Incidence, medical therapy, and outcomes in heart failure with improved ejection fraction across guideline definitions.

PURPOSE: To assess the incidence of heart failure with improved ejection fraction (HFimpEF) across guideline definitions (ACC/AHA, ESC, HFA/HFSA/JHFS) and to evaluate differences in guideline directed medical therapy (GDMT) utilization and rates of heart failure hospitalization (HF) or death among patients meeting each criterion. METHODS: We identified patients with incident heart failure with reduced ejection fraction (HFrEF) between January 2013 and December 2024 within the Kaiser Permanente Northern California (KPNC) healthcare system. HFimpEF was defined with a follow-up LVEF that satisfied at least one of three definitions: ACC/AHA (EF > 40%), HFA/HFSA/JHFS (EF > 40% with ≥10-point increase), and ESC (EF ≥ 50%). We assessed (1) HFimpEF incidence, (2) the one-year post-diagnosis mutually exclusive incidences of HF hospitalization or death, and (3) GDMT use across each definition. RESULTS: Of 37,443 patients with newly diagnosed HFrEF, 15,030 (40.1%) were classified as HFimpEF based on the ACC/AHA definition, 13,253 (35.4%) based on the HFA/HFSA/JHFS definition, and 10,304 (27.5%) based on the ESC definition. Mutually exclusive cumulative incidences of HF hospitalization or death at 10 years after HFimpEF were higher among patients whose EF improvement met the ACC/AHA definition but did not meet the other two (Figure 2, log-rank p<0.001). CONCLUSION: Based on definition used, the prevalence of HFimpEF ranges widely from 28-40%. Irrespective of definition, patients with HFimpEF remain at residual risk for clinical deterioration and share a similar prognosis despite improvement in EF. These data highlight the persistence of heart failure rather than true recovery; trials to optimize available and new HF treatments are warranted.