An Implantable Blood Pump for Adult Congenital Heart Disease Patients with a Failed Fontan Circulation

Approximately 0.6% of infants are born with a congenital heart defect. One of the most serious defects is the absence of the two normal left and right ventricles, resulting in a single functional ventricle. This occurs in 1 in 3,000 infants. While there is no cure for this condition, a surgical technique called the 'Fontan operation' is used to make the single ventricle into a functioning left ventricle, supplying blood to the body, and to bypass the normal right ventricle so that blood flows directly from the major veins into the pulmonary circulation. Over time, the procedure has improved such that the in-hospital mortality is now less than 5% and survival at 20 years is 85%. However, the absence of a right ventricle requires that the venous blood pressure must be abnormally high to maintain blood flow through the lungs. This venous congestion leads to loss of protein through the intestines, and liver congestion; the abnormal pulmonary blood flow leads to increased resistance (pulmonary hypertension) and low oxygen delivery; and the single ventricle may be weak or have an abnormal rhythm. The progression of these symptoms is referred to as a 'failing Fontan.' These patients require a high level of medical management and have a poor quality of life and are often unable to work.

As childhood mortality has been reduced, the cohort of adult Fontan survivors has continuously grown and mortality has shifted into adulthood. There is an increasing need for means to support patients with failing Fontan physiology. Other than medical management, heart transplantation is currently the only viable option, but the morbidity of the failing Fontan makes these patients suboptimal candidates for heart transplantation, and competition for available donor organs remains a limitation.

For adults with normal anatomy who develop congestive left heart failure, mechanical blood pumps (called left ventricular assist devices, or LVADs) are increasingly being used to support the failing ventricle for periods of over 5 years, and in 40% of patients LVADs are being used as an alternative to heart transplantation. However, these devices are not suitable for Fontan support because of the unique anatomy of the Fontan circulation and the fact that the right-sided pressures are lower than the left and the pumps are not designed for that condition.

A number of catheter-based pumps are being developed for short-term support (< 30 days) in a hospital setting. These pumps would be placed in the vein near the heart, and they require a cable exiting through the femoral or jugular vein.

Our group has developed a small pump called the Fontan Circulation Assist Device (FCAD), designed specifically for the anatomic and hemodynamic requirements of the right-sided circulation. Using computational fluid dynamics (CFD) and experimental measurements on prototype devices, we have optimized the pump for efficiency and size while minimizing blood damage. The pump has been successfully tested in four animal studies (adult sheep) for the intended duration of 30 days. The native right heart was surgically isolated, and the FCAD provided complete right heart function. The results demonstrated low blood damage and a low incidence of clot formation.

Under this Expansion Award, we propose to integrate the FCAD pump into a complete system with an implantable electronic controller and wireless power transfer. The FCAD can then function as a long-term, permanent right heart replacement, resulting in improved survival and quality of life.

The aims of this project are to (1) develop the FCAD Implantable System components and (2) perform preclinical testing to prepare for feasibility testing in humans.