The association of hyponatremia and clinical outcomes in patients with acute myocardial infarction: a cross-sectional study

INTRODUCTION: Hyponatremia is a common electrolyte abnormality that has been associated with poor outcomes in several conditions including acute myocardial infarction (AMI). However, those studies were performed in the era before percutaneous coronary intervention (PCI), focused mostly on ST-elevation myocardial infarction (STEMI), and sodium levels up to 72 h of admission. The purpose of this study was to identify the association between hyponatremia and clinical outcomes in patients with acute myocardial infarction. METHODS: We performed a retrospective analysis of patients with a diagnosis of non-ST-elevation myocardial infarction (NSTEMI) and STEMI presenting at our institution from March 2021 to September 2021. Our independent variables were sodium levels on the day of admission and up to 7 days later. Dependent variables were in-hospital mortality, 30-day mortality, length of hospital stay, intensive care admission, new heart failure diagnosis, and ejection fraction. RESULTS: 50.2% of patients had hyponatremia up to 7 days of admission. Intensive care admission was higher in patients with hyponatremia up to7 days (69.7% vs 54.3%, P 0.019, OR 1.9), they had worse 30-day mortality (12.7% vs to 2.2%, P 0.004, OR 6.5), in hospital mortality (9.9% vs 1.1%, P 0.006, OR 9.9), and new heart failure diagnosis (31.5% vs 17.9%, P < 0.043, OR 2.1). Hyponatremia on admission was associated with in-hopital mortality (16.3% vs 3.8%, P 0.004, OR 4.9), 30-day mortality (18.4% vs 5.9%, P 0.017, OR 3.5). CONCLUSIONS: This study suggests that hyponatremia on admission and at any point during the first seven days of hospitalization are associated with in-hospital and 30-day mortality. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12872-022-02700-y.