Objective: This study aims to investigate the prognostic value of the QRS complex duration in patients hospitalized due to heart failure with mildly reduced ejection fraction (HFmrEF). 

Background: Limited data regarding the prognostic impact of QRS complex duration in patients with HFmrEF is available. 

Methods: A large retrospective study was used including all consecutive hospitalized patients with HFmrEF (i.e., left ventricular ejection fraction (LVEF) 41 – 49%) from 2016 to 2022 according to current European guidelines. The prognostic impact of patients with wide QRS complex (i.e., ≥ 120 ms) was compared to patients with narrow QRS complexes (i.e., < 120 ms). The primary endpoint was the first heart-failure related re-hospitalization at 3 years. Secondary endpoints comprised amongst others in-hospital mortality. Kaplan-Meier, uni- and multivariable Cox regression analyses were applied for statistics.

Results: 803 consecutive patients with HFmrEF were included. A prolonged QRS duration was observed in 14% of HFmrEF patients (right bundle branch block (RBBB): 5%; left bundle branch block (LBBB): 5%; pacemaker ECG: 4%). QRS width correlated significantly with NT-pro BNP and TNI levels on admission. HFmrEF patients with QRS complex ≥ 120 ms were associated with an increased risk of heart-failure related re-hospitalization at 3 years (15% vs. 8%; log rank p=0.012; HR= 1.978; 95% CI 1.147 - 3.411; p=0.014), which was still evident after multivariable adjustment (HR= 1.868; 95% CI 1.042 – 3.347; p=0.036). In contrast, no association was found regarding cardiovascular re-hospitalization (23% vs. 18%; log rank p=0.240; HR= 1.287; 95% CI 0.844 – 1.964; p=0.241) and in-hospital mortality (4% vs. 4%; p=0.996).