Prothrombotic States in Transcatheter Heart Valve Leaflet Thrombosis (PROSTHESIS): Rationale and Early Results of the Observational Cohort Study

Subclinical leaflet thrombosis is an imaging phenomenon observed after transcatheter aortic valve implantation (TAVI) and characterized by hypoattenuating leaflet thickening (HALT) on computed tomography angiography. The clinical implications and underlying causes remain uncertain. Hypercoagulability, a component of Virchow's triad, may contribute to thrombus formation on bioprosthetic leaflets, but data on hypercoagulable disorders in TAVI patients and their impact on HALT are limited. The PROSTHESIS study (Prothrombotic States in Transcatheter Heart Valve Subclinical Leaflet Thrombosis) is a single-center observational cohort study aiming to include 130 TAVI patients. This pilot study aimed to (i) assess the effect of hypercoagulable disorders on HALT prevalence and (ii) evaluate their impact on the natural history of HALT. Patients were screened for common hypercoagulable disorders using genetic and functional assays and underwent multimodal imaging one year after TAVI to detect HALT. In patients with HALT, post-implant imaging was repeated after three months to assess its progression. Early results comparing 52 TAVI patients with 52 matched controls undergoing coronary angiography showed similar thrombophilia prevalence between the groups (16% vs. 12%, <i>p</i> = 0.565). HALT occurred in 15% of TAVI patients, more extensively in those with thrombophilia (712 mm³ vs. 135 mm³, <i>p</i> = 0.036). However, thrombophilia was not an independent predictor of HALT. One-year follow-up CTA revealed spontaneous HALT resolution in 63%, stability in 25%, and progression in 12%. This study aims to provide insights into HALT and its mechanisms, which may help prevent complications and improve bioprosthesis durability.