A ventricular septal defect is a congenital heart malformation, present from birth, in which an abnormal opening in the wall between the left and right ventricles allows oxygen-rich blood to shunt into the pulmonary circulation, and it is the most common congenital heart defect in infants and children.

Ventricular Septal Defect (VSD) in Paediatrics

Parameter	Detail
Incidence	~0.3–0.5 per 1,000 live births (some sources quote ~1/500) — this is the commonest congenital heart disease (CHD) overall ^[2]^[3]
Proportion of all CHD	~25–30% of all congenital heart defects
Sex	Slight female predominance (F:M ≈ 1.2:1) in isolated VSD
Hong Kong context	CHD prevalence ~8–9 per 1,000 live births in HK; VSD remains the most common individual lesion. Perimembranous VSD predominates; subarterial (doubly committed subarterial or outlet) VSD is notably more common in Asian populations (~15–30% in East Asian series vs. ~5% in Western series) — this is a key HK-relevant point ^[2]^[3]
Age at presentation	Small VSD: detected as incidental murmur in neonatal/infant period. Moderate-to-large VSD: heart failure symptoms emerge at ~1–2 months of age as PVR falls ^[2]^[3]
Natural history	Spontaneous closure in 60–80% (usually ≤5 years) — highest for small muscular VSDs; subarterial VSDs do NOT spontaneously close ^[2]^[3]

High Yield — Asian / Hong Kong Specifics

Subarterial (outlet/doubly committed juxta-arterial) VSD is significantly more prevalent in East Asian populations including Hong Kong Chinese. Unlike perimembranous or muscular defects, subarterial VSD does NOT spontaneously close and is associated with progressive aortic valve prolapse and aortic regurgitation — making early surgical referral important.

Risk Factors

Anatomy and Function of the Interventricular Septum

Understanding VSD types requires understanding the normal anatomy of the interventricular septum:

The interventricular septum is not one homogeneous structure — it is composed of four anatomical zones (think of it as a complex wall with different building materials in different regions):

Component	Location	Notes
Membranous septum	Small area beneath the aortic valve, adjacent to the tricuspid valve annulus	Thinnest part; most vulnerable to defects
Inlet septum	Posterior, beneath the AV valves	Separates the inflow portions of both ventricles
Trabecular (muscular) septum	Largest portion; central, apical, and marginal	Thick and muscular; can have multiple ("Swiss cheese") defects
Outlet (infundibular/conal) septum	Anterosuperior, just beneath the semilunar valves (aortic and pulmonary)	Defects here = subarterial/doubly committed; more common in Asian populations

Aetiology

Classification

Type	Frequency (Western)	Frequency (Asian/HK)	Location	Key Features
Perimembranous (infracristal)	~70%	~60%	Membranous septum, just beneath the aortic valve, adjacent to TV	Most common cause of clinically significant VSD; may be partially covered by tricuspid valve tissue ("aneurysm of membranous septum") leading to spontaneous reduction/closure ^[2]^[3]
Muscular (trabecular)	~20%	~15%	Entirely surrounded by muscle; can be central, apical, anterior, or multiple	Central muscular type more likely to spontaneously close; multiple defects = "Swiss cheese" septum ^[2]^[3]
Subarterial (outlet / doubly committed juxta-arterial / supracristal)	~5% (Western)	~15–30% (Asian)	Outlet septum, immediately beneath both semilunar valves	Associated with coronary cusp prolapse and aortic regurgitation (AR); does NOT spontaneously close; more common in Asian populations ^[2]^[3]
Inlet (AV canal-type)	~5%	~5%	Posterior septum beneath the AV valves	Associated with AVSD; seen in Down syndrome

Exam Pearl — Subarterial VSD and AR

Subarterial VSD is associated with coronary cusp prolapse and AR ^[2]^[3]. The mechanism: the defect removes support from the right coronary cusp of the aortic valve → the cusp prolapses into the VSD under the high aortic pressure → progressive AR. This is a classic exam question and an important reason why subarterial VSD requires early surgical closure even if the VSD itself is haemodynamically small.

Size	Diameter	Haemodynamic Significance
Small	* < 4 mm (or < 1/3 aortic annulus)*	Restrictive; high-velocity jet across defect; minimal volume overload; 75% spontaneously close within < 2 years; others usually benign ^[2]^[3]
Moderate	4–6 mm (or 1/3–2/3 aortic annulus)	Moderate shunt; some volume overload; less spontaneous closure but usually respond to medical treatment; does not develop Eisenmenger with medical treatment ^[2]^[3]
Large	* > 6 mm (or > 2/3 aortic annulus)*	Non-restrictive; RV pressure approaches LV pressure; significant volume overload; progressive ↑PVR due to pulmonary vascular changes → risk of developing Eisenmenger syndrome ^[2]^[3]

Pathophysiology

This is the key to understanding everything about VSD — from symptoms, to signs, to natural history, to complications.

Consequence	Mechanism
Pulmonary congestion / oedema	↑ pulmonary blood flow → ↑ pulmonary capillary hydrostatic pressure → fluid transudation into interstitium and alveoli
↑ work of breathing	Fluid-congested lungs are stiffer (↓ compliance) → tachypnoea, subcostal/intercostal recession
Feeding difficulty	Tachypnoea makes coordinating suck-swallow-breathe impossible; also ↑ metabolic demand of breathing
Failure to thrive	↑ caloric expenditure (from increased cardiac and respiratory work) + ↓ caloric intake (poor feeding) = energy deficit → growth faltering
Recurrent LRTI	Congested, oedematous lungs are fertile ground for infection
Pulmonary hypertension (pHTN)	Initially "hyperkinetic" (due to ↑ flow), then "reactive" (pulmonary vasoconstriction), then "fixed" (irreversible vascular remodelling → Eisenmenger)

VSD Size	Natural History
Small ( < 4 mm)	75% spontaneously close within < 2 years; others usually benign — children are asymptomatic; grow normally; require endocarditis awareness and surveillance ^[2]^[3]
Moderate (4–6 mm)	Less spontaneous closure, but usually respond to medical treatment (does not develop Eisenmenger with medical treatment) ^[2]^[3]
Large ( > 6 mm)	Symptomatic HF by 1–2 months; without intervention → progressive ↑PVR → Eisenmenger syndrome ^[2]^[3]
Subarterial	Does NOT spontaneously close; progressive AR from coronary cusp prolapse; early surgical referral needed regardless of size ^[2]^[3]

Mechanisms of Apparent Spontaneous Improvement

May have apparent improvement in HF symptoms due to: ^[2]^[3]

Coverage of perimembranous defect by tricuspid valve tissue — accessory TV tissue or a septal leaflet aneurysm herniates into the defect, partially or completely occluding it → true reduction in shunt
Development of infundibular stenosis — reactive hypertrophy of the RV outflow tract (infundibulum) creates a secondary obstruction → limits the flow through the shunt → less pulmonary overcirculation (but creates a new problem — essentially an acquired "TOF-like" physiology)
↑ Pulmonary vascular resistance (↓ shunting) — this is NOT a good sign; it means pulmonary vascular disease is developing → heading towards Eisenmenger

Clinical Trap

A child with a large VSD whose heart failure symptoms seem to be "improving" without treatment may NOT be getting better. If the apparent improvement is due to rising PVR (mechanism 3 above), the child is actually getting worse — developing irreversible pulmonary vascular disease. The murmur may become softer (less shunt flow) and P2 louder (pHTN). This requires urgent assessment, not reassurance!

Clinical Features

The clinical features of VSD are entirely driven by the pathophysiology described above. Let's systematically go through them.

Symptoms

HF symptoms at 1–2 months (timing determined by the postnatal fall in PVR) ^[2]^[3]

Symptom	Pathophysiological Basis
Tachypnoea / breathlessness	Pulmonary congestion → ↓ lung compliance → ↑ respiratory effort; also ↑ metabolic demand
Feeding difficulty (poor feeding, sweating with feeds, prolonged feeds)	Tachypnoeic infant cannot coordinate suck-swallow-breathe; also ↑ cardiac output demand during feeding → sweating (sympathetic activation)
Failure to thrive / poor weight gain	↑ caloric expenditure (cardiac + respiratory work) + ↓ caloric intake = chronic energy deficit → growth faltering. Weight affected first, then length, then head circumference
Recurrent lower respiratory tract infections	Pulmonary congestion → airway oedema → impaired mucociliary clearance → bacterial superinfection
Sweating (especially during feeds)	Sympathetic activation from heart failure → sweating as compensatory mechanism
Irritability / restlessness	Heart failure, hypoxia, discomfort from respiratory distress

Signs

Sign	Pathophysiological Basis
Failure to thrive (weight < length < head circumference)	Chronic energy deficit as above
Respiratory distress (tachypnoea, subcostal/intercostal recession)	Signs of HF (respiratory distress) — pulmonary congestion → stiff, oedematous lungs ^[3]
Hepatomegaly	Right heart congestion (in advanced or biventricular failure); back-pressure through RA → IVC → hepatic veins → liver engorgement
Sweating	Sympathetic activation

Paediatric HF vs Adult HF

In infants, heart failure presents very differently from adults. You will NOT see ankle oedema or JVP elevation as prominently. Instead, look for: tachypnoea, feeding difficulty, sweating during feeds, failure to thrive, hepatomegaly, and precordial bulge ^[3]. Gallop rhythm (S3) is also common. Pulmonary crackles are actually less common in infant HF than in adults.

