Brazil: A randomized clinical trial published in JAMA Cardiology has reported that in patients with heart failure with reduced ejection fraction (HFrEF) and left bundle-branch block (LBBB), Conduction System Pacing (CSP) was inferior to Biventricular Pacing (BiVP) for the composite outcome of death, heart failure hospitalizations, urgent HF visits, and change in left ventricular ejection fraction (LVEF) at 12 months. Therefore, these results do not support the routine use of CSP as the first-line cardiac resynchronization strategy in this population.  Cardiac resynchronization therapy is a key treatment for patients with HFrEF and electrical dyssynchrony, such as LBBB. While biventricular BiVP is the standard approach, CSP, particularly left bundle-branch area pacing, has emerged as a potentially more physiological and cost-effective alternative. However, its effect on major heart failure outcomes remains uncertain.
To examine this, André Zimerman and colleagues conducted the PhysioSync-HF trial, an investigator-initiated, multicenter, noninferiority randomized clinical study across 14 hospitals in Brazil. Adults with symptomatic HFrEF (New York Heart Association class II–III), LVEF ≤35%, and LBBB with QRS duration ≥130 milliseconds were enrolled between November 2022 and December 2023 and followed for 12 months.
The study included 173 patients (median age 62 years; 49.7% women), with about two-thirds having dilated cardiomyopathy. The median baseline LVEF was 26%, and the median QRS duration was 180 milliseconds. Participants were randomly assigned in a 1:1 ratio to receive either CSP—preferably left bundle-branch area pacing—or conventional BiVP.
The primary outcome was a hierarchical composite of all-cause death, heart failure hospitalizations, urgent heart failure visits, and change in LVEF at 12 months, with a prespecified noninferiority margin set at an odds ratio of 1.2.The trial
revealed the following findings:
Conduction
system pacing did not achieve noninferiority and was inferior to
biventricular pacing for the primary composite outcome at
follow-up.
The
composite endpoint showed an odds ratio of 2.36, indicating worse outcomes
with CSP compared with BiVP.
The
combined risk of death, heart failure hospitalization, or urgent heart
failure visit was higher in the CSP group.
Both
treatment strategies improved cardiac function over time.
Improvement
in cardiac function was greater with BiVP.
Mean
left ventricular ejection fraction increased to 35% in the CSP
group and to 39% in the BiVP group.
QRS
duration improved in both groups.
Symptom
burden measured by the Kansas City Cardiomyopathy Questionnaire improved
similarly in both groups.
New
York Heart Association functional class and natriuretic peptide levels
also showed comparable improvement between the groups.
Despite these clinical findings, CSP was associated with lower healthcare costs. The total direct medical cost related to the procedure and subsequent heart failure care was about $7,090 lower in the CSP group over 12 months.
The authors noted several limitations, including differences in care across participating centers and the possibility of a learning curve, as operators had less experience with CSP than with BiVP. The moderate sample size and relatively few clinical events also indicate that larger studies are needed to further evaluate these findings.Reference:Zimerman A, dal Forno A, Rohde LE, et al. Conduction System vs Biventricular Pacing in Heart Failure: The PhysioSync-HF Randomized Clinical Trial. JAMA Cardiol. Published online March 11, 2026. doi:10.1001/jamacardio.2026.0101