Hiroshi Hotei

Numerical Simulation of Nonpulsatile Left Ventricular Bypass

A computer simulation was carried out to investigate the influence of nonpulsatile left ventricular assistance on hemodynamics. A simulation circuit was constructed to represent the circulatory system. A source of current was added to denote the nonpulsatile blood pump. The left and right ventricles were replaced by variable compliances. Left heart failure was simulated by decreasing the amount of compliance change of the left ventricle. We introduced a pulsatility indicator (PI) to clarify the pulsatility characteristics in the hemodynamics; this PI was defined as the ratio of the pulse pressure (PP) to the mean aortic pressure (AoP). When nonpulsatile bypass flow increased, the mean AoP, tension time index (TTI), and diastolic pressure time index (DPTI) increased, and cardiac output, PP, and PI decreased. When assisted flow increased with the constant total flow rate, the mean AoP and DPTI changed little; the PP, TTI, and PI decreased, and the endocardial viability rate increased. The PI would be helpful in evaluating the effect of pulsatility.

Second Type of Linear Motor-Driven Total Artificial Heart

We evaluated the performance of the first type of linear motor-driven total artificial heart (TAH) in an acute animal experiment reported previously. Artificial circulation in an adult sheep was maintained for only 2 h, indicating that the linear motor needed more powerful thrust. A second type of linear motor-driven TAH was constructed, on the basis of the information obtained from the acute animal experiment. The second TAH has a maximum static thrust of 146 N, achieved by enlarging the thrust action area in the linear motor. The mass of the TAH is 1.9 kg, and the volume TAH is 560mL; this size is suitable for implantation in a human subject weighing 80 kg. The second TAH provides a left pump flow rate of 7.2 L/min at a pumping rate of 120 bpm in a mock circulatory system.