Syncope and bundle branch block. Diagnostic yield of a stepped use of electrophysiology study and implantable loop recorders.

INTRODUCTION AND OBJECTIVES The objective of this study was to determine the diagnostic yield of a stepped protocol involving an electrophysiologic study (EPS) and implantable loop recorders (ILR) in patients with syncope and bundle branch block (BBB). METHODS Eighty-five consecutive patients referred for syncope and BBB after initial non-diagnostic assessment underwent EPS including a pharmacological challenge with procainamide. Those patients without indication for defibrillator implantation received ILRs. Follow-up continued until diagnosis or end of battery life. RESULTS The EPS was diagnostic in 36 patients (42%). The most frequent diagnoses were paroxysmal atrioventricular block (AVB) (n=27), followed by ventricular tachycardia (VT) (n=6). All patients with VT had structural heart disease; left BBB was more prevalent in this group. Thirty-eight patients received ILRs and diagnosis was achieved in 13 (34%) of them; paroxysmal AVB (n=10) was the most frequent diagnosis. Median follow-up to diagnosis of paroxysmal AVB was 97 days (interquartile range 60-117 days). Paroxysmal AVB was more frequent in patients with right BBB and prolonged PR interval and/or axis deviation. We found no occurrence of VT or arrhythmic death during follow-up. CONCLUSIONS The most common etiology of syncope in patients with BBB was paroxysmal AVB, followed by VT. The stepped use of EPS and ILR in negative patients enables us to safely achieve a high diagnostic yield, given that VT is usually diagnosed during EPS.