Development of Total Artificial Heart with Economical and Durability Advantages

To develop a total artificial heart (TAH) pump system, we created a design paying particular attention to durability and cost. We adopted a pneumatically driven sac type artificial heart, where the configuration of the sac was decided according to the methodology of flow visualization. Its configuration is almost round to achieve as little stagnation as possible and a low turbulent flow. The main body of the sac was made using polyvinyl chloride (PVC) paste. The paste was poured into an external mold, and heated in a hot air drying oven. Coating was performed using polyurethane. The basic performance of this pump system was tested using a model circulation circuit, and a fitting study through acute animal experiment, using a healthy adult goat, was carried out. As for the TAH produced experimentally, a pump output exceeding 5.0 l/min in the model circulation circuit was provided. Implantation in the internal pleural cavity of a healthy adult goat, 55 kg in weight, proved possible and quite easy in comparison. It is thought that a more refined design in the connector part is desirable. Furthermore, a chronic experiment with the TAH will be carried out, and examination will need to be repeated in the future.

Can the Artificial Heart Make the Circulation Become Fractal?

In order to analyze the hemodynamic parameters in prosthetic circulation as an entity and not as decomposed parts, non linear mathematical analyzing techniques, including the fractal dimension analyzing theory, were utilized. Two pneumatically actuated ventricular assist devices were implanted, as biventricular bypasses (BVB), in chronic animal experiments, using four healthy adult goats. For the comparison between the natural and prosthetic circulation in the same animals, the BVB type complete prosthetic circulation model with ventricular fibrillation, was adopted. All hemodynamic parameters with natural and prosthetic circulation were recorded under awake conditions, and calculated with a personal computer system. Using the non-linear mathematical technique, the arterial blood pressure waveform was embedded into the return map as the beat-to-beat time series data and fractal dimension analysis were performed to analyze the reconstructed attractor. By the use of the Box counting method, fractal dimension analysis of the hemodynamics was performed. Return map of the hemodynamics during natural and artificial circulation showed fractal characteristics, and fractal dimension analysis of the arterial blood pressure revealed the fact that lower dimensional fractal dynamics were evident during prosthetic circulation. Fractal time series data is suggested to have robustness and error resistance, thus our results suggest that the circulatory regulatory system with an artificial heart may have these desired characteristics.