Stent procedure complicated by thrombus formation distal to the lesion within a muscle bridge.

We report here a case of a patient who underwent percutaneous intervention to the left anterior descending artery, complicated by thrombus formation within the myocardial bridge distal to the lesion. There was complete angiographic resolution of thrombus and restoration of the normal antegrade blood flow after infusion of glycoprotein IIb/IIIa antagonist (abciximab). Our observation may suggest that the presence of myocardial bridging distal to coronary lesions should be considered seriously in preprocedural evaluation of the lesions as a potential risk factor for intracoronary thrombus formation. The main coronary arteries and the proximal segments of their major branches lie free on the epicardial surface of the heart. However, in some instances these vessels may penetrate into the muscle being surrounded by the myocardium, with the overlying muscle referred to as a "bridge". Myocardial bridging appears to be a congenital anomaly, due to failure of exteriorization of the primitive coronary intratrabecular arterial network. It occurs in 5-86% of patients in autopsy studies, and it is observed as systolic coronary artery narrowing in 0.5-12% of patients undergoing coronary arteriography. Although the gross anatomist had long recognized that the epicardial coronary artery might on occasion course directly through a segment of cardiac muscle, the physiological significance of this phenomenon was considered benign. This is partly because traditional teaching concerning coronary blood flow delivery to the left ventricular myocardium emphasized the primacy of the diastolic phase of the cardiac cycle. However, myocardial bridging is not always a benign finding, with recent reports suggesting an association with myocardial ischemia, infarction, vasospasm, cardiac arrythmias, and sudden death.