, normal S2, normal ECG/CXR
Physiological PPS of newborn	ESM radiating to axillae/back	Resolves by 3–6 months; no RVH
ASD	ESM at LUSB, RV overload	Fixed split S2, normal P2, RV dilation (volume not pressure), pulmonary plethora
VSD (subarterial)	Murmur at LUSB	PSM character, LV volume overload, pulmonary plethora
PDA	Murmur at LUSB	Continuous murmur, wide pulse pressure, collapsing pulse
TOF ^[3]	ESM at LUSB, cyanosis, RVH	VSD, boot-shaped heart, small PA segment, Tet spells
PAIVS ^[10]	Neonatal cyanosis, duct-dependent	No forward PV flow, RV hypoplasia, ventriculo-coronary fistulae, single S2
TGA	Neonatal cyanosis	Egg-on-string CXR, parallel circulations, cyanosis out of proportion to respiratory distress
TAPVC (obstructed)	Neonatal cyanosis	Pulmonary oedema ("white-out" CXR), not oligaemic lungs
Pulmonary hypertension ^[11]	RVH, exertional symptoms	Loud P2 (not soft); dilated PAs with peripheral pruning
Tricuspid atresia	Cyanosis, reduced pulmonary flow	Left axis deviation on ECG, absent TV on echo
Ebstein anomaly	Cyanosis, RV dysfunction	Massive cardiomegaly, displaced TV, WPW on ECG

High Yield Summary — Differential Diagnosis of PS

ESM at LUSB differential: Valvular PS (ejection click, soft P2), ASD (fixed split S2, normal P2), innocent murmur (Grade ≤ 2, normal everything), PDA (continuous), VSD (PSM at LLSB/LUSB)
Cyanotic neonate with reduced pulmonary flow: Critical PS, PAIVS (no forward PV flow), severe TOF (VSD, boot-shaped heart), PAVSD, tricuspid atresia (LAD on ECG)
RVH differential: PS vs. pulmonary hypertension — soft P2 = PS; loud P2 = pHTN
TOF vs. isolated PS: TOF has VSD, boot-shaped heart, small PA segment; PS has no VSD, prominent PA segment (post-stenotic dilation)
PAIVS vs. critical PS: PAIVS has complete atresia (no forward flow), RV hypoplasia, possible RVDCC; critical PS has a pinhole opening with some forward flow
Syndromic clues: Noonan → dysplastic valvular PS; Williams/Rubella/Alagille → peripheral PPS; LEOPARD → PS + lentigines

Active Recall - Differential Diagnosis of Pulmonary Stenosis

References

^[1] Senior notes: Adrian Lui Pediatrics.pdf (p206) ^[2] Senior notes: Adrian Lui Pediatrics.pdf (p207) ^[3] Senior notes: Ryan Ho Cardiology.pdf (p187) ^[4] Senior notes: Ryan Ho Rheumatology.pdf (p185) ^[5] Lecture slides: GC 147. Heart failure and cyanosis in children acyanotic and cyanotic congenital heart disease - Part 2.pdf (p8) ^[6] Senior notes: Adrian Lui Pediatrics.pdf (p190) ^[7] Senior notes: Ryan Ho Cardiology.pdf (p193) ^[8] Senior notes: Ryan Ho Cardiology.pdf (p189) ^[9] Senior notes: Adrian Lui Pediatrics.pdf (p232) ^[10] Senior notes: Adrian Lui Pediatrics.pdf (p217) ^[11] Senior notes: Ryan Ho Respiratory.pdf (p39, p138) ^[12] Senior notes: Ryan Ho Cardiology.pdf (p185)

Diagnostic Criteria, Diagnostic Algorithm, and Investigations for Pulmonary Stenosis

Diagnostic Criteria

Unlike many medical conditions (e.g. rheumatic fever with Jones criteria, or Kawasaki disease), pulmonary stenosis does not have a formal set of published "diagnostic criteria" in the way a systemic disease does. Instead, the diagnosis is made by integrating clinical features with echocardiographic confirmation. Echocardiography is the gold standard — it establishes the diagnosis, defines the anatomical level of obstruction, quantifies severity, and guides management decisions.

However, we can operationally define the diagnostic framework:

Component	What it Establishes
1. Clinical suspicion	Murmur (ESM at LUSB ± ejection click), neonatal cyanosis, or incidental finding
2. Echocardiographic confirmation	Anatomical level of obstruction (valvular/subvalvular/supravalvular/peripheral); valve morphology (typical domed vs. dysplastic); presence of associated lesions (PFO, ASD, VSD)
3. Doppler-derived pressure gradient	Estimation of systolic pressure gradient across PV ^[1] — this is the cornerstone for severity grading and treatment decisions

The severity of PS is graded by the peak instantaneous pressure gradient measured by continuous-wave (CW) Doppler across the pulmonary valve using the modified Bernoulli equation:

$\Delta P = 4v^2$

Where v = peak velocity of the jet across the stenotic valve (m/s), and ΔP = pressure gradient (mmHg).

Severity	Peak Doppler Gradient	RV Systolic Pressure Relative to Systemic	Clinical Implication
Trivial	< 25 mmHg	< 1/3 systemic	No haemodynamic significance; no follow-up may be needed
Mild	25–49 mmHg	1/3–1/2 systemic	Usually asymptomatic; observe/no management ^[1]
Moderate	50–64 mmHg	1/2–3/4 systemic	Observe/no management in most; borderline for intervention ^[1]
Severe	> 64 mmHg	> 3/4 systemic (may exceed LV)	Balloon pulmonary valvuloplasty indicated (gradient > 60 mmHg) ^[1]
Critical	Near-atretic valve, minimal forward flow	Suprasystemic	Urgent PGE₁ + neonatal balloon valvuloplasty ^[1]; duct-dependent pulmonary circulation

Why 60 mmHg?

The threshold of > 60 mmHg (some guidelines use > 50 mmHg with symptoms, or > 60 mmHg regardless of symptoms) corresponds to RV pressure approaching systemic levels. At this point, the RV is chronically subjected to near-systemic afterload, risking progressive RV dysfunction, myocardial fibrosis, arrhythmia, and exercise intolerance. Intervention below this threshold generally does not improve outcomes and exposes the child to procedural risk unnecessarily. Observe/no management in mild/moderate PS ^[1].

Gradient Pitfall in Critical PS

In critical PS with very low cardiac output, the Doppler gradient may be misleadingly low — not because the stenosis is mild, but because there is so little flow across the valve that velocity (and therefore ΔP = 4v²) is low. Always correlate the gradient with RV function, valve morphology, and clinical status. A low gradient in a cyanotic, shocked neonate does NOT mean mild PS — it may mean critical PS with impending circulatory collapse.

Investigation Modalities

1. Echocardiography (Gold Standard)

Echocardiography is the definitive diagnostic tool for PS. It is non-invasive, radiation-free, portable (can be done at the bedside in NICU), and provides both anatomical and haemodynamic information in real-time. Let us break down exactly what echo tells you and why each finding matters.