Sign	Pathophysiological Basis
Precordial bulge	Chronic cardiomegaly in infancy → the compliant infant rib cage is pushed outward by the enlarged heart ^[3]
Displaced, thrusting (hyperdynamic) apex beat	LV volume overload → LV dilation → apex displaced laterally and inferiorly; the thrusting (volume-overloaded) character indicates LV dilation ^[3]
Parasternal heave	± RV pressure overload — develops if PVR is elevated; RV hypertrophies against increased afterload ^[3]
Palpable thrill	Turbulent flow through a restrictive VSD generates a palpable vibration (thrill) at the LLSB

This is a classic exam topic. The murmur characteristics depend on the type and size of the VSD:

Systolic murmur depending on type and size ^[3]:

Murmur	Auscultation Site	Mechanism
Pansystolic murmur (PSM) at LLSB (widely radiating, associated with thrill)	Left lower sternal border (3rd–4th intercostal space)	Blood flows across the VSD throughout systole (LV pressure > RV pressure throughout systole). In muscular defect ^[3] and perimembranous defects
PSM at LUSB	Left upper sternal border (2nd intercostal space)	In subarterial defect — the defect is located high, near the pulmonary valve ^[3]
Mid-diastolic murmur (MDM) at apex	Apex	Due to ↑ mitral valve (MV) flow — if the VSD is large, the increased pulmonary venous return creates a relative mitral stenosis (too much blood flowing through a normal-sized mitral valve) → "flow murmur" ^[3]
Ejection systolic murmur (ESM) at LUSB	Left upper sternal border	Due to ↑ pulmonary valve (PV) flow — increased blood flowing through the normal-sized pulmonary valve creates a flow murmur ^[3]

Key auscultatory principles:

Small restrictive VSD: LOUD pansystolic murmur (high-velocity jet through small hole = lots of turbulence = loud murmur). P2 is normal. No diastolic flow murmurs.
Large non-restrictive VSD with heart failure: The PSM may actually be softer and shorter (less pressure gradient if PVR is rising). But you'll hear the apical MDM (increased MV flow) and LUSB ESM (increased PV flow). P2 is loud (pHTN).
Eisenmenger (R-to-L shunt): The murmur may be barely audible or absent (minimal transeptal flow). Loud P2 or single S2 (severely elevated PVR) ^[3]. You may hear the murmur of pulmonary regurgitation (Graham Steell murmur).

Pulmonary hypertension (loud P2 or single S2) ^[3] — Why? S2 is composed of A2 (aortic valve closure) followed by P2 (pulmonary valve closure). Normally P2 is softer than A2. When PVR is elevated, the pulmonary artery pressure is high → pulmonary valve closes forcefully → loud P2. If PVR approaches SVR, the two components close simultaneously → single S2.

Murmur Paradox — A Louder Murmur is Better!

In VSD, a loud pansystolic murmur typically means a small, restrictive defect with a large pressure gradient — haemodynamically benign. A soft or disappearing murmur in a child with a known large VSD may indicate rising PVR (bad!) or Eisenmenger. Don't be fooled into thinking quieter = better.

Feature	Small VSD	Moderate VSD	Large VSD	Eisenmenger
Growth	Normal	May be affected	FTT	Variable
Precordium	Normal	Mild cardiomegaly	Precordial bulge, displaced apex, parasternal heave	RV heave prominent
Murmur	Loud PSM at LLSB ± thrill	PSM + possible MDM	Softer PSM + MDM at apex + ESM at LUSB	Soft/absent murmur
P2	Normal	Mildly loud	Loud P2	Loud P2 or single S2
S3	Absent	May be present	Present (gallop)	Absent
Diastolic murmur	Absent	Possible apical MDM	MDM at apex	PR murmur possible
Cyanosis	Absent	Absent	Absent	Present
Clubbing	Absent	Absent	Absent	Present

Age Group	Key Points
Neonate (0–28 days)	Usually asymptomatic even with large VSD (PVR still high); murmur may not yet be audible. Small VSD murmur may appear in first few days as PVR drops enough to create turbulent flow.
Infant (1–12 months)	HF symptoms at 1–2 months as PVR falls. This is the critical period for moderate-to-large VSD. Feeding difficulty, tachypnoea, FTT are the presenting features.
Toddler / Preschool (1–5 years)	Spontaneous closure peaks in this age group. Exercise intolerance if uncorrected large VSD.
School-age / Adolescent	If the child has an unrepaired large VSD and is still acyanotic, they may have been "protected" by infundibular stenosis. If cyanotic → Eisenmenger has developed.

Parental anxiety is high when a murmur is detected — clear, empathetic explanation is essential
For small VSDs: reassure parents that most close spontaneously; explain that a loud murmur ≠ a serious defect
For large VSDs: explain the timeline (why the baby was fine at birth but is now struggling), the need for medical and potentially surgical management
Consent: parental consent for all investigations/procedures; involve the child in discussions as appropriate for age (assent from ~7 years)
Genetic counselling if syndromic features present

High Yield Summary

VSD = commonest CHD (~25–30% of all CHD, ~1/500 live births)
Classification by location: Perimembranous (~70%, most clinically significant), Muscular (~20%, best spontaneous closure), Subarterial (~5% Western, up to 30% Asian — does NOT close spontaneously, causes AR from cusp prolapse), Inlet (~5%, associated with AVSD/Down syndrome)
Classification by size: Small ( < 4mm) = usually benign, 75% close by 2y; Moderate (4–6mm) = respond to medical Rx; Large ( > 6mm) = risk of Eisenmenger
Pathophysiology: In utero = no effect (high PVR); Postnatal = PVR falls by 2–3 months → L-to-R shunt → pulmonary overcirculation → volume overload of LA and LV (NOT RV in early stages) → heart failure symptoms
Presentation: Small = asymptomatic murmur; Moderate/large = HF at 1–2 months (tachypnoea, feeding difficulty, FTT, sweating)
Murmur: PSM at LLSB (perimembranous/muscular) or LUSB (subarterial); MDM at apex and ESM at LUSB in large VSD (flow murmurs)
Apparent improvement in HF may be due to: (1) TV tissue coverage, (2) infundibular stenosis, (3) rising PVR — mechanism (3) is dangerous
Complications: HF, pHTN, Eisenmenger syndrome, infective endocarditis (any size), AR (subarterial)
Spontaneous closure in 60–80% (usually ≤5 years) EXCEPT subarterial

Active Recall - Ventricular Septal Defect

Differential Diagnosis of Ventricular Septal Defect

When a child presents with findings suggestive of VSD — whether that's an asymptomatic systolic murmur in a well neonate, or heart failure at 1–2 months of age — you need to think systematically about what else could produce the same clinical picture. The differential diagnosis essentially falls into two clinical scenarios:

The infant/child with a systolic murmur (commonest presentation for small VSD)
The infant with heart failure at 1–2 months (presentation for moderate-to-large VSD)

Let's work through each scenario from first principles.

Clinical Scenario 1: Systolic Murmur in an Infant or Child

The key question here is: Is this murmur pathological (structural heart disease) or innocent?

Up to 50% of children will have an innocent murmur heard at some point ^[2]. These must be distinguished from VSD.

Features of innocent murmur: aSymptomatic, Soft blowing, Systolic, Left Sternal edge ^[2] — use the mnemonic of the "7 S's": Soft, Systolic, Short, Single (no associated clicks/gallops), aSymptomatic, Sitting/standing diminishes, Sternal (left) edge.

Feature	Innocent Murmur	VSD Murmur
Intensity	Soft (grade 1–2/6)	Often loud (grade 3–5/6), may have thrill
Character	Blowing, musical, vibratory	Harsh, blowing
Timing	Systolic, short	Pansystolic (extends to S2)
Variation	Changes with posture/fever/anaemia	Fixed, does not change with posture
Associated findings	No thrill, no heave, no click, normal S2	Thrill, displaced apex, loud P2 if large
Growth	Normal	May be impaired if moderate/large

Exam Pearl — When is a Murmur NOT Innocent?

Any murmur that is diastolic, pansystolic, loud (≥ grade 3/6), associated with a thrill, associated with an abnormal S2, or found in a child with symptoms (failure to thrive, tachypnoea, cyanosis) should be considered pathological until proven otherwise. All such murmurs require echocardiography.

Condition	Murmur Character & Location	How to Distinguish from VSD
Atrial Septal Defect (ASD)	ESM at LUSB (relative PS from ↑flow), wide and fixed splitting of S2	ASD produces an ESM (not PSM); the hallmark is fixed split S2. No thrill. RV volume overload (not LV).
Atrioventricular Septal Defect (AVSD)	PSM at LLSB/apex (VSD + MR component), MDM at apex; signs similar to ASD and VSD ^[2]	Often in Down syndrome. ECG shows superior axis (left axis deviation) — a key distinguishing feature. Combined ASD + VSD features.
Patent Ductus Arteriosus (PDA)	Continuous "machinery" murmur at left infraclavicular area, best in systole	The continuous nature (extends through S2 into diastole) distinguishes PDA from the purely systolic PSM of VSD. Bounding pulses from aortic run-off.
Aortic Stenosis (AS)	ESM at RUSB/aortic area, radiating to carotids; ejection click	ESM (crescendo-decrescendo), not PSM. Loudest at RUSB, not LLSB. May have ejection click. Narrow pulse pressure.
Pulmonary Stenosis (PS)	ESM at LUSB with ejection click; wide but NOT fixed split S2	ESM (not PSM). Click present. P2 is soft (opposite to large VSD where P2 is loud).
Mitral Regurgitation (MR)	PSM at apex radiating to axilla	PSM like VSD, but maximal at apex (not LLSB) and radiates to axilla. Often associated with mitral valve prolapse click.
Tricuspid Regurgitation (TR)	PSM at LLSB, increases with inspiration	Can be confused with VSD at LLSB, but augments with inspiration (Carvallo sign) because increased venous return to RV increases regurgitant flow. VSD does not consistently change.
Hypertrophic Cardiomyopathy (HCM)	ESM at LLSB, increases with Valsalva/standing	Dynamic LVOT obstruction. ESM (not PSM). Increases with manoeuvres that decrease preload. Family history often positive. ECG shows dramatic LVH.
Coarctation of Aorta	Soft, non-specific systolic murmur; often between scapulae	Coarctation is only associated with soft and non-specific murmurs → look hard for soft/absent femoral pulses ^[2]. Radio-femoral delay. Upper limb hypertension.

