Myocardial infarction (MI) complicated by heart failure (HF) is a common and severe clinical condition associated with poor outcomes. Estimated plasma volume status (ePVS), a marker of congestion derived from hemoglobin and hematocrit, has shown promise in predicting outcomes in various cardiovascular diseases. This study aimed to investigate the relationship between ePVS and both short-term and long-term prognosis in patients with MI complicated by HF.A retrospective cohort study was conducted using data from the Medical Information Mart for Intensive Care IV (MIMIC-IV) database, including 3,238 patients with MI complicated by HF. Patients were stratified into quartiles based on ePVS values. The primary outcomes were in-hospital mortality, 180-day mortality, and 1-year mortality. Kaplan-Meier curves, multivariate Cox regression analysis, and subgroup analyses were performed to assess the relationship between ePVS and outcomes.Kaplan-Meier analysis showed significant differences in survival rates across ePVS quartiles for all outcomes (P < 0.001). Multivariate logistic regression analysis revealed that patients in the highest quartile of ePVS (Q4 vs. Q1) had an independently increased risk of in-hospital mortality (OR 1.58, 95% CI 1.16-2.13, P = 0.003). Cox regression analysis further demonstrated that higher ePVS (Q4 vs. Q1) was associated with an increased risk of 180-day mortality (HR 1.45, 95% CI 1.19-1.75, P < 0.001) and 1-year mortality (HR 1.51, 95% CI 1.27-1.80, P < 0.001). Both Kaplan-Meier survival curves and restricted cubic spline models confirmed a positive association between ePVS and long-term mortality risks.The association between ePVS and long-term outcomes was stronger than for in-hospital mortality. Subgroup analyses revealed that the relationship between ePVS and long-term mortality was more pronounced in patients with systolic blood pressure below 140 mmHg, lower LODS and OASIS scores, and those without hemorrhagic disorders or anemia (P for interaction <0.05).ePVS was an independent predictor of both short-term and long-term mortality in patients with MI complicated by HF. Its prognostic value was particularly significant for long-term outcomes, suggesting its potential utility in risk stratification and guiding treatment strategies for this high-risk population.© 2025 Luo, Ma, Zhang, Jiang and Guo.