Left bundle branch pacing-optimized cardiac resynchronization vs biventricular therapy: electrical/echocardiographic response; according to QRS morphology/duration, indication and cardiomyopathy

Background Left bundle branch pacing - optimized cardiac resynchronization therapy (LOT-CRT) is a hybrid resynchronization modality that combines conventional resynchronization and conduction system pacing. It aims to achieve maximum electrical synchrony and overcome the previous limitations, such as conduction disturbances at different levels or variable latency periods, influenced by scars in left ventricle. Purpose To evaluate the response to conventional biventricular pacing (BIVP) versus LOT-CRT in different population subgroups based on key characteristics. Methods Single-center, observational cohort study. From January 2019 to December 2023, a total of 120 patients with CRT indication without defibrillation therapy were consecutively enrolled in a non-randomized manner. They were divided into two groups: BIVP (n=64 patients) and LOT-CRT (n=56 patients). Comparisons were made between electrical and imaging parameters in the overall population and by subgroups based on the presence of LBBB, QRS≥150 ms, implant indication and type of cardiomyopathy. Results There were 51(42.5%) women, mean age 76.6±8.1 years. LBBB 91(75.8%) patients. Baseline QRS duration was 153.6±25.3 ms (BIVP/LOT-CRT 148.4±22.8/159.5±27.0 ms, p=0.017) and final QRS duration was 124.7±11.6 ms (p=0.482). Heart failure (HF) vs need for pacing with LVEF<40% indication 68(56.7%)/52(43.3%) patients (p=0.168). Ischemic cardiomyopathy vs non-ischemic 25(20.8%) patients (p=0.881). The overall QRS shortening (ΔQRS) was -24.4±21.2 vs -36.0±28.6 ms BIVP/LOT-CRT (p=0.014), and the overall LVEF improvement (ΔLVEF) was +12.1±10.6% (p=0.872). In the analysis according to QRS morphology, if baseline LBBB, the ΔQRS was greater vs non-LBBB (-35.7±22.8/ -11.6±25.4 ms, p<0.0001); and LOT-CRT achieved a greater ΔQRS vs BIVP (-43.3±26.5/-29.3±16.9, p=0.005); but not in patients without LBBB (p=0.446). According to QRS duration, if ≥150 ms, ΔQRS was much greater than QRS <150 ms (-40.6±18.3/ -5.2±22.6 ms); in the first case there were significant differences between groups (BIVP -33.8±14.7/LOT-CRT -46.8±19.2 ms, p=0.001). In HF indication ΔQRS was -36.5±20.6 (-29.2±17.5/-46.0±20.5 ms BIVP/LOT-CRT, p<0.0001). In pacing indication ΔQRS was lower (-20.3±29.0 ms, p=0.297). In ischemic cardiomyopathy ΔQRS -25.7±26.8 (-12.5±27.6/-40.1±17.3 ms BIVP/LOT-CRT, p=0.010). In non-ischemic indication -30.9±25.3 (p=0.160). In ischemic heart disease, there were fewer super-responders (LVEF≥50% and/or LVEF increase ≥20%) than non-ischemic heart disease (7(31.8%)/ 55(64.0%), p=0.007), but LOT-CRT obtained more super-responders than BIVP (6(54.5%)/ 1(9.1%), respectively, p=0.032). There were no significant differences in ΔLVEF between LOT-CRT and CRT in any of the subgroups. Conclusion LOT-CRT obtained a higher ΔQRS than BIVP, which was more evident in the presence of baseline LBBB, QRS ≥150 ms, HF indication and ischemic cardiomyopathy. There were no differences in ΔLVEF.