Assessment of ventricular mechanical synchronization after left bundle branch pacing using 2-D speckle tracking echocardiography.

BACKGROUND The left bundle branch pacing (LBBP) makes the ventricular depolarization closer to the physiological state and shortens QRS duration. The purpose of this study is to explore the ventricular systolic mechanical synchronization after LBBP in comparison with traditional right ventricular pacing (RVP) using two-dimensional strain echocardiography (2D-STE). METHODS Thirty-two patients who received LBBP (n = 16) or RVP (n = 16) from October 2018 to October 2019 and met the inclusion criteria were included in this retrospective study. Electrocardiogram (ECG) characteristics, pacing parameters, pacing sites, and safety events were assessed before and after implantation. Acquisition and analysis of ventricular systolic synchronization were implemented using 2D-STE. RESULTS In RVP group, ECG showed left bundle branch block patterns. At LBBP, QRS morphology was in the form of right bundle branch block, and QRS durations were significantly shorter than that of the RVP QRS (109.38 ± 12.89 vs 149.38 \± 19.40 ms, P < .001). Both the maximum time differences (TD) and SDs of the 18-segments systolic time to peak systolic strain were significantly shorter under LBBP than under RVP (TD, 66.62 ± 37.2 vs 148.62 ± 43.67 ms, P < .01; SD, 21.80 ± 12.13 vs 52.70 ± 17.72 ms, P < .01), indicating that LBBP could provide better left ventricular mechanical synchronization. Left and right ventricular pre-ejection period difference was significantly longer in RVP group than in LBBP group (10.23 ± 3.07 vs 39.94 ± 14.81 ms, P < .05), indicating left and right ventricular contraction synchronization in LBBP group being better than in RVP group. CONCLUSION LBBP is able to provide a physiologic ventricular activation pattern, which results in ventricular mechanical contraction synchronization.