Effects of stress on myocardial perfusion and left ventricular synchrony in patients undergoing left bundle branch area pacing.

BACKGROUND: Left bundle branch area pacing (LBBAP), a physiologic pacing strategy, has gained increasing attention; however, its effects on left ventricular (LV) mechanical synchrony and myocardial perfusion under simulated physiological stress remain insufficiently characterized. OBJECTIVE: To quantitatively evaluate LV mechanical synchrony and myocardial perfusion in patients receiving LBBAP at rest and during adenosine triphosphate (ATP) stress using SPECT-myocardial perfusion imaging (MPI). METHODS: Twenty patients with sick sinus syndrome or atrioventricular block undergoing LBBAP were prospectively enrolled. Rest and ATP stress SPECT-MPI were performed within 3 days after implantation. Twenty healthy individuals served as controls. Phase-analysis indices, including phase bandwidth (PBW) and phase standard deviation (PSD), were used to assess mechanical synchrony, while perfusion scores—summed stress score (SSS), summed rest score (SRS), and summed difference score (SDS)—were used to assess global and regional myocardial perfusion. RESULTS: Of the 20 enrolled patients, 18 achieved Left bundle branch pacing (LBBP) and 2 received left ventricular septal pacing (LVSP), with a 100% overall procedural success rate and stable pacing parameters. In the LBBAP group, phase analysis showed significantly improved LV mechanical synchrony from rest to stress (PBW: 29.4 ± 11.7° vs. 22.5 ± 8.2°, P = 0.026; PSD: 7.3 ± 2.8° vs. 5.4 ± 2.5°, P = 0.021). Healthy controls demonstrated a similar stress-related improvement (PBW: 24 ± 9.7° vs. 19.2 ± 7.2°, P = 0.002; PSD: 5.9 ± 3.0 vs. 4.5 ± 1.9°, P = 0.003). Perfusion analysis revealed no significant perfusion defects in the LBBAP group except for one case with focal septal injury–related stress-induced defect. CONCLUSION: LBBAP significantly improves LV mechanical synchrony and demonstrates stress-induced synchrony and perfusion patterns similar to healthy individuals.