[Diurnal distribution of spontaneous ventricular tachyarrhythmias in patients with implanted cardioverter defibrillator].

The purpose of this study was to analyze temporal patterns of spontaneous ventricular tachyarrhythmias in patients (p) with implantable cardioverter-defibrillator (ICD). By reading out the ICD-data logs 725 arrhythmic episodes (e) from 43 patients were investigated. After grouping the episodes into four defined time periods (period 1: midnight to 6 a.m., period 2: 6 a.m. to noon, period 3: noon to 6 p.m., period 4: 6 p.m. to midnight) according to the data stored by the device, the percentage of episodes per time period has been calculated for each patient who experienced at least 10 arrhythmic events (n = 22). A significant peak occurrence (mean 34%) could been demonstrated for the morning hours (period 2). Analyzing patients individually, 4 subgroups could be identified: group 1 with an episode peak in period 2 (9 p, 277 e, p < 0.01), group with an episode peak in period 3 (4 p, 83 e, p < 0.01), group 3 with a peak occurrence in period 4 (3 p, 110 e, p < 0.01) and group 4 with an equal episode distribution over all four time periods (6 p, 187 e). Comparing sustained and nonsustained tachyarrhythmias, the nonsustained episodes were found to be distributed much more equally, meanwhile the circadian variation for fast (HR > or = 240/min) and slower (HR < 240/min) arrhythmias was identical. Regarding episodes of patients on beta-blocker or class III-antiarrhythmic therapy the same circadian variation has been found. There was no significant difference between the subgroups of patients with an episode peak in period 2 and the other patients concerning age, sex, cardiac disease, left ventricular ejection fraction, clinical arrhythmia, beta-blocker or class III-antiarrhythmics, number of recorded episodes or follow-up time. Further studies are needed to determine a possible correlation between these findings and different circadian variations in individual psychovegetative activity.