The V6-V1 interpeak interval: a novel criterion for the diagnosis of left bundle branch capture

We hypothesized that during left bundle branch (LBB) area pacing, the various possible combinations of direct capture/non-capture of the septal myocardium and the LBB result in distinct patterns of right and left ventricular activation. This could translate into different combinations of R-wave peak time (RWPT) in V₁ and V₆. Consequently, the V₆-V₁ interpeak interval could differentiate the three types of LBB area capture: non-selective (ns-)LBB, selective (s-)LBB, and left ventricular septal (LVS).

Patients with unquestionable evidence of LBB capture were included. The V₆-V₁ interpeak interval, V₆RWPT, and V₁RWPT were compared between different types of LBB area capture. A total of 468 patients from two centres were screened, with 124 patients (239 electrocardiograms) included in the analysis. Loss of LVS capture resulted in an increase in V₁RWPT by ≥15 ms but did not impact V₆RWPT. Loss of LBB capture resulted in an increase in V₆RWPT by ≥15 ms but only minimally influenced V₁RWPT. Consequently, the V₆-V₁ interval was longest during s-LBB capture (62.3 ± 21.4 ms), intermediate during ns-LBB capture (41.3 ± 14.0 ms), and shortest during LVS capture (26.5 ± 8.6 ms). The optimal value of the V₆-V₁ interval value for the differentiation between ns-LBB and LVS capture was 33 ms (area under the receiver operating characteristic curve of 84.7%). A specificity of 100% for the diagnosis of LBB capture was obtained with a cut-off value of >44 ms.

The V₆-V₁ interpeak interval is a promising novel criterion for the diagnosis of LBB area capture.