Transcatheter Aortic Valve Thrombogenesis: A Foreign Materials Perspective.

Abstract

The initiation of thrombus formation in transcatheter aortic valves (TAVs) is not well understood. The foreign material components of a TAV may play a key role in TAV thrombogenesis. The goal of this study was to evaluate the thrombogenic potential of a TAV (entire valve) and its stent (with skirt). Blood was collected from eight human donors with citrate anticoagulation and later reconstituted with calcium chloride. A low-volume steady flow loop (flow rate = 0.8 L/min) was designed to facilitate three separate conditions (experimental duration = 1h) per donor blood: (1) control (n = 8), (2) stent-with-skirt (leaflets removed from a 23mm SAPIEN XT valve; n = 8) and (3) entire valve (an intact 23mm SAPIEN XT valve; n = 8). Samples were collected at the start and end of each experiment. Serum D-Dimer and thrombin-antithrombin (TAT) concentrations were measured as markers of thrombogenicity. There was no significant change in serum D-Dimer and TAT concentration with time for the control group. An increasing trend in D-Dimer and TAT concentration was observed with time for the stent-with-skirt group. Interestingly, there was a decreasing trend in serum D-Dimer and TAT concentration with time for the entire valve (leaflet dominating) group. Moreover, changes in D-Dimer and TAT concentration were significantly different between the stent-with-skirt and entire valve (leaflet dominating) groups. Stent-with-skirt was found to impart the most prominent thrombogenic effect, indicating the significance of blood-stent and blood-skirt interactions in TAV thrombosis.