Congenital Heart Disease on Echo
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Direct answer
Roughly eight to ten of every thousand live births carry a congenital heart defect, and echocardiography is their diagnosis, surgical roadmap and lifelong follow-up in one machine. The segmental approach reads every heart in fixed order — situs (which way the atria face), ventricular loop, and great-artery relationships — before any lesion is described. The lesions themselves follow classic echo signatures: atrial septal defect with right ventricular volume overload and a septal drop-out (secundum in about 70-75 per cent, primum with a cleft mitral valve, sinus venosus near the SVC often with anomalous pulmonary venous drainage); ventricular septal defect typed by position (perimembranous 70-80 per cent); tetralogy with an overriding aorta, large VSD, right ventricular outflow obstruction and hypertrophy; and transposition with parallel, spiralling-failed great arteries. Shunt size is quantified as Qp:Qs, the pulmonary-to-systemic flow ratio.
What you must remember
- Segmental triad: determine atrial situs (situs solitus in the vast majority), ventricular positions (D-loop normal), and great-arterial relationship (normally related, TGA, or side-by-side) before describing any defect — the viva openers.
- ASD taxonomy with numbers: secundum about 70-75 per cent, primum (partial AV septal defect, cleft anterior mitral leaflet) 15-20 per cent, sinus venosus about 10 per cent (SVC type associated with partial anomalous pulmonary venous return); echo shows RA/RV dilation with paradoxical septal motion.
- VSD map: perimembranous 70-80 per cent, muscular 15-20 per cent, inlet (AV canal type, with Down syndrome) and outlet the remainder; a small defect gives a high-velocity jet — velocity falls as the hole and the pulmonary pressure rise.
- Tetralogy of Fallot echo: large perimembranous VSD, overriding aorta (aortic en face over the crest of the septum), RVOT obstruction with its gradient, RV hypertrophy; the degree of outflow obstruction determines the cyanosis.
- TGA signature: great arteries arise in parallel from the wrong ventricles — parallel "double-barrel" short-axis view instead of the normal circle-and-sausage; duct- and shunt-dependent mixing keeps neonates alive.
- PDA and coarctation: ductal continuous flow into the pulmonary artery on echo with a gradient across it; coarctation shows a shelf with high-velocity systolic (and diastolic run-off) flow, collaterals in adults, and 50 per cent of coarctation patients carry a bicuspid aortic valve.
- Qp:Qs arithmetic: shunt ratio from stroke volumes (VTI × area at pulmonary and aortic outflow) or from oximetry; 1.5:1 or greater is the traditional threshold where closure is considered; Eisenmenger reversal (right-to-left shunting once pulmonary vascular resistance exceeds systemic) forbids closure.
Reading a cyanotic newborn, step by step
A term baby desaturates to 78 per cent on day two with no respiratory distress. Pre-ductal and post-ductal saturations are measured simultaneously — a gradient over about 10 per cent flags ductal-level differential perfusion, with prostaglandin E1 already running to hold the duct open. The echo begins subcostally with situs: solitus, then two ventricles of reasonable size. The sweep finds parallel great arteries, the aorta committed to the right ventricle: d-transposition. The duct is patent but flow-restricted, the atrial septum nearly intact; mixing is the lifeline, so the report flags the need for an urgent balloon atrial septostomy. In congenital work the sequence — situs, connections, septal defects, outflows, duct, arch, pulmonary veins, function — is the safety net: a missed vein or arch defines the next decade of the child's surgeries.
Where students slip
Examiners probe four confusions. secundum versus primum ASD is answered by position on the septum and the mitral valve — a primum defect sits low with a cleft mitral leaflet and MR, and is part of the atrioventricular septal defect family. The overriding aorta of tetralogy is called "double-outlet right ventricle" — in DORV both arteries arise predominantly (over 50 per cent) from the right ventricle, not merely overriding it. The Eisenmenger question is graded wrongly: closure of a left-to-right shunt after pulmonary vascular disease has reversed flow is harmful, and the exam wants the direction of shunt and the PVR logic, not just the diagnosis. And the adult congenital patient — the repaired tetralogy with pulmonary regurgitation, the bicuspid aortic valve calcifying at 55 — is forgotten because "congenital means children", though grown-up congenital clinics now fill with surgically grown survivors needing quantitated follow-up.
Frequently asked questions
How is the Qp:Qs shunt ratio calculated?
Pulmonary flow divided by systemic flow, derived from Doppler (cross-sectional area times VTI) at the outflows or from oximetry; 1.5:1 or more traditionally supports defect closure.
Which ASD type associates with anomalous pulmonary venous drainage?
Sinus venosus defects, particularly the superior vena caval type, coexist with partial anomalous pulmonary venous return — one reason every ASD study must image all four pulmonary veins.
What are the four echo features of tetralogy of Fallot?
A large perimembranous ventricular septal defect, an overriding aorta, right ventricular outflow tract obstruction (with its gradient quantified), and right ventricular hypertrophy.
Why is the great-vessel relationship central to diagnosing transposition?
In d-TGA the aorta and pulmonary artery arise in parallel from the wrong ventricles, replacing the normal crossed arrangement. Life depends on mixing through the duct, atrial septal defect or septostomy until surgical correction.
What is the Eisenmenger syndrome and why does it forbid defect closure?
Chronic left-to-right shunting eventually raises pulmonary vascular resistance above systemic, reversing the shunt and producing cyanosis. Once resistance is irreversibly high, closing the defect removes the decompression route and worsens right heart failure.