A synchronous control system for a totally implanted circulatory assist device

Abstract

This paper has been prepared with the point of view that rehabilitative circulatory assist devices or heart replacements must not require permanent attachment of the patient to an external power and control system through percutaneous tubes. The Artificial Heart Program recently conducted a series of experiments designed to evaluate the problems of integrating the components of a circulatory assist device into a totally implantable system (including pump, controls and a source of power). This paper describes the work on 2 such systems, with reference to physiologic variables and the problem of control. A control method is described for a left ventricle to aorta pump. It produced synchronous operation, required no sensors in the blood stream, did not use the electrocardiogram and required no percutaneous leads. Evidence is presented which suggests that a single, fixed, best setting can be made which results in achieving the secondary goals: maximal reduction in peak left ventricular pressure and normal aortic pressure as a function of time (though shifted in phase with respect to pressure in the pulmonary artery). Evidence is presented which suggests that achievement of the secondary goals achieves the primary goal: support of the entire body in the presence of a failing heart. Finally, it is shown that information gained from developing an optimal control system for an assist device can, in turn, be valuable in improving and fixing the design of the device, subject to constraints of reliability, efficiency, materials, size, weight, cost and effectiveness. The systems described (including the control approach) were developed by a team effort of personnel in the Artificial Heart Program and many investigators working under contract; they should not be identified with the authors.