Importance: The US Food and Drug Administration (FDA) expanded labeling for sacubitril/valsartan for use in individuals with chronic heart failure (HF) with left ventricular ejection fraction (LVEF) lower than normal. The population-level implications of implementation of sacubitril/valsartan at higher LVEF ranges is unknown. While the Prospective Comparison of ARNI With ARB Global Outcomes in HF With Preserved Ejection Fraction (PARAGON-HF) trial did not meet its primary end point, the trial may provide useful information in projecting expected clinical events among treated individuals. Objective: To quantify newly eligible treatment candidates for sacubitril/valsartan under the expanded FDA labeling and to apply treatment effects and the number needed to treat (NNT) to prevent 1 worsening HF event derived from subgroups of the PARAGON-HF trial who fall under the revised FDA label. Design, Setting, and Participants: Newly eligible treatment candidates were estimated by mapping the LVEF distribution from 559520 adult patients hospitalized between 2014 and 2019 in the Get With The Guidelines-Heart Failure registry to adults self-identifying with HF in the National Health and Nutrition Examination Survey (2015 to 2018). The NNT with 3 years of treatment for 3 end points of interest (total HF hospitalizations, total HF hospitalizations and cardiovascular death, and total HF hospitalizations and urgent HF visits and cardiovascular death) were estimated from the PARAGON-HF trial. Data were analyzed from February to June 2021. Main Outcomes and Measures: Number of worsening HF events prevented or postponed if eligible patients were treated with sacubitril/valsartan for 3 years. Results: Of an estimated 4682098 adults, the mean (SE) age was 66.3 (0.8) years, 1995037 (42.6%) were women, and 748045 (16.0%) were Black. The potential number of adults projected to be newly eligible varied by the definition of FDA labeling of lower than normal LVEF from 643161 (95% CI, 534433-751888; LVEF of 41% to 50%) to 1838756 (95% CI, 1527911-2149601; LVEF of 41% to 60%). In the PARAGON-HF trial, the NNT to prevent a worsening HF event (range, 7 to 12 patients) was consistent irrespective of specific LVEF range selected. Comprehensive implementation of sacubitril/valsartan among newly eligible patients was empirically estimated to prevent up to 69268 (95% CI, 57558-80978) worsening HF events (LVEF of 41% to 50%) to 182592 (95% CI, 151725-213460) worsening HF events (LVEF of 41% to 60%). Conclusions and Relevance: The expanded FDA labeling is positioned to substantially increase the potential HF population eligible for sacubitril/valsartan by up to 1.8 million individuals and has the potential to prevent or postpone as many as 180000 worsening HF events, depending on the definition of normal LVEF.