Occluding the left atrial appendage when cardiac surgery is undertaken for other reasons in patients with atrial fibrillation can lower their stroke risk by one third, researchers say.

The findings of the randomised trial, known as LAAOS III, were reported at ACC.21, the virtual annual meeting of the American College of Cardiology, and published simultaneously in the New England Journal of Medicine.

All 4770 participants from centres in 27 countries had atrial fibrillation (AF) and a CHA₂DS₂-VASc score of at least two, and were scheduled to receive cardiac surgery with cardiopulmonary bypass.

They were randomly assigned to undergo or not undergo occlusion of the left atrial appendage during their surgery.