Opening in the interventricular septum causing a left-to-right shunt with a harsh holosystolic murmur at the LLSB.
Also known as: VSD, ventricular septal defect, perimembranous VSD, muscular VSD
Overview
Congenital communication between the right and left ventricles producing a left-to-right shunt. Anatomic subtypes include perimembranous (most common, ~80%), muscular, inlet (AV canal type, often Down syndrome), and outlet (supracristal or doubly committed subarterial, more common in Asian populations and prone to AR from prolapse of an aortic cusp into the defect).
Epidemiology
VSD is the most common congenital heart defect overall (excluding bicuspid aortic valve). Accounts for ~30-40% of CHD. Up to 90% of muscular and small perimembranous VSDs close spontaneously by age 10. Also a recognized complication of acute myocardial infarction (3-5 days post-MI, ventricular septal rupture).
Try two board-style Ventricular Septal Defect questions
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Question 1CardiovascularMedium
A 35-year-old male with congenital heart disease develops cyanosis, clubbing, and worsening dyspnea over 5 years. Initially he had a left-to-right shunt. Which of the following complications has most likely developed?
AIsolated tricuspid regurgitation from atrial enlargement
BEisenmenger syndrome
CInfective endocarditis
DRight ventricular hypertrophy without pulmonary disease
ELeft ventricular failure from chronic volume overload
Reveal answer & full explanation
Correct answer: B — Eisenmenger syndrome
AIsolated tricuspid regurgitation from atrial enlargement
BEisenmenger syndrome✓
CInfective endocarditis
DRight ventricular hypertrophy without pulmonary disease
ELeft ventricular failure from chronic volume overload
Why Eisenmenger syndrome is correct
Eisenmenger syndrome develops when an untreated left-to-right shunt (ventricular septal defect (VSD), atrial septal defect (ASD), or patent ductus arteriosus (PDA)) causes progressive pulmonary hypertension over years
Pulmonary vascular resistance eventually exceeds systemic resistance, reversing the shunt to right-to-left and producing cyanosis, clubbing, and polycythemia
Once Eisenmenger syndrome develops, surgical shunt closure is contraindicated because the right ventricle (RV) cannot tolerate the increased afterload
Treatment: pulmonary vasodilators (bosentan, sildenafil); transplantation for advanced disease
Why the others are wrong
Right ventricular hypertrophy without pulmonary disease — RV hypertrophy alone does not explain the reversal of the shunt and cyanosis; pulmonary vascular disease is the key mechanism
Left ventricular failure from chronic volume overload — left-to-right shunts do cause LV volume overload, but the progression to cyanosis reflects right-to-left shunting, not isolated LV failure
Isolated tricuspid regurgitation from atrial enlargement — tricuspid regurgitation does not account for cyanosis or the reversal of shunt direction
Infective endocarditis — congenital shunt lesions such as a VSD or PDA do carry a lifelong endocarditis risk, and subacute endocarditis can cause clubbing, but it runs a course of weeks to months with fever, a changing murmur, and embolic phenomena, and it does not explain years of progressive central cyanosis, which in a patient with a known shunt points to deoxygenated blood reaching the systemic circulation after the shunt reverses to right-to-left.
Question 2CardiovascularMedium
A 6-year-old boy is referred for a murmur found on a routine visit. He is asymptomatic and growing normally. On exam there is a grade 4/6 harsh holosystolic murmur at the lower left sternal border with a palpable thrill. Echocardiography shows a small, restrictive perimembranous ventricular septal defect with normal pulmonary artery pressures. Which factor best accounts for the loudness of his murmur?
AHigh pressure gradient across a small orifice
BIncreased left ventricular contractility
CThin chest wall of a young child
DEnlarged left ventricular cavity size
ELarge volume of left-to-right shunt flow
Reveal answer & full explanation
Correct answer: A — High pressure gradient across a small orifice
AHigh pressure gradient across a small orifice✓
BIncreased left ventricular contractility
CThin chest wall of a young child
DEnlarged left ventricular cavity size
ELarge volume of left-to-right shunt flow
Why High pressure gradient across a small orifice is correct
This is a small, restrictive ventricular septal defect (VSD).
Murmur intensity in a VSD reflects the velocity and turbulence of blood crossing the defect, which depend on the pressure gradient between the high-pressure left ventricle and the lower-pressure right ventricle.
