Non-selective His bundle pacing (HBP) is noninferior to selective HBP in patients undergoing de novo permanent pacemaker implantation for bradycardia, according to a study that revealed similar outcomes for death and heart failure (HF) between the two therapies.
The feasibility and safety of HBP, often considered as an alternative to right ventricular pacing due to the latter’s known correlation with cardiomyopathy and heart failure, has already been established, first author Dominik Beer, DO, and colleagues wrote in JACC: Clinical Electrophysiology. Selective HBP (S-HBP) implies capture of the His bundle alone with resulting conduction via the His-Purkinje axis, leading to a QRS duration and morphology identical to the patient’s native QRS duration; non-selective HBP (NS-HBP) implies the additional capture of the septal myocardium, resulting in right ventricular (RV) myocardial pre-excitation and initial slurring and widening of the QRS complex.
“In both S- and NS-HBP, the left ventricular (LV) activation occurs via the native conduction system maintaining LV synchrony and is expected to prevent adverse clinical outcomes,” Beer and co-authors wrote. “However, it is unknown whether the RV myocardial pre-excitation and resultant QRS prolongation during NS-HBP would result in adverse clinical outcomes when compared with outcomes for S-HBP.”
The authors attempted to answer that question with an analysis of 350 patients enrolled consecutively in the Geisinger and Rush University HBP registries, all of whom were treated successfully with HBP for bradyarrhythmic indications. To qualify, participants needed to demonstrate a 20% or greater burden of ventricular pacing three months post-implantation.
Patients were categorized into S-HBP or NS-HBP based on their QRS morphology at three months, resulting in a S-HBP study group of 232 individuals and an NS-HBP cohort of 118 individuals. Beer et al.’s primary outcome was a combined endpoint of all-cause mortality or HF hospitalization.
Compared to patients in the S-HBP group, those in the NS-HBP group:
- Were more often men (64% vs. 50% of S-HBP patients)
- Had higher rates of ischemic cardiomyopathy (24% vs. 14%)
- Had more cases of permanent atrial fibrillation (18% vs. 8%)
- Had a higher incidence of infranodal atrioventricular block (40% vs. 9%)
Eighty-one of 232 patients in the NS-HBP cohort (35%) and 23 of 118 patients in the S-HBP cohort (19%) reached the study’s primary analysis endpoint, Beer and colleagues reported. Subgroup analyses of patients at the highest risk for complications—those with higher pacing burden or lower LV ejection fraction—didn’t reveal any incremental risk with NS-HBP.
In a related editorial, Santosh K. Padala and Kenneth A. Ellenbogen pointed out it’s critical to understand that while the investigators found no evidence that the two treatments were different, it doesn’t necessarily mean they’re equivalent.
“In other words, ‘No proof of a difference is not equivalent to proof of no difference,’” Padala and Ellenbogen said, suggesting future work should analyze specific measurements that weren’t present in Beer and colleagues’ study.
“Future studies that focus on invasive hemodynamic measurements, echocardiographic measurements of cardiac chamber size and function, and noninvasive body surface mapping to document activation patterns should shed more light on the clinical consequences of long-term pacing with NS-HBP compared with S-HBP,” they wrote. “Clearly, we are at the beginning of our understanding of the factors that determine success in implanting pacing leads in the conduction system and the consequences of long-term pacing from different sites in the conduction system.”