Critical Trap — Coarctation of the Aorta

Coarctation of the aorta is only associated with soft and non-specific murmurs ^[2]. It can be missed if you rely on the murmur alone. The key is to always check femoral pulses in any infant with a murmur, heart failure, or shock. Absent or weak femoral pulses with strong upper limb pulses = coarctation until proven otherwise.

Clinical Scenario 2: Heart Failure in Infancy

Heart failure in CHD is more likely due to structural defects → excessive volume/pressure load instead of myocardial dysfunction ^[2].

The timing of heart failure presentation is a critical differentiating feature:

Timing of HF is essential ^[2]:

Neonatal: implies duct-dependent systemic circulation → HF with closure of duct ^[2] — presents in the first week of life with acute shock, weak lower limb pulses, oliguria, and severe metabolic acidosis ^[2]
Infant (1–3 months): implies L-to-R shunt → ↓postnatal pulmonary vascular resistance at 2–3 months → ↑↑L-to-R shunting with ↑pulmonary flow ^[2]
Children/adolescents: usually acquired myocardial disease (e.g., myocarditis, cardiomyopathy) or ventricular dysfunction with complex CHD despite surgery ^[2]

Large left-to-right shunts: ventricular septal defect, atrioventricular septal defect, persistent arterial duct — all present with later onset of symptoms (as compared to left ventricular outflow obstructive lesions) ^[1]

Feature	VSD	AVSD	PDA
Typical murmur	PSM at LLSB ± thrill	PSM at LLSB/apex + MR component	Continuous "machinery" murmur at left infraclavicular region
S2	Loud P2 if large	Loud P2 if large	Loud P2 if large
Additional murmurs	MDM at apex, ESM at LUSB if large	ASD component → fixed split S2	Bounding pulses, wide pulse pressure
ECG	LV volume overload (tall R in V5/V6)	Superior (left) axis deviation — this is almost pathognomonic for AVSD	LV volume overload
Associations	Isolated or part of complex CHD	40–50% Down syndrome-related ^[2]	Prematurity, maternal rubella
Mechanism of HF	↑Pulmonary blood flow → ↑pulmonary venous return → volume overload of LA and LV ^[1]	Same as VSD + ASD component + AV valve regurgitation	Aorta → PA shunt → pulmonary overcirculation → LV volume overload

These present EARLIER than VSD and are more dramatic:

Condition	Key Distinguishing Feature
Coarctation of Aorta	Shock at day 2–7; absent/weak femoral pulses; BP gradient between upper and lower limbs
Interrupted Aortic Arch	Complete absence of aortic segment; severe shock; associated with DiGeorge syndrome (22q11.2 deletion)
Critical Aortic Stenosis	Neonatal shock; harsh ESM at RUSB; weak pulses diffusely
Hypoplastic Left Heart Syndrome (HLHS)	Single S2; grey, shocked neonate; duct-dependent systemic circulation

The critical distinction: VSD presents with HF at 1–2 months (because PVR must fall first), whereas duct-dependent lesions present with shock at day 2 when the ductus arteriosus closes ^[1]^[2].

If VSD is found on echocardiography, always consider whether it is isolated or part of a syndrome/complex CHD:

Syndrome	Cardiac Defects	Dysmorphic Clues
Down syndrome (Trisomy 21)	AVSD, VSD, secundum ASD, PDA, TOF	Hypotonia, prominent medial epicanthic folds, upslanting palpebral fissures, flat nasal bridge, single transverse palmar crease ^[2]^[3]
DiGeorge syndrome (22q11.2 del)	Conotruncal abnormalities: interrupted aortic arch, truncus arteriosus, TOF, ASD/VSD	Abnormal facies, thymic hypo/aplasia, cleft palate, hypocalcaemia ^[2]^[3]
Turner syndrome (45,X)	Left-sided lesions: coarctation, bicuspid AV, valvular AS, HLHS	Short stature, webbed neck, low hairline, cubitus valgus, widely-spaced nipples ^[2]^[3]
Williams syndrome (7q11.23 del)	Supravalvular AS, peripheral pulmonary artery stenosis	Elfin facies, full cheeks, prominent lips, hypercalcaemia ^[2]^[3]
Noonan syndrome	Right-sided lesions: valvular PS (dysplastic cusps), ASD, HCM	Turner-like features, ptosis, downslanting palpebral fissures, cryptorchidism ^[2]^[3]

A child presenting with tachypnoea, poor feeding, and failure to thrive at 1–2 months may not have cardiac disease at all:

Condition	Distinguishing Features
Bronchiolitis (RSV)	Seasonal; coryzal prodrome; wheeze; no murmur; no cardiomegaly on CXR
Pneumonia	Fever; focal signs; CXR shows consolidation (not pulmonary plethora)
Sepsis	Fever, lethargy, poor feeding; positive blood cultures; no murmur
Metabolic disease (e.g., inborn errors of metabolism)	Encephalopathy, metabolic acidosis, hyperammonaemia; no murmur
Non-organic failure to thrive (inadequate feeding/neglect)	No respiratory distress; no murmur; normal cardiovascular exam; social history is key
Gastro-oesophageal reflux disease	Regurgitation, irritability, feeding refusal; no respiratory distress at rest; no murmur
Anaemia (severe)	Pallor; flow murmur possible but soft and systolic; tachycardia; check FBC

Clinical Approach — Always Listen and Feel

When faced with an infant with poor feeding and tachypnoea, auscultate the heart (murmur? loud P2? gallop?), palpate the precordium (heave? thrill? displaced apex?), feel the femoral pulses, and check the liver (hepatomegaly?). A chest X-ray looking for cardiomegaly and pulmonary plethora, and a four-limb blood pressure can rapidly narrow the differential. Echocardiography is the definitive investigation.

Point	Detail
Murmur location	PSM at LLSB (perimembranous/muscular) or LUSB (subarterial) — distinguishes from AS (RUSB), ASD (LUSB + ESM), PDA (continuous)
Timing of HF	1–2 months (not neonatal) — distinguishes from duct-dependent lesions
S2 character	Loud P2 in large VSD — distinguishes from PS (soft P2) and ASD (fixed split)
Femoral pulses	Normal in VSD — distinguishes from coarctation (absent/weak)
Pulse pressure	Normal in VSD — distinguishes from PDA (wide) and AS (narrow)
ECG axis	Normal or LV overload in VSD — distinguishes from AVSD (superior axis)

High Yield Summary

Differential diagnosis of VSD centres on two clinical scenarios:

Asymptomatic systolic murmur: Differentiate from innocent murmur (soft, systolic, short, asymptomatic, changes with posture), other acyanotic CHD (ASD, PS, AS, PDA, MR, HCM), and coarctation (feel the femorals!).
Heart failure at 1–2 months: Differentiate from other large L-to-R shunts (AVSD, PDA) ^[1] which present at a similar age, and from duct-dependent systemic lesions (coarctation, interrupted arch, critical AS, HLHS) which present earlier (day 2–7) with shock ^[2].

Key discriminators: Murmur character and location, timing of HF onset, S2 character, femoral pulses, pulse pressure, ECG axis, and syndromic features. Echocardiography is the definitive differentiating investigation.

Heart failure in CHD is more likely due to structural defects → excessive volume/pressure load instead of myocardial dysfunction ^[2]. Timing of HF is essential ^[2].

Active Recall - Differential Diagnosis of VSD

References

^[1] Lecture slides: GC 147. Heart failure and cyanosis in children acyanotic and cyanotic congenital heart disease - Part 1.pdf (p26–28) ^[2] Senior notes: Adrian Lui Pediatrics.pdf (p184, p190, p194, p201, p205) ^[3] Senior notes: Ryan Ho Cardiology.pdf (p185, p193)

Diagnostic Criteria, Algorithm, and Investigations for Ventricular Septal Defect

Investigation Modalities

The CXR is a first-line investigation in any child with suspected cardiac disease. It provides information about heart size, chamber enlargement, and pulmonary vascularity. The findings differ dramatically between small and large VSD:

CXR findings in VSD ^[2]^[3]:

Feature	Large VSD	Small VSD
Heart size	Cardiomegaly (LV dilatation)	Normal
Pulmonary vasculature	Pulmonary plethora	Normal
Specific chambers	LA and LV enlargement; ± PA prominence	Normal cardiac contour
Upper lobe veins	May show upper lobe pulmonary venous distension if significant pHTN	Normal

How to assess on paediatric CXR:

Cardiomegaly: assessed by the cardiothoracic ratio (CTR)
- CTR ≥ 0.5 in children/adults = cardiomegaly ^[2]
- CTR ≥ 0.6 in infants = cardiomegaly ^[2] (the infant heart is proportionally larger, and the thymus can obscure the mediastinal silhouette)

Thymus Trap

The thymus in infants/young children can simulate cardiomegaly → diagnostic difficulty ^[2]. The thymus sits in the anterior superior mediastinum and can make the cardiac silhouette appear wider than it truly is. Look for the classic "sail sign" (thymic shadow overlying the right heart border like a triangular sail). If in doubt, a lateral CXR can help distinguish thymus from true cardiomegaly. Echocardiography resolves any uncertainty.

