Chronic occlusion of the left main coronary artery: importance of collaterals.

Chronic occlusion of the left coronary artery is an infrequent finding in patients undergoing coronary angiography. These patients usually present symptoms of angina or heart failure. We describe a patient who was training regularly without cardiac symptoms until ventricular fibrillation suddenly occurred during a long-distance run. A chronic left main stem occlusion with well-developed right-to-left coronary collaterals was demonstrated by angiography. Up to this event, the collateral flow had been sufficient to allow physical exercise at a high performance level without symptoms. The patient later underwent coronary bypass surgery and recovered completely.