Washington: A new therapy called ‘His bundle’ pacing that engages and restores the heart’s natural physiology could pave the way for more treatment options for heart failure patients who also suffer from electrical disturbances, according to a pilot study.
The study called ‘His SYNC trial’ was published in the Journal of the American College of Cardiology.
Researchers compared the effectiveness of two different cardiac resynchronization therapies or treatments to correct irregularities in the heartbeat through implanted pacemakers and defibrillators.
The current standard of care, known as biventricular pacing, uses two pacing impulses in both lower chambers, whereas the newer approach, called ‘His bundle’ pacing, attempts to work toward engaging and restoring the heart’s natural physiology. The two approaches have never before been directly compared in a head-to-head clinical trial.
“This is the first prospective study in our field to compare outcomes between different ways to achieve cardiac resynchronization,” said cardiologist Roderick Tung, the Director of Cardiac Electrophysiology and EP Laboratories at the University of Chicago Medicine.
“Through ‘His bundle pacing’, we are trying to tap into the normal wiring of the heart and restore conduction the way nature intended. Previously, we have just accepted that we had to bypass it through pacing two ventricles at a time,” Tung added.
The trial involved 40 adult patients across seven institutions in the Midwest.
Biventricular pacing involves implanting wires, called leads, to simultaneously pace the right and left ventricles of the heart. A pacemaker then sends a timed electric pulse to the two leads with the goal of a synchronized contraction, which closely simulates the heart’s natural heartbeat.
Nevertheless, roughly 30 percent of patients do not respond to biventricular pacing treatment, which has been shown to improve survival in clinical trials.
Tung’s team looked to see if another resynchronization method could help reduce that number by doing a clinical trial comparison between biventricular pacing and ‘His bundle pacing’.
‘His bundle’ pacing involves implanting a single lead at the start of the heart’s wiring system, which then naturally branches in two to organically distribute the pacemaker’s electric pulse to both ventricles.
“Permanent ‘His bundle’ pacing has been around for almost 20 years, but until now there has not been a randomized clinical trial on how it compares to biventricular pacing,” Tung said.
Tung and his team believe a ‘His bundle’ pacing approach showed comparable rates of response, warranting further study.
“We need to learn how to better identify patients who cannot and will not respond to His bundle pacing,” Tung said.
“During this pilot study, we learned that the net was cast too wide, and patients with IVCD can’t be corrected and improved by ‘His bundle’ pacing. His SYNC II, our planned follow-up study, will specifically exclude these patients and this is perhaps the most valuable lesson from the pilot, in addition to estimated treatment effect size,” Tung added.
After six months, researchers compared the electrical synchronization and structural function of the two patient groups’ hearts. Although they expected ‘His bundle’ pacing to be superior, they found no overall significant differences in the two groups, with comparable rates of electrical resynchronization and echocardiographic response.
After one year, there were no differences in the number of hospitalizations or deaths.
Noting the pilot study was limited by its size, Tung said the results indicate further investigation is needed.
“Pilot studies are never meant to be conclusive. They are meant to inform us about effect size, safety and feasibility to help select appropriate patients and power larger studies,” Tung said.