Pulmonary plethora: increased pulmonary vascular markings extending to the periphery of both lung fields — indicates increased pulmonary blood flow (Qp > Qs). This is the hallmark CXR finding of a significant L-to-R shunt.
- Mechanism: L-to-R shunt (e.g., VSD) → pulmonary plethora + cardiomegaly (volume overload) ^[2]
- Contrast this with pulmonary venous congestion (e.g., MS): pulmonary plethora + hazy venous markings + no cardiomegaly ^[2]
- And with pulmonary outflow obstruction (e.g., TOF): pulmonary oligaemia (decreased vascular markings) ^[2]
Chamber-specific CXR signs ^[2]:
- LV enlargement (LVE): apex extends laterally and points downwards
- LA enlargement (LAE): small bulge on the left cardiac border (the "3rd mogul sign") inferior to the pulmonary artery shadow; also double density sign and splaying of the carina
- RV enlargement (RVE): increased CTR + cardiac apex tilts upwards and displaces laterally → "boot-shaped heart" (though this is more classically seen in TOF)

In a small VSD, the CXR is completely normal. This is an important point — you cannot "rule in" a small VSD on CXR, and a normal CXR does not exclude VSD.

2. Electrocardiogram (ECG)

ECG is an essential diagnostic tool ^[2] in paediatric cardiology. It provides information about chamber hypertrophy/dilatation, conduction abnormalities, and rhythm. Understanding the paediatric ECG requires appreciating age-related normal values.

ECG findings depend on VSD size ^[2]^[3]:

Feature	Large VSD	Small VSD
Overall	Multiple abnormalities	Normal
Axis	May be normal or left	Normal
LVH	Left axis deviation with tall R in V6, deep S in V1	Absent
LAE	P wave duration ≥ 0.10s → may be notched or biphasic	Absent
± RVH	Right axis deviation with tall R in V1, deep S in V6 (if significant pHTN)	Absent
± RAE	Tall and peaked P waves ≥ 3mm (if significant pHTN)	Absent
Katz-Wachtel phenomenon	Biphasic (large equiphasic) QRS complexes in mid-precordial leads V2–V5 — classical for VSD	Absent
LV strain	± LV strain pattern with inverted T in V6 or I	Absent

Let's understand each of these from first principles:

Why LVH? The large VSD causes a significant L-to-R shunt → increased pulmonary venous return → LV volume overload → LV dilation and hypertrophy → tall R waves in left-sided leads (V5, V6, I, aVL) and deep S waves in right-sided leads (V1, V2) ^[2].

Why LAE? The increased pulmonary venous return also overloads the LA → LA dilation → prolonged P wave duration (≥ 0.10s), notched P wave ("P mitrale") in lead II, and biphasic P wave in V1 ^[2].

Why RVH (when present)? If pulmonary hypertension develops, the RV faces increased afterload (pressure overload) → RV hypertrophy → tall R in V1, deep S in V6, right axis deviation. Upright T wave in V1 in children 3 days to 6 years suggests RVH ^[2].

Why RAE (when present)? Advanced pHTN → RV dysfunction → tricuspid regurgitation → RA pressure overload → RA enlargement → tall, peaked P waves ("P pulmonale") ≥ 3mm in lead II ^[2].

Katz-Wachtel phenomenon ^[2]^[3]: This is a classic exam favourite. It refers to large equiphasic QRS complexes in mid-precordial leads (V2–V5) ^[2]. The mechanism: when both LVH and RVH are present simultaneously (biventricular hypertrophy — LV from volume overload, RV from pressure overload due to pHTN), the electrical forces are large but roughly balanced between left and right → the QRS in the transitional chest leads (V2–V5) is very tall but biphasic (the R and S components are roughly equal in height). Large VSD with pHTN → RV pressure overload + LV volume overload → Katz-Wachtel ^[2].

Mnemonic: Katz-Wachtel = Kombined Wall hypertrophy (biventricular hypertrophy) in VSD.

3. Echocardiography (ECHO) — The Gold Standard

Echocardiography is diagnostic, estimates size, and evaluates haemodynamics ^[2]^[3]. This is the single most important investigation for VSD. It directly visualises the defect and provides comprehensive haemodynamic assessment without radiation or invasiveness.

Parameter	How It's Assessed	Clinical Significance
Defect location	2D imaging in multiple views (parasternal long axis, short axis, apical 4-chamber, subcostal)	Determines VSD type (perimembranous, muscular, subarterial, inlet) — essential for surgical planning and prognosis
Defect size	2D measurement in mm; comparison to aortic annulus diameter	Small ( < 4mm or < 1/3 aortic annulus), moderate (4–6mm), large ( > 6mm or > 2/3 aortic annulus)
Shunt direction	Colour-flow Doppler mapping	L-to-R (red flow towards transducer from LV into RV in parasternal views) confirms acyanotic physiology; bidirectional or R-to-L suggests elevated PVR / Eisenmenger
Shunt velocity / RV pressure	Continuous-wave (CW) Doppler across the VSD using modified Bernoulli equation: ΔP = 4V²	A high-velocity jet (e.g., 4–5 m/s) means a large pressure gradient = restrictive VSD (good). A low-velocity jet (e.g., 1–2 m/s) means pressures are nearly equalised = non-restrictive VSD (bad — pHTN likely). If systolic BP is 80 mmHg and ΔP across VSD is 60 mmHg → estimated RVSP = 80 – 60 = 20 mmHg (normal). If ΔP is only 20 mmHg → RVSP = 60 mmHg (significant pHTN)
Qp:Qs ratio	Calculated from Doppler flow measurements across RVOT and LVOT	Quantifies the magnitude of the shunt: < 1.5:1 = mild, 1.5–2:1 = moderate, > 2:1 = significant
PA pressure estimation	TR jet velocity (if TR present): RVSP = 4V²(TR) + estimated RAP	Estimates pulmonary artery systolic pressure; correlates with severity of pHTN
Chamber dimensions	M-mode and 2D measurements of LA, LV, RV	LA and LV dilation = significant volume overload; RV dilation/hypertrophy = pressure overload from pHTN
Ventricular function	LV ejection fraction (EF), fractional shortening (FS)	Usually preserved in early VSD; depressed EF suggests myocardial dysfunction or very longstanding volume overload
Associated lesions	Comprehensive sweep of all structures	Must rule out: aortic valve prolapse (subarterial VSD → AR), coarctation, AVSD, other complex CHD
Tricuspid valve tissue herniation	Direct visualisation	Perimembranous VSD may be partially occluded by tricuspid valve tissue forming an "aneurysm of the membranous septum" → this is a favourable sign suggesting possible spontaneous closure ^[2]^[3]

VSD Type	Best Echo View	What You See
Perimembranous	Parasternal long axis (PLAX); apical 5-chamber	Defect just below the aortic valve; may see TV tissue partially occluding it
Muscular	Parasternal short axis (PSAX); apical 4-chamber	Defect within the muscular septum; may be multiple ("Swiss cheese")
Subarterial	Parasternal short axis (high PSAX at great vessel level); PLAX	Defect just below both semilunar valves; look for aortic cusp prolapse
Inlet	Apical 4-chamber; subcostal	Defect posterior and inferior, beneath the AV valves; assess AV valve anatomy

Exam Pearl — Subarterial VSD and Aortic Valve Assessment

When a subarterial VSD is identified on echocardiography, the echocardiographer must specifically assess for coronary cusp prolapse and aortic regurgitation (AR) ^[2]^[3]. Use colour Doppler in the parasternal long-axis view to look for an AR jet. Even a small subarterial VSD with early cusp prolapse may warrant early surgical referral to prevent progressive AR — this is especially relevant in the Hong Kong / East Asian population where subarterial VSD is more prevalent ^[2].

4. Cardiac Catheterisation

Cardiac catheterisation is NOT routine for VSD diagnosis — echocardiography suffices in most cases. It is reserved for specific clinical scenarios:

Indication	Rationale
Assessment of PVR	When echo suggests elevated PA pressure and there is concern about Eisenmenger; catheterisation directly measures PA pressure, PVR, and SVR. The key question: is the PVR reversible? This determines operability.
Vasoreactivity testing	In borderline cases, acute vasodilator challenge (inhaled nitric oxide, IV adenosine, or 100% O₂) during catheterisation to see if PVR drops → if it does, the patient may still be operable
Qp:Qs measurement	Gold standard for shunt quantification; uses Fick principle with oximetry: measure O₂ saturations in SVC, PA, PV, and aorta → calculate Qp:Qs = (SaO₂ – SvO₂) / (SpvO₂ – SpaO₂)
Associated complex CHD	When echo cannot fully delineate the anatomy (rare with modern echo/MRI)
Transcatheter device closure	Select muscular VSDs or post-operative residual VSDs may be amenable to percutaneous device closure rather than re-operation

Finding	Interpretation
"Step-up" in O₂ saturation at RV level	Oxygenated blood from LV crosses VSD into RV → O₂ saturation in RV is higher than in RA. A step-up of > 7% at the RV level is significant. This is the hallmark catheterisation finding of VSD.
Elevated PA pressure	PA systolic pressure > 25 mmHg at rest; correlate with severity of pHTN
PVR calculation	PVR = (mean PA pressure – mean LA pressure) / Qp. PVR index > 6–8 Wood units·m² with PVR:SVR > 0.67 suggests inoperable Eisenmenger
Reversibility with vasodilator	If PVR drops > 20% or to < 6 Wood units·m² with nitric oxide challenge → favourable for surgical closure

Investigation	When / Why
Pulse oximetry (pre- and post-ductal)	Neonatal screening; important to exclude cyanotic CHD. In isolated VSD, saturations are normal (≥ 95%). If saturation is low → consider R-to-L shunt (Eisenmenger, cyanotic CHD)
Four-limb blood pressure	To exclude coarctation of aorta (upper limb BP > lower limb BP by > 20 mmHg); should be performed in any child with a cardiac murmur
Full blood count (FBC)	Exclude anaemia (which can unmask or exacerbate HF symptoms); check for polycythaemia in Eisenmenger syndrome
Blood gas (ABG/VBG)	In acutely unwell infant: metabolic acidosis suggests poor cardiac output or shock; respiratory alkalosis from tachypnoea in HF
BNP / NT-proBNP	Elevated in heart failure; can help distinguish cardiac from respiratory causes of tachypnoea in infancy; useful for monitoring treatment response
Renal function, electrolytes	Baseline before starting diuretics and ACE inhibitors; monitor for hypokalaemia (diuretics), hyperkalaemia (ACE inhibitors), and renal impairment
Genetic testing / karyotype	If dysmorphic features suggest a syndromic cause (e.g., Trisomy 21, 22q11.2 deletion)
Antenatal ultrasound	Incidental findings can also be found during antenatal cardiac US in routine anomaly scan ^[2]. Large VSDs may be detected at the 18–22 week anomaly scan; small muscular VSDs are often too small to detect antenatally.

