Bioprosthetic AVR Subclinical Leaflet Thrombosis
What is the temporal evolution of hypo-attenuating leaflet thickening and of hypo-attenuation affecting leaflet motion seen on computed tomography (CT) after transcatheter (TAVR) and surgical aortic valve replacement (SAVR)?
The SAVORY registry enrolled patients treated by TAVR (n = 75) or SAVR (n = 30) with two 4-dimensional volume-rendered CT scans fully interpretable for hypo-attenuating leaflet thickening and hypo-attenuation affecting leaflet motion, as well as unchanged antithrombotic medication between the scans. Logistic regression analysis was performed to examine the evolution of HALT and HAM while accounting for demographic and baseline variables, timing of both CT scans, valve type, and antithrombotic therapy.
The analysis population consisted of 84 patients in whom first and second CT scans were performed at 140 ± 152 days and 298 ± 141 days after valve implantation, respectively. Hypo-attenuation leaflet thickening was noted in 32 patients (38.1%), with hypo-attenuation affecting leaflet motion in 17 (20.2%). Both findings were dynamic, showing progression in 13 (15.5%) and regression in nine (10.7%) patients. Compared with antiplatelet therapy, progression was less likely among patients on oral anticoagulation with either vitamin K antagonists or non–vitamin K antagonist oral anticoagulants (odds ratio, 0.014; p = 0.036). Maintenance on chronic oral anticoagulation was not a significant predictor of regression. These findings were similar for both TAVR and SAVR bioprosthetic valves. No patients developed symptoms of valve dysfunction, and leaflet thickening was not clearly associated with any clinical events.
The authors concluded that subclinical leaflet thrombosis is a common finding after TAVR and SAVR, and that it may progress from normal leaflets to hypo-attenuation leaflet thickening and onto hypo-attenuation affecting leaflet motion. The phenomenon can develop and regress at variable intervals after valve implantation. Anticoagulants may have a protective effect against the development of hypo-attenuation leaflet thickening, but leaflet thickening also can regress without anticoagulation therapy.
The use of TAVR has ushered in an era of frequent imaging following AVR, and with it, knowledge of something that presumably has been happening since the advent of bioprosthetic AVR: A not insignificant number of patients after TAVR or SAVR develop what appears to be subclinical thrombus formation, sometimes but not always affecting leaflet motion, and sometimes but not always resulting in elevated gradients. This study, which included patients with serial CT scans, revealed that subclinical leaflet thrombosis after TAVR or SAVR is dynamic; although anticoagulants may have a protective effect against the development of subclinical leaflet thrombus formation, it also can regress without anticoagulant therapy. Current (2017 valvular heart disease focused update) American Heart Association/American College of Cardiology guidelines recommend anticoagulation with a vitamin K antagonist to achieve an international normalized ratio of 2.5 for 3-6 months after bioprosthetic SAVR among patients at low risk of bleeding (Class IIa), and for at least 3 months after TAVR among patients at low risk of bleeding (Class IIb).
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