AIMSWe tested the hypothesis that initiation versus non-initiation of sacubitril/valsartan is associated with a more favorable subsequent change in left ventricular ejection fraction (LVEF) in a real-world setting.METHODSA prospective, non-randomized, double-arm, open-label, cohort study had been conducted across 687 centers in 17 European countries enrolling HFrEF patients aged ≥18 years with symptoms of HF (New York Heart Association [NYHA] II-IV) and "reduced LVEF". For the current analysis, 2602 patients with LVEF measured at baseline and follow-up were chosen, of which 860 (33%, mean age 67 years, 26% women) were started on sacubitril/valsartan at baseline and 1742 (67%, 68 years, 23% women) were not. Patients started on sacubitril/valsartan had higher NYHA class and lower LVEF.RESULTSLVEF increased from mean 32.7% to 38.1% in the sacubitril/valsartan group versus from 35.9% to 38.7% in the non-sacubitril/valsartan group (mean difference in increase 2.6%, p < 0.001). LVEF increased from baseline in 64% versus 53% of patients and increased by ≥5% (absolute %) in 50% versus 35% of patients in the sacubitril/valsartan versus non-sacubitril/valsartan groups, respectively. In the overall cohort, initiation of sacubitril/valsartan was independently associated with any increase in LVEF (adjusted odds ratio [OR] 1.49 [1.26-1.75]) and with increase by ≥5% (OR 1.65 [1.39-1.95]).CONCLUSIONInitiating versus not initiating sacubitril/valsartan was independently associated with a greater subsequent increase in LVEF in this real-world setting. Reverse cardiac remodeling may be one mechanism of benefit of sacubitril/valsartan.