Investigation	Large VSD	Small VSD
CXR	Cardiomegaly (LV dilatation), pulmonary plethora	Normal
ECG	LVH, LAE, ± RVH or even RAE (if significant pHTN); Katz-Wachtel phenomenon: biphasic QRS in V2–V5 (classical for VSD)	Normal
Echo	Diagnostic, estimate size and evaluate haemodynamics — large defect, LA/LV dilatation, elevated PA pressure, ↑Qp:Qs	Diagnostic, estimate size and evaluate haemodynamics — small defect, normal chamber sizes, normal PA pressure
Catheterisation	Reserved for PVR assessment / operability	Not indicated

^[2]^[3]

High Yield Summary

Diagnostic approach to VSD is clinical + echocardiographic:

CXR: Large VSD → cardiomegaly + pulmonary plethora; Small VSD → normal ^[2]^[3]
ECG: Large VSD → LVH, LAE, ± RVH/RAE, Katz-Wachtel phenomenon (biphasic QRS V2–V5, classical for VSD); Small VSD → normal ^[2]^[3]
Echocardiography is the gold standard — diagnostic, determines location/type, estimates size, quantifies shunt (Qp:Qs), assesses PA pressure, and identifies associated lesions including aortic valve prolapse in subarterial VSD ^[2]^[3]
Cardiac catheterisation is reserved for PVR assessment and vasoreactivity testing in suspected Eisenmenger / borderline operability, and for transcatheter device closure
MRI is used when echo is not sufficient, e.g., in complex CHD ^[2]
Remember paediatric ECG norms: RV dominance in neonates is normal; upright T wave in V1 at age 3 days to 6 years suggests RVH; always use age-appropriate criteria ^[2]
Thymus can simulate cardiomegaly on infant CXR — use lateral view or echo to clarify ^[2]
CTR ≥ 0.6 (infants) or ≥ 0.5 (children/adults) = cardiomegaly ^[2]

Active Recall - Diagnosis and Investigations of VSD

References

^[1] Lecture slides: GC 147. Heart failure and cyanosis in children acyanotic and cyanotic congenital heart disease - Part 1.pdf (p26–27) ^[2] Senior notes: Adrian Lui Pediatrics.pdf (p184, p190, p194, p195, p198, p199, p201) ^[3] Senior notes: Ryan Ho Cardiology.pdf (p185, p192, p193) ^[4] Senior notes: Ryan Ho Fundamentals.pdf (p455, p456, p461)

Management of Ventricular Septal Defect in Paediatrics

No treatment in small, asymptomatic VSD ^[2]^[3].

Rationale: Small VSDs ( < 4mm): 75% spontaneously close in < 2 years, others usually benign ^[2]^[3]. The risk of surgical intervention far outweighs the minimal haemodynamic consequence.

What "conservative management" actually involves:

Component	Detail	Rationale
Regular follow-up	Clinical review + echocardiography at intervals (e.g., 6–12 monthly initially, then annually)	Monitor for: spontaneous closure, progressive shunting, development of AR (especially subarterial type), infective endocarditis signs
Endocarditis awareness	Educate parents about maintaining good dental hygiene; prompt treatment of febrile illness	Infective endocarditis can occur regardless of VSD size ^[2]^[3]. However, current guidelines (AHA/ESC 2021–2023 and Hong Kong practice) do NOT recommend routine antibiotic prophylaxis for isolated unrepaired VSD unless there is a prior history of IE or the VSD is adjacent to prosthetic material. This represents a change from older practice.
Growth monitoring	Plot on growth chart at each visit	Early detection of failure to thrive (weight plateau → length → HC) that might indicate haemodynamic deterioration
Activity	No restriction for small VSD	Child can participate fully in sports and physical activity
Immunisations	Standard childhood immunisation schedule + annual influenza vaccine + RSV prophylaxis (palivizumab) if indicated	Children with haemodynamically significant CHD are at risk of severe RSV bronchiolitis — but for small VSD, standard immunisations suffice

Antibiotic Prophylaxis — Updated Guidance

Current AHA (2021) and ESC (2023) guidelines have significantly narrowed the indications for infective endocarditis prophylaxis. For an isolated, unrepaired VSD without prior IE, routine antibiotic prophylaxis before dental procedures is generally not recommended. Prophylaxis IS recommended for: (1) prosthetic valve or prosthetic material used for VSD repair, (2) previous IE, (3) unrepaired cyanotic CHD, (4) repaired CHD with residual defects at or adjacent to the site of prosthetic patch/device. Always check local HK practice guidelines.

2. Medical Management of Heart Failure

Medical treatment of HF in symptomatic VSD (due to chance of spontaneous closure) ^[2]^[3].

The goal is to control symptoms (reduce pulmonary congestion, improve growth, reduce cardiac work) while buying time for either spontaneous closure or planned surgical repair.

Management of Paediatric Heart Failure ^[1]:

Identification of the cause and precipitating factors
Tackling of precipitating factors
General supportive management
Medical therapy of heart failure (diuretics, digoxin, ACEI, carvedilol)
Treatment of underlying cause, if possible, by surgical or catheter intervention
Mechanical circulatory support and heart transplantation

Before escalating therapy, always ask: what has made this child worse right now?

Precipitant	Action
Infection (respiratory tract infection, pneumonia)	Treat with appropriate antibiotics/antivirals; respiratory support
Anaemia	Transfuse if symptomatic; investigate cause
Arrhythmia	Treat according to type (e.g., SVT → vagal manoeuvres → adenosine)
Electrolyte disturbance	Correct; common with diuretic use (hypokalaemia, hyponatraemia)
Non-adherence to medications	Parental education; simplify regimen

General supportive management ^[1]^[2]:

Measure	Detail	Mechanism / Rationale
Nutritional support: high caloric diet	Calorie-dense formula (up to 1 kcal/mL or 30 kcal/oz); medium-chain triglyceride (MCT) supplementation; nasogastric (NG) tube feeds if oral intake insufficient	↑ metabolic demand in HF means the infant needs more calories but takes in fewer (poor feeding from tachypnoea). Continuous NG feeds bypass the problem of fatigue during oral feeding. Aim for 120–150 kcal/kg/day (vs. normal ~100 kcal/kg/day for infants) ^[2]
Fluid restriction	Restrict fluid intake (typically ~120–150 mL/kg/day rather than the normal ~150–180 mL/kg/day in infants)	Reduce preload → reduce pulmonary congestion. Must balance against adequate caloric intake — hence the need for calorie-dense formula ^[2]
Bed rest with elevation of bed head	Elevate head of cot/bed to 30°	Improve lung function — reduces work of breathing by allowing gravitational drainage of pulmonary oedema from apices; reduces diaphragmatic splinting from hepatomegaly ^[2]
Oxygen: use with CAUTION in large L-to-R shunts	Supplement O₂ only if SpO₂ < 92% or significant respiratory distress	Caution in large L-to-R shunt: ↑PAO₂ → pulmonary vasodilation → ↓PVR → ↑shunting ^[2]. Giving oxygen to an infant with a large VSD can paradoxically worsen heart failure by increasing the L-to-R shunt. Use judiciously.
RSV prophylaxis	Palivizumab (anti-RSV monoclonal antibody) during RSV season for infants with haemodynamically significant CHD	Prevents severe RSV bronchiolitis which can be catastrophic in an infant already in HF

Oxygen Paradox in L-to-R Shunts

Caution in large L-to-R shunt (e.g., VSD): ↑PAO₂ → pulmonary vasodilation → ↓PVR → ↑shunting ^[2]. This is a common exam trap. Supplemental oxygen is a potent pulmonary vasodilator — in a child with a large VSD, it reduces PVR and thereby increases the left-to-right shunt, worsening pulmonary overcirculation and heart failure. Only give O₂ if truly hypoxaemic (SpO₂ < 92%), not routinely for tachypnoea alone.

C. Pharmacological Therapy

Medical therapy of heart failure: diuretics, digoxin, ACEI, carvedilol ^[1]

Let's go through each drug class with paediatric-specific dosing and rationale:

Drug	Class	Mechanism	Paediatric Dose	Key Points
Furosemide (frusemide)	Loop diuretic	Blocks Na⁺/K⁺/2Cl⁻ co-transporter in the thick ascending limb of Loop of Henle → inhibits NaCl and water reabsorption → ↓ intravascular volume → ↓ preload → ↓ pulmonary congestion	PO: 1–2 mg/kg/dose 1–3× daily; IV: 0.5–1 mg/kg/dose	First drug started in symptomatic VSD. Rapid symptom relief (reduces tachypnoea, hepatomegaly). Monitor for hypokalaemia, hyponatraemia, metabolic alkalosis, ototoxicity (high doses).
Spironolactone	Potassium-sparing diuretic (mineralocorticoid receptor antagonist = MRA)	Blocks aldosterone in the distal convoluted tubule and collecting duct → mild diuresis + K⁺ retention. Also anti-fibrotic effects on the myocardium.	PO: 1–3 mg/kg/day in 1–2 divided doses	Often combined with furosemide to counteract K⁺ loss. The aldosterone-blocking effect also reduces cardiac remodelling. Monitor for hyperkalaemia (especially with concurrent ACEI).
Hydrochlorothiazide	Thiazide diuretic	Blocks Na⁺/Cl⁻ co-transporter in the distal convoluted tubule	PO: 1–2 mg/kg/day	Sometimes added for resistant oedema (sequential nephron blockade with furosemide). Watch for hypokalaemia, hyponatraemia.

