On-treatment comparison between corrective his bundle pacing and biventricular pacing for cardiac resynchronization: A secondary analysis of his-sync

Abstract Background The His-SYNC pilot trial was the first randomized comparison between His bundle pacing in lieu of an LV lead for cardiac resynchronization therapy (His-CRT) and biventricular pacing (BiV-CRT), but was limited by high rates of crossover. Objective To evaluate the results of the HIS SYNC pilot trial utilizing treatment-received (TR) and per-protocol (PP) analyses. Methods The His-SYNC pilot was a multicenter, prospective, single-blinded, randomized, controlled trial comparing His-CRT versus BiV-CRT in patients meeting standard indications for CRT (e.g., NYHA II-IV patients with QRS>120 ms). Crossovers were required based on prespecified criteria. The primary endpoints analyzed included improvement in QRS duration, LVEF, and freedom from cardiovascular (CV) hospitalization and mortality. Results Among 41 patients enrolled (64±13 yrs, 38% female, LVEF 28%, QRS 168±18 ms), 21 were randomized to His-CRT and 20 to BiV-CRT. Crossover occurred in 48% of His-CRT and 26% of BiV-CRT. The most common reason for crossover from His-CRT was inability to correct QRS due to nonspecific intraventricular conduction delay (IVCD=5). Patients treated with His-CRT demonstrated greater QRS narrowing compared to BiV (125±22 ms vs. 164±25 ms [TR], p Conclusions Patients receiving His-CRT on-treatment demonstrated superior electrical resynchronization and a trend toward higher echocardiographic response than BiV-CRT. Larger prospective studies may be justifiable with refinements in patient selection and implantation techniques to minimize crossovers.