Development of a circulatory model to predict the change in the hemodynamics between with and without pumping of a left ventricular assist device(LVAD)

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During the LVAD pumping, it is difficult to evaluate the degree of the cardiac function of the natural heart. To solve this problem, a mechanical circulatory model with which the cardiac function of the natural heart can be predicted without stopping of the LVAD pumping has been developed. This model was a closed circuit composed of three pulsatile pumps as the LVAD and the right and left heart, five compliance tanks as the capacitance elements of the blood vessels and three needle valves as the peripheral resistance. The outflow conduit from the left heart was specially designed by using a natural rubber tube, the inertance and capacitance of wich were similar to those of the natural aorta. To simulate some of the control of circulation, two servo mechanisms for the automatic control system were designed and incorporated in the simulator. One was used for the control of the cardiac output based on a "Staring's law, " and the other was used for the control of pre-capillary resistance simulating the autonomic control. The specifications of this system were determined on the basis of the physiological data. Twelve pairs of clinical hemodynamic data of on/off tests of LVAD pumping were analyzed with this simulation system. Firstly, the standard hydrodynamic condition during LVAD pumping were determined in the mock circulatory system referred from the pumping-on data of the clinical cases. Then, the LVAD was stopped and hydrodynamic simulation data during the stop of LVAD pumping were obtained. When these predicted data were compared with the corresponded human hemodynamics, the difference in the cardiac output between simulation and clinical data was kept within only ±0.1L/min in each test. The differences in the left atrial pressure and the aortic pressure were within ±2.5mmHg and ±5.0mmHg, respectively. These data suggested that our simulation model has an adequate characteristics to predict the change in the hemodynamics of the clinical cases and it will provide many useful informations to know the recovery process of the filing heart and to determine the optimal control strategy of the LVAD.
ライフサポート学会の論文

Development of a circulatory model to predict the change in the hemodynamics between with and without pumping of a left ventricular assist device(LVAD)

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