Relation between admission serum potassium levels and long-term mortality in acute coronary syndrome

Serum potassium homeostasis play an important role in myocardial function, but the impact of serum potassium levels on long-term mortality has not been well evaluated. In the current study, we investigated patients with acute coronary syndrome (ACS) and analyzed the relationship between admission serum potassium levels and long-term mortality. Between July 2008 and September 2012, 2369 patients with ACS that was confirmed by coronary angiography were enrolled in this study and completed the follow-up. The serum potassium level was evaluated within first 24 h after admission. The primary outcome in this study was all-cause mortality. Patients were categorized into five groups to determine the relation between admission serum potassium levels and long-term mortality: < 3.5, 3.5 to < 4.0, 4.0 to < 4.5, 4.5 to < 5.0, and > 5 mEq/L. There was a U-shaped relationship between admission serum potassium levels and long-term mortality that persisted after multivariable adjustment. The mortality risk was lowest in the group of patients with potassium levels of 3.5 to < 4.0 mEq/L, whereas mortality was higher in patients with potassium levels > 4.5 [hazard ratio (HR) 1.62, 95 % confidence interval (CI) 0.90 to 2.93 and HR 1.55, 95 % CI 0.54 to 4.49, for patients with potassium levels of 4.5 to < 5.0 mEq/L and ≥ 5.0 mEq/L, respectively] or < 3.5 mEq/L (HR 2.14, 95 % CI 1.28 to 3.59). There was a U-shaped relationship between admission serum potassium levels and long-term mortality for ACS patients; in particular, among the examined patients, the lowest mortality was observed in those with admission serum potassium levels of between 3.5 and < 4.5 mEq/L compared with those who had higher or lower potassium levels.