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BackgroundHis bundle pacing is a new method for delivering cardiac resynchronization therapy (CRT).ObjectivesThe authors performed a head-to-head, high-precision, acute crossover comparison between His bundle pacing and conventional biventricular CRT, measuring effects on ventricular activation and acute hemodynamic function.MethodsPatients with heart failure and left bundle branch block referred for conventional biventricular CRT were recruited. Using noninvasive epicardial electrocardiographic imaging, the authors identified patients in whom His bundle pacing shortened left ventricular activation time. In these patients, the authors compared the hemodynamic effects of His bundle pacing against biventricular pacing using a high-multiple repeated alternation protocol to minimize the effect of noise, as well as comparing effects on ventricular activation.ResultsIn 18 of 23 patients, left ventricular activation time was significantly shortened by His bundle pacing. Seventeen patients had a complete electromechanical dataset. In them, His bundle pacing was more effective at delivering ventricular resynchronization than biventricular pacing: greater reduction in QRS duration (−18.6 ms; 95% confidence interval [CI]: −31.6 to −5.7 ms; p = 0.007), left ventricular activation time (−26 ms; 95% CI: −41 to −21 ms; p = 0.002), and left ventricular dyssynchrony index (−11.2 ms; 95% CI: −16.8 to −5.6 ms; p < 0.001). His bundle pacing also produced a greater acute hemodynamic response (4.6 mm Hg; 95% CI: 0.2 to 9.1 mm Hg; p = 0.04). The incremental activation time reduction with His bundle pacing over biventricular pacing correlated with the incremental hemodynamic improvement with His bundle pacing over biventricular pacing (R = 0.70; p = 0.04).ConclusionsHis resynchronization delivers better ventricular resynchronization, and greater improvement in hemodynamic parameters, than biventricular pacing.

Background Cardiac resynchronization therapy utilizing biventricular pacing is an effective therapy for patients with left ventricular (LV) systolic dysfunction, left bundle branch block, and heart failure. Benefits of biventricular pacing may be limited in patients with right bundle branch block (RBBB). Permanent His bundle pacing (HBP) has recently been reported as an option for cardiac resynchronization therapy. The aim of the study was to assess the feasibility and outcomes of HBP in patients with RBBB and heart failure. Methods HBP was attempted as a primary or rescue (failed LV lead implant) strategy in patients with reduced LV ejection fraction, RBBB, QRS duration ≥120 ms, and New York Heart Association class II to IV heart failure. Implant characteristics, New York Heart Association functional class, and echocardiographic data were assessed in follow-up. Results Mean age was 72±10 years, female 15%, with an average LV ejection fraction of 31±10%. HBP was successful in 37 of 39 patients (95%) with narrowing of RBBB in 78% cases. His capture and bundle branch block correction thresholds were 1.1±0.6 V and 1.4±0.7 V at 1 ms, respectively. During a mean follow-up of 15±23 months, there was a significant narrowing of QRS from 158±24 to 127±17 ms ( P =0.0001), increase in LV ejection fraction from 31±10% to 39±13% ( P =0.004), and improvement in New York Heart Association functional class from 2.8±0.6 to 2±0.7 ( P =0.0001) with HBP. Increase in capture threshold occurred in 3 patients. Conclusions Permanent HBP was associated with significant narrowing of QRS duration and improvement in LV function in patients with RBBB and reduced LV ejection fraction. Permanent HBP is a promising option for cardiac resynchronization therapy in patients with RBBB and reduced LV ejection fraction.

Background His‐bundle pacing (HBP) provides physiological ventricular activation. Observational studies have demonstrated the techniques’ feasibility; however, data have come from a limited number of centers. Objectives We set out to explore the contemporary global practice in HBP focusing on the learning curve, procedural characteristics, and outcomes. Methods This is a retrospective, multicenter observational study of patients undergoing attempted HBP at seven centers. Pacing indication, fluoroscopy time, HBP thresholds, and lead reintervention and deactivation rates were recorded. Where centers had systematically recorded implant success rates from the outset, these were collated. Results A total of 529 patients underwent attempted HBP during the study period (2014‐19) with a mean follow‐up of 217 ± 303 days. Most implants were for bradycardia indications. In the three centers with the systematic collation of all attempts, the overall implant success rate was 81%, which improved to 87% after completion of 40 cases. All seven centers reported data on successful implants. The mean fluoroscopy time was 11.7 ± 12.0 minutes, the His‐bundle capture threshold at implant was 1.4 ± 0.9 V at 0.8 ± 0.3 ms, and it was 1.3 ± 1.2 V at 0.9 ± 0.2 ms at last device check. HBP lead reintervention or deactivation (for lead displacement or rise in threshold) occurred in 7.5% of successful implants. There was evidence of a learning curve: fluoroscopy time and HBP capture threshold reduced with greater experience, plateauing after approximately 30‐50 cases. Conclusion We found that it is feasible to establish a successful HBP program, using the currently available implantation tools. For physicians who are experienced at pacemaker implantation, the steepest part of the learning curve appears to be over the first 30‐50 cases.