PURPOSE: The purpose of this study is to determine the prevalence and prognostic implications of hyponatremia in the setting of acute myocardial infarction.
METHODS: The study sample comprised 128 consecutive patients admitted with acute MI (Including both STEMI & NSTEMI) to Jersey City Medical Center, between Jan 2010 and Jan 2011. The primary endpoint was all-cause mortality within the hospital stay. Venous blood samples were obtained on admission and at 24, 48, and 72 hours thereafter.
RESULTS: Hyponatremia was present on admission in 36 patients (28%). Hyponatremia (≤135 mEq/L) developed in 25 (19.9%) patients during the first 72 hours of hospitalization. Plasma sodium levels decreased to ≤130 mEq/L in 6 patients (4.3%); the lowest level was 119 mEq/L. In-patient mortality, a total of 13 deaths (10%) occurred within the hospital: 6.2% (3/55) of patients without hyponatremia, 19.8% (7/36) of patients with hyponatremia on admission, and 16.8% (4/25) of patients who developed hyponatremia after admission. Kaplan-Meier survival analysis indicated that patients who had hyponatremia at baseline or who developed hyponatremia after admission had significantly higher in-patient mortality compared with patients without hyponatremia. After adjusted logistic regression for other important covariates, both hyponatremia on admission and development of hyponatremia after admission remained independent predictors of in-patient mortality. In analyses of the association between the degree of hyponatremia and outcome, we observed that the risk of in-patient mortality increased with the severity of hyponatremia. Compared with patients without hyponatremia, the adjusted odds ratio for in-patient mortality was 2.1 in patients with sodium levels between 130 to 134 mEq/L and 3.4 in patients with levels ≤130 mEq/L.
CONCLUSIONS: Hyponatremia and Other Risk-Assessment Models in Myocardial Infarction both hyponatremia on admission and developing hyponatremia remained independent predictors of in-patient mortality after adjusting for the other risk factors.
CLINICAL IMPLICATIONS: Hyponatremia on admission or early development of hyponatremia in patients with acute myocardial infarction is an independent predictor of in-patient mortality, and prognosis worsens with the severity of hyponatremia. Further studies are required to determine if plasma sodium levels may serve as a simple marker to identify patients at high risk.
DISCLOSURE: The following authors have nothing to disclose: Fahad Aziz, Sujatha Doddi, Sudheer Penupolu, Dolores Del Castillo, Wajiha Raza, Swapna Kallu, Anshu Alok, Jyoti Matta
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