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A 25 year old man with Down's syndrome (trisomy 21) was evaluated for dyspnoea. Physical examination revealed cyanosis (systemic saturation 60%), clubbing, oedema, accentuated pulmonary component of second heart sound, and hepatomegaly. Chest x ray demonstrated cardiomegaly and pulmonary venous congestion. ECG revealed a sinus rhythm, QRS axis of 240°, first degree atrioventricular block (P-R interval 260 ms), and right ventricular hypertrophy. Transoesophageal echocardiography demonstrated a complete common atrioventricular canal (below left) with undivided anterior bridging leaflet. Cor triatriatum was present with a 5 mm ostium in the membrane partitioning the left atrium (RA, right atrium; LA, left atrium; RV, right ventricle; LV, left ventricle; CPV, common pulmonary vein; arrow, ostium of the left atrial membrane) resulting in obstruction to pulmonary venous return to left atrium (below centre). Right and left pulmonary veins were visualised and dilated. The patient expired following an episode of ventricular tachycardia. Postmortem examination revealed a balanced, complete common atrioventricular canal anomaly with a fibromuscular membrane (below right: LUPV, left upper pulmonary vein; LLPV, left lower pulmonary vein; arrow, ostium of left atrial membrane) partitioning the left atrium resulting in pulmonary venous obstruction. An isolated right upper pulmonary vein branch drained directly into the right sided superior vena cava.
Coexistence of cor triatriatum and atrioventricular canal anomalies is rare. The haemodynamics of complete common atrioventricular canal with cor triatriatum and pulmonary venous obstruction may be misinterpreted as non-reactive pulmonary vascular disease secondary to the atrioventricular canal anomaly. It is uncertain whether the presence of pulmonary venous obstruction with cor triatriatum has a salutary effect that delays evolution of pulmonary vascular changes in patients with complete common atrioventricular canal defects.