RF43. Simulation-Guided Design of Leaflet Height in Bicuspidization of the Aortic Valve

Objective: Bicuspidization repair is applied to severe congenital aortic valve lesions and increasingly recognized as an effective and durable surgical approach. The consequences of changes in leaflet geometry in this repair, however, are relatively unstudied. This work applied a computational approach to systematically study the effects of changes in leaflet height in symmetric bicuspidization repair.

Methods: Four model valves of a symmetric bicuspid aortic valve with varying geometric height, the three-dimensional leaflet height along its midline, were constructed. The sinotubular junction (STJ) diameter was fixed to 25 mm, and the virtual basal ring (VBR) diameter was fixed to 22.7 mm. Following our previous results, all models had free edge length approximately 1.57 times the VBR diameter. Fluid-structure interaction simulations were performed in a single patient-specific aortic geometry while varying valve geometry. Models were constructed such that the geometric height in diastole, which was determined by the coupled elastic response of valve tissue and its interaction with blood, varied from approximately half the annular diameter to approximately the annular diameter. Results were evaluated for stenosis (mean pressure gradient), regurgitant fraction, geometric height to VBR diameter ratio, geometric height to STJ diameter ratio, billow height, and qualitative hemodynamics and valve configuration.

Results: Case 1, which had geometric height approximately half the VBR diameter, showed moderate stenosis, moderate regurgitation and a "tented" or "doming" shape with restricted leaflet excursion during systole. Cases with geometric heights 0.7 times the VBR diameter or larger showed lower gradients and no regurgitation beyond an initial closing transient. As geometric height increased, cases showed increasing billow and the appearance of excess leaflet material.

Conclusions: Insufficient geometric height caused poor systolic and diastolic behavior. Increases in geometric height led to billow and the appearance of poor coaptation. Thus, an intermediate range of geometric height, 0.70-0.87 times the VBR diameter with the current free edge length, appeared optimal. The interdependence of geometric height and free edge length should be studied in detail in future work.

Alexander Kaiser (1), Perry Choi (2), Amit Sharir (1), Alison L. Marsden (2), Michael Ma (3), (1) Stanford University, Stanford, CA, (2) Stanford University, Palo Alto, CA, (3) Stanford University School of Medicine, Stanford, CA

Alexander Kaiser

Rapid Fire Abstract Presenter

Alexander D. Kaiser is an applied mathematician and computational scientist who researches modeling and simulation of heart valves, focused on congenital heart valve disease and its surgical treatment. His recent research explores simulation-guided design of aortic valve repair of complex congenital heart defects. He has developed novel, nearly first-principles modeling methods for heart valves called design-based elasticity. These methods produce robust and realistic flows in fluid-structure interaction simulations. Dr. Kaiser is an Instructor in Cardiothoracic Surgery at Stanford University working with Michael Ma and Alison Marsden. He completed his PhD in Mathematics with Charles Peskin at the Courant Institute of Mathematical Sciences at New York University, where he was awarded the Kurt O. Friedrichs Prize for Outstanding Dissertation in Mathematics.

Specialties: Congenital