Atrioventricular septal defect — clinical case

Case summary

This infant with Down syndrome presents with the classic constellation of a complete atrioventricular septal defect: failure to thrive, recurrent respiratory infections, the physical signs of a large left-to-right shunt with pulmonary hypertension, and the pathognomonic superior QRS axis. The combination of trisomy 21 and this clinical picture makes a complete AV canal the working diagnosis until echocardiography confirms it. [1]

Diagnosis and anatomy

The diagnosis rests on three pillars. Clinically, the heart failure with a hyperactive precordium and a pansystolic murmur of atrioventricular valve regurgitation point to a large shunt with valve involvement. The ECG, showing a superior QRS axis, is the single bedside fingerprint of a deficient atrioventricular septum and immediately separates this from a secundum atrial septal defect or a large ventricular septal defect. The loud pulmonary component reflects the early pulmonary hypertension that develops in unrepaired complete defects. [1] [2]

Echocardiography confirms the anatomy: a common atrioventricular junction at the crux, a primum atrial septal defect, a large inlet ventricular septal defect, a single common atrioventricular valve with bridging leaflets, and a Rastelli type that grades the superior bridging leaflet. The study also assesses ventricular balance, the competence of the left atrioventricular valve, and the pulmonary artery pressure from any tricuspid regurgitation jet. [2]

Management

The definitive management is surgical and the timing is urgent. A complete AVSD is repaired at three to six months of age to close both septal defects and reconstruct a competent left atrioventricular valve before the pulmonary vasculature becomes irreversibly remodelled. In Down syndrome the pulmonary arteries are more reactive, so this window is narrower and the principle of early repair applies with even greater force. [2] [3]

Until surgery, medical stabilisation supports growth and eases the work of breathing. Furosemide with spironolactone reduces pulmonary congestion, fortified feeds address the failure to thrive, and an angiotensin-converting enzyme inhibitor is added for the significant atrioventricular valve regurgitation. Medical therapy buys time and weight, but it does not buy a longer pulmonary vascular window — the surgical date is set now. [1]

Prognosis and counselling

The prognosis after timely repair is excellent, with operative mortality below five percent in modern centres and outcomes in Down syndrome comparable to non-syndromic children. The long-term issue to counsel the family about is left atrioventricular valve regurgitation, the leading cause of reoperation in roughly ten to fifteen percent over the long term. The child will require lifelong follow-up in a congenital cardiac service, with structured transition to an adult congenital programme in late adolescence. [1] [3]