CIRCADIAN VARIATION OF SUSTAINED VENTRICULAR-TACHYCARDIA IN PATIENTS WITH CORONARY-ARTERY DISEASE AND IMPLANTABLE CARDIOVERTER-DEFIBRILLATORS

Background While previous studies using epidemiological data and ambul atory ECG monitoring have shown peak occurrence of sudden death and no nsustained ventricular tachycardia in the morning, none have examined circadian variation of potentially life-threatening ventricular tachyc ardia (VT), nor has any study observed circadian behavior of any arrhy thmias in individuals followed longitudinally. We used the event memor y of multiprogrammable implantable cardioverter-defibrillators to eval uate the circadian pattern of sustained VT over time. Methods and Resu lts Data were reviewed from 32 consecutive patients with coronary arte ry disease and sustained VT who had received the Ventak PRX (CPI, Inc) cardioverter-defibrillator between May 1991 and August 1993 and had e xperienced at least one episode of VT terminated by their device. Mean follow-up was 14+/-7 months. Among the 2558 episodes recorded by the device logs, VT occurrence peaked between 6 AM and noon (P=.007 by ANO VA among four 6-hour time periods). Harmonic regression revealed a mor ning peak at 9 AM (P<.01). This morning peak occurred in patients with both frequent and infrequent events. Among 21 patients who experience d more than four VT events, 8 (38%) had an AM peak of VT occurrence (> 35% of VT between 6 AM and noon). Neither age, ejection fraction, even t frequency, presenting arrhythmia, nor drug therapy distinguished pat ients who displayed the AM VT peak. Conclusions In patients with coron ary artery disease, sustained VT displays circadian variation with pea k frequency in the morning, similar to that for sudden death. Individu al patients who display specific patterns of circadian variation over time can be identified using defibrillator logs. Investigation of circ adian variation of other phenomena to elucidate mechanisms of VT shoul d focus on these patients.