how stenosis affects overall TEVG performance
Presenting Author: Erica Leigh Schwarz
Institution: Stanford University
Additional Authors: Erica L. Schwarz, Stephanie E. Lindsey, Aekaansh Verma, John Kelly, Jay Humphrey,Christopher K. Breuer, and Alison L. Marsden
Background/Purpose: Infants born with a single functioning ventricle must undergo a three-step procedure called the Fontan procedure. These procedures create a total cavopulmonary connection (TCPC). TCPCs increases blood oxygenation, but exercise tolerance is still reduced in this patient population. Grafts made from synthetic polymers such as Gortex and Dacron are the standard choice for creating the TCPC. However, these synthetic grafts (SyGs) have non-physiologic material properties and lack growth potential. This can result in complications that include thrombus formation and reoperation. Tissue-engineered vascular grafts (TEVGs) have recently been used to address these issues as they can develop into neovessels that grow with the patient. TEVGs are a promising alternative to SyGs, but they are prone to stenose. It is unknown how this stenosis affects overall TEVG performance, especially during exercise. In this study we use a patient-specific closed-loop lumped parameter network (CL-LPN)
Methods: We created patient-specific models of Fontan physiology of four patients at two time points. MRI images were used to build 3D patient-specific models using SimVascular and material properties were tuned to match patient-specific clinically measured values. We performed patient-specific CFD simulations using a closed-loop lumped parameter network (CL-LPN) for boundary conditions. Parameters of the CL-LPN at rest and exercise were estimated using a patient-specific protocol. We then modified the patient-specific models to create artificial stenosis. We reran simulations at rest and exercise, modifying the CL-LPN to regularize for the occurrence of stenosis. Systemic values, pressure-volume loops, power loss, and cardiac output were calculated and analyzed for each condition and model.
Results: There was little difference between the cardiac output and systemic values at rest even at severe stenosis. During exercise mild stenosis had only small effects on cardiac output. However, there was a significant decrease in cardiac output from severe stenosis during exercise.
Conclusion: It is necessary to investigate systemic values of circulation to characterize the effects of stenosis. Mild stenosis has a negligible effect on circulation. Severe stenosis, however, can severely limit cardiac output during exercise.