Finding	Explanation (First Principles)
Incomplete opening of PV cusps ^[1]	In typical valvular PS, the fused commissures prevent full leaflet excursion. On 2D echo, you see the valve leaflets "dome" towards the PA during systole — they bow forward like a parachute rather than opening flat. This doming pattern is pathognomonic of valvular stenosis with commissural fusion and predicts good response to balloon valvuloplasty (the balloon will split the fused commissures).
Valve morphology: typical vs. dysplastic	Dysplastic valves (Noonan syndrome) show thick, myxomatous, immobile cusps ^[1]^[12] with minimal commissural fusion and often a hypoplastic annulus. This distinction is crucial because dysplastic valves do not respond to balloon valvuloplasty → require surgical valvotomy ^[1].
Post-stenotic dilatation of pulmonary trunk ^[1]	The turbulent jet exiting the stenotic valve impacts the wall of the MPA, causing localised dilation. Visible as an enlarged MPA on 2D echo. Not present in infundibular or supravalvular PS ^[1] — the turbulence pattern is different when the valve itself is normal.
RV wall thickness	RV free wall thickness > 5 mm in a child (age-dependent norms) indicates RV hypertrophy — the compensatory response to chronic pressure overload. Measured in the subcostal or parasternal short-axis view.
RV cavity size	In pressure overload (PS), the RV is hypertrophied but not dilated (concentric hypertrophy). This contrasts with volume overload (ASD) where the RV is dilated but not necessarily hypertrophied.
IVS and associated defects	Must assess for PFO, ASD, VSD to determine shunting pathways. In critical PS, identifying a PFO/ASD with R-to-L shunting explains the cyanosis mechanism.
Infundibular anatomy	Assess for subvalvular muscular obstruction (infundibular PS) — narrowing of the infundibulum by hypertrophied muscle bundles. Important to distinguish from valvular PS as management differs (enlargement of RVOT by resecting muscle bundles ± transannular patch ^[2] rather than balloon valvuloplasty).
Tricuspid valve	Assess for TR (tricuspid regurgitation) — TR jet velocity allows estimation of RV systolic pressure via the modified Bernoulli equation: RVSP = 4(TR jet velocity)² + estimated RAP. This provides an independent measure of RV pressure load.

Modality	What It Measures	Clinical Application
Colour-flow Doppler	Direction and turbulence of flow	Turbulent flow in pulmonary trunk ^[1] — appears as colour aliasing (mosaic pattern of red/blue/green) at and distal to the stenotic valve. Also identifies direction of shunt through PFO/ASD (R-to-L in critical PS).
Continuous-wave (CW) Doppler	Peak velocity across the stenosis	Estimation of systolic pressure gradient across PV ^[1] using ΔP = 4v². The CW Doppler beam is aligned parallel to the stenotic jet in the parasternal short-axis or subcostal views. Peak gradient is the primary metric for severity grading and intervention threshold.
Pulsed-wave (PW) Doppler	Velocity at a specific point	Useful for localising the exact level of obstruction — place the sample volume at different levels (below valve, at valve, above valve) to identify where the velocity step-up occurs. Also used for assessing diastolic function.

Doppler Gradient vs. Catheter Gradient

The Doppler-derived gradient is a peak instantaneous gradient (the maximum pressure difference at any single moment in systole). Cardiac catheterisation measures a peak-to-peak gradient (difference between peak RV pressure and peak PA pressure, which do NOT occur simultaneously). Therefore, Doppler gradients are typically higher than catheter gradients by approximately 10–15 mmHg. This is a common source of confusion in exams and clinical practice. Modern paediatric cardiology uses Doppler gradients as the standard for decision-making, with catheterisation reserved for intervention or discordant findings.

Scenario	Key Echo Findings
Critical PS (neonate)	Near-atretic valve with minimal forward flow; severe RVH with poor RV function; PFO/ASD with R-to-L shunting; PDA providing pulmonary blood flow
PAIVS (differential, not PS)	Imperforate PV with no forward flow; RV hypoplasia; detect abnormal Rt ventriculo-coronary sinusoidal flow ^[10]
Infundibular PS	Muscular narrowing below a normal-appearing PV; velocity step-up at subvalvular level on PW Doppler
Peripheral PPS	Normal PV and infundibulum; turbulence and velocity step-up at branch PA level; may require CT/MRI for detailed branch PA anatomy
Post-intervention follow-up	Residual gradient, degree of pulmonary regurgitation (PR), RV function

ECG is a first-line, widely available investigation that provides indirect evidence of the haemodynamic burden on the right heart. It does NOT diagnose PS directly, but supports the clinical assessment.

Paediatric ECG interpretation reminder: Normal ECG patterns change dramatically with age. Neonates have physiological right axis deviation and RV dominance (because the RV is the dominant pumping chamber in utero). By 6 months, the LV normally becomes dominant. RVH must be judged against age-appropriate norms.

Finding	Severity Correlation	Explanation (First Principles)
Normal ECG ^[1]	Mild PS	Minimal haemodynamic burden; the RV compensates easily without significant hypertrophy beyond normal for age
Right axis deviation (RAD) ^[1]	Moderate/Severe PS	The mean QRS axis shifts rightward (> +120° in children > 6 months) because the hypertrophied RV generates a larger electrical vector than the LV. In neonates, this must be interpreted cautiously as RAD is normal.
RV hypertrophy (RVH) ^[1]	Moderate/Severe PS	Tall R waves in V1 (right precordial leads) exceeding age-appropriate upper limits; deep S waves in V5–V6. In severe PS, a pure R wave in V1 (no S wave) with qR pattern suggests suprasystemic RV pressure. RV strain pattern (ST depression, T-wave inversion in right precordial leads) indicates severe, chronic pressure overload with subendocardial ischaemia.
RA enlargement (P pulmonale) ^[1]	Moderate/Severe PS	Tall, peaked P waves > 2.5 mm in lead II — the RA hypertrophies to overcome the stiff, hypertrophied RV with elevated RVEDP. The increased RA depolarisation voltage produces the tall P wave.
LV dominance with paucity of RV forces	PAIVS ^[10] (not PS)	In PAIVS, the RV is hypoplastic and generates minimal electrical force. The ECG paradoxically shows LV dominance in a cyanotic neonate — a strong diagnostic clue that helps differentiate PAIVS from critical valvular PS (which shows RVH).

ECG Severity Correlation — A Practical Guide

ECG Pattern	PS Severity	RV Pressure (Approximate)
Normal	Mild (gradient < 50 mmHg)	< 50% systemic
Mild RAD + slight RVH	Moderate (gradient 50–64 mmHg)	50–75% systemic
Marked RAD + prominent RVH + P pulmonale	Severe (gradient > 64 mmHg)	> 75% systemic
RVH + RV strain (ST/T changes in V1–V3)	Very severe / Critical	Near-systemic or suprasystemic

When to Worry About the ECG in PS

If you see RV strain pattern (ST depression + T-wave inversion in V1–V3) in a child with PS, this indicates severe chronic pressure overload with subendocardial ischaemia — the hypertrophied RV myocardium outstrips its coronary blood supply. This child needs urgent intervention regardless of whether they are symptomatic.

