Seminars

Two in every one thousand births in the U.S. are born with a single functional ventricle. In these patients, the our-chambered structure of the heart no longer exists, and the single ventricle must pump blood to both the systemic and pulmonary circulations. The Fontan procedure - which culminates with the creation of the total cavopulmonary connection (TCPC) - is a common surgical palliation of single ventricle congenital heart defects. This procedure results in adequate immediate patient outcomes but unfortunately, also in numerous long-term complications. These complications have been linked to TCPC hemodynamics. To better understand the fluid dynamics of the TCPC and enhance surgical/therapy planning to improve patient outcomes, a synergistic, multi-disciplinary approach involving engineering, computer science and cardiovascular medicine is utilized.

This surgical planning approach begins with the acquisition of magnetic resonance imaging (MRI). The images are segmented to reconstruct in vivo patient-specific anatomies and phase contrast MRI is used to obtain flow information. A recently-developed virtual surgery tool generates a series of surgical options whose hemodynamic performances are assessed using computational fluid dynamics (CFD) solvers. The “best performing” surgical options are then discussed with clinicians. The primary hemodynamic metrics of interest are fluid power loss across the connection and hepatic flow distribution (HFD). These metrics are linked to limited exercise capacity and pulmonary arteriovenous malformations, respectively.

Recent patient-specific modelling improvements have led to more accurate representations of true patient-specific TCPC hemodynamics. TCPC simulations were traditionally performed using time-averaged flow boundary conditions and rigid walls to save computational cost. The addition of pulsatile flow boundary conditions allows for cardiac pulsation considerations. Vessel compliance is considered by prescribing in vivo wall motion from cine MRI. Finally, global circulation effects are incorporated through the use of a lumped parameter model (LPM).

The surgical planning computational methodology is validated against both in vivo clinical and in vitro experimental measures. The surgical planning framework has helped pediatric cardiac surgeons and cardiologists in major pediatric heart centers make clinical decisions and plan surgeries.