Conduction system pacing versus biventricular pacing for cardiac resynchronization: the CSP-SYNC randomized single center study

AIMS: There are limited prospective randomized studies comparing left bundle branch area pacing (LBBAP) and biventricular (BiV) pacing for cardiac resynchronization therapy (CRT). The study tested whether LBBAP is non-inferior to BiV pacing in patients with Class I indication for CRT. METHODS AND RESULTS: The CSP-SYNC study is an investigator-initiated, randomized, single-centre study. Sixty-two patients were randomized 1:1 to LBBAP or BiV. The primary study endpoint was the change in left ventricular ejection fraction (LVEF) at 6 months. Secondary endpoints included changes in echo and clinical parameters after 6 months and 12 months. Thirty-one patients were randomized to each arm. Most patients were males (71%), and 32% had ischaemic cardiomyopathy. At 6 months, similar improvement of LVEF was observed in the LBBAP group compared to the BiV group [14.0% (95% confidence interval (CI): 11.2-16.8) in LBBAP vs. 8.5% (95% CI: 5.6-11.2) in BiV] with a mean intergroup difference of 5.6% (95% CI: 1.6-9.5; P < 0.001 for non-inferiority). Both groups showed comparable decrease in LVESV [-64 mL (95% CI: -78 to -50) vs. -40 mL (95% CI: -54 to -25) respectively, mean difference -24 mL (CI 95%: -44 to -4); P < 0.001 for non-inferiority] and changes in 6-min walk test (P < 0.001 for non-inferiority) and NYHA class (P = 0.011 for non-inferiority). Temporal trends of LV remodelling and heart failure hospitalization rates were also comparable. CONCLUSION: In patients with a Class I indication for CRT, LBBAP was non-inferior to BiV pacing in improving LVEF and provided similar structural and electrical remodelling.