Can V6 R-wave peak time be used as a substitute for negative dV/dTmax to assess local electrical activation? Implications for left bundle branch area pacing

Abstract Introduction Timing of local activation of unipolar signals is indicated by the maximum negative dV/dT. As this parameter cannot be measured using standard electrocardiographs, the stimulus to V6 R-wave peak time (V6RWPT) is used as a surrogate during left bundle branch area pacing (LBBAP) to evaluate conduction system capture. It is however unknown how these measurements are related and whether they may be used interchangeably. Furthermore, comparison of beat-to-beat variability of these measurements has not been reported. Objective To compare the automatic measures of V6RWPT and stimulus to maximum negative dV/dT in V6 (V6-dV/dTmax) Method A total of 50 patients (28% female, mean age 81.5 ± 9.0 years) undergoing LBBAP implantation were included and the ECGs of 10 consecutive paced beats at the final lead position were recorded at 1KHz and exported for analysis. After signal conditioning and power line noise removal, the signals were input to an algorithm in a novel EP recording System. The V6RWPT and V6-dV/dTmax intervals were automatically measured and compared. Beat-to-beat variability was evaluated by the variance of the measurements over the 10 consecutive beats. Results Of the 500 beats measured, 3 were excluded due to obvious morphological differences affecting the interval measurement. The timing from stimulus to V6RWPT and V6-dV/dTmax were 77.8 ± 13.2 ms and 95.9± 15.14 ms, respectively. The measurements showed excellent correlation (Pearson’s r = 0.94, p< 0.001) – see figure. The difference between the two measures was 18.1± 5.4 ms. There was a marginally greater beat-to-beat variability of the timings with V6-dV/dTmax (1.9ms vs 1.4ms, p=0.01). Conclusion Automatic measurement of V6RWPT and V6-dV/dTmax are strongly correlated with less beat-to-beat variability of V6RWPT. Therefore, V6RWPT may be used as surrogate marker for local depolarization during LBBAP implantation.Linear correlation plot