Serum Potassium Levels and Clinical Outcome in Patients with Chronic Heart Failure

Background: 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.

Methods: All patients with a diagnosis of HF at a health maintenance organization were evaluated and followed for cardiac related hospitalizations and death.

Results: The cohort consisted of 6,073 HF patients. Mean potassium levels were 4.57±0.53 mmol/L. The majority of patients (68%) had potassium levels in the normal range (4.0-5.0 mmol/L). High-normal potassium levels (5.0-5.5) 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 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 comorbidities and standard HF drug therapies demonstrated that high-normal potassium levels was independently associated with reduced mortality compared to normal reference levels, hazard ratio (HR) 0.78, 95% confidence interval (CI) 0.64–0.95, P=0.01. Subgroup analysis showed improved outcome with high-normal potassium levels in patients with reduced renal function, spironolactone and loop diuretic therapy. High-normal potassium levels was also independently associated with reduced out-of-hospital mortality (HR 0.73, 95% CI 0.55-0.96, P=0.03).

Conclusions: Potassium levels in the high-normal range appear to be safe and are associated with an improved outcome in patients with HF.