CXR is a simple, readily available investigation that provides useful supportive information, though it is not diagnostic on its own. Understanding the CXR findings requires linking back to the pathophysiology.

Finding	Present In	Explanation (First Principles)
Prominent pulmonary knob (post-stenotic dilation) ^[1]	Valvular PS only ^[1]	The high-velocity turbulent jet exiting through the stenotic valve impacts the wall of the MPA, causing localised wall stress and dilation. This produces a prominent convexity at the left upper heart border (the "pulmonary knob" or "PA segment"). Not present in infundibular/supravalvular PS ^[1] because when the valve is normal, there is no focused jet impacting the MPA wall in the same way.
Normal heart size ^[1]	Mild–Severe PS	RV pressure overload causes concentric hypertrophy (the wall thickens but the chamber does not dilate). Therefore, the cardiac silhouette remains normal in size. This contrasts sharply with RV volume overload (e.g., ASD) where the RV dilates and the heart enlarges.
Normal pulmonary vascular markings ^[1]	Mild–Moderate PS	Pulmonary blood flow is maintained because the RV compensates by generating higher pressure. The lung fields appear normal.
Oligaemic (decreased) pulmonary vascular markings	Critical/Very severe PS	When the stenosis is so severe that RV output to the lungs is significantly reduced, the pulmonary arteries are underfilled → the lung fields appear dark and "oligaemic" with sparse vascular markings.
Uptilted cardiac apex ("boot-shaped heart")	Severe PS with marked RVH; classically TOF ^[3]	The hypertrophied RV lifts the apex off the diaphragm. While classically described in TOF, any condition with marked RVH can produce this appearance. In PS, the heart size is typically normal in mild-moderate ^[1], and the boot shape is more characteristic when combined with a small/absent PA segment (as in TOF).
Cardiomegaly	Critical PS with RV failure or significant TR	If the RV fails and dilates, or if significant TR causes RA/RV dilation, the heart enlarges. In PAIVS, grossly enlarged RA/RV due to TR ^[10] can cause massive cardiomegaly.

CXR Comparison: PS vs. Key Differentials

Condition	Heart Size	PA Segment	Lung Fields
Valvular PS (mild/moderate)	Normal ^[1]	Prominent (post-stenotic dilation) ^[1]	Normal ^[1]
Critical PS	Normal or enlarged	Prominent or normal	Oligaemic
TOF	Normal	Small/absent ^[3]	Oligaemic ^[3]
PAIVS	Enlarged (RA dilation) ^[10]	Small/absent	Diminished ^[10]
ASD	Enlarged (RV dilation)	Prominent (↑flow)	Plethoric
VSD (large)	Enlarged (LV dilation) ^[7]	Prominent (↑flow)	Plethoric ^[7]

CXR Pearl: Prominent PA Segment + Normal Heart Size = Valvular PS

This is a classic radiographic pattern. The prominent PA knob from post-stenotic dilation combined with a normal-sized heart (because RV hypertrophy does not dilate the chamber) is highly suggestive of isolated valvular PS. If you see a prominent PA segment with cardiomegaly, think of ASD (volume overload) or large VSD/PDA instead.

This is specifically for the cyanotic neonate when the differential includes cardiac vs. respiratory cause of cyanosis.

Principle: Administer 100% FiO₂ for 10 minutes and measure post-ductal PaO₂ (from right radial or umbilical artery).

Result	Interpretation	Mechanism
PaO₂ > 150 mmHg (often > 200 mmHg)	Respiratory cause of cyanosis	Supplemental O₂ corrects V/Q mismatch; alveolar O₂ diffuses across healthy pulmonary capillary bed
PaO₂ < 100 mmHg (often < 50 mmHg)	Cardiac cause likely (fixed R-to-L shunt)	Deoxygenated blood bypasses the lungs entirely through an intracardiac shunt; no amount of alveolar O₂ can oxygenate blood that never reaches the lungs
PaO₂ 100–150 mmHg	Equivocal; consider mixing lesions, persistent pulmonary hypertension of the newborn (PPHN)	Partial mixing or variable shunting

In critical PS with R-to-L atrial shunting, the PaO₂ will remain low (< 100 mmHg) because the deoxygenated blood is shunting right-to-left at the atrial level, bypassing the lungs. This is a fixed shunt that does not respond to supplemental oxygen — the defining feature of cardiac cyanosis ^[5].

Practical note: If the hyperoxia test suggests cardiac cyanosis, start IV PGE₁ immediately ^[1] (do not wait for echo confirmation) and arrange urgent echocardiography.

6. Cardiac Catheterisation

In the modern era, cardiac catheterisation is not primarily diagnostic for PS — echocardiography has largely replaced it. However, catheterisation is performed in two specific contexts:

Indication	Rationale
Discordant echo/clinical findings	When echo gradient does not match clinical severity (e.g., very symptomatic child with apparently moderate gradient)
Complex anatomy	Multi-level obstruction, peripheral PPS requiring detailed branch PA anatomy mapping
Assessment of coronary anatomy in PAIVS	Detect abnormal Rt ventriculo-coronary sinusoidal flow ^[10] — critical for surgical planning, as decompression of a hypertensive RV in PAIVS with RVDCC can cause fatal coronary steal
Pre-operative assessment	Before complex surgical repair (e.g., TOF with multiple levels of obstruction)

Parameter	What It Tells You
RV systolic pressure	Direct measurement of RV pressure load; in severe PS, RV systolic pressure may exceed that of LV ^[1]
PA pressure	Confirms low PA pressure distal to the stenosis (distinguishes PS from pulmonary hypertension, where PA pressure is high)
Peak-to-peak gradient	Difference between peak RV and peak PA pressures (note: lower than Doppler peak instantaneous gradient by ~10–15 mmHg)
RV angiography	Demonstrates valve morphology (doming), level of obstruction, RV size, infundibular anatomy
Coronary angiography	In PAIVS, to delineate ventriculo-coronary fistulae and assess for coronary stenosis (RVDCC)
Oxygen saturations	Detect R-to-L shunting at atrial level (step-down in LA saturation); calculate Qp:Qs

These are adjunctive investigations, not first-line for isolated PS, but valuable in specific situations:

Modality	Indication	What It Adds
Cardiac MRI	Complex anatomy (TOF, PAVSD); quantification of RV volumes and function; assessment of PR (post-intervention); branch PA stenosis (PPS) detailed anatomy ^[2]	Gold standard for RV volumetric assessment; quantifies regurgitant fraction post-intervention; 3D reconstruction of PA anatomy
CT angiography	Peripheral PPS anatomy; aortopulmonary collaterals (MAPCAs in PAVSD); coronary anatomy when MRI is not feasible	Excellent spatial resolution for branch PA anatomy; fast acquisition (useful in young children who cannot tolerate long MRI); radiation exposure is a limitation in paediatrics

Paediatric consideration: MRI in young children ( < 6–7 years) typically requires general anaesthesia or deep sedation due to the long scan time and need for immobility. This adds procedural risk and resource requirements. CT is faster but involves ionising radiation. The decision between MRI and CT is made case-by-case, weighing anatomy complexity, child's age/cooperation, and available expertise.

