An incremental energy stimulation test to predict success in left bundle branch capture

Abstract

Abstract Introduction Left bundle branch (LBB) stimulation is guided by fluoroscopic projections and electrocardiographic criteria limited by positional variations. Purpose To evaluate an incremental energy stimulation test (IEST) to optimize success. Methods Prospective, non-randomized experimental study for proof-of-concept analysis (N=23), consisting on: (i) stimulation at three locations at the high, middle and low right mid-ventricular septum (right oblique 30o); and (ii) continuous unipolar stimulation (lumenless fixed helix electrode) at each location with increasing outputs (2 volt x 0.5 ms up to 10 vol x 1.5 ms). The final position for lead penetration was made by the operator blinded to the results of the IEST. Results IEST shortened the S-LVAT (δ-S-LVAT) up to 6.4±5 ms (range 0 to 18 ms), 8±8 ms (range 0 to 36 ms) and 5.5±5 ms (range 0 to 20 ms) respectively for high, mid, and low sites (Figure, panel A and B). There was not observed any paired correlation between the magnitude of the δ-S-LVAT at the three different positions (Pearson 0.36, 0.12 and 0.22; p= 0.1, 0.6 and 0.4 respectively), suggesting that the δ-S-LVAT is site specific. The final position for lead penetration was medium in 17 cases vs low in 6 cases. The low-output S-LVAT interval at the final position before lead penetration was positively correlated with the final S-LVAT achieved after lead penetration (Pearson 0.44; p=0.04), but the magnitude of the correlation increased with the high-output S-LVAT interval (Pearson 0.57; p=0.006) suggesting a better prediction performance (Figure, panel C). A complex relationship was observed where higher δ-S-LVAT values were associated with shorter S-LVAT after penetration and final position of the lead. In fact, for cases with low-output S-LVAT interval > 100 ms, the δ-S-LVAT significantly correlated with S-LVAT after penetration and final position of the lead (Pearson -0.61; p=0.026). Conclusions IEST lead to a site-specific shortening of the S-LVAT, pointing to optimized positions for LBB pacing. The technique provides with additional diagnostic criteria to determine the better site for lead penetration.