Atrio-ventricular (AV) optimized pacing may improve hemodynamic function in heart failure (HF) patients with long PR intervals without a left bundle branch block, according to research published in the Journal of the American College of Cardiology: Clinical Electrophysiology.
Approximately 34% of patients with HF have a left bundle branch block (LBBB). Direct His bundle pacing has been shown to successfully reverse LBBB when conventional left ventricle lead implantation was not possible. However, there has been no prior research to determine whether His bundle pacing could be used in HF patients with a narrow QRS duration and a long PR interval.
“The results of this study may be the first step towards extending pacing therapy for heart failure to a new population, namely patients with a long PR interval without left bundle branch block. Between 17% to 33% of heart failure patients in stable sinus rhythm have evidence of PR prolongation,” the authors wrote.
The study included patients diagnosed with systolic HF, PR prolongation, and narrow QRS or a right bundle branch block. Fourteen patients received temporary His bundle pacing and biventricular pacing. The researchers performed AV optimization on the participants using invasive systolic blood pressure to achieve parabolic responses.
The researchers compared systolic blood pressure with intrinsic ventricular conduction and found a mean rate of 4.1 mm Hg for His pacing, and 4.3 mm Hg for biventricular pacing. The mean increment of QRS duration was 22 ms longer with biventricular pacing, and only 0.5 ms longer with His pacing.
Researchers also performed right ventricular apical pacing in 11 of the patients, but they found no difference in characteristics between these patients and the rest of the cohort. The mean improvement rate in systolic blood pressure was 0.9 mmHg, which did not reflect significant improvement.
The overall improvement in acute hemodynamic function was approximately 60% of the effect size reported from biventricular pacing for LBBB.
Biventricular pacing has been shown to reduce mortality rates and symptoms for patients with LBBB, and further studies should be conducted to establish whether His bundle pacing could achieve the same effects. The authors noted that randomly assigned blind trials could determine whether the hemodynamic improvements could influence long-term benefits.
“Seeing hemodynamic improvements when another defect, in another part of the conduction system upstream of the bundle branches, is targeted with pacing therapy is encouraging,” they concluded. “The next step, like with biventricular pacing, is to see whether the acute improvements in function also translate into longer clinical benefit.”
- Sohaib SM, Wright I, Lim E, et al. AV Optimised Direct His Bundle Pacing Improves Acute Hemodynamic Function in Patients with Heart Failure and PR Prolongation without LBBB. JACC Clin Electrophysiol.. 2015; doi: 10.1016/j.jacep.2015.08.008.