ACASA-TAVI randomised 360 patients aged 65-80 undergoing transcatheter aortic valve implantation for severe aortic stenosis at the three Norwegian centres that perform most of the country's procedures. They received twelve months of monotherapy with either a factor Xa inhibitor or aspirin, with co-primary endpoints chosen to test efficacy and safety together.
The efficacy endpoint was hypoattenuated leaflet thickening on blinded core-laboratory 4D cardiac CT at twelve months. It occurred in 27 of 168 patients on NOAC (16.2%) against 48 of 168 on aspirin (28.6%), a risk ratio of 0.55 (95% CI 0.37-0.82, P = .004). The safety composite of VARC-3 bleeding, thromboembolic events and all-cause death was 7.5% against 10.6%, a risk difference of -3.3% (95% CI -9.5% to 2.8%), meeting non-inferiority.
Read the endpoint carefully before changing practice. Leaflet thickening on CT is a marker of valve thrombosis, not a clinical event, and its relationship to long-term durability is still being established. What the trial establishes is that in relatively young, relatively well TAVI patients, anticoagulation can be given without paying for it in bleeding. That makes it a reasonable option to discuss for a patient in whom valve durability matters most, which is precisely the younger cohort TAVI is expanding into.
- Leaflet thickening 16.2% on NOAC vs 28.6% on aspirin (RR 0.55)
- Safety composite non-inferior: 7.5% vs 10.6%
- Endpoint is blinded core-lab CT, not a clinical event
- Most relevant to the younger TAVI patients in whom durability matters
The statistics, in plain English
The efficacy interval, 0.37 to 0.82, sits entirely below 1.0, so the reduction in leaflet thickening is real. The safety interval, -9.5% to +2.8%, crosses zero, which is what non-inferiority requires: it shows no evidence of harm rather than proof of equivalence, and with 360 patients a modest bleeding excess could still hide inside it. The efficacy endpoint being an imaging finding is the main limit on how far this should be pushed.
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