Worldwide over 1 million children are born every year with congenital heart diseases such as hypoplastic left heart syndrome. A special heterogeneous subset of this group encompasses babies born with malformations of their heart chambers and connecting vessels that have only one functional ventricle. The incidence of patients born with functional univentricular physiology is approximately 2 per every 1000 births. Without surgical intervention, this combination of cardiac anomalies is fatal within the first 2 weeks of life. For these patients, the current treatment paradigm consists of three staged, open heart surgeries, which culminate in the Fontan (single-ventricle) physiology. As the patient ages, this paradoxical circulation gradually fails, because of its high venous pressure levels. Reversal of the Fontan paradox requires extra subpulmonic energy that can be provided through mechanical assist devices. All previously designed and available Fontan Assist Devices (FVADs) are externally powered and very expensive. PakFVAD is a totally implantable integrated aortic-turbine venous-assist device, which does not need an external drive power and maintains low venous pressure chronically, for the Fontan circulation.
Computational fluid dynamics (CFD) is a powerful tool to virtually characterize different designs of turbomachinery of all types including turbines and pumps, especially during the preliminary design phase. Design and analysis of a blood turbine coupled with a centrifugal pump, acting as a venous assist device are done to find the optimal design with reduced hemolysis and other related risks. Computational fluid dynamics analysis is performed on different initial designs. A stress-based CFD code is also implemented to estimate the quantitative hemolysis. The best designs with an aortic steal in a safe range and optimum performance are then selected and tested for hydraulic performance. The prototypes of the device operate at 800-1250 revolutions per minute and extract up to 15-25% systemic blood from the aorta to use this hydrodynamic energy to drive a blood turbine, which in turn drives a mixed-flow venous pump. The turbine is magnetically coupled with the pump to keep the oxygen-rich and deoxygenated blood from mixing. By transferring part of the available energy from the single-ventricle outlet to the venous side, the PakFVAD system is able to generate up to approximately 5 mmHg venous recovery while supplying the entire caval flow.
The study, in a nutshell, showed that a totally implantable integrated aortic-turbine venous-assist system is feasible, which will eliminate the need for external power for Fontan mechanical venous assist and combat gradual postoperative venous remodeling and Fontan failure. The numerical design, as well as the experimentation of the initial prototypes, have been completed. Now, different pivoting styles and impeller designs with minor iterations are under experimentation. Moreover, efforts are being made to develop a complete mock circulatory loop and carry out the in vitro testing of the devices as well as the experimental evaluation of hemodynamic performance. This initial design and development study will pave the way for future research and eventually a locally designed and manufactured totally implantable integrated aortic-turbine venous-assist system that will save many precious lives.