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 ventricul ar tachyarrhythmias (VT) in patients with implantable cardioverter defibril lators, stored electrograms of 364 VT episodes occurring in 40 patients wit h 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 pronounc ed evening peak. After exclusion of patients with atrial fibrillation, VT o nset was classified as (1) sudden if preceded by greater than or equal to 8 regular cycles without ventricular premature beats, (2) onset with a short -long-short interval, and (3) a more complex onset with variable patterns o f ventricular premature beats before initiation of VT. Sudden onset was fou nd in 26% and 21% of VTs in CAD and DCM respectively. A short-long-short in terval 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 6 5% of VTs in DCM (P < 0.05). In conclusion, patients with DCM and CAD had s imilar circadian distributions of VT episodes. The majority of episodes wer e preceded by complex occurrence of ventricular premature beats rather than by the classic short-long-short sequence. These findings have important im plications for the development of preventive pacing methods.