Subclinical leaflet thrombosis - a concern, but also an issue?

The Efficacy and Safety of Direct Oral Anticoagulants versus Standard of Care in Patients without an Indication of Anti-Coagulants after Transcatheter Aortic Valve Replacement: A Meta-Analysis of Randomized Controlled Trials

Transcatheter aortic valve replacement (TAVR) is now considered the mainstay of aortic stenosis management; however, the optimal antithrombotic therapy in patent without indications for an oral anticoagulant (OAC) is yet to be identified. Therefore, we conducted a systematic review and meta-analysis to evaluate the efficacy and safety of direct oral anticoagulant (DOAC) treatment versus the standard of care in patients without indications of OACs after TAVR. We synthesized randomized controlled trials (RCTs) from Web of Science, SCOPUS, EMBASE, PubMed, and Cochrane until 18 August 2022. We used the risk ratio (RR) for dichotomous outcomes with the corresponding 95% confidence interval (CI). We registered our protocol in PROSPERO with ID: CRD42022357027. Three RCTs with 2922 patients were identified. DOACs were significantly associated with higher incidence of all-cause mortality (RR: 1.68 with 95% CI [1.22, 2.30], p = 0.001), mortality due to non-cardiovascular causes (RR: 2.34 with 95% CI [1.36, 4.02], p = 0.002), and the composite outcome of death, myocardial infarction, or stroke (RR: 1.41 with 95% CI [1.13, 1.76], p = 0.002). However, DOACs were associated with decreased incidence of reduced leaflet motion (RLM) (RR: 0.19 with 95% CI [0.09, 0.41], p = 0.0001) and hypoattenuated leaflet thickening (HALT) (RR: 0.50 with 95% CI [0.36, 0.70], p = 0.0001). DOACs were effective to reduce RLM and HALT; however, the clinical effect of this is still controversial. DOACs were associated with worse efficacy and safety outcomes, including all-cause mortality. Further RCTs investigating the optimal antithrombotic regimen after TAVR.

Antithrombotic Therapy After Transcatheter Aortic Valve Replacement

Transcatheter aortic valve replacement (TAVR) is a treatment option for symptomatic patients with severe aortic stenosis who are candidates for a bioprosthesis across the entire spectrum of risk. However, TAVR carries a risk for thrombotic and bleeding events, underscoring the importance of defining the optimal adjuvant antithrombotic regimen. Antithrombotic considerations are convoluted by the fact that many patients undergoing TAVR are generally elderly and present with multiple comorbidities, including conditions that may require long-term oral anticoagulation (OAC) (eg, atrial fibrillation) and antiplatelet therapy (eg, coronary artery disease). After TAVR among patients without baseline indications for OAC, recent data suggest dual-antiplatelet therapy to be associated with an increased risk for bleeding events, particularly early postprocedure, compared with single-antiplatelet therapy with aspirin. Concerns surrounding the potential for thrombotic complications have raised the hypothesis of adjunctive use of OAC for patients with no baseline indications for anticoagulation. Although effective in modulating thrombus formation at the valve level, the bleeding hazard has shown to be unacceptably high, and the net benefit of combining antiplatelet and OAC therapy is unproven. For patients with indications for the use of long-term OAC, such as those with atrial fibrillation, the adjunctive use of antiplatelet therapy increases bleeding. Whether direct oral anticoagulant agents achieve better outcomes than vitamin K antagonists remains under investigation. Overall, single-antiplatelet therapy and OAC appear to be reasonable strategies in patients without and with indications for concurrent anticoagulation. The aim of the present review is to appraise the current published research and recommendations surrounding the management of antithrombotic therapy after TAVR, with perspectives on evolving paradigms and ongoing trials.

Antithrombotic Therapy After Transcatheter Aortic Valve Replacement

The performance of transcatheter aortic valve replacement has expanded considerably during the past decade. Technological advances and refinement in implantation techniques have resulted in improved procedural outcomes, whereas indications are progressively extending toward lower-risk patients. Ischemic/embolic complications and major bleeding remain important and strongly correlate to mortality. In this regard, the optimal antithrombotic regimen after successful transcatheter aortic valve replacement remains unclear, in the absence of randomized trials. For patients without an indication for oral anticoagulation, empirical treatment with dual antiplatelet therapy (aspirin plus clopidogrel) for 3 to 6 months is currently recommended. However, dual antiplatelet therapy has been preliminarily associated with increased risk of bleeding compared with single antiplatelet therapy without significant ischemic benefit. Non-vitamin K oral anticoagulants and warfarin have also entered clinical investigation, to address the issue of preexisting or new-onset of atrial fibrillation and potentially attenuate subclinical leaflet thrombosis. Clinical trials are necessary to systematically address the risks and benefits of these approaches. In this review, we present the pathophysiological mechanisms of post-transcatheter aortic valve replacement complications and provide updated insights on the rationale behind the various antithrombotic regimens being currently evaluated in large randomized trials.

Clinical Valve Thrombosis and Subclinical Leaflet Thrombosis Following Transcatheter Aortic Valve Replacement: Is There a Need for a Patient-Tailored Antithrombotic Therapy?

Transcatheter aortic valve replacement (TAVR) has become an established therapeutic option for patients with symptomatic, severe aortic valve stenosis at increased surgical risk. Antithrombotic therapy after TAVR aims to prevent transcatheter heart valve (THV) thrombosis, in which two different entities have to be recognized: clinical valve thrombosis and subclinical leaflet thrombosis. In clinical valve thrombosis, obstructive thrombus formation leads to an increased transvalvular gradient, often provoking heart failure symptoms. Subclinical leaflet thrombosis is most often an incidental finding, characterized by a thin layer of thrombus covering the aortic side of one or more leaflets; it is also referred to as Hypo-Attenuating Leaflet Thickening (HALT) as described on multi-detector computed tomography (MDCT) imaging. This phenomenon may also affect leaflet motion and is then classified as Hypo-Attenuation affecting Motion (HAM). Even in case of HAM, the transvalvular pressure gradient remains within normal range and does not provoke heart failure symptoms. Whereas, clinical valve thrombosis requires treatment, the clinical impact and need for intervention in subclinical leaflet thrombosis is still uncertain. Oral anticoagulant therapy protects against and resolves both clinical valve thrombosis and subclinical leaflet thrombosis; however, large-scale randomized clinical trials studying different antithrombotic strategies after TAVR are still under way. This review article summarizes the currently available data within the field of transcatheter aortic valve/leaflet thrombosis and discusses the need for a patient tailored antithrombotic approach.