Objective To explore the effect of serum potassium concentration on the prognosis of patients with acute ST-segment elevation myocardial infarction (STEMI) based on age and the appropriate serum potassium level for STEMI patients of different ages.

Methods Totally, 441 patients with acute STEMI admitted to the Department of Cardiology, Zhongshan Hospital, Fudan University from May 2017 to May 2018 were selected. Patients were divided into two groups according to their age: ≤65 years old (n=245) and >65 years old (n=196). Then 4 subgroups according to mean serum potassium levels were identified: < 3.5 mmol/L, 3.5-4.0 mmol/L, 4.0-4.5 mmol/L, and ≥4.5 mmol/L. Major adverse events (malignant arrhythmia and all-cause death) were recorded during the hospital stay.

Results The 3.5-4.0 mmol/L subgroup of ≤65 years old group had the lowest incidence of malignant arrhythmia (4.8%) and the lowest mortality rate (0.9%). After adjusting the baseline data, there was a significant difference in mortality among different subgroups (P=0.015). The incidence of malignant arrhythmia was the lowest (9.1%) and the mortality rate was the lowest (6.0%) in the 3.5-4.0 mmol/L subgroup of the group over 65 years old, respectively. After adjusting the baseline data, there were significant differences in the mortality among different subgroups (P=0.001).

Conclusions Serum potassium concentration is an important prognostic factor for patients with acute myocardial infarction during hospitalization, the appropriate potassium levels in the early hospitalization of STEMI patients might be 3.5-4.0 mmol/L.