Key result
QRS narrowing after CSP or BiVP predicts a ~1.2-point LVEF improvement per 10 ms.
Why the study?
The relative contribution of baseline characteristics and post-procedural electrical parameters to LVEF improvement in patients undergoing conduction system versus biventricular resynchronization strategies remains uncertain.
Does conduction system pacing compared to biventricular resynchronization improve left ventricular ejection fraction in adults with symptomatic heart failure, LVEF <35%, and left bundle branch block?
RCT (n=151)
Randomized
Yes
Does conduction system pacing compared to biventricular resynchronization improve left ventricular ejection fraction in adults with symptomatic heart failure, LVEF <35%, and left bundle branch block?
In patients with HFrEF and LBBB undergoing cardiac resynchronization, greater post-procedural QRS narrowing, lower baseline LVEF, lower natriuretic peptides, and randomization to BiVP are independently associated with greater 12-month LVEF improvement, regardless of whether CSP or BiVP is used.
Captured external expert commentary on this paper, strongest first. Original sources are linked where available.
“The odds of a worse [HF]-related outcome were approximately [two]-fold higher with CSP compared with BiVP, driven by a higher incidence of clinical events as well as lesser improvement in LVEF”
“In carefully selected patients with truly correctable LBBB, treated by highly experienced operators achieving reliable left bundle-branch capture, CSP may offer superior resynchronization and clinical outcomes compared to BiVP. However, in more heterogenous populations where CSP is delivered with variable technical success, BiVP may be better than CSP.”
“If we dig a little bit deeper, one realizes that, in fact, this wasn't truly a study on CSP, because about 1 in 5 of the patients received deep septal pacing, which was acceptable as per the design of the trial, but which may have been detrimental for the patients.”
Immediate QRS narrowing may guide expectations for LVEF gains after resynchronization; extends the association across CSP and BiVP strategies.
Background The degree of improvement in left ventricular ejection fraction following cardiac resynchronization therapy (CRT) is associated with baseline characteristics and post-procedural electrical parameters. However, the relative contribution of these factors in patients undergoing conduction system and biventricular resynchronization strategies remains uncertain. Purpose To explore baseline and post-procedural predictors of left ventricular ejection fraction (LVEF) change following conduction system and biventricular resynchronization. Methods PhysioSync-HF was a randomized, multicenter, investigator-led trial comparing conduction system pacing (CSP) with biventricular resynchronization (BiVP) in 173 adults with symptomatic heart failure, LVEF<35%, and left bundle branch block (QRS ≥130 ms). In this post hoc analysis, multivariable linear regression models were applied to assess predictors of change in LVEF (ΔLVEF) from baseline up to 12 months, incorporating baseline clinical variables (age, sex, BMI, LVEF strata, tertiles of BNP/NT-proBNP, non-ischemic etiology) and immediate post-procedural ΔQRS from baseline. A formal interaction analysis was conducted to assess whether the predictive effect of immediate post-procedural ΔQRS differed according to resynchronization strategy (CSP vs BiVP). Patients were analyzed according to randomization assignment (modified intention-to-treat). Results Among 173 randomized patients, 151 with complete baseline and follow-up data were included in the present analysis (51% female; median LVEF 27.1%; median QRS 180 ms). Across both CSP and BiVP arms, median 12-month ΔLVEF was +10.1% (IQR, 1 to 17.6%) and median post-procedural ΔQRS was -60 ms (IQR, -40 to -75.5 ms). In the multivariable model, ΔQRS was significantly associated with LVEF improvement (+1.2% per 10 ms reduction; 95% CI 0.33–2.1; p=0.008) (Table). Lower baseline LVEF, lower natriuretic peptides, and randomization to BiVP were also independently associated with LVEF improvement. No significant interaction was observed between resynchronization strategy and ΔQRS (p=0.51) (Figure). Conclusion In patients with HFrEF and LBBB undergoing CSP and BiVP resynchronization, lower baseline LVEF, lower values of natriuretic peptides, and greater post-procedural QRS narrowing were associated with a greater degree of LVEF improvement at 12 months, with no heterogeneity between resynchronization strategies. While no formal interaction was observed, the trend toward differential slopes across strategies highlights the need for further evaluation of treatment-effect heterogeneity.
No takes yet. Share an insight, caveat, or question.
Bitencourt et al. (2026) conducted an RCT in Symptomatic heart failure with reduced ejection fraction (LVEF <35%) and left bundle branch block (n=151). Conduction system pacing (CSP) vs. Biventricular resynchronization (BiVP) was evaluated on Change in left ventricular ejection fraction (ΔLVEF) from baseline up to 12 months per 10 ms post-procedural QRS reduction (+1.2% per 10 ms ΔQRS reduction, 95% CI 0.33-2.1, p=0.008). Post-procedural QRS narrowing after CSP or BiVP predicted 12-month LVEF improvement (+1.2% per 10 ms reduction; 95% CI 0.33-2.1; p=0.008) with no interaction by strategy (p=0.51).
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: