[Idiopathic dilatation of the right atrium in 2 infants disclosed by arrhythmia].

Idiopathic right atrial dilatation is a rare and probably congenital malformation. Two new cases are reported, in an 18 months old infant and a six week old baby, both presenting with supraventricular tachyarrhythmias. Clinical examination was normal. Chest X-ray showed bulging of the right heart border and electrocardiography revealed partial right bundle branch block. The diagnosis was made by echocardiography which showed aneurysmal dilatation of the right atrium. There were no signs of valvular heart disease or of an intracardiac shunt; the septal tricuspid leaflet was in its normal position. M-mode recordings showed no signs of Ebstein's anomaly. The diagnosis was confirmed by cardiac catheterisation in the first case; this investigation seemed to be pointless in the second case. Both children experienced many episodes of supraventricular tachyarrhythmias. The first developed tricuspid regurgitation but the second remains asymptomatic.