Quantifying paravalvular leakage (PVL) after transcatheter aortic valve replacement (TAVR) using particle image velocimetry (PIV)

Cardiovascular diseases (CVD) are the leading cause of death in the United States, claiming a life every 33 seconds. In 2021, CVD accounted for approximately 695,000 deaths, underscoring the urgent need for enhanced preventive and therapeutic strategies. Globally, the challenge of CVD continues to grow, with 19.05 million deaths in 2020, highlighting the escalating burden of cardiovascular diseases. Heart diseases, particularly valvular diseases, play a significant role in global health issues, especially among the elderly population. Valvular conditions, such as aortic stenosis, are prevalent and complex, disrupting critical cardiovascular functions. Aortic stenosis, primarily caused by age-related calcification of the aortic valve, restricts blood flow from the left ventricle to the aorta. This condition affects 0.4% of the general population and 1.7% of those over 65. The primary treatment strategies for aortic stenosis include Surgical Aortic Valve Replacement (SAVR) and Transcatheter Aortic Valve Replacement (TAVR). TAVR, a less invasive procedure developed as an alternative to open-heart surgery, involves inserting a new valve into the heart through a small cut, typically in the leg or chest. Despite advancements in TAVR technology, mild to moderate Paravalvular Leak (PVL) still occurs in up to 19.7% of procedures. PVL is a complication where blood leaks around the edges of the implanted valve due to imperfect sealing, leading to inefficient blood flow and increased cardiac workload. Given the prevalence and impact of PVL, there is a critical need to study and mitigate this issue to improve patient outcomes. This thesis investigates PVL in an experimental way using a custom-built left heart simulator and Particle Image Velocimetry (PIV). The experimental setup replicates the human left heart, featuring a Pulsatile Pump ViVitro, an em-tec flow meter, pressure taps, and a transparent acrylic test chamber housing a heart valve. The working fluid, a water-glycerin mix, mimics the viscosity and density of blood and is maintained at a constant temperature of 37°C to replicate human physiological conditions. The first chapter introduces the cardiovascular system and heart diseases, focusing on valvular diseases like aortic stenosis. It highlights Transcatheter Aortic Valve Replacement (TAVR) as a less invasive option than traditional surgery and explains Paravalvular Leak (PVL), its causes, prevalence, and impact on patient outcomes. The thesis then describes the experimental setup, detailing the design and components of a custom-built left heart simulator that replicates human cardiovascular conditions. Next, the methodology covers data acquisition procedures, including the Particle Image Velocimetry (PIV) system setup, laser and camera alignment, and measurement techniques. It explains data analysis methods and emphasizes the calibration process for the PIV system using a plenoptic camera. The experimental results are presented through 2D and 3D visualizations, showing the velocity field, turbulent kinetic energy (TKE), viscous shear stress (VSS), and Reynolds shear stress (RSS).