In CRT candidates, left septal myocardial capture in close proximity to the left bundle branch provides the same LV work effectivity and left ventricular synchrony as direct left bundle branch pacing

Two types of left septal myocardial pacing (LVSP) could be recognized. In the general form of LVSP, left bundle branch pacing (LBBP) is not achievable even with higher pacing output. The second type of LVSP transits from LBBP by decreasing the pacing output, indicating a minimal distance between the lead tip and LBB fibers (LVSP close to LBBP). However, the effects of LVSP in close proximity to the LBB have not yet been evaluated in CRT patients.

This study aimed to compare ventricular synchrony and acute hemodynamic response during nonselective left bundle brunch capture (nsLBBP) and myocardial capture in close proximity to the left bundle brunch in CRT candidates.

The study included consecutive CRT patients with LBBB and transition from nsLBBP to LVSP in close proximity to LBB during decremental output pacing at CRT implantation. Ventricular electrical dyssynchrony was assessed using UHF-ECG with the standard V1–V8 chest leads placement. The acute hemodynamic response was assessed using the high-precision hemodynamic protocol with invasive beat-by-beat systolic blood pressure measurements and alternations from nsLBBP to LVSP in close proximity to LBB.

Our study included 15 patients (10 males), 67 ± 8 years old, with an average LVEF of 28 ± 6 % and ischemic cardiomyopathy present in 7. The average intrinsic QRSd was 168 ± 24 ms. LVSP in close proximity to LBB had longer V6RWPT (98 ± 14 vs 79 ± 13, p < 0.001) and shorter QRSd then nsLBBP (150 ± 16 vs 160 ± 20, p = 0.162).

The systolic blood pressure and left ventricular dyssynchrony were during LVSP in close proximity to LBBP the same as during nsLBBP (121 ± 19 mmHg vs. 122 ± 19 mmHg, p = 0.179 and 14 ± 6 ms vs. 16 ± 7 ms vs, p = 0.312). nsLBBP was associated with greater left-to-right ventricular dyssynchrony than LVSP in close proximity to LBBP (26 ± 12 ms vs 19 ± 7 ms, p = 0.048).

LVSP in close proximity to the LBB does not differ from LBBP in terms of electrical ventricular dyssynchrony and acute hemodynamic response in patients with LBBB and indicated for CRT. For these reasons LVSP in close proximity to the LBB may serve as alternative CRT method to LBBP and BVP.