0372: Outcomes of patients with unexplained syncope, bundle branch block and normal electrophysiological study

BackgroundLittle is known about predictors of high-degree atrioventricular block (AVB) in patients without evidence of advanced His-Purkinje conduction disturbances at electrophysiological study (EPS) performed for unexplained syncope associated with bundle branch block (BBB).AimsIdentify electrocardiographic predictors of high-degree AVB during follow-up of these patients. Methods. In this multicenter cohort, patients were included if they had: (1) unexplained syncope, (2) bundle branch block (>120ms), (3) no HPCD at EPS, i.e. baseline HV interval <70ms, and absence of 2nd- or 3rd-degree AVB induced with atrial pacing or ajmaline challenge.ResultsAmong the 150 studied patients (72±14 years, 62% male, mean left ventricular ejection fraction 57±8%), index electrocardiograms showed right BBB (70%; n=105), left BBB (2.7%; n=41), and nonspecific intraventricular conduction disturbance (3%; n=4). A first-degree AVB was noted in 62 patients (44.3%). During a mean follow-up of 584±88 days, high-degree AVB was documented in 25 patients (17%). The presence of a first-degree AVB on the index electrocardiogram was associated with an increased risk of subsequent high-degree AVB [72% vs. 35%; p