Blood tests do not diagnose PS but are essential in the acute management of critical PS:

Test	Relevance
Arterial blood gas (ABG)	Critical PS: severe metabolic acidosis (lactic acidosis from tissue hypoxia) + hypoxaemia; guides resuscitation
Lactate	Elevated in critical PS with shock — reflects tissue hypoperfusion
Full blood count (FBC)	Chronic cyanosis → secondary polycythaemia (erythropoietin-driven ↑RBC production to improve O₂-carrying capacity); may see elevated Hb/Hct
Renal function, electrolytes	Assess for end-organ damage in critical PS with shock
Genetic testing	If syndromic features present (e.g., Noonan syndrome — RASopathy gene panel including PTPN11, SOS1, RAF1, KRAS ^[12]^[4]; Williams syndrome — FISH or microarray for 7q11.23 deletion; Alagille — JAG1/NOTCH2 sequencing)

Scenario	First-Line	Key Findings	Additional Investigations
Cyanotic neonate (suspected critical PS)	Hyperoxia test → PGE₁ → urgent echo	Low PaO₂; near-atretic valve; R-to-L atrial shunt; PDA	ABG (acidosis), lactate, pre/post-ductal SpO₂; CXR + ECG as adjuncts; catheterisation for intervention
Infant/child with ESM at LUSB	Echocardiography	Domed valve, post-stenotic dilation, Doppler gradient	ECG (RVH?), CXR (PA knob?); if mild → observe; if severe → refer for BPV
Suspected peripheral PPS	Echocardiography	Branch PA turbulence; normal PV	CT angiography or cardiac MRI for detailed branch PA anatomy; repeated balloon angioplasty ± stenting ^[2]
Syndromic child (e.g., Noonan)	Echocardiography + genetic testing	Thick dysplastic valve cusps ^[12]; may be associated with HCM	Genetic panel; surgical planning (not BPV)

High Yield Summary — Diagnosis of Pulmonary Stenosis

Gold standard: Echocardiography — confirms anatomy, valve morphology, Doppler gradient, associated defects
Modified Bernoulli equation: ΔP = 4v² — cornerstone of non-invasive severity grading
Severity thresholds: Mild < 50 mmHg (observe); Severe > 60 mmHg (BPV); Critical = near-atretic, duct-dependent (urgent PGE₁ + BPV)
Typical vs. dysplastic valve: Echo morphology determines balloon vs. surgery — dysplastic valves (Noonan) do not respond to BPV
CXR triad of valvular PS: Prominent PA knob + normal heart size + normal lung markings
ECG correlation: Normal in mild; RAD + RVH + P pulmonale in severe; RV strain = urgent intervention
Post-stenotic dilation: Present ONLY in valvular PS (not infundibular/supravalvular)
Hyperoxia test: In cyanotic neonates — PaO₂ < 100 mmHg = cardiac cause → start PGE₁ before echo
Catheterisation: Now primarily therapeutic (BPV); diagnostic role limited to complex anatomy, discordant findings, or coronary assessment in PAIVS
Beware low gradient in critical PS: Low flow → low velocity → falsely low gradient; always correlate with clinical status

Active Recall - Diagnosis of Pulmonary Stenosis

References

^[1] Senior notes: Adrian Lui Pediatrics.pdf (p206) ^[2] Senior notes: Adrian Lui Pediatrics.pdf (p207) ^[3] Senior notes: Ryan Ho Cardiology.pdf (p187) ^[4] Senior notes: Ryan Ho Rheumatology.pdf (p172) ^[5] Lecture slides: GC 147. Heart failure and cyanosis in children acyanotic and cyanotic congenital heart disease - Part 2.pdf (p8) ^[7] Senior notes: Ryan Ho Cardiology.pdf (p193) ^[10] Senior notes: Adrian Lui Pediatrics.pdf (p217) ^[12] Senior notes: Ryan Ho Cardiology.pdf (p185)

Management of Pulmonary Stenosis

A. Emergency Management: Critical PS in the Neonate

Critical PS is a duct-dependent lesion — the PDA is the sole or major source of pulmonary blood flow. When the duct closes (typically within hours to days of birth), the neonate becomes profoundly cyanotic and rapidly deteriorates. Management must be immediate and aggressive.

Action	Rationale
Airway, Breathing, Circulation (ABC)	Standard neonatal resuscitation; ensure adequate ventilation and perfusion
IV access (umbilical vein if peripheral access difficult)	For drug administration and fluid resuscitation
Supplemental O₂	May provide marginal benefit but will NOT significantly improve SpO₂ in fixed cardiac shunt (the problem is not V/Q mismatch but R-to-L shunting); avoid hyperoxia which can promote ductal closure
Correct metabolic acidosis	NaHCO₃ if severe acidosis (pH < 7.1); tissue hypoperfusion from inadequate pulmonary blood flow causes lactic acidosis
Volume resuscitation	IV fluids to increase RV preload ^[13] — a higher preload may help push more blood across even a severely stenotic valve

Urgent PGE₁ + neonatal balloon valvuloplasty in critical PS ^[1]

Why PGE₁ works: The ductus arteriosus is kept patent in utero by circulating prostaglandins (PGE₂ from the placenta) and low PaO₂. At birth, the rise in PaO₂ and fall in PGE₂ trigger ductal constriction. Exogenous PGE₁ reverses this process by directly relaxing the smooth muscle of the ductus wall, reopening it and restoring the PDA → pulmonary blood flow.

Parameter	Detail
Drug	Prostaglandin E₁ (alprostadil)
Route	Continuous IV infusion (via central or peripheral line; ideally via umbilical venous catheter)
Starting dose	5–10 ng/kg/min (some protocols start at 50–100 ng/kg/min for rapid duct opening, then wean)
Maintenance dose	5–20 ng/kg/min (lowest effective dose to minimise side effects)
Key side effects	Apnoea (most important — 12% of neonates; always have intubation equipment ready and a plan for ventilatory support), hypotension, fever, flushing, seizures, cortical hyperostosis (long-term use)
Duration	Until definitive intervention (balloon valvuloplasty or surgery); avoid prolonged use if possible

PGE₁ and Apnoea

Apnoea is the most dangerous side effect of PGE₁ in neonates. Always be prepared to intubate. In practice, many centres will prophylactically intubate and ventilate the neonate before starting PGE₁, especially if the infant is being transferred to a cardiac centre. Never start PGE₁ without monitoring and resuscitation capability.

