Left ventricular subendocardial pacing provides the same left ventricular synchrony and work efficiency as direct...

Left ventricular (LV) septal myocardial pacing (LVSP) is present in the areas where left bundle branch (LBB) capture is not feasible with high pacing output (general LVSP), or in LV subendocardial locations, where it transits from LBB pacing (LBBP) during the decremental output pacing (LV subendocardial pacing [LVSeP]).

This study aimed to compare electrical ventricular synchrony and acute hemodynamic response between LBBP and LVSeP.

Consecutive cardiac resynchronization therapy (CRT) patients with transition from nonselective left bundle branch capture to LVSeP during decremental output pacing were enrolled. Ventricular dyssynchrony was assessed using ultra-high-frequency electrocardiogram. The acute hemodynamic response was assessed using a high-precision hemodynamic protocol with invasive measurements of systolic blood pressure. An invasive intracardiac mapping of the left ventricular septum was performed during both captures.

The study included 21 patients. LVSeP and LBBP had the same QRS duration (159 ± 18 ms vs 151 ± 15 ms, P = .26), but LVSeP had a longer V6RWPT (98 ± 13 ms vs 79 ± 12 ms, P < .001) and post-pacing isoelectric interval (48 ± 9 vs 39 ± 9, P < .001). However, no significant difference was observed in LV synchrony (14 ± 5 ms vs 16 ± 6 ms, P = .21) and average systolic blood pressure (121 ± 18 mmHg vs 122 ± 17 mmHg, P = .78). Intracardiac mapping of one patient showed that both LVSeP and LBBP activated the LV septum at the recording site via the His-Purkinje system.

In CRT candidates, LVSeP preserved LV synchrony and acute hemodynamic response at the same level as direct LBBP. Further clinical research is warranted to better understand the differences between various types of left septal pacing.