Hypokalemia, Kidney Function, and Clinical Outcomes in Heart Failure With Preserved Ejection Fraction

Background: Heart failure with preserved ejection fraction (HFpEF) is an increasing health problem associated with high morbidity and mortality rates. Several reports have shown an association between hypokalemia and clinical outcomes in patients with heart failure (HF). However, the association of hypokalemia with kidney function and clinical outcomes in patients with HFpEF remains unclear. Methods and Results: We measured serum potassium levels and kidney function in 454 patients with HFpEF (mean age 76 years; 55% men) at admission. Hypokalemia (K+ <3.5 mmol/L) and hyperkalemia (K+ >5.0 mmol/L) were identified in 58 (12.7%) and 11 (2.4%) patients, respectively. Patients with hypokalemia showed renal tubular damage (RTD), defined as a urinary beta(2)-microglobulin to creatinine ratio >= 300 mu g/gCr, preserved estimated glomerular filtration rate (eGFR), and plasma volume expansion. Multivariate logistic analysis demonstrated that RTD, preserved eGFR, and plasma volume expansion were significantly associated with hypokalemia. During the median follow-up period of 1,000 days, 82 HF-related events occurred. Kaplan-Meier analysis showed that patients with hypokalemia had a higher rate of HF-related events than those without hypokalemia. Multivariate Cox proportional hazard regression analysis demonstrated that hypokalemia was significantly associated with HF-related events after adjusting for confounding factors. Conclusions: Hypokalemia is affected by kidney function, notably RTD, in patients with HFpEF. Hypokalemia is a risk factor for HF-related events in patients with HFpEF.