A controllable artificial afterload for isolated heart studies

This paper presents an artificial afterload, based on the Westerhof model, for use in isolated heart preparations. The system has adjustable elements representing peripheral resistance and total arterial compliance, together with a fixed element representing aortic impedance. It is controlled by a computer in a manner which incorporates feed forward and feedback techniques. The system maintains constant 'arterial' pressure in the face of large excursions of the flow through it. It can be programmed to change this pressure in a dynamic fashion. The time taken to recover from large changes in flow and to reset the pressure is at most 3 S. Absolute values of peripheral resistance are easily obtained without any knowledge of the actual flow being required. Tests of the system demonstrate its stability and rapid transient characteristics.