Elevated Potassium Levels in Patients With Congestive Heart Failure: Occurrence, Risk Factors, and Clinical Outcomes: A Danish Population‐Based Cohort Study

BACKGROUND: Data on the true burden of hyperkalemia in patients with heart failure (HF) in a real‐world setting are limited. METHODS AND RESULTS: Incidence rates of hyperkalemia (first blood test with a potassium level >5.0 mmol/L) in primary or hospital care were assessed in a population‐based cohort of patients with incident HF diagnoses in northern Denmark from 2000 to 2012. Risk factors and clinical outcomes were compared in patients with HF with versus without hyperkalemia. Of 31 649 patients with HF, 39% experienced hyperkalemia (mean follow‐up, 2.2 years). Risks of experiencing a second, third, or fourth event were 43%, 54%, and 60%, respectively. Among patients with HF with stage 3A, 3B, 4, or 5 kidney dysfunction, 26%, 35%, 44%, and 48% experienced hyperkalemia within the first year. Important hyperkalemia risk factors included chronic kidney disease (prevalence ratio, 1.46; 95% confidence interval [CI], 1.43−1.49), diabetes mellitus (prevalence ratio, 1.38; 95% CI, 1.32−1.45), and spironolactone use (prevalence ratio, 1.48; 95% CI, 1.42−1.54). In patients with HF who developed hyperkalemia, 53% had any acute‐care hospitalization 6 months before the hyperkalemia event, increasing to 74% 6 months after hyperkalemia (before‐after risk ratio, 1.41; 95% CI, 1.38−1.44). Compared with matched patients with HF without hyperkalemia, adjusted 6‐month hazard ratios in patients with hyperkalemia were 2.75‐fold (95% CI, 2.65–2.85) higher for acute‐care hospitalization and 3.39‐fold (95% CI, 3.19–3.61) higher for death. CONCLUSIONS: Almost 4 in 10 patients with HF develop hyperkalemia, and many patients have recurrent hyperkalemia episodes. Hyperkalemia risk is strongly associated with degree of reduced kidney function and use of spironolactone. Hyperkalemia is associated with severe clinical outcomes and death in HF.