Different left bundle branch block morphologies and response to CRT: a cohort study

Although left bundle branch block (LBBB) is a strong predictor of response to cardiac resynchronization therapy (CRT), a significant number of patients remain non-responders.

The study sought to evaluate the impact of different morphologies of LBBB on CRT response in patients with heart failure (HF).

This is a retrospectively analyzed cohort of heart failure (HF) patients with LBBB admitted for CRT implantation. Patients were analyzed according to the fulfillment of the following LBBB criteria: Strauss, Marriott, Perrin, European Society of Cardiology (ESC) 2013, ESC 2021, World Health Organization (WHO) and a group that fulfilled all the criteria simultaneously. The response to CRT was defined as an increase in left ventricular ejection fraction (LVEF) ≥ 10% or a decrease in left-ventricular end-systolic volume (LVESV) ≥ 15% at six months of follow-up. The analysis of the 12-lead electrocardiogram (ECG) was performed after scanning so that it could be studied in digital form. The recording rate of the ECG was 25 mm/s, and the sensitivity was 10 mm/mV. Analyses were performed with R software. Logistic regression models were used to evaluate the association between examined LBBB criteria and response after CRT. Multivariable models were built upon variable selection following univariate analysis to provide odds ratios (OR) with 95% confidence intervals (CI) adjusted for sex, age, paroxysmal atrial fibrillation, heart failure type, QRS duration and use of angiotensin receptor/neprilysin inhibitor.

Totally, 109 patients (87/109 [80%] males, 95/109 [87%] in sinus rhythm) with ischemic (32/109 [29%]) and non-ischemic HF (77/109 [71%]) were analyzed. Participants’ mean (standard deviation) of age and LVEF were 66 (11) years 29% (4.5) respectively. Sixty-eight (68/109 [62%]) patients fulfilled the Strauss LBBB, 42/109 (39%) the Mariott, 43/109 (39%) the Perrin, 85/109 (78%) the ESC 2013, 42/109 (39%) the ESC 2021, 42/109 (39%) the WHO, while 37/109 (34%) fulfilled all the above criteria. Among examined LBBB criteria, CRT response was more likely to occur in the following order: Strauss (OR=6.88, 95% CI [2.42, 21.81]; p<0.001), all LBBB criteria fulfilled (OR=2.60, 95% CI [0.91, 7.98]; p=0.082), WHO (OR=2.23, 95% CI [0.82, 6.33]; p=0.122), ESC 2013 (OR=2.22, 95% CI [0.75, 6.79]; p=0.15), Perrin (OR=2.09, 95% CI [0.78, 5.79]; p=0.146), ESC 2021 (OR=1.98, 95% CI [0.74, 5.46]; p=0.178) and Marriott (OR=1.48, 95% CI [0.55, 4.02]; p=0.437) (Figure).

Patients with St-LBBB criteria present the greatest benefit with respect to CRT response. Implementation of these criteria could improve patient selection for CRT.