Giant T waves simulating apical hypertrophic myocardiopathy that disappear with sodium nitroprusside administration. Case report of pheochromocytoma.

Giant inverted T waves (amplitude greater than 1 mV) in precordial leads have been described in various disease processes. However, the pathophysiology of these anomalies has not been studied in depth. This paper analyzes repolarization abnormalities occurring in a case of pheochromocytoma in which giant T waves were unaffected by alpha-adrenergic blockade but were affected by administration of sodium nitroprusside. It is postulated that the probable cause of this aberration is myocardial ischemia of noncoronary origin resulting from an imbalance of supply and demand of oxygen that is relieved by the hemodynamic action of nitroprusside when left ventricular wall stress is reduced.