A small (restrictive) defect preserves a large LV-to-RV gradient, so blood jets across the narrow opening at high velocity, generating a loud, harsh holosystolic murmur often with a palpable thrill.
Why the others are wrong
Increased left ventricular contractility — a more forceful ventricle raises jet velocity somewhat, but contractility is normal in this asymptomatic child and murmur intensity here is set by the trans-septal pressure difference, not by inotropy.
Thin chest wall of a young child — a thin chest wall transmits sound more efficiently and can make any murmur seem louder, but transmission alone does not generate a grade 4/6 murmur with a palpable thrill, which requires high-velocity turbulent flow.
Enlarged left ventricular cavity size — an enlarged left ventricular cavity reflects chronic volume overload from a large shunt but does not determine the loudness of the murmur, which is governed by the trans-septal gradient and flow velocity.
Large volume of left-to-right shunt flow — it is natural to assume a louder murmur means a bigger shunt, but a small restrictive defect carries little shunt volume; intensity reflects jet velocity from the preserved LV-to-RV gradient, which is why small VSDs are often louder than large ones
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Acquired: ventricular septal rupture after acute MI (anterior or inferior)
Pathophysiology
The magnitude and direction of the shunt depend on defect size and relative resistances of the systemic and pulmonary vascular beds. Restrictive (small) VSDs limit shunt by virtue of high resistance across the defect — produce a loud murmur with little hemodynamic impact. Nonrestrictive (large) VSDs equalize ventricular pressures; shunt magnitude is governed by pulmonary vascular resistance, leading to pulmonary overcirculation, LA and LV volume overload, and eventually pulmonary vascular disease (pulmonary arteriolar medial hypertrophy, intimal proliferation, and later plexiform lesions that raise PVR irreversibly) and shunt reversal (Eisenmenger syndrome).
Clinical presentation
Symptoms
Small VSD: asymptomatic, identified by murmur on routine examination
Moderate-to-large VSD in infancy: poor feeding, diaphoresis with feeds, failure to thrive, tachypnea, recurrent pulmonary infections, signs of HF by 4-8 weeks (as PVR falls)
Post-MI VSD: acute cardiogenic shock, pulmonary edema, new harsh murmur
Signs / physical exam
Harsh holosystolic murmur at left lower sternal border, often with palpable thrill
Smaller defects often produce LOUDER murmurs (high pressure gradient, turbulent flow)
Loud P2, narrow split S2 in pulmonary hypertension
Mid-diastolic rumble at the apex from increased mitral inflow in large shunts
Signs of LV volume overload: displaced apical impulse, S3 gallop
Classic findings
Harsh, blowing holosystolic murmur with palpable thrill at the LLSB; intensity inversely related to defect size in many cases.
Differential diagnosis
Mitral regurgitation — Holosystolic murmur at apex radiating to axilla, not LLSB; echo distinguishes
Tricuspid regurgitation — Holosystolic at LLSB but increases with inspiration (Carvallo sign), prominent V wave on JVP
ASD — Wide and fixed split S2, mid-systolic flow murmur, not holosystolic
Hypertrophic cardiomyopathy with LVOT obstruction — Systolic murmur that increases with Valsalva and standing; bisferiens pulse
Pulmonic stenosis — Mid-systolic ejection murmur at ULSB with ejection click
Post-MI ventricular septal rupture — New harsh holosystolic murmur and thrill 3-7 days after MI with hemodynamic deterioration; echo shows defect, often with RV enlargement and tricuspid jet
Papillary muscle rupture (acute MR) — Also abrupt shock and pulmonary edema with a new holosystolic murmur 2-7 days post-MI (often inferior MI), but the murmur is apical radiating to the axilla, echo shows a flail mitral leaflet, and there is NO oxygen step-up from RA to RV
Diagnostic workup
Labs
Basic labs are typically normal
BNP if HF symptoms
Imaging
Transthoracic echocardiography with color Doppler — diagnostic; defines anatomy, size, shunt direction, chamber size, RV pressure, presence of AR (especially outlet VSD) or AV valve abnormalities
ECG: normal in small VSDs; LA enlargement and LVH with moderate-to-large shunts; biventricular hypertrophy with significant pulmonary HTN; right axis deviation if Eisenmenger
CXR: cardiomegaly, prominent pulmonary vascularity in moderate-to-large shunts; pruning of distal pulmonary arteries in Eisenmenger
Cardiac MRI or CT — useful for complex anatomy or quantifying shunt fraction
Cardiac catheterization with measurement of pulmonary vascular resistance before closure of long-standing large defects
Right-heart catheterization with oximetry: an oxygen saturation step-up from RA to RV localizes a ventricular-level left-to-right shunt (e.g., post-MI septal rupture); bedside echo is usually the first test
Diagnostic algorithm
VSD Type
Anatomic Location
Frequency
Notable Associations
Perimembranous
Membranous septum, just below aortic valve
~80%
Can develop tricuspid pouch, may close spontaneously
Muscular
Trabecular septum
~5-20%
High spontaneous closure rate; may be multiple ('Swiss cheese')
Inlet (AV canal type)
Inferior septum, beneath AV valves
~5-8%
Down syndrome, AV canal defects
Outlet (supracristal / subarterial)
Just below pulmonary valve
~5% (higher in Asians)
AR from aortic cusp prolapse — close even when small
Anatomic subtypes of VSD with characteristic features and management implications.
