Potassium uptitration and risk of atrial fibrillation - a prespecified analysis of the POTCAST randomised clinical trial
C Zheng, U C G Winsloew, E M Danielsen, T Sakthivel, K K Iversen, H S Bosselmann, N Risum, C Jons, H BundgaardAbstract
Background
Hypokalaemia and low-normal plasma potassium levels are associated with increased risk of atrial fibrillation. This study examined if a potassium-increasing treatment strategy reduces the risk of clinically significant atrial fibrillation.
Methods
This is a prespecified analysis of the POTCAST trial; adults with an implantable cardioverter-defibrillator and plasma potassium level ≤4.3 mmol/L at baseline were randomised to a potassium-increasing treatment strategy consisting of dietary guidance on potassium rich foods combined with administration of a mineralocorticoid receptor antagonist, potassium supplements or both aimed at reaching high-normal plasma potassium levels (4.5-5.0 mmol/L) in addition to standard care (high-normal potassium group) or standard care alone (control group). The endpoint was a composite of acute hospitalisations due to atrial fibrillation leading to change of pharmacological treatment or due to inappropriate shock therapy, hospitalisation for electrical cardioversion or ablation of atrial fibrillation, and loading with amiodarone for atrial fibrillation in an out-patient setting or during an elective hospitalisation. The endpoint was evaluated in time-to-first-event analyses using the Fine-Gray subdistribution hazard model with death as competing risk. The cumulative incidence of clinically significant atrial fibrillation between randomisation groups was depicted using the Aalen-Johansen estimator account for death as a competing risk.
Results
Among 1200 participants (600 in each group, mean age 62.7±12.0 years, 80.3% male), 390 (32.5%) had a history of atrial fibrillation. Plasma potassium levels were increased by 0.3 mmol/L on average after uptitration in the high-normal potassium group compared to the control group. 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), as compared with 73 participants in the control group (12.2%, 4.30 events per 100 person-years) (subdistribution hazard ratio, 0.65; 95% confidence interval, 0.45-0.93, P=0.02) (Figure 1). The treatment effect appeared similar across subgroups, including those with versus without a history of atrial fibrillation (Figure 2).
Conclusion
In adults with any cardiac disease, treated with an implantable cardioverter-defibrillator, uptitration of plasma-potassium levels targeting high-normal range significantly reduced the risk of clinically significant atrial fibrillation.Figure 1– Cumulative incidencesFigure 2- Subgroup analyses