Left bundle branch pacing compared to left ventricular septal myocardial pacing increases interventricular dyssynchrony but accelerates left ventricular lateral wall depolarization

BACKGROUND Nonselective His-bundle pacing (nsHBp), nonselective left bundle branch pacing (nsLBBp), and left ventricular septal myocardial pacing (LVSP) are recognized as physiological pacing tech niques.OBJECTIVE The purpose of this study was to compare differences in ventricular depolarization between these techniques using ultrahigh-frequency electrocardiography (UHF-ECG).METHODS In patients with bradycardia, nsHBp, nsLBBp (confirmed concomitant left bundle branch [LBB] and myocardial capture), and LVSP (pacing in left ventricular [LV] septal position without proven LBB capture) were performed. Timings of ventricular activations in precordial leads were displayed using UHF-ECG, and electrical dyssynchrony (e-DYS) was calculated as the difference between the first and last activation. Duration of local depolarization (Vd) was determined as width of the UHF-QRS complex at 50% of its amplitude.RESULTS In 68 patients, data were collected during nsLBBp (35), LVSP (96), and nsHBp (55). nsLBBp resulted in larger e-DYS than did LVSP and nsH Bp [- 24 ms (-28;-19) vs -12 ms (-16;-9) vs 10 ms (7;14), respectively; P <.001]. nsLBBp produced similar values of Vd in leads V-5 -V-8 (36-43 ms vs 38-43 ms; P = NS in all leads) but longer Vd in leads V-1 -V-4 (47-59 ms vs 41-44 ms; P <.05) as nsH Bp. LVSP caused prolonged Vd in leads V-1 -V-8 compared to nsH Bp and longer Vd in leads V-5 -V-8 compared to nsLBBp (44-51 ms vs 36-43 ms; P <.05) regardless of R-wave peak time in lead V-5 or QRS morphology in lead V-1 present during LVSP.CONCLUSION nslbbp preserves physiological LV depolarization but increases interventricular electrical dyssynchrony. LV lateral wall depolarization during LVSP is prolonged, but interventricular synchrony is preserved.