CIRCADIAN PATTERN OF SPONTANEOUS VENTRICU LAR TACHYARRHYTHMIAS IN PATIENTS WITH IMPLANTABLE CARDIOVERTER-DEFIBRILLATOR

The purpose of this study was to analyze temporal patterns of spontane ous ventricular tachyarrhythmias in patients (p) with implantable card ioverter-defibrillator (ICD). By reading out the ICD-data logs 725 arr hythmic episodes le) from 43 patients were investigated. After groupin g 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 per centage of episodes per time period has been calculated for each patie nt who experienced at least 10 arrhythmic events (n = 23). A significa nt 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 2 with an episode peak in period 3 (4 p, 83 e. p < 0.0 1), 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 peri ods (6 p, 187 e). Comparing sustained and nonsustained tachyarrhythmia s, the nonsustained episodes were found to be distributed much more eq ually, meanwhile the circadian variation for fast (HR greater than or equal to 240/min) and slower (HR < 240/min) arrhythmias was identical. Regarding episodes of patients on beta-blocker or class III-antiarrhy thmic therapy the same circadian variation has been found. There was n o significant difference between the subgroups of patients with an epi sode peak in period 2 and the other patients concerning age, sex, card iac disease, left ventricular ejection fraction, clinical arrhythmia, beta-blocker or class III-antiarrhythmics, number of recorded episodes or follow-up time. Further studies art: needed to determine a possibl e correlation between these findings and different circadian variation s in individual psychovegetative activity.