Potassium plays a key role in normal myocardial function, and current guidelines recommend that serum
potassium levels be maintained from 4.0 to 5.0 mEq/L in patients with acute
myocardial infarction (AMI). However, the impact of serum
potassium levels on long-term mortality has not been evaluated. We retrospectively studied 1,924 patients diagnosed with AMI. The average serum
potassium levels measured throughout the hospitalization were obtained and statistically analyzed. Patients were categorized into 5 groups to determine the relation between mean serum
potassium 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. The long-term mortality was lowest in the group of patients with
potassium levels of 3.5 to <4.0 mEq/L, whereas mortality was higher in the patients with
potassium levels≥4.5 or <3.5 mEq/L. In a multivariate Cox-proportional regression analysis, the mortality risk was greater for serum
potassium levels of >4.5 mEq/L (hazard ratio [HR] 1.71, 95% confidence interval [CI] 1.04 to 2.81 and HR 4.78, 95% CI 2.14 to 10.69, for patients with
potassium levels of 4.5 to <5.0 mEq/L and ≥5.0, respectively) compared with patients with
potassium levels of 3.5 to <4.0 mEq/L. The mortality risk was also higher for patients with
potassium levels<3.5 mEq/L (HR 1.55, 95% CI 0.94 to 2.56). In contrast to the association with long-term mortality, there was no relation between serum
potassium levels and the occurrence of ventricular arrhythmias. The results of the current analysis suggest that there is a need for change in our current concepts of the ideal serum
potassium levels in patients with AMI.