Sudden death in cardiomyopathy: role of bradycardia-dependent repolarization changes.

A 20-year-old man presented with cardiomegaly, frequent PVC's, and abdominal pain. On the nineteenth hospital day the patient developed ventricular fibrillation and died. Analysis of a Holter recording initiated 16 hours previously demonstrated an increase in the corrected QT interval (QTc) to 0.48 second and a prematurity index less than 1.0 only during the minute terminated by ventricular fibrillation. This report documents changes in sinus rate, coupling interval, QTc, and prematurity index for 16 hours preceding ventricular fibrillation in a patient with cardiomyopathy. The timing of the terminal arrhythmia coincided with significant changes in the QTc and prematurity index characterized by bradycardia-dependent QTc prolongation and a post-extrasystolic reduction in prematurity index.