Improvement in electrocardiographic parameters of repolarization related to sudden death in patients with ventricular dysfunction and left bundle branch block after cardiac resynchronization through His bundle pacing

Background Cardiac resynchronization therapy (CRT) through permanent His bundle pacing (p-HBP) normalizes interventricular conduction disorders and QRS. Similarly, there are immediate and long-term changes in repolarization, which could be prognostic of a lower risk of sudden death (SD) at follow-up. We aimed to compare the changes in different electrocardiographic (ECG) repolarization parameters related to the risk of SD before and after CRT through p-HBP.Methods In this prospective, descriptive single-center study (May 2019 to December 2021), we compared the ECG parameters of repolarization related to SD in patients with non-ischemic dilated cardiomyopathy, left bundle branch block (LBBB), and CRT indications, at baseline and after CRT through p-HBP.Results Forty-three patients were included. Compared to baseline, after CRT through p-HBP, there were immediate significant changes in the QT interval (ms): 445 [407.5-480] vs 410 [385-440] (p = 0.006), QT dispersion (ms): 80 [60-100] vs 40 [40-65] (p < 0.001), Tp-Te (ms): 90 [80-110] vs 80 [60-95] (p < 0.001), Tp-Te/QT ratio: 0.22 [0.19-0.23] vs 0.19 [0.16-0.21] (p < 0.001), T wave amplitude (mm): 6.25 [4.88-10] vs - 2.5 [- 7-2.25] (p < 0.001), and T wave duration (ms): 190 [157.5-200] vs 140 [120-160] (p = 0.001). In the cases of the corrected QT (Bazzett and Friederichia) and the Tp-Te dispersion, changes only became significant at 1 month post-implant (468.5 [428.8-501.5] vs 440 [410-475.25] (p = 0.015); 462.5 [420.8-488.8] vs 440 [400-452.5] (p = 0.004), and 40 [30-52.5] vs 30 [20-40] (p < 0.001), respectively) (Table 1). Finally, two parameters did not improve until 6 months post-implant: the rdT/JT index, 0.25 [0.21-0.28] baseline vs 0.20 [0.19-0.23] 6 months post-implant (p = 0.011), and the JT interval, 300 [240-340] baseline vs 280 [257-302] 6 months post-implant (p = 0.027). Additionally, most of the parameters continued improving as compared with immediate post-implantation.Conclusions After CRT through His bundle pacing and LBBB correction, there was an improvement in all parameters of repolarization related to increased SD reported in the literature.