Research Highlights:
- Left bundle branch pacing, a pacemaker technique that follows the heart's natural electrical pathway, led to better outcomes for people with an implanted pacemaker compared to those with pacemakers with right ventricular pacing, the standard treatment for people with atrioventricular block, a condition also known as heart block, which is a type of heart rhythm disorder.
- The international, multicenter, clinical OptimPacing trial with nearly 700 adults found that people with pacemakers using left bundle branch pacing had fewer deaths, hospitalizations for heart failure and incidences of pacing-induced cardiomyopathy (weakened heart muscle) compared to people with pacemakers using right ventricular pacing.
- During a planned interim analysis, left bundle branch pacing met the study's pre-established criteria for superiority over right ventricular pacing, leading an independent monitoring committee and the study's steering committee to recommend ending the trial early.
- Note: This trial is simultaneously published today as a full manuscript in the peer-reviewed scientific journal NEJM.
This news release contains updated information provided by the researchers and not listed in the abstract.
CHICAGO, Nov. 8, 2026 — People with heart block, a type of heart rhythm disorder, had lower incidences of death, hospitalization for heart failure and pacing-induced cardiomyopathy when the pacemaker technique implemented was left bundle branch pacing rather than right ventricular pacing, according to independent, preliminary, late-breaking science presented today at the American Heart Association's Scientific Sessions 2026. The meeting on Nov. 6-9 in Chicago is a premier global exchange of the latest scientific advancements, research and evidence-based clinical practice updates in cardiovascular science.
Atrioventricular block, also known as heart block, is a condition in which electrical signals between the heart's upper chambers (atria) and lower chambers (ventricles) are delayed or interrupted. This can cause symptoms including a very slow heart rate (known as bradycardia), fatigue, dizziness, fainting, chest pain and, in severe cases, cardiac arrest.
The standard treatment for heart block is a pacemaker that sends electrical signals to the heart's right ventricle. The pacemaker technique that is the current standard of care for heart block is called right ventricular pacing, and it has been routinely used for decades to prevent bradycardia and cardiac arrest in people with atrioventricular block. Although it can keep the heart from beating too slowly, pacing only the right side can make the heart's lower chambers beat out of sync. Over time, this imbalance may enlarge or weaken the heart muscle (pacing-induced cardiomyopathy) and contribute to heart failure in some people.
A newer pacing technique called left bundle branch pacing sends the pacemaker signal into part of the heart's own electrical pathway. It mimics the heart's natural electrical activation sequence, which helps the lower chambers squeeze in a more coordinated pattern.
"Not all pacing options are the same, and people who need a pacemaker to keep their heart beating properly should talk with their healthcare team about which pacing approach is appropriate for their condition," said study author Jiangang Zou, M.D., Ph.D., a professor of cardiology at First Affiliated Hospital, Nanjing Medical University in Nanjing, China. "Our findings show that left bundle branch pacing helped the heart beat in a more natural way and was linked to fewer serious heart-related events than the standard pacing approach of right ventricular pacing."
The international, multicenter OptimPacing trial tracked nearly 700 men and women with atrioventricular block being treated with a pacemaker over a five-year period.
What are the study's key findings?
- Left bundle branch pacing was associated with a 59% lower risk of death, heart failure hospitalization or cardiomyopathy compared with outcomes in the right ventricular pacing group.
- At four years, an estimated 8.5% of participants in the left bundle branch pacing group had died, were hospitalized for heart failure or developed pacing-induced cardiomyopathy, compared with 19.2% in the right ventricular pacing group.
- No participants in the left bundle branch pacing group developed pacing-induced cardiomyopathy, compared with 11.7% in the right ventricular pacing group.
- Heart failure hospitalization occurred in 1.5% of the left bundle branch pacing group vs. 2.9% of the right ventricular pacing group.
- An independent data monitoring committee reviewed the results of the planned interim analysis after a median 3-year follow up, which found that the primary outcome of mortality, heart failure hospitalization and pacing-induced cardiomyopathy occurred in 8.5% of patients receiving left bundle branch pacing compared with 19.2% receiving right ventricular pacing. The committee recommended ending the trial early because left bundle branch pacing met the study's pre-established threshold for superiority.
"We expected that the group with left bundle branch pacing would do better than the group with right ventricular pacing. However, the difference between the two groups was greater than we expected. This study shows that left bundle branch pacing should be the first choice for patients with heart block who need a pacemaker," Zou said.
What are the study's details, background, design and limitations?
- The trial was conducted at 17 centers in mainland China, Hong Kong, the United Kingdom, Poland and the United States from June 2021 to January 2025.
- The trial included 685 adults with an average age of 68.4 years, and 57.5% were men. Participants had second-degree or complete atrioventricular block, or ongoing atrial fibrillation with an average heart rate below 50 beats per minute and related symptoms. Most of the participants had normal left ventricular ejection fraction (LVEF), a measure of the heart's pumping strength, at the start of the study.
- Half of the participants were randomly assigned to get pacemakers with left bundle branch pacing, and the other half received pacemakers with right ventricular pacing.
- Information was collected before the participants were assigned to left bundle branch pacing or right ventricular pacing, immediately after pacemaker implantation, at 6 and 12 months post-implantation, and then annually thereafter.
- Researchers tracked participants' deaths, heart failure hospitalizations, pacing-induced cardiomyopathy, other safety events, heart ultrasound results and pacemaker data.
- All major health events were independently reviewed and confirmed by a committee that did not know which treatment the patients received.
- The study had several limitations. The trial's early termination could potentially lead to an overestimation of the benefits of left bundle branch pacing and reduce the precision of estimates. Most participants started with normal heart pumping strength (normal ejection fraction), so the findings may not apply to people with already reduced heart function. All left bundle branch pacing procedures used the same type of lead, so it is not known whether the results apply to other pacing tools.
"Future research is needed to refine which pacing technique is most appropriate for which patients, compare different pacing approaches that follow the heart's natural electrical system, and examine long‑term safety and cost‑effectiveness to help inform updates to clinical guidelines," Zou said.
Co-authors and disclosures are listed in the abstract. The Project on New Technology of Jiangsu Province, Clinical Competence Improvement Project of Jiangsu Province Hospital, National Natural Science Foundation of China and 135 Project for Disciplines of Excellence–Clinical Research Incubation Project of West China Hospital funded the study.
Statements and conclusions of studies that are presented at the American Heart Association's scientific meetings are solely those of the study authors and do not necessarily reflect the Association's policy or position. The Association makes no representation or guarantee as to their accuracy or reliability. Abstracts presented at the Association's scientific meetings are not peer-reviewed, rather, they are curated by independent review panels and are considered based on the potential to add to the diversity of scientific issues and views discussed at the meeting. The findings are considered preliminary until published as a full manuscript in a peer-reviewed scientific journal.
