Intermittent left anterior hemiblock during treadmill exercise test. Correlation with coronary arteriogram.

Two patients in whom left anterior hemiblock occurred during a treadmill exercise test were found at cardiac catheterization to have significant obstruction of the proximal portion of the left anterior descending coronary artery. After successful myocardial revascularization in one of these patients, a disturbance in conduction no longer appeared during treadmill testing. To our knowledge, this association has not been previously reported, and this finding may be a useful clinical marker for significant obstructive disease of the proximal portion of the left anterior descending coronary artery.