Linde C, et al. - In this retrospective, observational study involving a UK cohort of patients with incident heart failure, researchers examined the links between mortality, major adverse cardiac events, and renin–angiotensin–aldosterone system inhibitor (RAASi) discontinuation across serum potassium levels. The study sample consisted of 21,334 patients. The number of serum potassium measurements more than each threshold (< 3.5, ≥ 5.0, ≥ 5.5, and ≥ 6.0 mmol/L), without such a measurement in the preceding 7 days, were used to define hypokalemia and hyperkalemia episodes. Increased mortality risk was observed in relation to both hypokalemia and hyperkalemia, and increased likelihood of RAASi discontinuation was reported in association with hyperkalemia. For monitoring for heart failure outcomes and management, serum potassium could be significant.