Left bundle branch pacing compared to left ventricular septal myocardial pacing increases interventricular dyssynchrony but accelerates left ventricular lateral wall depolarization
Abstract
BACKGROUND: Nonselective His bundle (nsHBp), nonselective left bundle branch (nsLBBp), and left ventricular septal myocardial pacing (LVSP) are recognized as physiological pacing techniques. OBJECTIVE: To compare differences in ventricular depolarization between these techniques using ultra-high-frequency ECG (UHF-ECG).
METHODS: In patients with bradycardia, we performed nsHBp, nsLBBp (confirmed concomitant LBB and myocardial capture), and LVSP (pacing in LV septal position without proven LBB capture). 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.
The 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 LVSP and nsHBp; e-DYS - 24 ms (-28;-19) vs -12 ms (-16;-9) vs 10 ms (7;14, p<0.001), respectively. nsLBBp produced similar values of Vd in leads V5-V8 (36-43 ms vs. 38-43 ms; p = NS in all leads), but longer Vd in V1-V4 (47-59 ms vs. 41-44 ms, p < 0.05) as nsHBp.
LVSP caused prolonged Vd in V1-V8 compared to nsHBp and longer Vd in V5-V8 compared to nsLBBp (44-51 ms vs. 36-43 ms, p < 0.05) regardless of R wave peak time in V5 or QRS morphology in lead V1 present during LVSP. CONCLUSIONS: nsLBBp preserves physiological LV depolarization, but it increases interventricular electrical dyssynchrony.
LV lateral wall depolarization is during LVSP prolonged, but interventricular synchrony is preserved.