VASODEPRESSOR SYNCOPE DUE TO SUBCLINICAL MYOCARDIAL-ISCHEMIA

Introduction: Vasodepressor syncope is a common cause of syncope, but the initiating event that triggers the vasodepressor response remains incompletely understood. Although ischemia due to acute right coronary occlusion may precipitate hypotension and bradycardia through the Bez old-Jarisch reflex, an ischemic precipitant for the common vasodepress or faint has not been previously identified. In the present study, we present evidence for a causal relationship between myocardial ischemia and vasodepressor syncope. Methods and Results: Two patients referred for evaluation of syncope underwent upright tilt table testing with e ither ST segment monitoring, sestamibi scintigraphy and echocardiograp hy during the tilt test, or coronary angiography. Both patients had po sitive tilt table tests during the control study. Patient 1 was docume nted to have reproducible ischemic ECG changes during atypical chest p ressure induced by upright tilt, despite a normal coronary angiogram w ith ergonovine provocation. Subsequent tilt testing with simultaneous sestamibi perfusion imaging and echocardiography revealed reversible a nterolateral hypoperfusion corresponding with anterolateral hypokinesi s during upright tilt that preceded syncope. Ischemic ECG changes duri ng incremental rapid atrial pacing further suggested ischemia on the b asis of microvascular disease. Follow-up tilt testing on verapamil was negative. Patient 2 developed ischemic ECG changes during the recover y phase of an exercise stress test, which was followed by a vasodepres sor response and frank syncope. Coronary angiography revealed a 90% di stal right coronary artery stenosis that was successfully dilated, aft er which follow-up tilt table testing off all other medication was neg ative. Conclusions: These two cases illustrate a previously unrecogniz ed causality between myocardial ischemia and clinical vasodepressor sy ncope, and demonstrate that subtle manifestations of myocardial ischem ia, associated with either atypical angina or silent ischemia, can pro voke syncope.