Improving hemocompatibility in ventricular assist device therapy using physiological controlstrategies

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Heart failure is one of the main causes of mortality in the developed world. Despite the rapid growth in the number of ventricular assist device (VAD) implantations in recent years, heart transplantation remains the gold standard therapy for terminal stage heart failure. Nevertheless, the number of transplanted hearts is significantly lower than the existing need. There is no expected solution to the problem of donor heart availability in the near future. The basic function of a VAD is to assist the heart in pumping blood from the left ventricle into the aorta. Most of todays available systems are based on rotary blood pumps (RBP) which are typically operated at either constant speed or constant flow. More advanced operating schemes aim at adapting blood flow to the time-variant demand of the cardiovascular system (CVS) and the changing performance of the heart. This requires the interaction between the CVS and the RBP, which can be achieved by a physiological controller. One of the main technical issues in building a VAD system is the minimization of hemolysis, the destruction of blood cells due to the exposure of blood to the artificial pumping mechanism. Much work has been dedicated in the past to optimize the geometry of the pumping mechanism as well as the conducting flow path in this respect. So far this has been mainly done in respect to static operating conditions, which never happens in a physiological context. Within the proposed project, we want to investigate if hemocompatibility can be improved by optimizing the dynamic control of the RBP. In order to achieve this, a model of hemolysis dependent on operating conditions has to be found. For this, we will use two alternative approaches. A data driven approach, where a mapping function is determined by parameter estimation from measurement data and a physics driven approach, where a computational fluid dynamics (CFD) simulation of the hydraulic system is used. In parallel to these activities, we will update our laboratory hybrid mock circulatory loop to facilitate hemocompatibility testing under a wide range of dynamic, physiological and pathological load conditions. Based on models and testing results, we will then develop control algorithms, which incorporate hemocompatibility as objective in a robust optimal control problem. Additionally, a pump flow estimator for the Sputnik VAD will be developed to support the dynamic operation and hemocompatibility performance. The optimized controller will be evaluated in dynamic close-to-physiology-testing in the hemocompatible mock circulatory loop using animal blood. The intended result of this project is an integrated pump system, which can not only provide the required hemodynamics but also decrease blood damage by using an optimal control strategy.