Paced QRS morphology and lead location in left bundle branch area pacing assessed by photon-counting cardiac computed tomography.

BACKGROUND

The relationship between the intra-septal lead position in left bundle branch area pacing (LBBAP) and paced QRS morphology remains incompletely understood. We used ultra high-resolution photon-counting computed tomography (PC-CT) to evaluate lead-tip location.

OBJECTIVE

We retrospectively analyzed 20 patients who underwent contrast-enhanced PC-CT after LBBAP implantations (9 with left bundle branch pacing [LBBP], 9 with left ventricular septal pacing [LVSP], and 2 with deep septal pacing [DSP]).

METHODS

Distances from the lead-tip to the LV and right ventricular (RV) endocardium (lead-tip to LV/RV), lead-tip to the presumed His bundle, and interventricular septal thickness were assessed.

RESULTS

The lead-tip to LV was significantly shorter in the LBBP group than in the other groups (LBBP: 1.8 ± 1.5 mm vs LVSP: 4.1 ± 1.4 mm vs DSP: 6.4 ± 0.4 mm, P < .01), with no significant differences in other anatomical parameters. Receiver operating characteristic analysis identified 3.2 mm as the optimal cutoff for LBB capture (area under the curve, 0.91; sensitivity, 100%; specificity, 81.8%). An initial q wave in lead V6 was observed exclusively in patients with a lead-tip to LV ≤3.2 mm (54.5% vs 0%, P < .01). The V1 R-wave peak time (V1RWPT) showed a moderate positive correlation with the lead-tip to RV (r = 0.636, P < 0.01). Pre-procedural echocardiographic septal thickness significantly underestimated the septal thickness at the penetration site (10.0 ± 1.9 mm vs 12.5 ± 3.8 mm, P < .01).

CONCLUSION

A lead-tip to LV distance ≤3.2 mm predicted LBB capture. An initial q wave in lead V6 may serve as a marker of lead positioning. V1RWPT was partially influenced by the lead-tip to RV.