Blood Thinners Beat Aspirin at Preventing Clots After Heart Valve Procedure, Trial Finds

A clinical trial has found that blood-thinning anticoagulant drugs work better than aspirin-type antiplatelet agents at preventing clots from forming on replacement heart valves after a procedure called transcatheter aortic valve implantation (TAVI). The ACASA-TAVI trial was presented in a Hot Line session at ESC Congress 2026 and published simultaneously in JAMA.

TAVI is used to treat severe aortic valve stenosis, a narrowing of the heart's aortic valve, and its use has grown rapidly since the first successful procedure two decades ago. Clots that form on the new valve's leaflets can go undetected but have been linked to a higher risk of stroke and death, said principal investigator Dr Oyvind Lie of Oslo University Hospital Rikshospitalet, Norway. Until now there was a gap in knowledge about which drug best prevents this.

The trial, conducted across three hospitals in Norway, randomly assigned 360 patients aged 65 to 80 who had undergone successful TAVI to 12 months of either a non-vitamin K oral anticoagulant (NOAC) or aspirin (or clopidogrel for patients who could not take aspirin). At 12 months, imaging signs of leaflet clotting occurred in 17.2% of patients on NOACs compared with 32.6% on aspirin, a 45% reduction. Safety outcomes, including bleeding and death, were not worse with NOACs: 7.5% of the NOAC group had a safety event compared with 10.6% of the aspirin group. Two patients on NOACs died during the study, compared with ten patients on aspirin.

Dr Lie said bleeding events were numerically higher with aspirin, and that life-threatening or fatal bleeding occurred only in the aspirin group. He said the results could inform future treatment guidelines, and the researchers will continue following participants for ten years to study the drugs' effect on valve durability.