His-bundle pacing versus biventricular pacing in cardiac resynchronization therapy patients: A crossover design comparison
Introduction
Biventricular pacing (BiVP) is the technique by which cardiac resynchronization therapy (CRT) is implemented. The BiVP concept grew from the intuitive notion that simultaneous left ventricular (LV) and right ventricular (RV) pacing would mimic normal ventricular activation sufficiently to reverse LV compromise due to eccentric ventricular activation, the latter caused by bundle branch block (BBB).1 This therapy has proven effective, although the nonresponder rate remains around 30% to 40%.2 One limitation may be that BiVP insufficiently mimics rapid parallel ventricular activation by the His–Purkinje system. His-bundle pacing (HBP) can address this limitation.
BBB can be the result of discrete disease in the proximal His bundle. The observation in 1919 by Kaufman and Rothberger of longitudinal fascicular dissociation in the His bundle was explained by ultrastructural and electrophysiologic studies 6 decades later.3, 4 By pacing into the His bundle in canine models and human BBB, Scherlag et al5, 6 demonstrated normalization of the QRS, thus confirming the concept of longitudinal dissociation. In the current era of CRT, one would expect that normalization of the QRS by HBP (electrical resynchronization) would, in a truly physiologic manner, effect mechanical resynchronization.
We previously demonstrated HBP-induced electrical resynchronization in 8 of 10 consecutively tested patients at the time of biventricular implant, temporarily actively fixing a pacing lead in the His position.7 The study raised the question explored in this study: can electrical resynchronization effect mechanical resynchronization, and might it be sufficient to result in CRT? Herein we report the results of a crossover comparison of HBP and BiVP in sequential patients presenting for CRT.
Section snippets
Patient selection
Patients presenting for CRT with QRS duration >130 ms were candidates for the study if they were 18 years or older and able to provide consent. Exclusion criteria included previous CRT, atrial fibrillation, complete infrahisian block, irreversible New York Heart Association (NYHA) class IV congestive heart failure, and life expectancy <12 months. Twenty-nine patients were enrolled at 2 participating centers, and 4 implanting physicians participated in the trial. The patients provided informed
Enrollment
Twenty-nine patients consented to the study and were brought to the laboratory for attempted implantation. Twenty-eight patients had left bundle branch block (LBBB), with average QRS duration 162 ms (138–186 ms). Demographic data are given in Online Supplementary Table 1. One patient had atypical right bundle branch block (RBBB) with rightward axis and QRS duration 188 ms. Twenty-one of 29 patients (72%) demonstrated QRS narrowing in response to HBP at the time of implant. Fourteen of 16
Discussion
Using a crossover study design, we compared the clinical response to permanent HBP and BiVP in patients with standard indications for CRT. Despite the absence of a His-bundle–specific pacing system and the fact that we were targeting diseased His–Purkinje tissue, we were able to demonstrate the feasibility of HBP to reengage preserved left fascicular tissue with QRS normalization in the majority of patients tested and to show a clinical response that was similar to BiVP. Of the patients
Conclusion
In this study, we showed that it is feasible to normalize the QRS in patients with BBB disease with a permanently implanted HBP lead, and that HBP can elicit a 6-month CRT response comparable to that of BiVP. Consistent with our previous publication7 and with registry data from the Italian School,9 acute implementation of HBP in this study was not difficult, which is notable given that the system we are using was not specifically designed or optimized to obtain HBP sites. A variety of
Acknowledgments
We thank the following contributors without whose assistance this work would not have been possible: Joseph Miller and Susan Calame for assiduous data acquisition and helpful insights; Terri Wright of Medtronic, Minneapolis, who was the clinical manager of the study; and Dr. Alan Bank, Ryan Gage, and Kevin Burns from St. Paul Heart in Minnesota, who provided expertise as the blinded echocardiographic core laboratory. Additional thanks to Dr. Zach Whinnett of Imperial College, London, for
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This work was funded by a clinical research grant from Medtronic Inc. Dr. Lustgarten receives research support from, and is a consultant and advisor for, Medtronic. J. Koehler, E. Liberman, and T. Sheldon are employees of Medtronic