Hemodynamics of the Total Cavopulmonary Connection
Background:
Single ventricle congenital heart defects afflict 2 per every 1000 births. They are characterized by cyanotic mixing between the de-oxygenated blood coming back from the systemic circulation and the oxygenated blood from the pulmonary circulation. Prior to introduction of the Fontan procedure in 1971, surgical options for single ventricle patients were limited. The Fontan operation involves a series of three palliative procedures aimed at the separation of systemic and pulmonary circulations and reducing the long term effects of chronic hypoxia and ventricular volume overload. The first stage, called the Norwood procedure, is performed in the neonatal period with a systemic to pulmonary artery shunt followed by an aortic reconstruction when needed. In the second stage, the superior vena cava (SVC) is anastomosed to the pulmonary arteries in a bidirectional cavopulmonary connection (BCPC) configuration. The total cavopulmonary connection (TCPC) is completed in the final stage of the surgery with the anastomosis of the inferior vena cava (IVC) to the BCPC.
However, there are several long term consequences of this procedure, such as heart failure, elevated central venous pressure, protein losing enteropathy, progressive cyanosis and poor exercise capacity.
Objective of this research project:
The goal of this project is to adopt a multi-modality approach using novel imaging, image analysis, computational and experimental fluid dynamics techniques for patient specific surgical optimization of the total cavopulmonary connection.
Methodology:
The overall methodology can be summarized via the following flow chart.
Patient specific geometries and flows are reconstructed from magnetic resonance images (MRI) and used for generating computational and experimental models and ultimately assess the hemodynamic performance of a given TCPC geometry via either in vitro experiments or computational fluid dynamics (CFD) simulations.
From Left to Right: Intra Atrial, Extra Cardiac, IVC MPA, Bilateral SVC, Interrupted IVC
CFD tool development:
The ultimate goal of this project is to design a surgical planning tool that would predict the post-surgical hemodynamics in these patient specific anatomies using computational fluid dynamics (CFD) only. In the development phase the concurrent use of experimental and CFD methods on identical geometries allow for a thorough CFD validation. Patient-specific TCPC anatomies pose significant challenges for accurate CFD simulations due to (1) their complex geometries and (2) the inherent flow instabilities (experimental & numerical visualization of flow instabilities) that arise inside the connection even when submitted to non-pulsatile inflow conditions.
Computational studies and comparison with experiments
Surgem: Next Generation Anatomy Editing Tool:
Recently, a next-generation surgical planning framework has been established in collaboration with Dr. Jarek Rossignac in the college of computing. Realistic patient specific geometries along with the surrounding anatomic structures are reconstructed, and a virtual surgery is performed using the 2 haptic controllers with three degrees of freedom. A computational mesh is generated and a CFD simulation is conducted for visualizing post operative hemodynamics. The following figures show the different figures associated with the anatomic reconstructions, experimental and computational simulations performed in realistic TCPC models.
Patient Specific Surgical Planning: 1) bidirectional Glenn; 2) surrounding anatomy; 3) and 4) baffle placement; and 5) final geometry
