J-shaped Association Between Serum Potassium and 30-day Mortality in Heart Failure: a Secondary Analysis of Cohort Study

Background: Multiple observational studies suggest that the association between serum potassium and mortality is U-shaped in heart failure patients, but mostly failed to control for potential confounders of other electrolytes. We explored serum potassium in relation to 30-day mortality in heart failure patients by controlling serum sodium and calcium. Methods: : Data were drawn from Electrolyte imbalances in an unselected population in an emergency department: a retrospective cohort study, Dryad, Dataset, https://doi.org/10.5061/dryad.f3h26j3. This study involved 31,966 patients aged 18 years or older at the emergency department in Diakonhjemmet Hospital in Oslo, Norway, between January 1, 2010 and December 31, 2015. 30-day mortality was examined according to seven predefined potassium levels: 2.60-3.40(hypokalaemia), 3.5–3.8, 3.9–4.1, 4.2–4.4, 4.5–4.7, 4.80-5.00, and 5.1–7.4(hyperkalemia) mmol/L. We estimated the risk of 30-day mortality using multivariable logistic regression, with serum potassium at 4.2–4.4 mmol/L as reference. Results: : A total of 1810 patients were included, and 258 (14.25%) patients died within 30-day. After multivariable adjustment, the 30-day mortality significantly increased for patients with hyperkalemia (OR=2.18, 95% CI: 1.32,3.59), but not with normal serum potassium levels: 4.8-5.0mmol/L (OR=1.08, 95% CI: 0.62,1.87) , 4.5-4.7mmol/L (OR=1.06, 95% CI: 0.67,1.68), 3.9-4.1mmol/L (OR=1.01, 95% CI: 0.65,1.58), 3.5-3.8mmol/L (OR=0.71, 95% CI: 0.42,1.20), nor with hypokalaemia (OR=0.89, 95% CI: 0.44,1.80). A J-shaped relationship between serum potassium and 30-day mortality was found, with a cut-off point at 4.8 mmol/L. When serum potassium exceeded 4.8 mmol/L, the risk of 30-day mortality increased 192 % for each 1 mmol/L increase in serum potassium (OR=2.92, 95CI: 1.74,4.89). Conclusions: : J-shaped association between serum potassium and 30-day mortality in heart failure was found, with increased mortality when serum potassium exceeded 4.8 mmol/L.