Transcatheter Heart Valve Implantation in Bicuspid Patients with Self-Expanding Device

Abstract

Bicuspid aortic valve (BAV) patients are conventionally not treated by transcathether aortic valve implantation (TAVI) because of anatomic constraint with unfavorable outcome. Patient-specific numerical simulation of TAVI in BAV may predict important clinical insights to assess the conformability of the transcathether heart valves (THV) implanted on the aortic root of members of this challenging patient population. We aimed to develop a computational approach and virtually simulate TAVI in a group of n.6 stenotic BAV patients using the self-expanding Evolut Pro THV. Specifically, the structural mechanics were evaluated by a finite-element model to estimate the deformed THV configuration in the oval bicuspid anatomy. Then, a fluid-solid interaction analysis based on the smoothed-particle hydrodynamics (SPH) technique was adopted to quantify the blood-flow patterns as well as the regions at high risk of paravalvular leakage (PVL). Simulations demonstrated a slight asymmetric and elliptical expansion of the THV stent frame in the BAV anatomy. The contact pressure between the luminal aortic root surface and the THV stent frame was determined to quantify the device anchoring force at the level of the aortic annulus and mid-ascending aorta. At late diastole, PVL was found in the gap between the aortic wall and THV stent frame. Though the modeling framework was not validated by clinical data, this study could be considered a further step towards the use of numerical simulations for the assessment of TAVI in BAV, aiming at understanding patients not suitable for device implantation on an anatomic basis.

Keywords: bicuspid aortic valve; finite-element analysis; fluid–solid interaction; transcatheter aortic valve implantation.

Figure 1

Different steps of the kinematics of THV deployment by the sleeve lifting from the initial crimped configuration.

Figure 2

Model adopted for the fluid–solid interaction analysis and physiological pressure boundary conditions adopted to move the SPH particle.

Figure 3

(A) Deformed configuration of deployed THV showing the contact between the aortic wall and THV at different cross-section and (B) resulting maximum principal stress distribution for Patient #5 with a pure BAV phenotype.

Figure 4

Deformed configuration of TAVI for each patient at a cross-section corresponding to the sinus of Valsalva.

Figure 5

Distribution of the contact pressure between the inner aortic wall surface and the deployed THV for four patients.

Figure 6

Map of flow velocity for Patient #5 showing the region of PVL; flow velocity shown from acceleration, to peak systole, early diastole, ending with late diastole, at three analysis planes.

Figure 7

Map of flow velocity for Patient #2 with no sign of PVL; flow velocity shown from acceleration, to peak systole, early diastole, ending with late diastole, at three analysis planes.