Background: Urinary sodium (UNa) has been increasingly studied in heart failure as a marker of diuretic response, but its prognostic role in acute myocardial infarction (MI) remains unclear. The aim was to evaluate whether admission UNa could provide prognostic information in patients with non–ST-elevation MI (NSTEMI).

Methods: This prospective observational study included 47 selected NSTEMI patients admitted to the coronary care unit. Spot urinary sodium was measured at admission and patients were stratified according to the median UNa value (92 mmol/L). Clinical outcomes, including peak troponin, Global Registry of Acute Coronary Events (GRACE) score, need for in-hospital diuretic therapy, and length of stay, were assessed.

Results: Patients with lower UNa (<92 mmol/L) had significantly higher peak troponin levels (median 1089 vs. 350 ng/L, P = .004) and a greater need for diuretic therapy during hospitalization (70.8% vs. 26.1%, P = .002). Urinary sodium was inversely correlated with peak troponin (r = −0.37, P = .011) and diuretic requirement (r = −0.54, P < .001). In multivariable regression, admission UNa remained an independent predictor of myocardial injury. Receiver operating characteristic analysis showed moderate discriminative ability of UNa for both troponin elevation (area under the curve [AUC]: 0.73) and need for diuretic use (AUC: 0.81).

Conclusion: Admission urinary sodium may serve as a simple, non-invasive adjunctive marker for risk stratification in NSTEMI, reflecting the neurohormonal activation. These findings suggest that UNa may complement established tools such as troponin and GRACE score in early evaluation.