True versus LBBB-like patterns: differential remodeling and outcomes following CRT
J Simoes De Azevedo Massa Pereira, S Andraz, L Hamann, J Guerreiro Pereira, D Carvalho, R Fernandes, D Bento, J Sousa Bispo, P Azevedo, R Candeias, H Alex Costa, J MimosoAbstract
Introduction
Differences in LBBB morphology—true complete LBBB (tcLBBB), due to conduction system degeneration, and LBBB-like pattern (lpLBBB), reflecting myocardial pathology—are common and may influence CRT response. However, their association with CRT outcomes is not fully established.
Objective
To assess the association between LBBB morphology/pattern and clinical outcomes in CRT patients.
Methods
A retrospective analysis (2020–2023) involved 95 patients who underwent CRT implantation. Data collected included demographics, risk factors and echocardiographic/electrocardiographic parameters. Patients were classified as lpLBBB or tcLBBB using European Society of Cardiology criteria. The primary outcome was the composite of all-cause death and/or heart failure (HF) hospitalization. Predictors were identified through multivariate logistic regression.
Results
The final cohort included 88 patients (58% lpLBBB; 42% tcLBBB) mean age 69.5±10.4 years, 77.3% male. Baseline QRS duration was 166±24ms, with a wider QRS in tcLBBB (178±21ms, p=0.006). Mean biventricular pacing was 95.9% with no differences between groups. QRS reduction ≥ 26ms (51.4%, p<0.001), LBBB duration > 150ms (98.8%, p=0.001), use of mineralocorticoids receptor antagonists drugs (81.1%, p=0.047), QRS variation (28.2±20.5, p<0.001) and greater improvement in LVEF (29.7% --> 44.2%, p=0.001) and LVEDV (210ml --> 159ml, p=0.006) were more frequent among tcLBBB. CRT super-response occurred in 23 patients (39.7%), significantly more frequent in tcLBBB (62.5%, p=0.003). The primary outcome occurred in 26 patients (29.5%) with no significant difference between groups (lpLBBB 33.3% vs tcLBBB 24.3%, p=0.361). However, all-cause mortality was lower in the tcLBBB group (16.2%, p=0.021). Super-response was not associated with improved clinical outcomes (20.8%, p=0.583). In multivariate analysis, predictors of the primary outcome included smoking (OR 11.54, p=0.033), while non-ischemic etiology (OR 0.003, p = 0.045) and tcLBBB morphology (OR 0.002, p = 0.043) were protective.
Conclusions
In this cohort, tcLBBB morphology prior to CRT implantation was associated with greater reverse remodeling—reflected by improvements in LVEF, LVEDV, and higher rates of super-response. However, these parameters were not associated with a lower risk of the composite outcome of death or HF hospitalization, although all-cause mortality alone was lower among patients with tcLBBB. Predictors of the primary outcome were tcLBBB and non-ischemic etiology (both protective) and smoking (risk factor) in a medium/long term follow-up. These findings suggested that although the presence of a tcLBBB is likely necessary for CRT response, it is unlikely to be sufficient to be linked to a better prognosis alone, and other variables should be considered like the presence of LV scar as well as the subtype of cardiomyopathy.For image description, please refer to the figure legend and surrounding text.