HIS bundle pacing as good as CRT, the "catch" is higher thresholds, HIS-Alternative study.
For patients with heart failure who require cardiac resynchronization therapy (CRT) to correct left bundle branch block (LBBB), His-bundle pacing may be a feasible alternative to traditional biventricular pacing, suggests a pilot randomized trial published this week in JACC. The present study is the largest randomised study between His-CRT and biventricular pacing (BiV-CRT) to date.
Though biventricular-CRT has been an established treatment for patients with symptomatic heart failure and LBBB for over a decade, it has limitations like difficulty of finding a spot to place the LV lead in many patients and the possibility of phrenic nerve stimulation and high pacing thresholds in others. His-bundle pacing, thought to perhaps provide better activation of the heart's electrical system, has emerged as a potential alternative. "We can almost get normal conduction in those that we can succeed in placing the lead in the right spot", Michael Vinther, MD, PhD (The Heart Centre, Rigshospitalet, Copenhagen, Denmark), reported at the virtual European Heart Rhythm Association (EHRA) Congress 2021.
The study included 50 patients (mean age 66 years; 64% men) who had symptomatic systolic heart failure, LBBB defined according to strict criteria, and an indication for CRT. Most patients (78%) had nonischemic cardiomyopathy, with an average LVEF of 29% at baseline.
Patients were randomized to a first attempt with either His-CRT or biventricular-CRT; the alternate approach was tried if that failed. Ultimately, the planned lead was placed in all but one patient in the biventricular group, whereas seven patients in the His-CRT group (28%) needed to crossover to biventricular pacing.
Procedure time was longer in the His-CRT group (137 vs 102 min; P < 0.01), with no differences in fluoroscopy time or radiation dose.
In the intention-to-treat analysis, both types of pacing improved QRS duration, LVEF (increasing to about 45%), LV end-systolic volume (decreasing by about 35%), NT-proBNP level, 6-minute walk distance, and NYHA class after 6 months, with no differences between trial arms.
Pacing thresholds were higher in the His-CRT versus biventricular-CRT group at baseline (1.8 vs 1.2 V) and at 6 months (2.3 vs 1.4 V; P < 0.05 for both), indicating that His-CRT will drain batteries more quickly and require more-frequent device changes, Vinther said.
Vinther acknowledged that His-pacing is not yet ready to be considered as a first-line therapy in clinical practice, noting that the required tools are not yet optimal, that failure to implant the leads will be more frequent, and that thresholds will be higher.
"We can hope that with better tools and maybe also better leads or maybe even other pacemakers, we could overcome that in the future," Vinther noted.
The trial was limited by its small size (50 patients) and its conduct at a single center, but "we are confident to say that His-CRT holds promise as an alternative to biventricular pacing in selected heart failure patients," Vinther concluded. "And we hope that our study, among others, can pave the way for a larger randomized study that can establish the position of His-CRT as either superior or noninferior to BiV-CRT and establish its place in the guidelines."
• Source: JACC Electrophysiology Vinther M, Risum N, Svendsen JH, et al. A randomized trial of His pacing versus biventricular pacing in symptomatic heart failure patients with left bundle branch block (His-Alternative). J Am Coll Cardiol EP. 2021;Epub ahead of print.
