Nonlinear object-oriented modeling based optimal control of the heart: Performing precise preload manipulation maneuvers using a ventricular assist device

This paper presents a simulation study of an optimal control approach being applied to control the volume trajectory of a heart's ventricle using a ventricular assist device (VAD). Usually VADs are used for heart failure therapy. However, in this study a novel VAD application within the context of animal trials will be investigated. Preload (the volume of blood within the ventricle just before the contraction) is an important determinant of heart function and therefore an interesting quantity to be manipulated in trials. To overcome limitations of classical preload manipulation techniques we propose to use a VAD to manipulate preload. The aim of this study will be to find the input trajectories for the VAD which are required to precisely hit specific preload values. Two different test scenarios were defined: the first scenario aims at resembling a traditional preload reduction technique. The second scenario defines a preload progression which is not possible to realize with traditional preload manipulation techniques. Besides the test scenarios, a comparison to experimentally obtained data is drawn. Object-oriented Modélica models of a simplified cardiovascular system and the VAD were developed to formulate a nonlinear optimal control problem. A fully open-source software tool-chain was used to automatically discretize the problem into a collocation scheme and to generate the necessary inputs for the nonlinear optimization solver. This tool-chain includes the software packages JModelica, CasADi and Ipopt. Object-oriented modeling in combination with the automated tool-chain allow for easy and fast modifications of the underlying models as well as the introduction of new objectives. Hence, the presented approach can easily be modified to be applied to other scopes of VAD and cardiovascular research.