Supraventricular arrhythmia as the cause of sudden death in hypertrophic cardiomyopathy.

Electrophysiological studies with simultaneous echocardiographic control and invasive measurement of intravascular pressures were carried out in a 13-year-old boy with hypertrophic cardiomyopathy who was hospitalized after an episode of aborted sudden death. Ventricular stimulation did not induce ventricular tachycardia, but atrial stimulation induced atrial fibrillation, atrial flutter and non-sustained ventricular tachycardia. Atrial stimulation (S1) at 200 beats.min-1 (10-15 s) also induced significant repolarization abnormalities in the 5-10 post-stimulation beats. Akinesia of the ventricular septum and posterior wall without opening of the mitral valve was documented by echocardiography. A complete anterior systolic motion, not observed under basal conditions, was detected in the first post-stimulation beat. Atrial stimulation at rates over 120 beats.min-1 caused a drop in systolic blood pressure, a rise in pulmonary artery pressure, and a decrease in cardiac output. Despite therapy with propranolol and amiodarone, the patient died suddenly.