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Background Left ventricular assist devices (LVADs) are nowadays a widespread option for the effective treatment of heart failure. We hypothesized that the European System for Cardiac Operative Risk Evaluation II (EuroSCORE II) might be a superior tool in clinical decision making compared with other established score systems. Methods In this retrospective, single-center analysis, between 2008 and 2014, 40 consecutive patients were followed for up to 36 months after LVAD (Thoratec Heart- Mate II) implantation. Postoperative survival was correlated to the Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) levels, Destination Therapy Risk Score (DTRS), HeartMate II Risk Score (HMRS), and EuroSCORE II. Results Overall, a positive outcome (survival, transplantation, or weaning) was reached in 87.5% (30 days), 70% (1 year), and 60% (2 and 3 years) of cases. Patients were categorized as high, medium, and low risk by use of the different scores. With in the created subgroups, the following 1-year positive outcomes were achieved--INTERMACS: high risk 58% versus low risk 68%; EuroSCORE II: high risk 17% versus low risk 89%; DTRS: high risk 44% versus low risk 75%; and HMRS: high risk 60% versus low risk 100%. After 1 year, the EuroSCORE II classification's area under the receiver operating characteristic curve (AUC) was superior (AUC = 0.78) and Fisher exact test revealed a significant predictive value for this classification (p = 0.0037) but not for INTERMACS levels, DTRS, or HMRS classifications. Conclusion These results support the assumption that EuroSCORE II risk classification may be useful to predict survival in LVAD patients. In our observation, it proved to be superior to INTERMACS, DTRS, and HMRS after 1 year. [ABSTRACT FROM AUTHOR]

The implantation of a left ventricular assist device (LVAD) is often the only therapy in terminal heart failure (HF). However, despite technical advancements, the physical fitness of the patients is still limited. One strategy to improve the benefits of ventricular assist device therapy might be the implementation of load adaptive control strategies. Two control strategies and a constant speed controller (CS) were implemented in an acute animal model where four healthy pigs received LVAD implantations. In the first strategy (preload recruitable stroke work [SW] controller, PRS), the desired pump work was computed in relation to the end-diastolic volume. In the second strategy, the controller was programmed to keep a fixed ratio of the mean hydraulic power of the assist device to the mean hydraulic power of the left ventricle (power relation controller, PR). Preload reduction, afterload increase experiments and short-term coronary artery occlusions were conducted to test the behavior of the control strategies under variable conditions. Within the experiments, the PR controller demonstrated the best preload sensitivity. The PRS controller had the best response to an increased afterload and to a reduced ventricular contractility in terms of effectively preventing ventricular overloading and increasing VAD support. No significant differences in systemic flow were observed., (© 2020 Walter de Gruyter GmbH, Berlin/Boston.)

Terminal heart failure (HF) is the most prevalent cause of death in the Western world and the implantation of a left ventricular assist device (LVAD) has become the gold standard therapy today. Most of the actually implanted devices are driven at a constant speed (CS) regardless of the patient's physiological demand. A new physiological controller [power ratio (PR) controller], which keeps a constant ratio between LVAD power and left ventricular power, a previous concept [preload responsive speed (PRS) controller], which adds a variable LVAD power to reach a defined stroke work, and a CS controller were compared with an unimpaired ventricle in a full heart computer simulation model. The effects of changes in preload, afterload and left ventricular contractility are displayed by global hemodynamics and ventricular pressure-volume loops. Both physiological controllers demonstrated the desired load dependency, whereas the PR controller exceeded the PRS controller in response to an increased load and contractility. Response was inferior when preload or contractility was decreased. Thus, the PR controller might lead to an increased exercise tolerance of the patient. Additional studies are required to evaluate the controllers in vivo.

Computational models of biophysical systems generally constitute an essential component in the realization of smart biomedical technological applications. Typically, the development process of such models is characterized by a great extent of collaboration between different interdisciplinary parties. Furthermore, due to the fact that many underlying mechanisms and the necessary degree of abstraction of biophysical system models are unknown beforehand, the steps of the development process of the application are iteratively repeated when the model is refined. This paper presents some methods and tools to facilitate the development process. First, the principle of object-oriented (OO) modeling is presented and the advantages over classical signal-oriented modeling are emphasized. Second, our self-developed simulation tool ModeliChart is presented. ModeliChart was designed specifically for clinical users and allows independently performing in silico studies in real time including intuitive interaction with the model. Furthermore, ModeliChart is capable of interacting with hardware such as sensors and actuators. Finally, it is presented how optimal control methods in combination with OO models can be used to realize clinically motivated control applications. All methods presented are illustrated on an exemplary clinically oriented use case of the artificial perfusion of the systemic circulation.