SYNCOPE: PACING VERSUS RECORDING IN THE LATER YEARS. A RANDOMIZED PRAGMATIC CLINICAL TRIAL OF STRATEGIES OF PERMANENT PACEMAKER VERSUS IMPLANTABLE CARDIAC MONITOR IN OLDER PATIENTS WITH SYNCOPE

Abstract

Syncope with bifascicular block may be caused by intermittent complete heart block, but competing diagnoses may co-exist. We tested the hypothesis that in patients with syncope and bifascicular heart block a strategy of empiric permanent pacing (PM) reduces major adverse events more effectively than acting on the results of an implantable cardiac monitor (ICM). 115 patients >50.0 y old with bifascicular block, preserved left ventricular function, and ≥1 syncope in the preceding year were randomized to receive a PM or ICM in a prospective, open label, pragmatic randomized trial. The primary outcome measure was a composite of Major Adverse Study-Related Events (MASRE) over ≥2 years up to study completion. MASRE included death, syncope, symptomatic bradycardia, asymptomatic actionable bradycardia, and device complications. Enrollment ended May 22, 2015 with follow-up ending May 22, 2017. There were 56 and 59 subjects randomized to receive a PM or implantable cardiac monitor ICM in 23 sites (17 Canadian). The PM and ICM groups were similar in age (74±9 vs 77±9 y), sex (20 vs 14 female), lifetime syncopes (medians 2), syncope in prior year (medians 2), duration of symptoms (medians 1 year), no prodrome (40/56 vs 39/59), and baseline systolic BP (137±20 vs 133±21 mmHg). 40 pts had left bundle branch block and 75 had right bundle branch block and a left hemiblock. Patients were followed for median 30 months and 21 exited the study (death 8, withdrew consent after 2 years 6, cancer 4, dementia 3). PM effectively prevented the primary outcome with end study MASRE-free survivals in PM (63%) and ICM (22%) group (figure, left panel, p < 0.001 Wilcoxon). Proportions of pts with syncope were similar in PM and ICM groups (figure, middle panel, 27 vs 31%, p=0.50, Wilcoxon). Other outcomes were far higher in ICM than PM pts: asymptomatic actionable heart block (40% vs 0%, p < 0.001), and symptomatic bradycardia (40% vs 0%, p < 0.001). Fully 35/59 ICM pts (59%) crossed over to PM. There were 5 pacemaker complications requiring reintervention. In on treatment analysis syncope-free survival was far higher in the PM group (80% vs 50%, figure, right panel, p=0.002, Wilcoxon). Syncope recurs frequently in elderly pts with few but recent syncopal spells and bifascicular block. Permanent pacing compared to ICM is a preferred strategy due to high crossover rates from ICM to PM, and on-treatment efficacy in prevention of syncope by PM.