Very Low Ventricular Pacing Rates Can Be Achieved Safely in a Heterogeneous Pacemaker Population and Provide Clinical Benefits: the CANadian Multi-Centre Randomised Study-Spontaneous AtrioVEntricular Conduction pReservation (CAN-SAVE R) Trial

Background: it is well recognized that right ventricular apical pacing can have deleterious effects on ventricular function. we performed a head-to-head comparison of the safer pacing algorithm versus ddd pacing with a long atrioventricular delay in a heterogeneous population of patients with dual-chamber pacemakers.methods and results: in a multicenter prospective double-blinded randomized trial conducted at 10 centers in canada,373 patients,age 71±11 years,with indications for dual chamber dc pacemakers were randomized 1:1 to safer or ddd pacing with a long atrioventricular delay (250 ms). the primary objective was twofold: (1) reduction in the proportion of ventricular paced beats at 1 year; and (2) impact on atrial fibrillation burden at 3 years,defined as the ratio between cumulative duration of mode-switches divided by follow-up time. statistical significance of both co-primary end points was required for the trial to be considered positive. at 1 year of follow-up,the median proportion of ventricular-paced beats was 4.0% with ddd versus 0% with safer (p<0.001). at 3 years of follow-up,the atrial fibrillation burden was not significantly reduced with safer versus ddd (median 0.00%,interquartile range [0.00% to 0.23%] versus median 0.01%,interquartile range [0.00% to 0.44%],respectively,p=0.178]),despite a persistent reduction in the median proportion of ventricular-paced beats (10% with ddd compared to 0% with safer).conclusions: a ventricular-paced rate <1% was safely achieved with safer in a population with a wide spectrum of indications for dual-chamber pacing. however,the lower percentage of ventricular pacing did not translate into a significant reduction in atrial fibrillation burden.clinical trial registration: url: https://www.clinicaltrials.gov/ unique identifier: nct01219621. © 2015 the authors. published on behalf of the american heart association,inc.,by wiley blackwell.