18F-GP1 Positron Emission Tomography and Bioprosthetic Aortic Valve Thrombus.

Background: Bioprosthetic valve thrombosis may have implications for valve function and durability.
Objectives: Using a novel glycoprotein IIb/IIIa receptor radiotracer 18F-GP1, we investigated whether positron emission tomography (PET)-computed tomography (CT) could detect thrombus formation on bioprosthetic aortic valves.
Methods: Ex vivo experiments were performed on human platelets and explanted bioprosthetic aortic valves. In a prospective cross-sectional study, patients with either bioprosthetic or normal native aortic valves underwent echocardiography, CT angiography, and 18F-GP1 PET-CT.
Results: Flow cytometric analysis, histology, immunohistochemistry, and autoradiography demonstrated selective binding of 18F-GP1 to activated platelet glycoprotein IIb/IIIa receptors and thrombus adherent to prosthetic valves. In total, 75 participants were recruited: 53 with bioprosthetic valves (median time from implantation 37 months [IQR: 12-80 months]) and 22 with normal native aortic valves. Three participants had obstructive valve thrombosis, and a further 3 participants had asymptomatic hypoattenuated leaflet thickening on CT angiography. All bioprosthetic valves, but none of the native aortic valves, demonstrated focal 18F-GP1 uptake on the valve leaflets: median maximum target-to-background ratio 2.81 (IQR: 2.29-3.48) vs 1.43 (IQR: 1.28-1.53) (P < 0.001). Higher 18F-GP1 uptake was independently associated with duration of valve implantation and hypoattenuated leaflet thickening. All 3 participants with obstructive valve thrombosis were anticoagulated for 3 months, leading to resolution of their symptoms, improvement in mean valve gradients, and a reduction in 18F-GP1 uptake.
Conclusions: Adherence of activated platelets is a common and sustained finding on bioprosthetic aortic valves. 18F-GP1 uptake is higher in the presence of thrombus, regresses with anticoagulation, and has potential use as an adjunctive clinical tool. (18F-GP1 PET-CT to Detect Bioprosthetic Aortic Valve Thrombosis; NCT04073875).
Competing Interests: Funding Support and Author Disclosures This work was funded by the British Heart Foundation, London, United Kingdom (RG/16/10/32375 and PG/19/40/34422). The Edinburgh Clinical Research Facilities and Edinburgh Imaging facility is supported by the National Health Service Research Scotland (NRS) through National Health Service Lothian Health Board. This work and Drs Bing, Tzolos, Williams, Dweck, and Newby are supported by the British Heart Foundation (PG/19/40/34422, FS/ICRF/20/26002, FS/CRTF/20/24086, FS/14/78/31020, CH/09/002, RG/16/10/32375, RE/18/5/34216, FS/SCRF/21/32010). Dr van Beek is supported by the Scottish Imaging Network. Dr Sellers is supported by fellowships from the Michael Smith Foundation for Health Research and the Canadian Institutes of Health Research. Drs Koglin and Stephens are employees of Life Molecular Imaging GmbH, who provided reagents for radiotracer production. Dr Leipsic is supported by a Canadian Research Chair in Advanced CardioPulmonary Imaging and the Jon DeHaan Award for Innovation in Cardiology; is a consultant for Edward Lifesciences; and provides computed tomography core laboratory services to Edwards Lifesciences, Medtronic, Neovasc, Aegis, and Tendyne, for which no direct compensation is received. Dr Williams is supported by The Chief Scientist Office of the Scottish Government Health and Social Care Directorates (PCL/17/04). Dr Newby is the recipient of a Wellcome Trust Senior Investigator Award (WT103782AIA). All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.
(Copyright © 2022 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)