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

Figures

• 

  Figure 1. Left bundle branch (LBB) area pacing with hypothesized ventricular activation patterns during QRS morphology transitions. (A) Transition from non-selective LBB capture to selective LBB capture results in delay of right ventricular (RV) activation due to loss of RV depolarization via direct septal myocardial activation. RV activation proceeds via transseptal conduction from left septal fascicles. Electrocardiographic markers of delayed RV activation are V1 R-wave peak time prolongation and increase in V6-V1 interval. (B) Transition from non-selective LBB capture to septal does not influence right ventricular activation but delays left ventricular activation due to loss of direct LBB capture.

• 

  Figure 2. Three types of capture during left bundle branch area pacing (LBB-P) observed in the same patient during pacemaker implantation; leads V1 and V6 are recorded simultaneously. During the transition from non-selective LBB-P to selective LBB-P, there is an increase in V1 R-wave peak time (V1RWPT) but not in V6RWPT, resulting in a wider V6-V1 interpeak distance. In contrast, during the transition from non-selective LBB-P to left ventricular septal (LVS) myocardial capture there is an increase in V6RWPT but not in V1RWPT, resulting in a shorter V6-V1 interpeak distance.

• 

  Figure 3. Receiver operating characteristic curve for lead V6-V1 interpeak interval for the diagnosis of non-selective left bundle branch capture vs. left ventricular septal capture; the V6-V1 interpeak interval value of 32.5 ms was found as an optimal cut-off point with a sensitivity of 71.8% and a specificity of 90.0%. AUC, area under the curve.

• 

  Figure 4. The distribution of V6-V1 interval values (upper panel) shows better separation between different left bundle branch area capture types than either the distribution of V1RWPT (middle panel) or V6RWPT (lower panel). Although there is a considerable overlap of V6-V1 interval values (upper panel), as short interval is observed with all types of left bundle branch area capture, long values (indicating larger RV delay) are only possible with LBB capture and this makes this criterion diagnostically valuable.

• 

  Figure 5. The distribution of V6 R-wave peak time (RWPT) values during non-selective left bundle branch capture in patients with V6-V1 interpeak interval ≥33 ms (blue line) and V6-V1 interpeak interval <33 ms (red line). In approximately half of the patients with V6-V1 interpeak interval indicating left bundle branch capture (i.e. ≥33 ms, blue line), the V6RWPT was >75 ms (shaded area), indicating left ventricular septal myocardial capture and leading to misdiagnosis.

• 

  Figure 6. Impact of native QRS type on V1 R-wave peak time (V1RWPT), V6RWPT, and V6-V1 interpeak interval in patients with narrow QRS, right bundle branch block (RBBB), and more diseased conduction system, including RBBB with anterior or posterior fascicular block (FB), left bundle branch block (LBBB), non-specific intraventricular conduction disturbance (NIVCD), or ventricular escape rhythm/asystole. In patients with more severely diseased conduction system, the V1RWPT and V6RWPT were prolonged to a similar degree; consequently, their difference, the V6-V1 interval, remained stable, that is it was not affected by the type of native QRS. Measurements were done during non-selective left bundle branch capture.