B. Balloon Pulmonary Valvuloplasty (BPV) — The Cornerstone Intervention

Breaking down the name: "balloon" = inflatable catheter device; "pulmonary" = pulmonary valve; "valvuloplasty" (Latin valvula = small valve + Greek plastia = moulding/repair) = reshaping/opening of the valve.

BPV is the first-line treatment for typical valvular PS in children. It was introduced in 1982 and has since become the gold standard due to its excellent efficacy, low complication rate, and avoidance of open-heart surgery.

Indication	Evidence / Rationale
Severe PS with peak Doppler gradient > 60 mmHg ^[1]	RV pressure approaching systemic → risk of irreversible RV dysfunction, arrhythmia, exercise limitation
Critical PS in neonates (after PGE₁ stabilisation) ^[1]	Life-saving; restores anterograde pulmonary flow
Moderate PS (gradient 50–60 mmHg) with symptoms	Exertional dyspnoea, syncope, or exercise limitation attributable to PS; borderline gradient but clinically significant
Moderate PS with RV strain on ECG or progressive RVH	Evidence of myocardial compromise despite "moderate" gradient; intervene before irreversible RV damage

Situation	Reason	Alternative
Dysplastic PV (e.g. Noonan syndrome) ^[1]	Thick, myxomatous leaflets without commissural fusion → balloon cannot split what is not fused ^[1]	Surgical valvotomy ^[1]
Infundibular (subvalvular) PS	The obstruction is muscular, below the valve; a balloon at the valve level will not address subvalvular muscular hypertrophy	Surgical enlargement of RVOT by resecting muscle bundles ± transannular patch ^[2]
Severe infundibular hypertrophy secondary to valvular PS	After BPV of the valve, residual dynamic infundibular obstruction may worsen transiently (the hypertrophied infundibulum contracts against reduced afterload — "suicide RV")	Managed conservatively with beta-blockers; resolves over weeks as the infundibular muscle regresses
Supravalvular PS	The obstruction is above the valve; balloon at valve level is ineffective	Surgical patch repair or stenting depending on anatomy
Peripheral branch PA stenosis	Multiple discrete stenoses in branch PAs; valve-level balloon is irrelevant	Repeated balloon angioplasty ± stenting for stenotic arteries ^[2]

Parameter	Detail
Immediate success rate	> 90% in typical valvular PS; gradient usually falls by > 50%
Long-term outcomes	Excellent; most children do not need re-intervention; freedom from re-intervention > 85% at 10 years
Complications	Rare ( < 2%): vascular injury (femoral vein), cardiac perforation (very rare), severe PR (usually from oversized balloon), transient arrhythmia, infundibular spasm
Pulmonary regurgitation	Some degree of PR is expected and usually well-tolerated; severe PR is uncommon with appropriately sized balloons
Restenosis	Uncommon ( < 5–10%); more likely in neonates with hypoplastic annulus; may require repeat BPV or surgery

Post-BPV Infundibular Spasm — The 'Suicide RV'

After successful BPV, the sudden reduction in afterload can unmask dynamic infundibular obstruction — the chronically hypertrophied infundibular muscle, which was previously stretched by high RV pressure, now contracts vigorously against a lower-resistance outflow. This can transiently worsen the gradient. It is managed conservatively (beta-blockers ± volume loading) and resolves over weeks to months as the infundibular muscle regresses. Do NOT re-balloon for this — it will not help and may worsen PR.

C. Surgical Management

Surgery is reserved for cases where catheter-based intervention is not feasible or has failed. In the era of excellent catheter techniques, surgery for isolated PS is uncommon but remains essential for specific indications.

Indicated in dysplastic PV (e.g. Noonan syndrome) → do not respond to BPV ^[1]

Parameter	Detail
Approach	Open-heart surgery via median sternotomy with cardiopulmonary bypass (CPB)
Procedure	Direct incision of the thickened, dysplastic valve leaflets under direct vision; partial excision of myxomatous tissue; may include annular enlargement if the annulus is hypoplastic
Outcome	Effective relief of obstruction; low operative mortality ( < 1% in experienced centres)
Complications	Pulmonary regurgitation (more likely if aggressive tissue excision), bleeding, infection, heart block (rare), need for CPB-related complications

For infundibular (subvalvular) PS: enlargement of RVOT by resecting muscle bundles ± transannular patch ^[2]

Parameter	Detail
Indication	Primary infundibular PS (isolated or as part of TOF, double-chambered RV)
Procedure	Resection of the hypertrophied muscle bundles causing the subvalvular obstruction; if the RVOT is too narrow even after muscle resection, a transannular patch is placed — a patch of pericardium or synthetic material that bridges the annulus, widening the outflow tract
Key consideration	Transannular patch causes obligatory pulmonary regurgitation ^[3] — by destroying the valve annulus integrity, the patch creates free PR. This is the principal long-term complication of TOF repair and applies equally here.
Long-term consequence of PR	RV volume overload → RV dilation → RV dysfunction → arrhythmia (VT, atrial flutter/fibrillation) → exercise intolerance → potential sudden cardiac death; requires long-term follow-up with serial echo and MRI

Observe/no management in mild/moderate PS ^[1]

This is the most common management scenario, as the majority of children with PS have mild or moderate disease.

Management	Detail
No intervention needed	Mild PS (gradient < 50 mmHg) is haemodynamically insignificant; the RV compensates easily; there is no risk of sudden death or rapid deterioration
Serial echocardiographic follow-up	Every 1–3 years depending on severity; monitor for progression of gradient, development of RVH, change in RV function
No exercise restriction	Children with mild-moderate PS can participate in all activities including competitive sports; unlike aortic stenosis, there is virtually no risk of sudden death with exercise in mild-moderate PS
Reassurance to family	Parents should be told: "This is a very common and mild heart condition. Your child can lead a completely normal life. We will keep an eye on it with regular scans, but the vast majority of children with mild PS never need any treatment."
Natural history	Mild PS rarely progresses significantly; many children have stable or even decreasing gradients over time as they grow (somatic growth may outpace valve stenosis). Moderate PS occasionally progresses and may eventually meet intervention thresholds.

Progression of PS — When to Worry

While most mild PS remains stable, a small subset may progress — particularly in infancy when rapid somatic growth can outstrip valve growth. Neonates with "moderate" PS at birth should be followed closely (echo every 3–6 months initially) because they may progress to severe PS during the first year. After infancy, progression is uncommon.

Unlike heart failure from volume overload lesions (VSD, PDA) where diuretics, ACE inhibitors, and digoxin play central roles, there is no primary medical therapy for PS. PS is a fixed mechanical obstruction — no drug can widen a stenotic valve.

