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

Abstract

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.

Violin plot data: A concerto of crucial information on valve thrombogenicity categorized in vitro by valve motion and inferred flow velocity

“…At near valve closure, flow dynamics can be considered analogous to transient valve stenosis, whereby regurgitation is increasingly constrained until complete, motionless, closed-valve conditions occur. During brief crucial moments preceding valve closure, localized prothrombotic microenvironments may be relevant to generation of high velocity leakage jets, flow unsteadiness, valve flutter, cyclic variability of PDVA, turbulence, and excessive shear forces that may induce blood element damage [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31]. These influences may impact multiple valve types for:…”

“… conduction abnormalities,  reduced valve leaflet mobility, sub-clinical thrombosis [17,23,[26][27][28]30],  potential for pannus formation,  silent cerebral micro-infarction [24,25],  acute and sub-acute embolic stroke and other adverse cerebrovascular events including TIA [24,26],  cavitation and high intensity trans-cranial signals (HITS) [6].…”

Transcatheter management of severe aortic stenosis during the COVID-19 pandemic

“…33 The results have been similar in other series and for self-expanding transcatheter aortic valves. 34 Mechanical issues with TAVI valves may also become an issue; subclinical leaflet thrombosis, which occurs at a significantly higher incidence after TAVI compared with sAVR, has unknown clinical significance and haemodynamic consequences, 35 and this will need to be studied further. Prosthesis degeneration, valve durability and the need for aortic valve reintervention will also need to be further evaluated in this group of younger patients.…”

The Issue of Subclinical Leaflet Thrombosis After Transcatheter Aortic Valve Implantation

“…According to the guidelines, patients who undergo TAVI should be pre-treated with aspirin and clopidogrel, which should be maintained for up to 6 months. These initial recommendations were empirical; the knowledge of the impact of dual antiplatelet therapy (DAPT) on thrombotic events and the bleeding occurring in patients undergoing percutaneous coronary intervention are among the factors taken into consideration [18].…”