ECG-Based Assessment in Acute Heart Failure with Left Bundle Branch Block: Insights from a Retrospective Cohort

BACKGROUND: Left bundle branch block (LBBB) complicates electrocardiographic interpretation in acute heart failure (AHF). This study aimed to evaluate the relationship between electrocardiographic parameters, including QRS duration, QRS morphology, and the Selvester QRS score (SQS), and echocardiographic findings in patients with AHF presenting with LBBB across different heart failure phenotypes. METHODS: In this retrospective cohort, 275 patients hospitalized with AHF and LBBB were analyzed. Patients were classified as heart failure with reduced ejection fraction (HFrEF, left ventricular ejection fraction [LVEF] <40%), heart failure with mildly reduced ejection fraction (HFmrEF, LVEF 40-49%), or heart failure with preserved ejection fraction (HFpEF, LVEF ≥50%). Associations between electrocardiographic (ECG) and echocardiographic parameters were evaluated using Spearman correlation and multivariable regression. Discriminatory performance for reduced systolic function was assessed by receiver operating characteristic (ROC) analysis. RESULTS: Mean age was 61.7±13.8 years and 70.5% were male; median LVEF was 40% (IQR 27-48%). HFrEF was present in 49.8%. Among ECG indices, only SQS correlated significantly with echocardiographic measures: LVEF (r=-0.447), left ventricular end-diastolic diameter (LVEDD, r=0.346), left ventricular end-systolic diameter (LVESD, r=0.373), and LV mass index (r=0.205) (all p<0.001). In multivariable analysis, SQS (OR=1.373, 95%CI 1.255-1.501, p<0.001) and LV mass index independently predicted HFrEF. The Hosmer-Lemeshow test confirmed adequate calibration (p=0.49). ROC analysis showed SQS had moderate discriminatory ability (area under the curve [AUC] 0.768, 95%CI 0.711-0.825), with an optimal cutoff >43 yielding 74.5% sensitivity and 69.6% specificity. QRS duration and morphology demonstrated no meaningful predictive value (AUC≈0.49). CONCLUSION: In AHF patients with LBBB, SQS outperforms conventional QRS metrics in identifying reduced LV systolic function. An SQS >43 provides moderate diagnostic accuracy and may support early risk stratification when echocardiography is not immediately available.