Refining patient selection for CRT: the role of true LBBB morphology in CRT response
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
One of the most potent predictors of cardiac resynchronization therapy (CRT) benefit is the presence of left bundle branch block (LBBB). Differences in LBBB morphology, i.e, true complete LBBB (tcLBBB) due to conduction system degeneration or LBBB like pattern (lpLBBB) with conduction delay reflecting myocardial pathology are often seen in the clinical setting and may impact response to CRT. Although, an association with LBBB morphology and response/super-response to CRT is not fully established.
Objective
To assess the association LBBB morphology/pattern and super-response in CRT patients.
Methods
A retrospective analysis between 2020 and 2023 included 95 patients who underwent CRT implantation. Collected data included demographics, cardiovascular risk factors and echocardiographic and electrocardiographic parameters. Super-response to CRT was defined as an absolute increase in left ventricular ejection fraction (LVEF) ≥ 10% and/or ≥ 30% reduction in left ventricular end-systolic volume and/or ≥ 20% reduction in left ventricular end-diastolic volume (LVEDV). Patients were classified according to LBBB morphology (lpLBBB vs tcLBBB). LBBB European Society of Cardiology criteria was used to identify tcLBBB morphology. Predictors of super-response were identified using multivariate logistic regression.
Results
The final cohort consisted of 88 patients, of whom 51 (58%) with lpLBBB and 37 (42%) with tcLBBB. The mean age was 69.5±10.4 years, with 77.3% being male. Mean baseline QRS duration was 166±23.5ms, with a wider QRS at baseline in tcLBBB (178±21.1ms, p=0.006). Mean biventricular pacing was 95.9% and without differences between groups. QRS reduction ≥ 26ms (51.4%, p<0.001), baseline LBBB > 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 the degree of LVEF improvement (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). tcLBBB independently predicted super-response, increasing the likelihood by 21-fold (OR=21.54, p=0.015). Other predictors were QRS variation ≥ 26ms (OR=9.612, p=0.043), non-ischemic etiology (OR=20.14, p=0.009) and the use of ACEi (OR=15.16, p=0.022).
Conclusions
In this cohort, tcLBBB morphology prior to CRT implantation was associated/predictor with more pronounced reverse remodeling, as reflected by improvements in LVEF, LVEDV, and super-response rates during medium- to long-term follow-up. These findings reinforce the concept that tcLBBB morphology is an important and specific surrogate of LV electrical activation and response to resynchronization. Further studies are needed to confirm these findings and determine their impact on hard clinical outcomes.Baseline clinical characteristicsFor image description, please refer to the figure legend and surrounding text.