Key result
Mechanical dyssynchrony and perfusion heterogeneity predict adverse LV remodeling and major events, unlike LBBB alone.
Why the study?
Not all patients with LBBB develop cardiomyopathy, dyssynchrony can occur without conduction defects, and the role of microvascular dysfunction remains uncertain.
Do mechanical dyssynchrony and perfusion heterogeneity predict adverse LV remodeling and clinical outcomes in patients with and without LBBB?
Cohort (n=1,165)
Yes
Do mechanical dyssynchrony and perfusion heterogeneity predict adverse LV remodeling and clinical outcomes in patients with and without LBBB?
Hazard Ratio: 1.02
p-value: p=0.011
Mechanical dyssynchrony and perfusion heterogeneity, rather than the presence of LBBB itself, are independent predictors of adverse LV remodeling, mortality, and heart failure hospitalization.
Should not yet alter LBBB-based decisions; hypothesis-generating for phase entropy and perfusion heterogeneity in observational cohorts.
Aims Left bundle branch block (LBBB) is associated with mechanical dyssynchrony, heterogeneous perfusion, and adverse left ventricular (LV) remodeling. However, not all patients with LBBB develop cardiomyopathy, and dyssynchrony can occur without conduction defects. The role of microvascular dysfunction remains uncertain. We aimed to assess how mechanical dyssynchrony and perfusion heterogeneity relate to LV remodeling and function in patients with and without LBBB. Methods and results We retrospectively analyzed 233 patients with isolated LBBB and 932 matched controls who underwent PET myocardial perfusion imaging, assessing mechanical dyssynchrony (phase entropy), myocardial blood flow (MBF), coronary vascular resistance (CVR), myocardial flow reserve (MFR), septal-to-lateral MBF ratio (SLR) for perfusion heterogeneity, LV volumes, and ejection fraction (EF). Compared to controls, patients with LBBB had greater dyssynchrony (56% vs. 40%), larger LV volumes, and lower EF (54% vs. 67%) (all p <0.001), and had higher stress CVR (37 vs. 34 mmHg/mL·min⁻¹·g⁻¹), lower stress MBF (2.4 vs. 2.6 mL/min/g), reduced MFR (2.4 vs. 2.6), and lower SLR (0.95 vs. 1.00) (all p <0.05). Among patients with dyssynchrony, SLR<1.0 identified those with more adverse remodeling. In multivariable regression, phase entropy and SLR independently predicted LV volumes and EF, with adverse effects of SLR reduction amplified in LBBB (interaction p <0.01). In the Cox proportional hazards analysis, phase entropy (HR:1.02, p =0.01), MFR (HR:0.62, p <0.001), and LVEF (HR:0.97, p <0.001) were independently associated with mortality and heart failure hospitalization, whereas LBBB was not. Conclusions Mechanical dyssynchrony and perfusion heterogeneity independently predict adverse LV remodeling, irrespective of LBBB. Integrated imaging enhances cardiomyopathy stratification.
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Brandao et al. (2026) conducted a cohort in Left bundle branch block (LBBB) and mechanical dyssynchrony (n=1,165). Mechanical dyssynchrony (phase entropy) vs. Lower mechanical dyssynchrony was evaluated on Composite of all-cause mortality and heart failure hospitalization (HR 1.02, p=0.011). Mechanical dyssynchrony (phase entropy) and perfusion heterogeneity independently predicted adverse left ventricular remodeling and a composite of mortality and heart failure hospitalization, whereas LBBB itself did not.
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