Mild hyperkalemia and outcomes in chronic heart failure: A propensity matched study

BackgroundCompared with serum potassium levels 4–5.5 mEq/L, those < 4 mEq/L have been shown to increase mortality in chronic heart failure (HF). Expert opinions suggest that serum potassium levels > 5.5 mEq/L may be harmful in HF. However, little is known about the safety of serum potassium 5–5.5 mEq/L.MethodsOf the 7788 chronic HF patients in the Digitalis Investigation Group trial, 5656 had serum potassium 4–5.5 mEq/L. Of these, 567 had mild hyperkalemia (5–5.5 mEq/L) and 5089 had normokalemia (4–4.9 mEq/L). Propensity scores for mild hyperkalemia were used to assemble a balanced cohort of 548 patients with mild hyperkalemia and 1629 patients with normokalemia. Cox regression models were used to estimate hazard ratios (HR) and 95% confidence intervals (CI) for association between mild hyperkalemia and mortality during a median follow-up of 38 months.ResultsAll-cause mortality occurred in 36% and 38% of matched patients with normokalemia and mild hyperkalemia respectively (HR, 1.07; 95% CI, 0.90–1.26; P = 0.458). Unadjusted, multivariable-adjusted, and propensity-adjusted HRs for mortality associated with mild hyperkalemia were 1.33 (95% CI, 1.15–1.52; P < 0.0001), 1.16 (95% CI, 1.01–1.34; P = 0.040) and 1.13 (95% CI, 0.98–1.31; P = 0.091) respectively. Mild hyperkalemia had no association with cardiovascular or HF mortality or all-cause or cardiovascular hospitalization.ConclusionSerum potassium 4–4.9 mEq/L is optimal and 5–5.5 mEq/L appears relatively safe in HF. Despite lack of an intrinsic association , the bivariate association of mild-hyperkalemia with mortality suggests that it may be useful as a biomarker of poor prognosis in HF.