Left main coronary artery spasm. A potential cause for angiographic misdiagnosis of severe coronary artery disease.

Two patients had catheter-induced spasm of the left main coronary artery during diagnostic coronary arteriography. One patient had no coronary artery disease, and the other had minimal disease of the right coronary artery. Spasm was relieved by nitrates; however, in one patient several doses were needed over 35 minutes. Catheter-induced spasm must be considered in the diagnosis of left main coronary artery disease, particularly on a patient with isolated left main coronary artery disease.