Association between potassium level and outcomes in heart failure with reduced ejection fraction: a cohort study from the Swedish Heart Failure Registry.

In this nationwide registry, the relationship between potassium and mortality was U-shaped, with an optimal potassium value of 4.2 mmol/L. After multivariable adjustment, hypokalaemia was associated with increased long-term mortality but hyperkalaemia was associated with increased short-term mortality.