Prevalence and incidence of intraventricular conduction delays and outcomes in patients with heart failure and reduced ejection fraction: Insights from PARADIGM-HF and ATMOSPHERE

Aims The importance of intraventricular conduction delay (IVCD), incidence of new IVCD and its relationship to outcomes in heart failure and reduced ejection fraction (HFrEF) is not well studied. We addressed these questions in the PARADIGM‐HF and ATMOSPHERE trials. Methods and Results Risk of the primary composite outcome of cardiovascular death or HF hospitalization and all‐cause mortality were estimated by use of Cox regression according to baseline QRS duration and morphology in 11,861 patients without an intracardiac device. At baseline, 1,789 (15.1%) patients had left bundle branch block (LBBB), 524 (4.4%) RBBB, 454 (3.8%) non‐specific IVCD, 2588 (21.8%) “mildly abnormal” QRS (110‐129 milliseconds [ms]) and 6506 (54.9%) QRS <110 ms. During a median follow‐up of 2.5 years, the risk of the primary composite endpoint was higher among those with a wide QRS, irrespective of morphology: hazard ratios (95% CI) LBBB 1.36 (1.23, 1.50), RBBB 1.54 (1.31, 1.79), nonspecific IVCD 1.65 (1.40, 1.94) and QRS 110‐129 ms 1.35 (95% CI 1.23, 1.47), compared with QRS duration <110 ms. A total of 1,234 (15.6%) patients developed new‐onset QRS‐widening ≥130 ms (6.1 per 100 py). Incident LBBB occurred in 495 (6.3%) patients (2.4 per 100 py) and was associated with a higher risk of the primary composite outcome; HR 1.42 (1.12, 1.82). Conclusion In patients with HFrEF, a wide QRS was associated with worse clinical outcomes irrespective of morphology. The annual incidence of new‐onset LBBB was around 2.5%, and associated with a higher risk of adverse outcomes, highlighting the importance of repeat ECG review.