Plasma CA125 as a Prognostic Marker in Very Elderly Patients Hospitalized for Acute Heart Failure

<b>Background/Objectives:</b> Acute heart failure (AHF) is a leading cause of hospitalization and mortality among very old patients, yet this group is underrepresented in prognostic studies. Carbohydrate antigen 125 (CA125) has emerged as a potential biomarker of congestion and inflammation, but its value in patients aged 80 years and over remains unclear. We aimed to evaluate the prognostic value of plasma CA125 measured at admission for 12-month all-cause mortality and the composite outcome of mortality or heart failure (HF) readmission in very elderly patients hospitalized for AHF. <b>Methods:</b> We conducted a prospective observational study of patients aged ≥80 years admitted to an acute geriatric unit for AHF. CA125 and NT-proBNP were measured within 24 h of admission. Outcomes were assessed at 12 months. Survival analyses were performed using Kaplan-Meier curves, Cox regression models, and restricted cubic splines. <b>Results:</b> A total of 210 patients (mean age 89.8 ± 5.3 years; 75.3% females; 88.1% frail) were recruited. During the one-year follow-up, 70 deaths (37.2%) and 68 HF hospital readmissions (36.1%) were recorded. Patients in the highest CA125 tertile had an increased cumulative mortality risk (log-rank <i>p</i> = 0.061). A CA125 value ≥ 100 U/mL independently predicted both mortality (HR 1.88, 95% CI 1.15-3.09; <i>p</i> = 0.012) and the composite endpoint (HR 1.54, 95% CI 1.04-2.29; <i>p</i> = 0.031). Measures of functional dependence and frailty demonstrated greater discriminative ability than biomarkers. <b>Conclusions:</b> In very elderly patients hospitalized for AHF, elevated CA125 at admission independently predicted 12-month mortality and HF readmission. CA125 provides complementary prognostic information to geriatric assessment and may support risk stratification in this vulnerable population.