Why diuretics first? In VSD with HF, the primary problem is volume overload from excessive pulmonary blood flow returning to the left heart. Diuretics reduce intravascular volume, thereby reducing preload to the LA/LV, which reduces pulmonary congestion and symptoms. They do NOT fix the underlying defect — they just buy time.

Drug	Mechanism	Paediatric Dose	Key Points
Captopril	Inhibits angiotensin-converting enzyme → ↓ angiotensin II → ↓ SVR (afterload reduction) + ↓ aldosterone → ↓ fluid retention	Neonates: 0.05–0.1 mg/kg/dose TDS (start LOW); Infants: 0.1–0.5 mg/kg/dose TDS; Children: 0.5–1 mg/kg/dose TDS	Short-acting, allows careful dose titration. Most commonly used ACEI in neonates/infants due to flexibility.
Enalapril	Same as captopril but longer-acting (prodrug converted to enalaprilat)	PO: 0.05–0.1 mg/kg/day initially, ↑ to 0.1–0.5 mg/kg/day in 1–2 doses	Longer-acting, better compliance. Used in older infants/children.

Why ACE inhibitors in VSD? The key concept: by reducing SVR, ACEI increases the proportion of LV output that goes into the aorta (systemic circulation) rather than through the VSD into the RV and lungs. This favourably redirects flow away from the pulmonary circulation → reduces pulmonary overcirculation → reduces pulmonary congestion → reduces LV volume overload. Additionally, ACEI blocks neurohormonal activation (RAAS) that is upregulated in HF, reducing harmful cardiac remodelling.

Side Effects	Monitoring
Hypotension (especially first dose in neonates — start VERY low)	BP monitoring before and after first dose
Hyperkalaemia (especially with spironolactone)	Serum K⁺ regularly
Renal impairment (↓ renal perfusion if pre-renal state)	RFT (creatinine, urea)
Cough (due to ↑ bradykinin)	Clinical monitoring
Teratogenic	Not relevant in paediatric age, but important for adolescent females

Drug	Mechanism	Paediatric Dose	Key Points
Digoxin	Inhibits Na⁺/K⁺-ATPase on cardiac myocytes → ↑ intracellular Na⁺ → ↑ intracellular Ca²⁺ via Na⁺/Ca²⁺ exchanger → ↑ contractility (positive inotrope). Also ↑ vagal tone → ↓ HR (negative chronotrope).	Loading: 10–15 µg/kg PO in divided doses (neonates/infants); Maintenance: 5–10 µg/kg/day PO in 2 divided doses	Digoxin: seldom used due to narrow therapeutic index ^[2]. Risk of toxicity (nausea, vomiting, arrhythmias, visual disturbance). Requires drug level monitoring (therapeutic range 0.8–2.0 ng/mL). Toxicity enhanced by hypokalaemia (from diuretics) — must monitor K⁺. Still used in some centres as adjunctive therapy.

Digoxin in Paediatric HF — Proceed with Caution

Digoxin is seldom used due to its narrow therapeutic index ^[2]. In the paediatric setting, the margin between therapeutic and toxic doses is very small. Toxicity is potentiated by hypokalaemia (common from furosemide use), hypomagnesaemia, hypothyroidism, and renal impairment. Signs of toxicity in infants: poor feeding, vomiting, bradycardia, new arrhythmias. Always check the serum potassium before giving digoxin and monitor drug levels.

Drug	Mechanism	Paediatric Dose	Key Points
Carvedilol	Non-selective β-blocker + α1-blocker → ↓ HR (↓ myocardial O₂ demand) + vasodilation (↓ afterload) + anti-remodelling effects	Start: 0.05 mg/kg/dose BD; Titrate slowly to 0.2–0.4 mg/kg/dose BD	Used in chronic HF management. Must be started at very low dose and titrated slowly — acute β-blockade can worsen HF by ↓ contractility. Contraindicated in acute decompensated HF.

Stage D: above + IV inotropes (e.g., dobutamine), diuretics, non-drug Tx ^[2]

Agent	Mechanism	Use in VSD
IV Dobutamine	β1-agonist → ↑ contractility + mild vasodilation	Acute decompensated HF; bridge to surgery
Milrinone	Phosphodiesterase-3 inhibitor ("inodilator" = inotrope + vasodilator) → ↑ contractility + ↓ SVR + ↓ PVR	Excellent in paediatric HF — provides inotropy AND afterload reduction. Particularly useful post-operatively.
IV Nitroprusside	Direct NO donor → arterial + venous dilation → ↓ preload + ↓ afterload	Acute HF with hypertension; requires continuous BP monitoring. Risk of cyanide toxicity with prolonged use.
IV Furosemide	As above but IV for rapid effect	Acute pulmonary oedema

Paediatric HF staging ^[2]:

Stage	Description	Medical Therapy
A	At risk of HF but no structural/functional abnormality	No specific treatment ^[2]
B	Structural/functional abnormality, no symptoms	ACEI/ARB + BB (e.g., carvedilol) ^[2]
C	Structural disease with current or previous HF symptoms	ACEI/ARB + BB + MRA ± diuretics for fluid overload ^[2]
D	Refractory HF requiring specialised interventions	Above + IV inotropes, mechanical circulatory support, transplant ^[2]

3. Surgical Management

Surgical closure if: ^[2]^[3]

Indication	Definition / Criteria	Rationale
Refractory to maximal medical treatment	Refractory HF, failure to thrive, recurrent chest infections despite optimal medical therapy	If medical therapy cannot control symptoms, the child is not growing, and the natural history is not heading towards spontaneous closure → surgery is needed to prevent irreversible complications ^[2]^[3]
Moderate/severe VSD with pHTN	Defined as pulmonary arterial pressure > 50% systemic	Persistent elevated PA pressure indicates significant haemodynamic burden and risk of progressive pulmonary vascular disease → early closure prevents Eisenmenger ^[2]^[3]
Persistent L-to-R shunt with LV dilatation	Defined as Qp:Qs > 2:1	Significant volume overload is present; the LV is dilating; waiting further is unlikely to result in spontaneous closure and risks LV dysfunction ^[2]^[3]
Unlikely to close spontaneously	e.g., subarterial defect, associated with RVOT infundibular stenosis	Subarterial VSDs do NOT close spontaneously and carry risk of progressive aortic valve prolapse/AR. RVOT infundibular stenosis complicates the haemodynamics further. ^[2]^[3]
History of infective endocarditis	Previous episode of IE	Ongoing VSD provides a nidus for recurrent IE ^[2]^[3]

Contraindication: PAP suprasystemic or PVR > 12 Wood units (WU) → risk of precipitating acute RV HF + ↓ LV output ^[2]^[3]

This is the Eisenmenger situation. Let's understand why surgery is contraindicated from first principles:

In Eisenmenger syndrome, PVR is fixed at suprasystemic levels
The RV is now pumping against a massively elevated afterload (fixed high PVR)
The VSD acts as a "pop-off valve" — the RV can decompress by shunting blood R-to-L through the VSD into the LV and aorta
If you close the VSD surgically, the RV loses its escape route → it faces the full brunt of the suprasystemic PVR → acute RV failure (cannot generate enough output against fixed high PVR)
Simultaneously, the LV loses the contribution of R-to-L shunt blood to its output → ↓ LV output → cardiogenic shock → death

Caution: PAP 75–100% systemic, PVR 8–12 WU → associated with ↑ risk of perioperative complications ^[2]^[3] — these are the "borderline" cases where vasoreactivity testing at cardiac catheterisation helps determine operability.

PVR / PAP	Management
PVR < 8 WU, PAP < 75% systemic	Safe to proceed with surgery
PVR 8–12 WU, PAP 75–100% systemic	↑ Risk — vasoreactivity testing, case-by-case ^[2]^[3]
PVR > 12 WU or PAP suprasystemic	Surgery CONTRAINDICATED ^[2]^[3]

Surgical Procedures

Parameter	Detail
Procedure	Open-heart surgery via median sternotomy with cardiopulmonary bypass (CPB). The VSD is closed with a synthetic patch (e.g., Dacron or Gore-Tex) or autologous pericardial patch, sutured to the margins of the defect.
Mortality	Low mortality ( < 1%) ^[2]^[3]
Re-operation rate	Low
Advantages	Definitive; applicable to all VSD types and sizes; well-established technique with excellent long-term outcomes
Risks	Complete heart block (damage to AV node/His bundle — especially perimembranous VSD; risk ~1–3%), residual VSD (patch leak), tricuspid regurgitation, aortic regurgitation (if subarterial with prior cusp prolapse), post-CPB complications

Surgical approach varies by VSD type:

VSD Type	Surgical Approach
Perimembranous	Right atrial approach (through RA → tricuspid valve → access the VSD from the RV side). Careful suture placement to avoid the conduction system (His bundle runs along the posteroinferior margin).
Muscular	Can be approached via RA, or via right or left ventriculotomy for apical defects. Multiple muscular ("Swiss cheese") VSDs are technically challenging — may require combined surgical + device approach.
Subarterial	Approached via pulmonary arteriotomy or right atrial approach. Aortic valve must be inspected; if the coronary cusp has prolapsed, concurrent aortic valve repair (valvuloplasty) or replacement may be needed.
Inlet	Via RA approach, similar to AVSD repair.

