Clinical and Experimental Evidence for a Strain-Based Classification of Left Bundle Branch Block-Induced Cardiac Remodeling

Abstract

BACKGROUND: Septal strain patterns measured by echocardiography reflect the severity of left bundle branch block (LBBB)-induced left ventricular (LV) dysfunction. We investigated whether these LBBB strain stages predicted the response to cardiac resynchronization therapy in an observational study and developed a sheep model of LBBB-induced cardiomyopathy. METHODS: The clinical study enrolled cardiac resynchronization therapy patients who underwent echocardiographic examination with speckle-tracking strain analysis before cardiac resynchronization therapy implant. In an experimental sheep model with pacing-induced dyssynchrony, LV remodeling and strain were assessed at baseline, at 8 and 16 weeks. Septal strain curves were classified into 5 patterns (LBBB-0 to LBBB-4). RESULTS: The clinical study involved 250 patients (age 65 [58; 72] years; 79% men; 89% LBBB) with a median LV ejection fraction of 25 [21; 30]%. Across the stages, cardiac resynchronization therapy resulted in a gradual volumetric response, ranging from no response in LBBB-0 patients (ΔLV end-systolic volume 0 [−12; 15]%) to super-response in LBBB-4 patients (ΔLV end-systolic volume −44 [−64; −18]%) ( P< 0.001). LBBB-0 patients had a less favorable long-term outcome compared with those in stage LBBB≥1 (log-rank P =0.003). In 13 sheep, acute right ventricular pacing resulted in LBBB-1 (23%) and LBBB-2 (77%) patterns. Over the course of 8−16 weeks, continued pacing resulted in progressive LBBB-induced dysfunction, coincident with a transition to advanced strain patterns (92% LBBB-2 and 8% LBBB-3 at week 8; 75% LBBB-3 and 25% LBBB-4 at week 16) ( P =0.023). CONCLUSIONS: The strain-based LBBB classification reflects a pathophysiological continuum of LBBB-induced remodeling over time and is associated with the extent of reverse remodeling in observational cardiac resynchronization therapy-eligible patients.

Contractile asymmetry and survival in patients with left bundle branch abnormality treated with cardiac resynchronization therapy

“…However, to gain deeper insights, additional prospective studies are warranted. ICA combined with distinct stages of LBBB delineated by septal deformation, as recently described by Calle et al , 26 , 27 warrants a specific consideration in future research. Interaction between ICA and optimal position of CRT leads should be elucidated as well.…”

Prediction of a major adverse coronary event in Women through CORSWO

“…In the observational retrospective CODE study, 1,529,971 patients were investigated with a mean follow-up of 3.7 years, and LBBB had higher risk of overall mortality (HR 1.77; CI 95% 1.55 to 2.01) 34 . Also, in some patients, septal strain patterns evaluated by mean of echocardiography reflect the severity of LBBB induced left ventricular dysfunction 35 . Moreover, women are more likely to develop angina pectoris as their first coronary artery disease symptom and are less likely to present an acute myocardial infarction 36 .…”

Left Bundle Branch Block and Cardiac Resynchronization Therapy: Effector or Bystander?

“…In this issue of the Journal, Calle and colleagues, 3 continuing a tradition of contributions to the field of LV dyssynchrony mechanisms, present a study with information that is potentially relevant to the above considerations. They report on a well-constructed retrospective clinical analysis and a prospective preclinical experiment, designed to explore the association between isolated LBBB and the development of LV systolic dysfunction (preclinical model) and between a strain imaging-based staging of LBBB-induced mechanical dyssynchrony/LV remodeling and the effects of CRT (retrospective clinical study).…”