Design of an Experimental Mock Circulatory System for the Fontan Circulation

Abstract

Each year, a small fraction of children are born with univentricular hearts, causing the lethal blue baby syndrome. Several preliminary operations are required to buy time until the child’s blood vessels grow to sufficient size. Once the child reaches an age of 3–5 years, the blood vessels have grown enough for the Stage 3 Fontan operation, in which the superior and inferior vena cavae are coupled directly to the pulmonary arteries in a cruciform junction [2,3]. After this operation, the heart is only pumping blood to the systemic circulation. Only residual pressure in the systemic veins and intrathoracic pressure change with respiration drive the flow into the lungs [5]. This circulation decreases the load on the heart, allowing the patients to survive with normal blood oxygen levels. This circulation decreases the load on the heart, allowing the patients to survive into their 20s and 30s. An aim of this study is to develop an experimental model of the Fontan circulation that can be readily adapted to simulate patient specific anatomies so as to assist in potential surgical decisions. Of interest is the study of chronic venous hypertension, a result of the Fontan circulation having no heart “vacuum” at the end of the vena cavae; it is known to cause liver failure. We also intend to examine the hypothesis of Hsia et al. [6] that decreasing sub-diaphragmatic venous flow reversal will improve functional outcome of the Fontan.

Computational modeling and engineering in pediatric and congenital heart disease

“…Validation of CFD has generally relied on in vitro experiments, with more complex models, such as single ventricle physiology, implemented in mock circulatory loops[21–23]. Flow visualization and measurement are typically performed using phase-contrast MRI or particle image velocimetry (PIV).…”

Imaging and patient-specific simulations for the Fontan surgery: Current methodologies and clinical applications

“…An exciting new development is the use of in vitro mock circuits to simulate the part of or the entire circulatory system. in, for example, the three stages of Fontan repair, which are currently being developed by Figliola and colleagues (see related article in this issue) (Gohean, Figliola et al 2006; Camp, Stewart et al 2007; Chiulli, Conover et al 2010). Alternatively, Steele and colleagues used an in-vivo sheep model of the Fontan circulation to quantify the effect of respiration on the pulmonary circulation and validate their coupled 1D/structured-tree representation of the pulmonary vasculature (Lucas, Ketner et al 2006; Clipp 2007).…”