Parameter	Detail
Procedure	Percutaneous approach (via femoral vein/artery); a septal occluder device (e.g., Amplatzer™ muscular VSD occluder) is deployed across the defect under fluoroscopic and echocardiographic guidance
Indications	Technically challenging, only in selected patients ^[2]^[3] — primarily for muscular VSDs (especially mid-muscular or apical, which are surgically difficult to access); also for residual post-operative VSDs
Limitations	Long-term outcome uncertain ^[2]^[3]. Perimembranous VSD device closure carries risk of complete heart block (proximity to conduction system) and device embolisation. Subarterial VSD generally not amenable to device closure.
Contraindications	Perimembranous VSD in many centres (too close to aortic and tricuspid valves; risk of conduction block and valvular damage); Eisenmenger syndrome; very young infants (vessel size too small for delivery sheath)

Parameter	Detail
Procedure	A band is placed around the main pulmonary artery to create an artificial stenosis → ↑ resistance to pulmonary flow → ↓ L-to-R shunt → "protects" the pulmonary vasculature from high-pressure high-flow damage
Indication	Now rarely used for isolated VSD (primary repair is preferred). May still be used in: (1) Swiss-cheese multiple muscular VSDs (too many to close surgically in infancy), (2) complex associated anomalies where definitive repair must be delayed, (3) very low birth weight neonates where CPB carries excessive risk
Disadvantages	Does not fix the VSD; creates RV pressure overload and RV hypertrophy; band migration; requires a second operation for debanding + VSD closure

4. Management of Specific Scenarios

Surgery is CONTRAINDICATED ^[2]^[3]. Management is palliative and supportive:

Measure	Detail
Pulmonary vasodilator therapy	Bosentan (endothelin receptor antagonist — "bos-" = blocks endothelin, a potent vasoconstrictor); Sildenafil (PDE-5 inhibitor — ↑ cGMP → pulmonary vasodilation); IV epoprostenol or inhaled iloprost (prostacyclin analogues)
Avoid precipitants of decompensation	Dehydration (↓ preload → ↓ RV output → worsening R-to-L shunt); High altitude/hypoxia (↑ PVR → ↑ R-to-L shunt); Anaesthesia (vasodilation → cardiovascular collapse); Pregnancy (CONTRAINDICATED — maternal mortality ~30–50%)
Phlebotomy	If symptomatic hyperviscosity from severe secondary polycythaemia (Hct > 65%); cautious, with volume replacement
Heart-lung transplantation	Last resort for refractory Eisenmenger; limited by donor availability
Iron supplementation	Relative iron deficiency is common due to chronic erythropoiesis; iron-deficient erythrocytes are less deformable → worsen hyperviscosity symptoms even at lower Hct

Aspect	Detail
Residual defect	Small residual VSDs may be present around the patch margins; usually haemodynamically insignificant; serial echo monitoring
Conduction abnormalities	Risk of complete heart block (especially perimembranous VSD) — may require permanent pacemaker (~1–3% risk)
Valvular regurgitation	TR (from surgery near tricuspid valve), AR (if subarterial with cusp prolapse) — monitor on echo
Endocarditis prophylaxis post-repair	Recommended for 6 months after surgical closure (while prosthetic material endothelialises). After 6 months, if no residual defect → discontinue prophylaxis. If residual defect near prosthetic material → continue prophylaxis indefinitely.
Exercise	After successful closure with no residual haemodynamic issues → no exercise restriction. If residual pHTN or ventricular dysfunction → graded activity guidance.
Growth	Rapid catch-up growth typically occurs after successful repair; document on growth charts

Aspect	Detail
Parental education	Explain the natural history (most close spontaneously); explain why surgery is needed if it is; explain the risks and benefits in age-appropriate language
Feeding support	Lactation consultant involvement; teach parents about nasogastric feeding if needed; reassure that feeding difficulties improve after repair
Psychological support	Cardiac diagnosis in a newborn/infant causes significant parental anxiety; offer support groups, social worker involvement
Developmental surveillance	Children with CHD are at risk of neurodevelopmental delay (from chronic hypoxia, prolonged hospitalisation, CPB); ensure developmental assessments at key milestones
Genetic counselling	If syndromic features or family history of CHD; recurrence risk discussion for future pregnancies
Transition care	Adolescents with repaired VSD need transition to adult congenital heart disease services; discuss contraception (especially if residual pHTN), career, and activity guidance

High Yield Summary

Management of VSD is stratified by size, symptoms, and haemodynamics:

Small, asymptomatic VSD → No treatment; follow-up; endocarditis awareness ^[2]^[3]
Symptomatic VSD → Medical therapy of HF (diuretics, ACEI, ± digoxin, ± carvedilol) to buy time for spontaneous closure ^[1]^[2]^[3]
Surgical closure (usually < 6 months) if: refractory HF/FTT/recurrent LRTI; PA pressure > 50% systemic; Qp:Qs > 2:1; unlikely to close (subarterial); prior IE ^[2]^[3]
1st line surgical procedure: direct patch closure (mortality < 1%); transcatheter closure in selected muscular VSDs only ^[2]^[3]
Surgery CONTRAINDICATED if PAP suprasystemic or PVR > 12 WU → Eisenmenger → pulmonary vasodilator therapy ^[2]^[3]
Caution with O₂ in large L-to-R shunts — ↓PVR → ↑shunting ^[2]
Digoxin seldom used due to narrow therapeutic index ^[2]
Subarterial VSD: early surgical referral regardless of size (no spontaneous closure + progressive AR risk) — especially important in Hong Kong/East Asian populations

Active Recall - Management of VSD

References

^[1] Lecture slides: GC 147. Heart failure and cyanosis in children acyanotic and cyanotic congenital heart disease - Part 1.pdf (p26–27, p36–38) ^[2] Senior notes: Adrian Lui Pediatrics.pdf (p200, p201, p202, p205) ^[3] Senior notes: Ryan Ho Cardiology.pdf (p193, p194)

Complications of Ventricular Septal Defect

Complications of VSD can be conceptualised as arising from the natural history of the unrepaired defect, from the specific anatomical subtype, or from the surgical repair itself. Let's work through each systematically, explaining the "why" behind every complication from first principles.

Category	Complications
Haemodynamic (unrepaired)	Heart failure, pulmonary hypertension, Eisenmenger syndrome
Infectious	Infective endocarditis, recurrent lower respiratory tract infections
Anatomical subtype-specific	Aortic regurgitation (subarterial VSD), RVOT infundibular stenosis (perimembranous/outlet VSD)
Growth and development	Failure to thrive, neurodevelopmental delay
Post-surgical	Complete heart block, residual VSD, tricuspid regurgitation, aortic regurgitation, post-pericardiotomy syndrome

2. Pulmonary Hypertension and Eisenmenger Syndrome

This is the most feared and irreversible long-term complication of unrepaired large VSD.

Grade	Pathological Change	Reversibility
I	Medial hypertrophy of pulmonary arterioles	Reversible
II	Intimal cellular proliferation	Reversible
III	Intimal fibrosis with medial hypertrophy	Partially reversible — this is the borderline
IV	Progressive intimal fibrosis with plexiform lesions beginning	Irreversible
V	Plexiform lesions, angiomatoid lesions, thinning of media	Irreversible
VI	Necrotising arteritis	Irreversible

Clinical significance: Surgical closure of VSD can reverse grades I–II and possibly III, but is contraindicated at grades IV–VI (Eisenmenger). This is why early repair (before 6 months) is crucial for large VSDs — to operate before irreversible vascular changes develop.

Lesion	Typical Age of Eisenmenger	Why?
Large VSD	Early childhood (can be as early as 1–2 years) ^[2]^[3]	Exposes pulmonary vasculature to systemic-level pressure (non-restrictive VSD equalises pressures)
Large PDA	Early childhood (similar to VSD)	Also transmits systemic pressure to PA
Large ASD	3rd–4th decade (rare, < 10%) ^[3]	ASD transmits volume but not pressure (atrial pressures are low); therefore, pulmonary vascular damage occurs much more slowly

Eisenmenger incidence: up to 80% in large VSD and PDA in infancy/early childhood if unrepaired ^[3]

Complications of Eisenmenger syndrome ^[2]^[3]:

System	Complications	Mechanism
Cardiac	Progressive right heart failure, arrhythmia, IE (rare)	RV progressively fails against fixed elevated PVR; chronic RV dilation predisposes to re-entrant arrhythmias (atrial flutter, AF, VT)
Pulmonary	Pulmonary artery thrombosis, massive haemoptysis due to rupture of major vessel	Sluggish flow in dilated, diseased pulmonary arteries → in-situ thrombosis. Enlarged bronchial arteries (collateral supply) → rupture → massive haemoptysis
Systemic	Stunted growth from hypoxia, polycythaemia, cerebral embolism/abscess	Chronic hypoxaemia → reactive erythrocytosis (polycythaemia) → hyperviscosity → ↑ risk of stroke. R-to-L shunt bypasses pulmonary filter → paradoxical embolism → brain abscess or stroke

Prognosis: 30–40% 10-year mortality with mean age of death at 37 years if transplant not done ^[2]^[3]

3. Infective Endocarditis

Infective endocarditis (regardless of size) ^[2]^[3]

This is a complication that affects VSDs of all sizes, including small, haemodynamically insignificant defects.

4. Aortic Regurgitation (Subarterial VSD)

Subarterial VSD: associated with coronary cusp prolapse and AR ^[2]^[3]

This is an anatomical subtype-specific complication particularly important in the Hong Kong / East Asian population.

