Performance Characteristics of Centrifugal Pump Impeller for Heart Failure Therapy: Numerical and In-vitro Approach

Abstract

Heart failure (HF) is a common cause of hospitalisation and mortality across industrialised countries. The number of hospitalisations and deaths attributed to heart failure is increasing, and this trend is predicted to continue. Numerical and in-vitro simulations of the human cardiovascular system constitute the basic tools for enhancing diagnostic and therapeutic technologies for HF and this would in turn, have significant effects on morbidity,mortality, and healthcare expenditure. Mechanical Circulatory Support (MCS) as a destination therapy for HF is rising significantly as it provides a cost-effective alternative to long-term treatment and cardiac transplantation. However, long-term versatility is far from ideal and incidence of transient and permanent neurological events is still high. To this end, evolution of MCS devices calls for more sophisticated design and evaluation methods. The purpose of this work is to develop a numerical model and to implemented a novel in-vitro model of the cardiovascular system with the intention of evaluating the performance characteristics of a purposely selected centrifugal pump impeller for the treatment of both Class III and IV HF conditions when placed in series with the heart at two different anatomic locations: Ascending Aorta and Descending Aorta. An existing lumped-parameter model of the CV system, that included models for the heart, the pulmonary and the systemic circulatory loops by adapting a modified version of the fourth-element Windkessel model was enhanced by dividing the systemic circulation into six parallel vascular beds, and by including an autoregulatory system to control both pressures and volumes throughout the system. As part of the novelty of the present work, a volume reflex loop was included with the purpose of simulating volume overload conditions, as commonly found in HF conditions, and obtaining a more realistic analysis of volume displacement, while using a MCS device. The in-vitro model implemented in this work adopted most of the features included in the mathematical counterpart with the purpose of validating the numerical results. As a result of the combination of models and proper optimisation of the system parameters, predictions of pathophysiological trends and MCS usage are satisfactorily obtained. The models implemented in this work offer a valuable tool for the selection and performance evaluation of MCS devices for the treatment of HF conditions.