Circadian variation and onset mechanisms of ventricular tachyarrhythmias in patients with coronary disease versus idiopathic dilated cardiomyopathy.

To determine the circadian variations and the onset mechanisms of ventricular tachyarrhythmias (VT) in patients with implantable cardioverter defibrillators, stored electrograms of 364 VT episodes occurring in 40 patients with coronary artery disease (CAD) and in 29 patients with idiopathic dilated cardiomyopathy (DCM) were analyzed. A similar circadian distribution of VT episodes was observed in both groups, with a morning peak and less pronounced evening peak. After exclusion of patients with atrial fibrillation, VT onset was classified as (1) sudden if preceded by > or = 8 regular cycles without ventricular premature beats, (2) onset with a short-long-short interval, and (3) a more complex onset with variable patterns of ventricular premature beats before initiation of VT. Sudden onset was found in 26% and 21% of VTs in CAD and DCM respectively. A short-long-short interval preceded 29% of VTs in CAD compared to 14% of VTs in DCM (P < 0.05). A more complex onset was observed in the remaining 45% of VTs in CAD and 65% of VTs in DCM (P < 0.05). In conclusion, patients with DCM and CAD had similar circadian distributions of VT episodes. The majority of episodes were preceded by complex occurrence of ventricular premature beats rather than by the classic short-long-short sequence. These findings have important implications for the development of preventive pacing methods.