Hyponatremia in Acute Coronary Syndrome: Prevalence, Severity and Clinical Phenotype in a Tertiary-Care Cohort

Abstract

Background: Hyponatremia is frequently encountered during acute coronary syndromes (ACS), but its clinical importance may be under-recognized when sodium abnormalities are mild. We characterized the burden and clinical phenotype of hyponatremia among adults presenting with ACS at a tertiary-care teaching hospital.
Methods: This cross-sectional observational study included 143 adults presenting within 12 hours of symptom onset with STEMI, NSTEMI or unstable angina. Patients with previous coronary artery disease, arrhythmia, cardiomyopathy/heart failure, or prior diuretic use were excluded. Serum sodium was measured at admission, 48 hours and discharge. Demographic characteristics, cardiovascular risk factors, presenting symptoms, ACS subtype, cardiac biomarkers, lipid profile and left ventricular ejection fraction (LVEF) were recorded.
Results: The cohort was predominantly male (94/143, 65.7%), with the largest age group being 51–60 years (42/143, 29.4%). Hypertension, diabetes and smoking were present in 56.6%, 44.8% and 38.4%, respectively. STEMI accounted for 56.6% of ACS presentations. Hyponatremia (<135 mmol/L) was present in 93/143 patients (65.0%). Mild hyponatremia (130–134 mmol/L) was most common (48.3%), followed by moderate (11.9%) and severe hyponatremia (4.9%). Mean sodium increased from 132.2±3.7 mmol/L at admission to 134.6±3.2 mmol/L at discharge. Severe LV systolic dysfunction (LVEF <40%) was present in 28.7% of the cohort.
Conclusions: Hyponatremia affected nearly two-thirds of this selected ACS cohort and was predominantly mild. The high frequency of sodium disturbance across a population with substantial cardiometabolic risk and LV dysfunction supports routine electrolyte assessment during the initial evaluation and hospitalization of ACS patients. Prospective studies should determine whether sodium trajectories add prognostic information beyond established clinical risk scores.