Prior observational studies have reported two abnormalities -- leaflet thickening and reduced leaflet motion -- as possible consequences of TAVR that could increase a patient's risk of stroke. An international team of researchers recently conducted a large randomized trial to evaluate the potential of anticoagulants to help reduce the risk of these abnormalities. The trial was called the Global Study Comparing a Rivaroxaban-based Antithrombotic Strategy to an Antiplatelet-based Strategy after Transcatheter Aortic Valve Replacement to Optimize Clinical Outcomes (GALILEO).
In a substudy of the trial, called GALILEO-4D, the researchers used 4D CT to determine whether an anticoagulant or antiplatelet drug was more effective at preventing leaflet-motion abnormalities in 231 patients who underwent TAVR. Each of the participants received a post-TAVR management strategy that involved taking aspirin with either an anticoagulant (rivaroxaban) or antiplatelet medication (clopidogrel), followed by a 4D CT scan roughly 90 days after starting treatment (NEJM, January 9, 2020, Vol. 382:2, pp. 130-139).
Hypoattenuated leaflet thickening
4D CT scans showing varying degrees of hypoattenuated leaflet thickening. Image courtesy of the New England Journal of Medicine. © 2020.
Overall, 4D CT revealed that the incidence of subclinical leaflet-motion abnormalities was significantly lower in those who took the anticoagulant than in those who took the antiplatelet medication (p = 0.01).
To be specific, only 2.1% of the anticoagulant group had one prosthetic valve leaflet or more with significant motion reduction (grade 3 or higher) evident on 4D CT scans, compared with 10.9% in the antiplatelet group. In addition, at least one of the valve leaflets showed thickening in 12.4% of the anticoagulant group, compared with 32.4% in the antiplatelet group.
The differences were statistically significant (p = 0.01).
|Comparison of treatment plans to reduce post-TAVR leaflet abnormalities
|% of patients with reduced motion in at least one valve leaflet on 4D CT
|% of patients with thickening in at least one valve leaflet on 4D CT
Despite the beneficial effect of anticoagulation seen on 4D CT, the rivaroxaban-based strategy was associated with a higher risk of death or thromboembolic complications and a higher risk of major bleeding than the antiplatelet-based strategy, noted lead author Dr. Ole de Backer, PhD, from the University of Copenhagen in Denmark and colleagues. The increased risk of adverse events in the anticoagulation group prompted the trial's early termination.
Whether the major adverse outcomes were directly related to the anticoagulant itself is questionable, especially considering that most of the deaths were "due to noncardiovascular causes" and "occurred long after drug discontinuation," wrote Drs. Rick Nishimura and David Holmes from the Mayo Clinic in Rochester, MN, in an accompanying editorial.
"Further studies are needed to address some of these questions before completely ruling out the benefit of direct oral anticoagulants after TAVR. ... In the interim, we as clinicians should take heed from these results and refrain from the routine use of direct oral anticoagulants after TAVR until we have more answers," they concluded.
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