Treatment
First-line
Small, restrictive, asymptomatic VSD: observation; spontaneous closure is common in muscular and small perimembranous defects
Hemodynamically significant VSD (HF symptoms, growth failure, pulmonary hypertension reversible): surgical patch closure is the standard, typically in infancy or early childhood
Selected muscular VSDs may be amenable to transcatheter device closure
Medical management of HF in infants while awaiting surgery: diuretics (furosemide), digoxin (selected), ACE inhibitor (captopril, enalapril); high-calorie feeds for growth
Second-line / adjunct
Endocarditis prophylaxis NOT routinely required for unrepaired VSD per current AHA guidelines (indicated only for unrepaired cyanotic CHD or palliative shunts/conduits, the first 6 months after complete repair with prosthetic material or a device, or a residual defect at or adjacent to a prosthetic patch or device)
Pulmonary vasodilator therapy (sildenafil, bosentan, ambrisentan) for Eisenmenger physiology; closure is contraindicated when PVR is severely fixed
Heart-lung or lung transplantation for severe Eisenmenger syndrome
Post-MI VSD: urgent surgical repair or transcatheter closure with mechanical circulatory support (IABP, Impella, VA-ECMO) for stabilization
Complications
Heart failure from chronic volume overload
Pulmonary hypertension and Eisenmenger syndrome
Aortic regurgitation (especially outlet/supracristal VSDs with aortic cusp prolapse)
Infective endocarditis (small high-velocity jets can damage the tricuspid valve or RV endocardium)
Arrhythmias and conduction defects (especially after septal patch surgery)
Sudden cardiac death (rare)
PANCE pearls
Counterintuitively, smaller VSDs produce louder murmurs due to greater pressure gradient and turbulent flow; Eisenmenger physiology may extinguish the murmur entirely.
Post-MI ventricular septal rupture occurs 3-7 days after MI, more common with first MI, anterior wall involvement, female sex, and elderly — requires urgent surgical or transcatheter repair.
Outlet (supracristal) VSDs are at high risk of progressive AR from aortic cusp prolapse and warrant closure even when small.
Bedside maneuvers: VSD murmur INCREASES with handgrip (afterload increases the shunt); HCM and MVP murmurs increase with Valsalva, while VSD murmur typically decreases or stays the same.
An infant with a VSD typically presents with HF around 4-8 weeks of age as pulmonary vascular resistance falls and the L-to-R shunt magnifies.
References
ACC/AHA 2025 — 2025 ACC/AHA/HRS/ISACHD/SCAI Guideline for the Management of Adults With Congenital Heart Disease (Gurvitz et al., J Am Coll Cardiol 2026;87:822-976)
AHA 2021 — Prevention of Viridans Group Streptococcal Infective Endocarditis: AHA Scientific Statement (Wilson et al., Circulation 2021)
ACC/AHA 2025 — 2025 ACC/AHA/ACEP/NAEMSP/SCAI Guideline for the Management of Patients With Acute Coronary Syndromes (Rao et al., Circulation 2025;151:e771-e862)
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