Effect of hyponatremia (<135 mEq/L) on outcome in patients with non-ST-elevation acute coronary syndrome.

Hyponatremia is associated with adverse outcomes in patients with heart failure and ST-elevation myocardial infarction (STEMI). We evaluated the effect of hyponatremia on outcomes in patients with suspected acute coronary syndrome and non-STEMI. All patients had a sodium level determined at time of admission, at 24 and 48 hours, and at discharge. Of 1,478 patients, 341 (23.1%) were hyponatremic (sodium <135 mEq/L) on presentation. Patients who had hyponatremia on admission were significantly more likely to die or have recurrent myocardial infarction in the next 30 days (odds ratio 1.98, 95% confidence interval 1.35 to 2.89, p <0.001). This relation persisted after adjusting for factors such as age, left ventricular ejection fraction, use of diuretics before admission, hypotension on presentation, anemia, chronic renal insufficiency, pulmonary edema, and high troponin levels (odds ratio 1.7, 95% confidence interval 1.1 to 2.5, p = 0.01). In conclusion, hyponatremia on admission is associated with 30-day adverse outcome in patients presenting with suspected acute coronary syndrome/non-STEMI.