However, medical therapy has specific supporting roles:

Drug / Intervention	Role in PS Management	Mechanism
PGE₁ (alprostadil) ^[1]	Maintain ductal patency in critical PS	Relaxes ductus arteriosus smooth muscle; restores pulmonary blood flow
Beta-blockers (e.g. propranolol)	Post-BPV infundibular spasm ("suicide RV")	Reduces heart rate, decreases contractility → reduces dynamic infundibular obstruction
Inotropes (e.g. dobutamine, dopamine)	Critical PS with cardiogenic shock	Augments cardiac contractility and maintains systemic perfusion while awaiting intervention
NaHCO₃	Correction of severe metabolic acidosis in critical PS	Buffering agent; restores intracellular enzyme function and myocardial contractility
Diuretics, digoxin, ACEI, carvedilol ^[14]	If RV failure develops (late complication of severe/untreated PS)	Standard heart failure management ^[14]; diuretics reduce preload/congestion; ACEI reduces afterload; digoxin augments contractility; carvedilol provides beta-blockade with alpha-mediated vasodilation

Do NOT Use ACEI/ARB in PS with Associated Intracardiac Shunt

If PS coexists with a VSD (as in TOF), avoid ACEI/ARB ^[3] — these reduce systemic vascular resistance (SVR), which increases the pressure gradient favouring right-to-left shunting through the VSD, potentially triggering Tet spells ^[3]. This is a critical pharmacological pitfall in paediatric cardiology.

Aspect	Recommendation
Current guidelines (AHA/ESC 2023–2025)	Antibiotic prophylaxis is NOT routinely recommended for isolated native valvular PS
Exception	Prophylaxis IS recommended for 6 months after BPV or surgical valvotomy, or if there is a residual defect at the site of a prosthetic patch or device
High-risk procedures	Dental procedures involving gingival manipulation or perforation of oral mucosa
Drug of choice	Amoxicillin 50 mg/kg (max 2g) PO 30–60 min before the procedure; clindamycin 20 mg/kg (max 600 mg) if penicillin-allergic

Even after successful intervention, children with PS require lifelong follow-up (though the frequency decreases with time and favourable outcomes).

Scenario	Follow-Up Schedule	Key Monitoring
Mild PS (no intervention)	Echo every 1–3 years	Gradient stability, RV function
Post-BPV (successful)	Echo at 1 month, 6 months, 1 year, then every 1–2 years	Residual gradient, degree of PR, RV function
Post-surgical valvotomy	Echo + ECG at 1 month, then 6-monthly for first year, then annually	Residual gradient, PR, arrhythmia screening
Post-RVOT reconstruction with transannular patch	Long-term F/U and exercise testing every 3–4 years ^[3]	PR severity (MRI regurgitant fraction), RV volumes, RV function, arrhythmia screening; PV replacement if MRI shows RVH + > 25% regurgitant fraction or if symptomatic ^[3]
PPS post-stenting	Annual echo + CT/MRI as needed	In-stent restenosis, stent fracture, need for re-dilation as child grows

Paediatric consideration: Stents placed in growing children will become relatively stenotic as the child grows — planned serial re-dilation is often necessary. This is a key difference from adult stenting where the vessels are full-size.

H. Special Populations

Level	Primary Intervention	Alternative / Adjunct
Valvular PS (typical)	Balloon pulmonary valvuloplasty (BPV) if gradient > 60 mmHg ^[1]	Observe if mild/moderate
Valvular PS (dysplastic)	Surgical valvotomy ^[1]	BPV may be attempted first but usually fails
Infundibular PS	Surgical enlargement of RVOT ± transannular patch ^[2]	If part of TOF: full repair with VSD closure
Supravalvular PS	Surgical patch repair	Stenting in selected cases
Peripheral PA stenosis	Repeated balloon angioplasty ± stenting ^[2]	Surgical patch augmentation if catheter approach fails
Critical PS (any type)	Urgent PGE₁ → emergent BPV or surgery ^[1]	mBTS as bridge if anatomy unfavourable for primary intervention

High Yield Summary — Management of Pulmonary Stenosis

Mild/Moderate PS: Observe, no intervention ^[1]; serial echo every 1–3 years; no exercise restriction; reassure family
Severe PS (gradient > 60 mmHg): Balloon pulmonary valvuloplasty (BPV) is first-line ^[1] for typical domed valves
Critical PS (neonate): Urgent IV PGE₁ to reopen ductus ^[1] → emergent BPV or surgical valvotomy
Dysplastic valve (Noonan): BPV fails → surgical valvotomy required ^[1]
Infundibular PS: Surgical RVOT resection ± transannular patch ^[2]; NOT amenable to balloon
Peripheral PPS: Repeated balloon angioplasty ± stenting ^[2]
Post-BPV infundibular spasm: Manage with beta-blockers; self-resolving over weeks
Transannular patch = obligatory PR: Long-term follow-up essential; PV replacement if RVH + > 25% regurgitant fraction on MRI or if symptomatic
IE prophylaxis: NOT routinely needed for native PS; needed for 6 months post-intervention
ACEI/ARB contraindicated if PS coexists with VSD (TOF) → risk of triggering Tet spells

Active Recall - Management of Pulmonary Stenosis

References

^[1] Senior notes: Adrian Lui Pediatrics.pdf (p206) ^[2] Senior notes: Adrian Lui Pediatrics.pdf (p207) ^[3] Senior notes: Ryan Ho Cardiology.pdf (p188) ^[12] Senior notes: Ryan Ho Cardiology.pdf (p185) ^[13] Senior notes: Adrian Lui Pediatrics.pdf (p216) ^[14] Lecture slides: GC 147. Heart failure and cyanosis in children acyanotic and cyanotic congenital heart disease - Part 1.pdf (p36) ^[15] Senior notes: Adrian Lui Pediatrics.pdf (p222) ^[16] Lecture slides: GC 147. Heart failure and cyanosis in children acyanotic and cyanotic congenital heart disease - Part 2.pdf (p35)

Complications of Pulmonary Stenosis

Complications of PS can be divided into those arising from the natural history of untreated/undertreated disease, those arising from intervention (BPV or surgery), and those related to associated conditions. Understanding each complication requires tracing back to the underlying pathophysiology — every complication is a logical consequence of the haemodynamic derangement or the treatment applied.

