Syncope in patients with an implantable cardioverter-defibrillator: incidence, prediction and implications for driving restrictions.

Abstract

This retrospective study was undertaken to provide information on occurrence, risk prediction and prevention of syncope in patients with an implantable cardioverter-defibrillator (ICD). ICDs effectively terminate ventricular tachycardia and fibrillation (VT/VF). Incapacitating symptoms, such as syncope, may still occur. We performed a retrospective analysis of data from 421 patients (clinical history, outpatient chart reviews and episode data) with mean (+/-SD) follow-up of 26 +/- 18 months. Of 421 patients, 229 (54.4%) had recurrent VT/VF, and 62 (14.7%) had syncope. The actuarial survival rate free of VT/VF was 58%, 45% and 37% and that for survival free of syncope was 90%, 85% and 81% at 12, 24 and 36 months after implantation, respectively. Once VT/VF had occurred, 76%, 68% and 62% of patients remained free of syncope during the following 12, 24 and 36 months, and 68%, 64% and 56% remained free of second syncope 12, 24 and 36 months after first syncope, respectively. In cases of syncope, the mean cycle length (CL) of VT was 251 +/- 56 ms. A low baseline left ventricular ejection fraction (LVEF), induction of fast VT (CL <300 ms) during programmed ventricular stimulation and chronic atrial fibrillation (AF) were associated with an increased risk of syncope. If the LVEF was >40%, fast VT had not been induced, and patients had no chronic AF; 96%, 92% and 92% of patients remained free of syncope after 12, 24 and 36 months, respectively. Once patients had a VT recurrence, syncope during the first VT and a high VT rate were the strongest risk predictors of future syncope. Identification of patients with an ICD with a low and high risk of syncope seems to be feasible and might help as a guide to driving restrictions in such patients.