TL;DR
The international OptimPacing trial was stopped early after interim results favored left bundle branch pacing (LBBP) over conventional right ventricular pacing for a combined outcome in patients with atrioventricular block and a high expected pacing burden. The four-year estimated event rates were 8.5% with LBBP and 19.2% with right ventricular pacing; questions remain about which patients benefit and how the results should change practice.
An international randomized trial comparing left bundle branch pacing (LBBP) with conventional right ventricular pacing was stopped early for superiority after interim results favored LBBP for a combined outcome among patients with atrioventricular (AV) block and a high expected need for ventricular pacing. At an interim analysis after a median 35.1 months, the estimated four-year rate of death, heart-failure hospitalization or pacing-induced cardiomyopathy was 8.5% with LBBP, compared with 19.2% with right ventricular pacing.
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Researchers reported the OptimPacing results at the American Heart Association annual meeting in Chicago on November 9, 2026, and the study was published simultaneously in the New England Journal of Medicine. The primary outcome combined all-cause mortality, hospitalization for heart failure, and pacing-induced cardiomyopathy. The hazard ratio was 0.41 (95% confidence interval 0.23 to 0.75), favoring LBBP. The trial report says the study stopped early after the interim analysis showed superiority; the available material does not give the stopping committee’s detailed decision process.
In the individual outcomes reported, pacing-induced cardiomyopathy occurred in 0% of LBBP patients and 11.7% of those assigned to right ventricular pacing. Heart-failure hospitalization rates were 1.5% and 2.9%, respectively, while all-cause mortality was 7.4% and 7.7%. These component results are distinct from the combined primary outcome, and the mortality figures were similar between groups.
The trial randomized 702 patients in China, Europe and the United States from 2021 to 2025; 685 were included in the final analysis. Participants had an indication for a permanent pacemaker, an expected high ventricular pacing burden and a left ventricular ejection fraction above 35%. Their mean age was 68.4, and average ejection fraction was 63%. LBBP was successfully implanted in 96.8% of patients assigned to it, with left bundle branch capture confirmed in 87.6%. Procedure- and pacing-system-related complications were reported in 3.8% of the LBBP group and 3.2% of the right ventricular pacing group; two patients in each group required lead revision.
How Pacing Choice May Change
The findings address a practical decision for people who need a pacemaker and are expected to rely heavily on ventricular pacing. Conventional right ventricular pacing can alter the heart’s electrical activation; LBBP aims to engage the heart’s conduction system and maintain more natural electrical and mechanical coordination. The trial’s lower rate of pacing-induced cardiomyopathy is consistent with that rationale, while the difference in the composite outcome suggests the potential relevance extends beyond a change in ejection fraction alone.
Still, the results do not show that LBBP reduced every outcome individually: mortality was similar in the two groups, and the trial’s primary finding was a combined endpoint. The study could affect discussions about routine pacing strategies and future guidelines, but it does not by itself establish that LBBP is appropriate for every patient or every implant setting. Implant success, confirmed electrical capture, the patient’s underlying condition and the operator’s experience remain relevant.
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What OptimPacing Compared
OptimPacing was an open-label randomized trial of two ways to pace the ventricles. In the LBBP group, clinicians advanced a specialized lead through the interventricular septum toward the left ventricular subendocardium and used prespecified criteria to assess capture. In the comparison group, clinicians implanted a conventional active lead in the right ventricular septum or apex. The trial report says ventricular pacing burden exceeded 90% in both groups.
Earlier guidance had already recognized cardiac physiologic pacing as an option for selected patients. The 2023 Heart Rhythm Society guidelines gave it a class IIa recommendation for patients with an ejection fraction of 36% to 50% expected to need substantial ventricular pacing, and a class IIb recommendation for patients with normal ejection fraction in similar circumstances. The OptimPacing results may inform future discussion of those recommendations, but the source material does not report a guideline change.
The study excluded some patients, including candidates for an implantable cardioverter-defibrillator, cardiac resynchronization therapy, or CRT-defibrillator therapy. It also excluded patients with an ejection fraction of 36% to 50% who were willing to receive biventricular pacing. That selection matters when applying the results to people outside the trial’s population.
“This study provides evidence supporting the consideration of LBBP as a first-line pacing strategy for patients with an anticipated high ventricular pacing requirement.”
— Jiangang Zou, MD, PhD
Who Benefits Beyond the Trial
The reported results do not settle whether LBBP should be the default for all patients who need a pacemaker. The trial enrolled people with a high expected pacing burden and an ejection fraction above 35%; it excluded several groups who may be considered for other device strategies. How well the findings apply to people with different heart conditions remains uncertain. Wan specifically questioned whether patients with infiltrative heart disease, such as amyloidosis, would have similar effects.
The source material gives the interim follow-up duration and estimated four-year event rates but does not provide the full trial report’s stopping rules, detailed subgroup findings, or longer-term outcomes. It also does not explain how the early stop may affect estimates of treatment effect. Those details matter when interpreting the size and durability of the reported difference. The complication percentages were close, but the provided account does not give enough detail to compare specific types or severity of complications.
Guidelines and Longer Follow-Up
The immediate next step is for clinicians and guideline groups to assess the published trial alongside other evidence, including the population studied, the early stopping decision and the distinction between the combined endpoint and its individual components. No guideline revision is reported in the available material, and Zou’s suggestion that LBBP be considered first-line is an interpretation of the findings rather than a formal recommendation.
Further follow-up and more detailed reporting could clarify whether the reduction in the combined outcome persists over time, how outcomes vary across patient groups, and how reliably LBBP can be implanted with confirmed conduction-system capture in different settings. For now, the trial supports a closer evaluation of pacing strategy for patients expected to have a high ventricular pacing burden; the best option for an individual patient depends on clinical circumstances and should be discussed with their treating cardiology team.
Key Questions
Why was the OptimPacing trial stopped early?
The trial was stopped after an interim analysis showed that LBBP was superior to right ventricular pacing for the combined primary outcome. The source account does not provide the detailed stopping rules or the committee’s full rationale.
What outcomes made up the primary endpoint?
The endpoint combined all-cause death, heart-failure hospitalization and pacing-induced cardiomyopathy. The estimated four-year rates were 8.5% with LBBP and 19.2% with right ventricular pacing.
Did LBBP lower mortality in the trial?
Reported all-cause mortality was 7.4% with LBBP and 7.7% with right ventricular pacing. The main reported difference was in the combined outcome, with pacing-induced cardiomyopathy also reported less often in the LBBP group.
Does the trial mean everyone who needs a pacemaker should receive LBBP?
No. The study focused on patients with a high expected ventricular pacing burden and an ejection fraction above 35%, and it excluded some patients considered for other device therapies. The findings do not establish LBBP as the right choice for every patient.
Has a professional guideline changed because of OptimPacing?
No guideline change is reported in the available source material. Researchers and clinicians said the results could inform future discussion, but a change in recommendations has not been announced.
Source: medpagetoday.com
