The U.S. FDA has given its nod for a new trial of Abbott Laboratories’ Amplatzer Amulet left atrial appendage (LAA) occluder for those with atrial fibrillation (AF) who are at risk of stroke. Known as the CATALYST trial, it is the first study comparing the effectiveness of a LAA closure device to non-vitamin K antagonist oral anticoagulant (NOAC) drugs, a newer class of blood thinners, the Abbott Park, Ill.-based company said.