Optimal serum potassium concentrations in heart failure: an individual patient data meta-analysis

BACKGROUND AND AIMS: It remains unclear what the safe serum potassium range is in heart failure (HF) and whether it is the same in HF with reduced ejection fraction (HFrEF) and HF with preserved ejection fraction (HFpEF). METHODS: A patient-level pooled analysis from 12 randomized controlled trials including 32 346 HFrEF and 13 723 HFpEF patients was performed. Baseline serum potassium level was categorized into six groups (<3.5, ≥3.5-<4.0, ≥4.0-<4.5, ≥4.5-<5.0, ≥5.0-<5.5, and ≥5.5 mmol/L) and serum potassium level at baseline was also analysed as a continuous variable using restricted cubic splines. The primary outcome was all-cause mortality. Secondary outcomes included cardiovascular death, sudden death, pump failure death, first HF hospitalization, and composites of HF hospitalization and cardiovascular or all-cause death. RESULTS: The median follow-up was 24.2 and 36.8 months in HFrEF and HFpEF trials, respectively. In HFrEF, serum potassium levels showed a reverse J-shaped association with outcomes. Compared with ≥4.0-4.5 mmol/L (reference), potassium <3.5 mmol/L was associated with higher risks of all-cause mortality (adjusted hazard ratio 1.49; 95% confidence interval, 1.27-1.76), as well as cardiovascular, sudden, and pump failure death. The lowest risk for all outcomes was observed within the baseline serum potassium range of 4.2-5.0 mmol/L, but even 'mild hyperkalaemia' (5.0-5.5 mmol/L) was not associated with worse outcomes in HFrEF. Although the risk curve was U-shaped and flatter in HFpEF, the lowest incidence of all outcomes was observed over the same potassium range as HFrEF. CONCLUSION: In HFrEF, hypokalaemia is strongly associated with worse outcomes and should be avoided. In terms of safety, the optimal serum potassium concentration in both HFrEF and HFpEF appears to be in the range 4.2-5.0 mmol/L.