A 37 year old man presented with a continuous murmur throughout both phases of systole and diastole. A transthoracic echocardiogram showed an enlarged left main stem (1.15 cm) coronary artery (panel A) with colour flow predominantly upwards into the left circumflex artery (panel B). The parasternal short axis view at the papillary muscle level showed coils of the fistula posteriorly (panel C) with flow demonstrated on the colour flow Doppler (panel D). The four chamber apical view demonstrated in panel E shows an enlarged coronary sinus (CS). On coronary angiogram there was a large left circumflex artery draining via a tortuous fistula into the coronary sinus.

Congenital coronary artery fistula is a rare anomaly for which the gold standard for diagnosis is coronary angiography. Transthoracic echocardiography was, however, able to assess the coronary anatomy accurately in this case.