Serum Potassium Levels and Outcome in Patients With Chronic Heart Failure

Potassium levels are often abnormal in patients with heart failure (HF) and have a detrimental effect on clinical outcome. We evaluated potassium levels in a real-world cohort of patients with HF and its effect on mortality. All patients with a diagnosis of HF at a health maintenance organization were evaluated and followed for cardiac-related hospitalizations and death. The cohort consisted of 6,073 patients with HF. Mean potassium levels were 4.57 ± 0.53 mmol/L. Most patients (68%) had potassium levels in the normal range (4.0 to 5.0 mmol/L). High-normal potassium levels (5.0 to 5.5) were present in 17% of the patients, low potassium levels (<4.0) in 11%, and hyperkalemia (K ≥5.5) in 4%. Mean follow-up was 576 days. The overall mortality rate during this period was 14%. Survival rate by Kaplan-Meier analysis demonstrated that hypokalemia (K ≤3.5) was associated with the lowest survival rate. Survival was highest in patients with high-normal potassium levels. Cox regression analysis after adjustment for significant predictors including co-morbidities and standard HF drug therapies demonstrated that high-normal potassium levels were independently associated with reduced mortality compared with normal reference levels (hazard ratio 0.78, 95 confidence interval [CI] 0.64 to 0.95, p = 0.01). Subgroup analysis showed improved outcome with high-normal potassium levels in patients with reduced renal function, spironolactone, and loop diuretic therapy. In conclusion, potassium levels in the high-normal range appear to be safe and are associated with an improved outcome in patients with HF.