A. Complications of Untreated or Undertreated PS

Arrhythmia Type	Mechanism	Clinical Significance
Atrial arrhythmias (atrial flutter, atrial fibrillation, SVT)	Chronic RA dilation and pressure overload → atrial fibrosis → re-entrant circuits	May cause haemodynamic compromise, embolic events; more common in longstanding severe PS
Ventricular arrhythmias (VT, VF)	RV myocardial fibrosis from chronic pressure overload → substrate for re-entry; also post-surgical scarring (see below)	Risk of sudden cardiac death; arrhythmia (VT, AFlu, AF), sudden cardiac death noted as complications of post-repair PS/TOF ^[3]
Heart block	Rare in isolated PS; more relevant post-surgically if conduction tissue is damaged	May require permanent pacemaker

Duct-dependent pulmonary circulation occurs in critical PS ^[1]^[17]:

Complication	Mechanism
Severe hypoxaemia	Ductal closure → loss of pulmonary blood flow → no gas exchange → profound desaturation ^[17]
Severe metabolic (lactic) acidosis	Tissue hypoperfusion from inadequate cardiac output + anaerobic metabolism from hypoxaemia
Seizures	Cerebral hypoxia from profound desaturation
Cardiogenic shock	Acute RV failure from suprasystemic RV pressure with no outflow; compromised LV filling (interventricular interdependence)
Multi-organ failure and death	Uniformly fatal if untreated (~50% die ≤ 2 weeks, 85% die < 6 months) ^[10] — this statistic applies to PAIVS, but critical PS without intervention follows a similarly grim trajectory

B. Complications of Intervention

Complication	Incidence	Mechanism	Management
Pulmonary regurgitation (PR)	Almost universal (mild); severe in ~5%	Balloon inflation disrupts valve leaflet integrity; oversized balloons damage cusps more	Mild PR is well-tolerated; severe PR requires follow-up and potential PV replacement (see below)
Residual stenosis	5–10% (higher in neonates with hypoplastic annulus)	Incomplete commissural splitting; hypoplastic annulus that limits balloon expansion	Re-BPV or surgical valvotomy
Dynamic infundibular obstruction ("suicide RV")	Transient; common after successful BPV in severe PS	Hypertrophied infundibular muscle contracts vigorously against reduced afterload	Beta-blockers (propranolol); self-resolves over weeks–months as muscle regresses
Vascular complications	~1–2%	Femoral vein injury (thrombosis, pseudoaneurysm, AV fistula) from catheter access in small infants	Heparin, compression; surgical repair if severe
Cardiac perforation	Very rare ( < 0.5%)	Wire or catheter tip perforates thin-walled RV or PA	Pericardiocentesis; emergent surgery if tamponade
Tricuspid valve damage	Rare	Catheter passage through TV may damage chordae or leaflets	Usually haemodynamically insignificant; rarely needs repair
Arrhythmia	Transient; common during procedure	Catheter irritation of conduction system; RBBB pattern common	Usually self-limiting; rarely requires temporary pacing

Complication	Mechanism	Management
Pulmonary regurgitation (PR) — principal late complication ^[3]	↑Aggressive repair → ↑risk of PV damage (especially if transannular patch used → obligatory PR) ^[3]	See section below on PR management
Residual RVOT obstruction	Incomplete muscle resection; scar tissue formation	Re-operation or catheter-based intervention
Heart block	Damage to conduction tissue (bundle of His) during surgical resection near the membranous septum	Temporary pacing → permanent pacemaker if persistent
Bleeding / Infection	Standard surgical complications; risk increased in neonates	Standard post-operative management
Pericardial effusion / Tamponade	Post-operative inflammation; surgical trauma to pericardium	Echocardiographic surveillance; pericardiocentesis if haemodynamically significant
Sternal wound complications	Open-heart surgery via median sternotomy	Wound care; antibiotics if infected; delayed sternal closure in neonates if chest oedema

This deserves special attention as it is the principal late complication ^[3] of both BPV and surgical repair, particularly when a transannular patch is used (which destroys the valve annulus and creates obligatory PR).

Pathophysiology of PR from first principles:

Incompetent PV → diastolic backflow from PA into RV
→ RV volume overload (must accommodate both normal venous return + regurgitant volume)
→ RV dilation (eccentric hypertrophy)
→ Stretched RV wall → impaired contractility
→ RV dysfunction
→ Tricuspid annular dilation (from RV dilation) → secondary TR
→ RA dilation → atrial arrhythmias
→ Reduced effective forward cardiac output → exercise intolerance
→ Ventricular arrhythmias from stretched, fibrotic RV myocardium
→ Risk of sudden cardiac death

Problems of post-repair PR: RV dilation and dysfunction, ↓exercise tolerance, arrhythmia (VT, atrial flutter, AF), sudden cardiac death ^[3]

Monitoring: Require long-term follow-up and exercise testing every 3–4 years ^[3]

Indications for pulmonary valve replacement (PVR):

PV replacement indicated if: (1) MRI shows RVH + > 25% regurgitant fraction, or (2) symptomatic (RV failure, arrhythmia) ^[3]

PVR Approach	Detail
Surgical PVR	Open-heart surgery; biological or mechanical valve prosthesis; definitive but requires sternotomy
Percutaneous PVR (Melody valve / Edwards SAPIEN)	Catheter-based valve implantation into a pre-existing RV-PA conduit; less invasive; increasingly used in paediatric/adolescent patients with suitable conduit anatomy
Paediatric consideration	Any prosthetic valve placed in a growing child will eventually become relatively stenotic or outgrown, necessitating future re-intervention. This is a lifelong consideration in paediatric valve surgery.

Transannular Patch = Obligatory PR — A Surgical Trade-Off

The transannular patch creates obligatory PR ^[3] because the native valve annulus is destroyed to widen the RVOT. This is a deliberate surgical trade-off: the surgeon accepts future PR in exchange for immediate relief of RVOT obstruction. The clinical impact of PR may not manifest for 10–20 years, but eventually most patients with significant PR will need PV replacement. This is why lifelong follow-up is essential for all patients who have undergone RVOT reconstruction.

When PS occurs in the context of Noonan syndrome, additional complications relate to the syndrome itself:

Complication	Mechanism
Hypertrophic cardiomyopathy (HCM)	RASopathy → abnormal RAS-MAPK signalling → myocardial hypertrophy independent of PS
Bleeding diathesis	Platelet dysfunction, factor deficiencies (factor XI, XII), and thrombocytopenia are common in Noonan syndrome — important perioperatively
Lymphatic dysplasia	Chylothorax, lymphoedema — can complicate post-operative recovery
Neurodevelopmental delay	Variable intellectual disability; ADHD common; impacts long-term management compliance
Short stature	Growth failure beyond cardiac cause; may benefit from growth hormone therapy (with caution if HCM present)

Category	Complication	Key Mechanism
Natural history (untreated)	RVH → RV dysfunction → RV failure	Chronic pressure overload → fibrosis → decompensation
	Arrhythmias (atrial + ventricular)	Atrial/RV dilation + fibrosis → re-entrant circuits
	Exercise-related syncope	Fixed RVOT obstruction → inability to augment CO
	Infective endocarditis	Turbulent flow → endothelial damage → bacterial nidus
	Growth failure	Chronic low CO + hypoxia (if cyanotic)
	Polycythaemia + cerebral events	Chronic hypoxia → erythrocytosis → hyperviscosity; paradoxical embolism
Critical PS (neonatal)	Hypoxaemia, acidosis, shock, seizure, death	Duct-dependent pulmonary circulation; ductal closure → catastrophic ^[17]
Post-BPV	PR (mild, usually well-tolerated)	Balloon disrupts valve leaflets
	Residual stenosis	Incomplete commissural splitting
	Infundibular spasm	Dynamic obstruction from hypertrophied muscle
	Vascular injury	Femoral vein access in small infant
Post-surgery	PR (principal late complication) ^[3]	Transannular patch = obligatory PR ^[3]
	RV dilation, dysfunction, arrhythmia, SCD ^[3]	Chronic volume overload from PR
	Heart block	Conduction tissue damage during resection
Associated conditions	Eisenmenger (if coexisting shunt) ^[18]	Irreversible pulmonary vascular disease from chronic ↑flow
	Noonan-related: HCM, bleeding, lymphatic	Underlying RASopathy
	Fontan complications (if univentricular pathway) ^[20]	Chronic venous congestion without subpulmonary ventricle

