Tight K was a pragmatic, multicentre, non-inferiority randomised clinical trial based in the UK and Germany. The study investigated whether a strategy of supplementing potassium when serum potassium levels fell below 3.6 mEq/L is non-inferior to supplementation when serum potassium levels fell below 4.5 mEq/L on the occurrence of new onset atrial fibrillation after cardiac surgery. The first participant was recruited in October 2020 and recruitment completed in November 2023. In total, 1690 participants were enrolled in the study. The trial was funded by the British Heart Foundation and sponsored by Barts Health NHS Trust.

To find out more about the study as well as the results of the trial, read our paper published in the Journal of the American Medical Association and this summary by the British Heart Foundation.