title: Left ventricle afterload impedance control by an axial flow ventricular assist device: a potential tool for ventricular recovery.
abstract: Ventricular assist devices (VADs) are increasingly used for supporting blood circulation in heart failure patients. To protect or even to restore the myocardial function, a defined loading of the ventricle for training would be important. Therefore, a VAD control strategy was developed that provides an explicitly definable loading condition for the failing ventricle. A mathematical model of the cardiovascular system with an axial flow VAD was used to test the control strategy in the presence of a failing left ventricle, slight physical activity, and a recovering scenario. Furthermore, the proposed control strategy was compared to a conventional constant speed mode during hemodynamic changes (reduced venous return and arterial vasoconstriction). The physiological benefit of the control strategy was manifested by a large increase in the ventricular Frank-Starling reserve and by restoration of normal hemodynamics (5.1 L/min cardiac output at a left atrial pressure of 10 mmHg vs. 4.2 L/min at 21 mmHg in the unassisted case). The control strategy automatically reduced the pump speed in response to reduced venous return and kept the pump flow independent of the vasoconstriction condition. Most importantly, the ventricular load was kept stable within 1%, compared to a change of 75% for the constant speed. As a key feature, the proposed control strategy provides a defined and adjustable load to the failing ventricle by an automatic regulation of the VAD speed and allows a controlled training of the myocardium. This, in turn, may represent a potential additional tool to increase the number of patients showing recovery.
authors.affiliation: Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria. francesco.moscato@meduniwien.ac.at
authors.forename: Francesco
authors.initials: F
authors.lastname: Moscato
authors.forename: Maurizio
authors.initials: M
authors.lastname: Arabia
authors.forename: Francesco M
authors.initials: FM
authors.lastname: Colacino
authors.forename: Phornphop
authors.initials: P
authors.lastname: Naiyanetr
authors.forename: Guido A
authors.initials: GA
authors.lastname: Danieli
authors.forename: Heinrich
authors.initials: H
authors.lastname: Schima
mesh_terms: D001794:Blood Pressure; D001810:Blood Volume; D003198:Computer Simulation; D005240:Feasibility Studies; D006333:Heart Failure / Q000503:physiopathology / Q000628:therapy*; D006353:Heart-Assist Devices; D006439:Hemodynamics; D006801:Humans; D008955:Models, Cardiovascular; D009716:Numerical Analysis, Computer-Assisted; D011474:Prosthesis Design; D020127:Recovery of Function; D013997:Time Factors; D014655:Vascular Resistance; D014661:Vasoconstriction; D016277:Ventricular Function, Left; D017725:Ventricular Pressure; D020257:Ventricular Remodeling