New Trial Challenges High-Normal Potassium Levels for Post-Surgery AF Prevention, Suggests Cost-Effective Alternative

The researchers revealed that for atrial fibrillation after cardiac surgery (AFACS) prophylaxis, supplementing potassium only when serum levels dropped below 3.6 mEq/L is as effective as the current standard practice of maintaining levels above 4.5 mEq/L. The lower threshold for supplementation did not result in a higher incidence of dysrhythmias or adverse clinical outcomes.

Maintaining high-normal serum potassium levels through supplementation is a common strategy to prevent atrial fibrillation after cardiac surgery. However, this approach lacks strong evidence, poses potential risks, and incurs significant costs. Benjamin O’Brien, St Bartholomew’s Hospital, Barts Health NHS Trust, London, United Kingdom, and colleagues aimed to determine whether a lower serum potassium concentration trigger for supplementation is noninferior to a high-normal trigger.

This open-label, noninferiority randomized clinical trial was conducted across 23 cardiac surgical centers in the United Kingdom and Germany. Enrolled between October 20, 2020, and November 16, 2023, were patients scheduled for isolated coronary artery bypass grafting (CABG) surgery who had no history of atrial dysrhythmias. The final patient was discharged from the hospital on December 11, 2023.

Participants were randomly assigned to either a tight or relaxed potassium control strategy: the tight control group received supplementation if serum potassium fell below 4.5 mEq/L, while the relaxed control group was supplemented only if levels fell below 3.6 mEq/L. Patients wore ambulatory heart rhythm monitors, and the data were analyzed by a core laboratory blinded to the treatment assignment.

The primary outcome was the incidence of new-onset AFACS, either clinically detected or confirmed by electrocardiography, within the first 120 hours post-surgery or until hospital discharge, whichever came first. Noninferiority of the relaxed potassium control strategy was defined as a risk difference for new-onset AFACS with the upper bound of a 1-sided 97.5% confidence interval of less than 10%. Secondary outcomes assessed included other heart rhythm-related events, clinical outcomes, and intervention-related costs.

The researchers reported the following findings:

• 1690 patients (mean age, 65 years; 15% females) were randomized.
• The primary endpoint occurred in 26.2% of patients (n = 219) in the tight group and 27.8% of patients (n = 231) in the relaxed group, which is a risk difference of 1.7%.
• There was no difference between the groups in the incidence of at least 1 AFACS episode detected by any means or by ambulatory heart rhythm monitor alone, non-AFACS dysrhythmias, in-patient mortality, or length of stay.
• Per-patient cost for purchasing and administering potassium was significantly lower in the relaxed group (mean difference, $111.89).

"The common practice of maintaining high-normal serum potassium levels after CABG surgery can be discontinued. This change will lower healthcare costs and minimize patient risks associated with an unnecessary intervention," the researchers concluded.

Reference:

O’Brien B, Campbell NG, Allen E, et al. Potassium Supplementation and Prevention of Atrial Fibrillation After Cardiac Surgery: The TIGHT K Randomized Clinical Trial. JAMA. Published online August 31, 2024. doi:10.1001/jama.2024.17888