Syncope in Patients With an Implantable Cardioverter-Defibrillator: Incidence, Prediction and Implications for Driving Restrictions

Objectives. This retrospective study was undertaken to provide information on occurrence, risk prediction and prevention of syncope in patients with an implantable cardioverter-defibrillator (ICD). Background. ICDs effectively terminate ventricular tachycardi and fibrillation (VT/VF). Incapacitating symptoms, such as syncope, may still occur. Methods. We performed retrospective analysis of dat from 421 patients (clinical history, outpatient chart reviews and episode data) with mean (±SD) follow-up of 26 ± 18 months. Results. 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. 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 VT recurrence, syncope during the first VT and high VT rate were the strongest risk predictors of future syncope. Conclusions. Identification of patients with an ICD with low and high risk of syncope seems to be feasible and might help as guide to driving restrictions in such patients.