The CSP-SYNC trial comparing conduction system pacing (His bundle or left bundle branch area) with biventricular pacing for CRT showed that conduction system pacing is noninferior and potentially superior. The results support physiologic pacing as a viable CRT alternative.
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.
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.
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.
