Increasing plasma potassium and risk of atrial fibrillation: the POTCAST trial.

BACKGROUND AND AIMS: Hypokalaemia and low-normal plasma potassium levels are associated with increased risk of atrial fibrillation. This study examined if potassium-increasing treatment reduces the risk of atrial fibrillation-related clinical events. METHODS: This is a prespecified analysis of the POTCAST trial. Adults with an implantable cardioverter-defibrillator (ICD) or cardiac resynchronization therapy-defibrillator (CRT-D) and plasma potassium ≤4.3 mmol/L were randomized to potassium-increasing treatment and standard care (high-normal potassium group) or standard care alone (control group). The endpoint was a composite of acute hospitalizations due to atrial fibrillation leading to a change in pharmacological treatment or due to inappropriate shock therapy, hospitalization for electrical cardioversion or ablation of atrial fibrillation, and loading with amiodarone for atrial fibrillation. The endpoint was evaluated in time-to-first-event analyses with death as competing risk. RESULTS: Among 1200 participants [600 in each group, median age 64 years (interquartile range, 56-72), 80.3% male], 390 (32.5%) had a history of atrial fibrillation. Plasma potassium increased by .3 mmol/L after uptitration in the high-normal potassium group compared with the controls. After a median follow-up of 3.3 person-years, the endpoint had occurred in 48 participants in the high-normal potassium group (8.0%, 2.80 events per 100 person-years), when compared with 73 participants in the control group (12.2%, 4.30 events per 100 person-years) (subdistribution hazard ratio, .65; 95% confidence interval, .45-.93, P = .02). The treatment effect appeared similar across subgroups, including those with vs without a history of atrial fibrillation. CONCLUSIONS: In adults with any cardiac disease, treated with an ICD or CRT-D, uptitration of plasma potassium levels within the normal range reduced the risk of atrial fibrillation-related clinical events.