Aortic Flow Patterns After Simulated Implantation of Transcatheter Aortic Valves

The functional behavior and hemodynamic characteristics of percutaneously implanted bioprosthetic valves are not known.

We created aortic models after the simulated implantation of two of the most widely used bioprosthetic valves: the Edwards SAPIEN, and the Medtronic CoreValve. By using computational fluid dynamics analysis we sought to investigate variations in the aortic flow patterns induced by the two valve designs and their association with detrimental phenomena such as vascular remodeling, vascular wall damage and thrombosis.

The simulated implantation of models that resemble the two valves resulted in different aortic flow conditions. Vortex formation in the upper ascending aorta was more persistent in the case of the simulated Medtronic valve. The ranges of average wall shear stress (WSS) values were 2.4-3.5 Pa for Edwards and 3.0-5.3 Pa for Medtronic; the calculated WSS values induced endothelial quiescence and an atheroprotective setting in both valves. The average shear stress on the simulated valve leaflets was low; however, hotspots were present in both valves (155.0 Pa for Edwards and 250.0 Pa for Medtronic) which would in theory be able to cause platelet activation and thus promote thrombosis. The pressure drops along the aorta were slightly lower for the Edwards compared to the Medtronic valve (198.0 Pa versus 218.0 Pa).

The presented method allows the assessment of aortic flow conditions following the implantation of bioprosthetic valves. It may be useful in predicting detrimental flow phenomena, thus facilitating the selection of appropriate valve designs.