Association Between Fluid Balance Trajectories and Prognosis in Patients with Heart Failure and Preserved Ejection Fraction

Abstract Background Fluid balance (FB) is a critical prognostic factor in heart failure, yet its longitudinal impact on critically ill HFpEF patients remains unclear. This study evaluates how FB trajectory changes influence 30-day mortality in HFpEF patients. Methods Using MIMIC-IV data, we conducted a retrospective cohort study of HFpEF patients. Group-based trajectory modeling (GBTM) identified distinct FB trajectory subgroups. Survival differences were assessed via Kaplan-Meier analysis, and Cox regression models evaluated associations between FB trajectories and mortality. Results Among 1,089 HFpEF patients, four FB trajectories emerged: T1 (Negative balance stability), T2 (Rapid transition to negative balance), T3 (Positive balance gradual decline), and T4 (High-level decline). K-M analysis revealed significantly higher mortality in T3 and T4. Fluid-overloaded patients had worse survival than non-overloaded. Adjusted Cox models showed lower mortality in T1 (HR = 0.67, 95%CI 0.53–0.85) and T2 (HR = 0.60, 95%CI 0.45–0.80) vs. T3, with no T3–T4 difference (p = 0.35). Subgroup and sensitivity analyses supported these findings. Conclusions HFpEF patients with positive balance gradual decline (T3) or high-level decline FB (T4) had the poorest prognosis, while those maintaining negative balance (T1/T2) exhibited better survival. GBTM effectively stratifies risk, aiding clinical subgroup identification.