Statistical Shape Modeling for Cavopulmonary Assist Device Development: Variability of Vascular Graft Geometry and Implications for Hemodynamics

Patients born with a single functional ventricle typically undergo three-staged surgical palliation in the first years of life, with the last stage realizing a cross-like total cavopulmonary connection (TCPC) of superior and inferior vena cavas (SVC and IVC) with both left and right pulmonary arteries (LPA and RPA), allowing all deoxygenated blood to flow passively back to the lungs (Fontan circulation). Even though within the past decades more patients survive into adulthood, the connection comes at the prize of deficiencies such as chronic systemic venous hypertension and low cardiac output (CO), which ultimately may lead to Fontan failure. Many studies have suggested that the TCPC’s inherent insufficiencies might be addressed by adding a cavopulmonary assist device (CPAD) to provide the necessary pressure boost. While many device concepts are being explored, few take into account the complex cardiac anatomy typically associated with TCPCs. In this study, we focus on the extra cardiac conduit (ECC) vascular graft connecting IVC and pulmonary arteries (PAs) as one possible landing zone for a CPAD and describe its geometric variability in a cohort of 18 patients that had their TCPC realized with a 20 mm vascular graft. We report traditional morphometric parameters and apply statistical shape modeling (SSM) to determine the main contributors of graft shape variability. Such information may prove useful when designing CPADs that are adapted to the challenging anatomical boundaries in Fontan patients. We further compute the anatomical mean 3D graft shape (template graft) as a representative of key shape features of our cohort and prove this template graft to be a significantly better approximation of population and individual patient’s hemodynamics than a commonly used simplified tube geometry. We therefore conclude that statistical shape modeling results can provide better models of geometric and hemodynamic boundary conditions associated with complex cardiac anatomy, which in turn may impact on improved cardiac device development.

Modeling of Patient-Specific Fontan Physiology From MRI Images for CFD Testing of a Cavopulmonary Assist Device

Single ventricle heart disease is a congenital condition characterized by the inoperability of one ventricle of an infant’s heart. Those suffering from this condition face a series of palliative surgeries called the Fontan procedure, which bypasses the non-functional ventricle by creating a total cavopulmonary connection, or TCPC. This TCPC forms from the anastomosis of the superior and inferior vena cavae (SVC, IVC) to the left and right pulmonary arteries (LPA, RPA), thus allowing systemic blood flow to bypass the heart and flow passively to the lungs. The Fontan procedure creates this junction with three surgeries separated by months or years.

Design of a Novel Cavopulmonary Assist Device for Fontan Procedures: CFD, PIV, and Hydraulic Testing

Single ventricle heart disease is the leading cause of death for birth defects in children under one years of age [1]. The current surgical procedure requires the use of a shunt for the first stage of the surgery. The following surgeries remove the shunt but cannot be performed on a newborn due to higher lung resistance during the first weeks of life. The overall surgical process, known as the Fontan procedure, results in a reconstructed anatomy where the left and right pulmonary arteries are sutured to the superior and inferior vena cavae (SVC/IVC), hence bypassing the right heart. This anatomy is called a total cavopulmonary connection or TCPC.