Exercise-induced left bundle branch block: resolution after calcium antagonist therapy.

We describe a middle-aged man who developed angina and transient left bundle branch block during an exercise test. Coronary arteriography failed to shown significant atherosclerotic lesions and therapy with calcium antagonist nifedipine resolved both the symptoms and the electrocardiographic abnormalities. Previous reports of transient conduction defects have been related to severe obstructive lesions of the coronary arteries. The minimal lesions found in our patient suggest that coronary spasm may have been the causative mechanism.