DESIGN OF A SYSTEM TO SIMULATE THE FLUID MECHANICS OF THE HUMAN LEFT VENTRICLE

Abstract

This chapter focuses on the design of a system to simulate the fluid mechanics of the human left ventricle. Simulation of left ventricular fluid mechanics is particularly difficult because of the complexities of left ventricular geometry and flow conditions. The left ventricular chamber consists of stationary and moving parts that are similar to those of the Davila et al. test chamber. However, instead of a postmortem heart, the left atrium and ventricle are constructed from rectangular blocks of plexiglas that are machined internally according to specifications reported by Wieting. These chambers are assembled in a vertical plane with the atrium directly above the ventricle. Pumping is accomplished by displacing a diaphragm at the base of the ventricle. Flow exits from the left ventricle through the aortic branch that is located adjacent to the mitral valve at the top of the ventricle and offset from the center of the chamber as in the normal human heart. This provides for a pattern of flow within the left ventricular chamber that is similar to that of a natural heart in that the flow must turn nearly 180 degrees before leaving the ventricle through the aortic valve. The system is also provided with capacitance, resistance and an elevated main reservoir to enable adjustment of pressure readings to physiological values. Other features of the system include a weir in the main reservoir, a siphon tube leading to the left atrial chamber and a diffuser located directly below the diaphragm. The function of the siphon tube is to help maintain the mean left atrial pressure at a reasonable level since if the atrial reservoir were placed above the left atrial chamber the mean atrial pressure would be too high.