Design of an Experimental Mock Circulatory System for the Fontan Circulation

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.Copyright © 2010 by ASME