Resident Dalhousie University halifax, Nova Scotia, Canada
Background: Importance: Certain conduction abnormalities contribute to the pathophysiology of heart failure. However, the prevalence and prognostic significance of these abnormalities have not been systematically studied in a contemporary heart failure population.
Objective: To determine the prevalence and prognostic implications of conduction abnormalities, including Left bundle branch block (LBBB), Right bundle branch block (RBBB), and QRS duration, in patients with heart failure.
METHODS AND RESULTS: Methods This is a multicentre, retrospective observational cohort study. Patients with Heart failure with reduced ejection fraction (HFrEF) and heart failure with preserved ejection fraction (HFpEF) were defined as Left ventricular (LV) EF <= 40 and ≥41 respectively. Electrocardiograms were reviewed for conduction abnormalities; left bundle branch block was identified using the Strauss criteria. Results 1,442 patients were enrolled, 220 (15.3%) had LBBB and 109 (7.6%) had RBBB. The mean QRS duration was 125.8 ± 34 ms in HFrEF and 113.1 ± 34 ms in HFpEF. In HFpEF, a 10-unit increase in QRS duration was associated with increased cardiovascular (CV) hospitalization risk (HR 1.026 [1.002–1.052]), but not with mortality or heart failure hospitalization. In HFrEF, a 10 unit increase in QRS duration was associated with higher risk of all-cause mortality (HR 1.063 [1.015–1.114]), combined mortality and heart failure hospitalization (HR 1.066 [1.020–1.115]), CV hospitalization (HR 1.058 [1.013–1.106]), and CV mortality (HR 1.086 [1.020–1.156]). LBBB was associated with increased risk of combined all-cause mortality and heart failure hospitalization in HFrEF (HR 1.669 [1.072–2.213]), but not in HFpEF. In HFrEF, RBBB was associated with increased risk of combined mortality and heart failure hospitalization (HR 2.745 [1.469–5.129]) and CV hospitalization (HR 2.509 [1.348–4.671]).
Conclusion: In this study, conduction system abnormalities are associated with increased risk of mortality and heart failure hospitalization in patients with HFrEF, but not HFpEF. The presence of RBBB was associated with the greatest risk of adverse outcomes. Optimization of correction of conduction abnormalities may further improve outcomes in patients with HFrEF. Further understanding of conduction abnormalities in HFpEF on cardiovascular outcomes is required.
