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A descriptive incremental nonlinear single-input-multiple-output (SIMO) model of the hemodynamic response (cardiac output (CO) and mean aortic pressure (MAP)) to the inotropic drug dopamine in acute ischemic heart failure is constructed to facilitate the design of closed-loop control systems. The structure of the CO component of the model is a first-order system with a sigmoidal relationship. The MAP component is a first-order system with a threshold. Parameter identification is performed on data collected during positive step (drug on) and negative step (drug off) testing using multiple levels (206 mcg/kg/min) of infusion of dopamine in a canine model of acute ischemic heart failure. Parameter estimation utilized a least-squares objective function and a linearized form of the step response of the model in the time domain. This study in dogs suggests the response to dopamine of a heart in failure is fundamentally different from that of a heart not in failure. Assuming that canine preparations approximate human systems, it is reasonable to conclude that a closed-loop controller for the delivery of dopamine using this model will have greater success in eventual human applications than those based on models of healthy canine hearts.