Empiric pacemaker compared with a monitoring strategy in patients with syncope and bifascicular conduction block--rationale and design of the Syncope: Pacing or Recording in ThE Later Years (SPRITELY) study.

AIM This study seeks to identify the optimal management strategy for patients with syncope in the context of bifascicular block and preserved left ventricular systolic function. METHODS AND RESULTS This multicentre, randomized, open label, parallel group pragmatic randomized trial will test the hypothesis that a strategy of empiric permanent pacemaker implantation in patients with syncope and bifascicular heart block improves future outcome more effectively than a strategy of therapy guided by prolonged monitoring with an implantable loop recorder (ILR). A total of 120 patients with bifascicular block, preserved left ventricular function, and ≥ 1 syncopal spell in the preceding year will be randomized to receive a permanent pacemaker or ILR in at least 20 centres in Canada, the USA, Asia, and Europe. The primary outcome measure will be a composite of Major Adverse Study-Related Events (MASRE) in a 2-year observation period, wherein the events are death, syncope, symptomatic bradycardia, asymptomatic diagnostic bradycardia, and acute and chronic device complications. Prespecified secondary endpoints will include syncope symptoms, quality of life, and economic burden. CONCLUSION This trial will provide high-level and generalizable evidence for the use of either permanent pacing or implantable loop recorders as a first line intervention for patients with syncope, preserved systolic function, and bifascicular block.