Histopathology of Embolic Debris Captured During Transcatheter Aortic Valve Replacement

BACKGROUND: Recent transcatheter aortic valve replacement studies have raised concerns about adverse cerebrovascular events. The etiopathology of the embolized material is currently unknown. METHODS AND RESULTS: A total of 40 patients underwent transcatheter aortic valve replacement with the use of a dual filter-based embolic protection device (Montage Dual Filter System, Claret Medical, Inc). Macroscopic material liberated during the transcatheter aortic valve replacement procedure was captured in the device filter baskets in 30 (75%) patients and sent for histopathologic analysis. The captured material varied in size from 0.15 to 4.0 mm. Amorphous calcified material (size, 0.55-1.8 mm) was identified in 5 patients (17%). In 8 patients (27%), the captured material (size, 0.25-4.0 mm) contained valve tissue composed of loose connective tissue (collagen and elastic fibers) with focal areas of myxoid stroma, with or without coverage by endothelial cells and intermixed with fibrin. In another 13 (43%) patients, collagenous tissue, which may represent elements of vessel wall and valvelike structures, was identified. In 9 patients (30%), thrombotic material was intermixed with neutrophils (size, 0.15-2.0 mm). Overall, thrombotic material was found in 52% of patients, and tissue fragments compatible with aortic valve leaflet or aortic wall origin were found in 52% (21/40) of patients. CONCLUSIONS: Embolic debris traveling to the brain was captured in 75% of transcatheter aortic valve replacement procedures where a filter-based embolic protection device was used. The debris consisted of fibrin, or amorphous calcium and connective tissue derived most likely from either the native aortic valve leaflets or aortic wall.