5. Acquired RVOT Infundibular Stenosis (Double-Chambered Right Ventricle)

6. Recurrent Lower Respiratory Tract Infections

7. Failure to Thrive and Growth Impairment

The growth impairment in moderate-to-large VSD is multifactorial:

Factor	Mechanism
↑ Energy expenditure	Increased cardiac work (↑ heart rate, ↑ stroke volume) + increased respiratory work (tachypnoea, accessory muscle use) → resting metabolic rate is 25–50% higher than normal
↓ Energy intake	Tachypnoeic infant cannot coordinate suck-swallow-breathe effectively → feeds are slow, effortful, and often incomplete; sweating and exhaustion during feeds
Recurrent infections	Each infection is a catabolic event; anorexia of illness further reduces intake
Malabsorption	Gut mucosal oedema from venous congestion (in severe HF) → impaired nutrient absorption

8. Neurodevelopmental Delay

9. Complications of Surgical Repair

Direct patch closure (1st line): open heart operation, associated with low mortality ( < 1%) and re-operation rate ^[2]^[3] — but complications, though uncommon, do occur:

Aspect	Detail
Incidence	~1–3% of surgical VSD closures
Mechanism	The atrioventricular (AV) node lies at the apex of the triangle of Koch, and the His bundle penetrates through the membranous septum, running along the posteroinferior margin of a perimembranous VSD. Sutures placed to secure the patch can directly injure or oedematously compress the conduction system.
Presentation	Bradycardia intra-operatively or in the immediate post-operative period; haemodynamic instability
Management	Temporary epicardial pacing wires (placed at surgery). If CHB persists beyond 7–10 days → permanent pacemaker required. If CHB resolves within 7 days → likely oedema-related → recovery expected.
Prevention	Meticulous surgical technique with sutures placed away from the conduction tissue (on the RV side, staying on the right side of the septum to avoid the His bundle which runs on the LV side)

Exam Pearl — Conduction System and Perimembranous VSD

The His bundle runs along the posteroinferior rim of a perimembranous VSD. Surgeons place sutures on the right (RV) side of the septum margin, slightly away from the edge of the defect, to avoid the His bundle. Despite this, complete heart block remains the most significant surgical complication of perimembranous VSD repair.

Aspect	Detail
Incidence	~5–10% immediately post-op (many are trivial and close spontaneously); clinically significant residual VSD in < 2%
Mechanism	Incomplete patch coverage, suture dehiscence, or additional unrecognised muscular VSDs
Detection	Intra-operative transoesophageal echocardiography (TOE); post-operative transthoracic echocardiography
Management	Small residual VSD → observe (most are haemodynamically insignificant); large residual → re-operation or transcatheter device closure

Aspect	Detail
Mechanism	Perimembranous VSD repair requires retraction of the tricuspid valve septal leaflet for exposure → can damage the leaflet, chordae, or papillary muscle → post-operative TR
Prevention	Gentle retraction; some surgeons place the patch partially on the tricuspid valve tissue (detachment then reattachment technique)
Clinical significance	Mild TR is common and usually well-tolerated; moderate-to-severe TR is rare and may require valve repair

Aspect	Detail
Incidence	~10–30% of all open-heart surgeries in children
Mechanism	Autoimmune inflammatory response to surgical trauma of the pericardium. Pericardial injury exposes cardiac antigens → immune-mediated pericarditis (similar mechanism to Dressler syndrome post-MI)
Timing	Typically 1–6 weeks post-operatively
Features	Fever, chest pain (pleuritic), pericardial friction rub, pericardial effusion (can progress to tamponade), pleural effusion
Diagnosis	Echocardiography (pericardial effusion); elevated ESR/CRP; clinical features
Management	NSAIDs (first-line); corticosteroids for refractory cases; colchicine for prevention of recurrence; pericardiocentesis if tamponade develops

Complication	Mechanism
Patch infection / endocarditis	Foreign material (synthetic patch) provides a nidus for bacterial colonisation; endocarditis prophylaxis recommended for 6 months post-repair
Wound infection / mediastinitis	Post-sternotomy; rare but serious
Diaphragmatic paresis	Phrenic nerve injury during surgery → elevated hemidiaphragm → respiratory compromise (especially in infants where diaphragmatic breathing is dominant)
Chylothorax	Injury to the thoracic duct during surgery → chylous pleural effusion → nutritional loss (lymph contains fat, protein, lymphocytes)

Complication	Applies To	Mechanism (Brief)	Timing
Heart failure	Moderate-to-large VSD	↓PVR → ↑L-to-R shunt → pulmonary overcirculation → LV volume overload	1–2 months of age
Pulmonary hypertension	Large unrepaired VSD	Chronic high-flow high-pressure → pulmonary vascular remodelling	Months to years
Eisenmenger syndrome	Large unrepaired VSD	Irreversible ↑PVR → shunt reversal → cyanosis	Early childhood if large ^[2]^[3]
Infective endocarditis	Regardless of size ^[2]^[3]	Turbulent jet → endothelial damage → nidus for infection	Any age
Aortic regurgitation	Subarterial VSD ^[2]^[3]	Unsupported coronary cusp prolapse into defect	Progressive; childhood
RVOT infundibular stenosis	Perimembranous/outlet VSD	Reactive muscle hypertrophy from jet impact	Months to years
Recurrent LRTI	Moderate-to-large VSD	Pulmonary congestion → airway oedema → mucus stasis	Infancy
Failure to thrive	Moderate-to-large VSD	↑ energy expenditure + ↓ intake	Infancy
Neurodevelopmental delay	Any significant VSD	Chronic illness, ↓ perfusion, hospitalisations, CPB	Childhood
Complete heart block	Post-surgical (perimembranous)	His bundle injury during suturing	Intra/post-operative
Residual VSD	Post-surgical	Incomplete patch coverage / suture dehiscence	Post-operative
Post-pericardiotomy syndrome	Post-surgical	Autoimmune pericarditis	1–6 weeks post-op

High Yield Summary

Key complications of VSD to remember:

Eisenmenger syndrome — irreversible complication of large unrepaired VSD; up to 80% incidence in infancy/early childhood if unrepaired; triad of congenital L-to-R shunt + pulmonary arterial disease + cyanosis; prognosis: 30–40% 10-year mortality, mean age of death 37 years ^[2]^[3]
Infective endocarditis — regardless of VSD size ^[2]^[3]; turbulent jet damages endocardium creating a nidus; prior IE is an indication for surgical closure
Aortic regurgitation — specific to subarterial VSD; coronary cusp prolapse; particularly prevalent in Chinese ^[2]; requires early surgical closure regardless of defect size
Heart failure at 1–2 months (moderate-to-large VSD) — reversible with medical and surgical management
Apparent improvement in HF may indicate developing Eisenmenger (↑PVR → ↓shunting) or infundibular stenosis — not always a good sign ^[2]^[3]
Complete heart block post-repair (~1–3%) — His bundle runs along the posteroinferior margin of perimembranous VSD; may require permanent pacemaker
Eisenmenger complications: progressive RHF, arrhythmia, PA thrombosis, massive haemoptysis, polycythaemia, cerebral embolism/abscess, stunted growth ^[2]^[3]

Active Recall - Complications of VSD

References

^[1] Lecture slides: GC 147. Heart failure and cyanosis in children acyanotic and cyanotic congenital heart disease - Part 1.pdf (p26–27) ^[2] Senior notes: Adrian Lui Pediatrics.pdf (p193, p201, p202, p203) ^[3] Senior notes: Ryan Ho Cardiology.pdf (p186, p193, p194)

Ventricular Septal Defect

Definition

Epidemiology

Risk Factors

Genetic / Chromosomal

Maternal / Environmental

Syndromic Associations

Anatomy and Function of the Interventricular Septum

Components of the Interventricular Septum

Important Adjacent Structures

Normal Function

Aetiology

Congenital (vast majority in paediatrics)

Acquired (rare in paediatrics, included for completeness)

Classification

By Anatomical Location (most clinically relevant)

By Size

By Haemodynamic Effect

Pathophysiology

Fetal Life

Postnatal Transition

Haemodynamic Consequences of L-to-R Shunt

The "Qp:Qs Ratio"

Consequences of Pulmonary Overcirculation

Pulmonary Vascular Disease and Eisenmenger Syndrome

Natural History

Clinical Features

Symptoms

Small VSD

Moderate-to-Large VSD

Eisenmenger Syndrome (late, if unrepaired large VSD)

Infective Endocarditis (any size VSD)

Signs

General Examination

Precordium

Auscultation — The Murmurs of VSD

Summary Table: Signs by VSD Size

Age-Specific Considerations in Paediatrics

Growth and Development Impact

Communication and Family-Centred Care

Active Recall - Ventricular Septal Defect

References

Clinical Scenario 1: Systolic Murmur in an Infant or Child

Innocent Murmurs

Structural Heart Disease Mimicking VSD — Acyanotic Lesions with Systolic Murmur

Clinical Scenario 2: Heart Failure in Infancy

Differentiating Large L-to-R Shunt Lesions (HF at 1–2 months)

Duct-Dependent Systemic Lesions (HF / Shock in First Week)

Differential by Presentation — Syndromic Associations

Non-Cardiac Differential Diagnoses

Systematic Differential Diagnosis Algorithm

Summary: Key Differentiating Points for VSD

Active Recall - Differential Diagnosis of VSD

Diagnostic Criteria — Conceptual Framework

Diagnostic Algorithm

Investigation Modalities

1. Chest X-Ray (CXR)

2. Electrocardiogram (ECG)

Paediatric ECG — Key Age-Related Principles

ECG Findings in VSD

3. Echocardiography (ECHO) — The Gold Standard

What Echo Can Tell You

Echo Views for VSD Localisation

4. Cardiac Catheterisation

Indications in Paediatric VSD

Key Catheterisation Findings

5. Cardiac MRI

6. Other Investigations

Summary: Investigation Findings by VSD Size

Active Recall - Diagnosis and Investigations of VSD

Overview — Management Philosophy

Management Algorithm

1. Conservative Management (Small, Asymptomatic VSD)

2. Medical Management of Heart Failure

A. Identification and Tackling of Precipitating Factors

B. General Supportive Measures

C. Pharmacological Therapy

Diuretics — First-Line for Fluid Overload

ACE Inhibitors (ACEI) — Afterload Reduction

Digoxin — Positive Inotrope