Heart Valve Fluid Mechanics; Transcatheter Aortic Valve Replacement; Medical Device Design
With recent advances in transcatheter aortic valve replacement (TAVR), off-label use of these devices is increasing, posing unknown risks to patients. Clinicians who are using these devices in an off-label manner are doing so with limited basis for judgment except experience. In recent years, with an aging population of surgical aortic valve replacement (SAVR) patients, it is becoming increasingly more common to correct a failing bioprosthesis with a TAVR in a procedure known as valve-in-valve (VIV). It should be clearly noted that based on ISO Failure Mode Effect Analysis standards (5840-2,3) and FDA 201X Heart Valve guidelines, the design intent of the current generation of TAVR designs does not address VIV use. Furthermore, the Valve-in-Valve International Data Registry documents a number of hemodynamic and structural complications associated with this type of off-label use, which may compromise patient safety. Providing clinicians with an engineering basis to compliment an otherwise experience-based decision making process could lead to even more favorable patient outcomes. Based on generalized valve characteristics, this study aims to clarify what type, size, and deployment positioning of a TAVR will yield the most favorable performance evaluated by 1) hemodynamic pressures and flows, 2) flow field characterization via high-speed particle image velocimetry (PIV) and particle tracking, 3) level of sinus obstruction via trans-TAVR gradient, 4) valve dynamics via high-speed en face photogrammetry, and 5) migration risk through uniaxial pullout force measurements and elevated cardiac output conditions. The results of this study will help better inform the VIV procedural decision-making process.