Progressive Calcification in Bicuspid Valves: A Coupled Hemodynamics and Multiscale Structural Computations.

Area of Science:

• Cardiovascular Engineering
• Biomedical Imaging
• Computational Fluid Dynamics

Background:

• Bicuspid aortic valve (BAV) is the most common congenital heart defect.
• Calcific aortic valve disease (CAVD) is the primary cause of aortic stenosis (AS), with BAV patients experiencing accelerated progression.
• Understanding the biomechanical factors driving CAVD progression in BAV is crucial for effective treatment.

Purpose of the Study:

• To develop a computational modeling approach for BAV calcification progression.
• To simulate the biomechanical response of BAV using fluid-structure interaction (FSI) during disease progression.
• To elucidate the fluid-structure mechanisms underlying CAVD progression in BAV.

Main Methods:

• Patient-specific BAV leaflet geometry reconstructed from Micro-CT images.
• Novel reverse calcification technique to generate multilayered calcified structures representing disease progression (healthy, mild, moderate, severe).
• FSI simulations of four progressive BAV models throughout the cardiac cycle.
• In-vitro validation of the severe model using a pulse duplicator and validation of the healthy model against echocardiography.

Main Results:

• Progressive AS models showed increased systolic jet flow velocities (2.08 to 3.85 m/s).
• Elevated velocities induced intense vortices and irregular recirculation backflow patterns.
• These hemodynamic changes led to increased viscous shear stresses on the BAV leaflets.

Conclusions:

• The study presents a novel computational approach to model BAV calcification and its biomechanical consequences.
• Fluid-structure interaction dynamics, including jet flow, vortices, and shear stress, are identified as key drivers of CAVD progression in BAV.
• Findings offer insights into the mechanisms of accelerated AS progression in BAV patients.