China Science

Marsden,AL; Vignon-Clementel,IE; Chan,FP; Feinstein,JA; Taylor,CA

Abstract Congenital heart defects with a single functional ventricle, such ashypoplastic left heart syndrome and tricuspid atresia, require a staged surgical approach toseparate the systemic and pulmonary circulations. Ultimately, the venous or pulmonary side of theheart is bypassed by directly connecting the vena cava to the pulmonary arteries with a modifiedt-shaped junction. The Fontan procedure (total cavopulmonary connection, TCPC) completes thisprocess of separation. To date, computational fluid dynamics (CFD) simulations in this low pressure,passive flow, intrathoracic system have neglected the presumed important effects of respiration onphysiology and higher ”stress” states such as with exercise have never been considered. Wehypothesize that incorporating effects of respiration and exercise would provide more realisticestimates of TCPC performance. Time-dependent, 3D blood flow simulations are performed by a customfinite element solver for two patient-specific Fontan models with a novel respiration model,developed to generate physiologic time-varying flow conditions. Blood flow features, pressure, andenergy efficiency are analyzed at rest and with increasing flow rates to simulate exerciseconditions. The simulations produce realistic pressure and flow data, comparable to that measured bycatheterization and echocardiography, and demonstrate substantial increases in energy dissipation(i.e. decreased performance) with exercise and respiration due to increasing intensity of smallscale vortices in the flow. As would be expected, these changes are highly dependent onpatient-specific anatomy and Fontan geometry. We propose that respiration and exercise should beincorporated into TCPC CFD simulations to provide increasingly realistic evaluations of TCPCperformance.

Keywords Blood Flow Velocity; Exertion; Heart Bypass, Right; Models, Cardiovascular

Annals of Biomedical Engineering
0090-6964, Volume 35, Issue 2, 2007, Pages 3-263