Evaluation of Acute Electrical and Hemodynamic Improvement During Left Bundle‐Branch Area Pacing Modalities for Resynchronization Therapy

Background While cardiac resynchronization therapy is effective in dyssynchronous heart failure, suboptimal response remains frequent. The acute hemodynamic profile of different left bundle‐branch (LBB) area pacing modalities is poorly defined. Moreover, atrioventricular optimization guided by QRS duration (QRSd) may not yield the greatest hemodynamic benefit. Methods Twenty‐four patients with heart failure, reduced ejection fraction, and LBB block underwent sequential testing of right ventricular septal pacing, left ventricular septal pacing, nonselective LBB pacing, and selective LBB pacing during cardiac resynchronization therapy implantation in a prospective, within‐subject physiological study. At each modality, electrical end points were QRSd and vectorcardiographic QRS area; hemodynamics were assessed with beat‐to‐beat systolic blood pressure (SBP). The atrioventricular interval producing maximal SBP improvement was compared with that producing the narrowest QRSd. Results LBB area pacing modalities significantly reduced QRSd , compared with right ventricular septal pacing (nonselective LBB pacing, 114.0±16.8 milliseconds; selective LBB pacing , 118.4±14.1 milliseconds; left ventricular septal pacing, 124.6±16.0 milliseconds; right ventricular septal pacing, 144.4±27.6 milliseconds; all P <0.01). At the atrioventricular interval that produced maximized SBP improvement, QRSd remained narrower with LBB area pacing than right ventricular septal pacing, and selective LBB pacing provided the greatest hemodynamic improvement ( ΔSBP 16.3±5.2 mm Hg ), exceeding left ventricular septal pacing (13.5±6.2 mm Hg ) and nonselective LBB pacing (12.8±6.3 mm Hg ; all P <0.05). Across modalities, the atrioventricular interval that maximized ΔSBP was consistently shorter than that minimizing QRSd (mean difference, 18–29 milliseconds). Conclusions Selective LBB pacing yields the greatest acute hemodynamic benefit, and the hemodynamic‐optimal atrioventricular interval is shorter than the electrical‐optimal atrioventricular interval, suggesting that modest atrioventricular interval shortening after electrical optimization may better maximize hemodynamics. Registration URL: https://www.clinicaltrials.gov ; Unique Identifier: NCT07032064.