Scenario	Prognosis
Mild PS, untreated	Excellent; normal life expectancy; most never need intervention
Severe PS, successfully treated with BPV	Excellent; > 90% event-free survival at 10 years; need for re-intervention is low
Critical PS, promptly treated	Good if treated urgently; mortality < 5% with modern neonatal intensive care and interventional cardiology
Critical PS, untreated	Uniformly fatal ^[10]^[17]
TOF with PS, complete repair	Good — 93% 25-year survival after complete repair ^[3]
Eisenmenger syndrome (if PS + shunt untreated)	Poor — 30–40% 10-year mortality; mean age of death 37 years ^[18]
Univentricular + PS → Fontan pathway	Variable; increasing late morbidity from Fontan-associated complications; high surgical risks with uncertain long-term outcome (60–70% 3–6 year survival in highest-risk groups) ^[21]

High Yield Summary — Complications of Pulmonary Stenosis

RV pressure overload is the root cause of almost all natural-history complications: RVH → fibrosis → RV failure → arrhythmia → sudden death
Critical PS = neonatal emergency: Duct-dependent; ductal closure → hypoxaemia, acidosis, seizures, shock, death if untreated
PR is the principal late complication of both BPV and surgical repair, especially with transannular patch (obligatory PR)
PR consequences: RV dilation → dysfunction → arrhythmia (VT, AFL, AF) → SCD; requires lifelong follow-up
PV replacement indicated when MRI shows RVH + regurgitant fraction > 25% or patient is symptomatic
IE is possible but rare in isolated mild PS; higher risk post-intervention with prosthetic material
Eisenmenger only occurs if PS coexists with an unrepaired shunt; paradoxically, PS in TOF is partially protective
Polycythaemia + paradoxical embolism are complications of chronic cyanotic PS — risk of stroke and cerebral abscess
Post-BPV infundibular spasm ("suicide RV") is transient and managed with beta-blockers, not re-intervention
Fontan complications (liver disease, PLE, CKD, arrhythmia) apply when PS is part of univentricular physiology

Active Recall - Complications of Pulmonary Stenosis

References

^[1] Senior notes: Adrian Lui Pediatrics.pdf (p206) ^[2] Senior notes: Adrian Lui Pediatrics.pdf (p207) ^[3] Senior notes: Ryan Ho Cardiology.pdf (p188) ^[10] Senior notes: Adrian Lui Pediatrics.pdf (p217) ^[16] Lecture slides: GC 147. Heart failure and cyanosis in children acyanotic and cyanotic congenital heart disease - Part 2.pdf (p35) ^[17] Senior notes: Adrian Lui Pediatrics.pdf (p193) ^[18] Senior notes: Ryan Ho Cardiology.pdf (p186) ^[19] Senior notes: Ryan Ho Fundamentals.pdf (p210) ^[20] Senior notes: Adrian Lui Pediatrics.pdf (p223) ^[21] Senior notes: Adrian Lui Pediatrics.pdf (p228)

Pulmonary Stenosis

Definition

Epidemiology

Anatomy and Function

Normal Pulmonary Valve and RVOT Anatomy

Normal Physiology

Aetiology and Classification

1. Valvular PS (Most Common)

2. Infundibular (Subvalvular) PS

3. Supravalvular PS

4. Peripheral Pulmonary Arterial Stenosis (PPS)

Pathophysiology

Step-by-Step Haemodynamic Chain

Severity Classification by Pressure Gradient

Relationship Between PS Severity and Pulmonary Flow / Cyanosis

Clinical Features

Symptoms

Signs

Auscultation — The Core of PS Clinical Examination

Palpation

Inspection

Summary: Signs by Severity

Special Paediatric Considerations

Investigations (Overview — Detailed in Diagnosis Section)

Chest X-Ray (CXR)

ECG

Echocardiography

Active Recall - Pulmonary Stenosis: Definition to Clinical Features

References

Conceptual Framework

A. Differential of an ESM at the Left Upper Sternal Border (LUSB)

1. Innocent (Physiological) Murmurs

2. Atrial Septal Defect (ASD)

3. Ventricular Septal Defect (VSD)

4. Patent Ductus Arteriosus (PDA)

5. Tetralogy of Fallot (TOF)

B. Differential of the Cyanotic Neonate with Reduced Pulmonary Blood Flow

1. Pulmonary Atresia with Intact Ventricular Septum (PAIVS)

2. Tetralogy of Fallot with Severe PS or Pulmonary Atresia (TOF/PA)

3. Pulmonary Atresia with VSD (PAVSD)

4. Tricuspid Atresia

5. Ebstein Anomaly

6. Transposition of Great Arteries (TGA)

7. Total Anomalous Pulmonary Venous Connection (TAPVC)

C. Differential of RV Hypertrophy on ECG/Echo

D. Syndromic Associations — Narrowing the Differential

E. Approach to Differentiating PS from Key Mimics — Summary Mermaid Diagram

F. Summary Table: Key Differentials of Pulmonary Stenosis by Presentation

Active Recall - Differential Diagnosis of Pulmonary Stenosis

Diagnostic Criteria

Operational Diagnostic Requirements

Severity Grading (Doppler Echocardiography)

Diagnostic Algorithm

Investigation Modalities

1. Echocardiography (Gold Standard)

2D (Two-Dimensional) Echocardiography

Doppler Echocardiography

Echocardiographic Assessment in Special Scenarios

2. Electrocardiography (ECG)

3. Chest X-Ray (CXR)

4. Hyperoxia Test (Nitrogen Washout Test)

5. Pulse Oximetry Screening (Newborn)

6. Cardiac Catheterisation

A. Interventional Catheterisation (Therapeutic)

B. Diagnostic Catheterisation (Specific Indications)

Catheterisation Measurements

7. Cardiac MRI (CMR) and CT Angiography

8. Blood Tests (Supportive, Not Diagnostic)

Summary: Investigation Algorithm by Clinical Scenario

Active Recall - Diagnosis of Pulmonary Stenosis

Guiding Principles

Management Algorithm

A. Emergency Management: Critical PS in the Neonate

Step 1: Stabilisation

Step 2: Prostaglandin E₁ (PGE₁ / Alprostadil)

Step 3: Definitive Neonatal Intervention

B. Balloon Pulmonary Valvuloplasty (BPV) — The Cornerstone Intervention

Mechanism of Action

Indications

Contraindications / Situations Where BPV is NOT Appropriate