A Mock Circulatory System to Assess the Performance of Continuous-Flow Left Ventricular Assist Devices (LVADs): Does Axial Flow Unload Better Than Centrifugal LVAD?

Sénage, Thomas*†; Février, Dorothée*; Michel, Magali*; Pichot, Emmanuel*; Duveau, Daniel*; Tsui, Steven; Trochu, Jean Noel*; Roussel, Jean Christian*

ASAIO Journal:
doi: 10.1097/MAT.0000000000000045
Adult Circulatory Support

Hemodynamic performances comparisons between different types of left ventricular assist devices (LVADs) remain difficult in a clinical context. The aim of this study was to create an experimental model to assess and compare two types of LVAD under hemodynamic conditions that simulated physical effort and pulmonary hypertension. An experimental mock circulatory system was created to simulate the systemic and pulmonary circulations and consisted of pulsatile left and right cardiac simulators (cardiowest pump), air/water tanks to model compliances, and tubes to model the venous and arterial resistances. Two types of continuous-flow ventricular assist devices were connected to this pulsated model: an axial flow pump, Heartmate II (HTM II), and a centrifugal pump, VentrAssist (VTA). The hemodynamic conditions at rest and during exercise were replicated. Mean aortic pressures were not significantly different at rest and during effort but mean flow under maximum pump speed was higher with HTM II (13 L vs. 10 L, p = 0.02). Left atrial pressure was lower at rest and during effort for the HTM II (11 mm Hg vs. 3 mm Hg, p = 0.02 and 9 mm Hg vs. 2 mm Hg, p = 0.008) than with the VTA, but with greater risk of left-ventricle suck-down for the axial flow. Power consumption for a similar flow was lower with the VTA during rest (4.7 W vs. 6.9 W, p = 0.002) and during effort (4.3 W vs. 6.6 W, p = 0.008). In case of high pulmonary vascular resistance with preserved right ventricular function, lower right ventricular pressure was obtained with HTM II (21 mm Hg vs. 28 mm Hg, p = 0.03). Observed results are in favor of a better discharge of the left and right cavities with the HTM II compared to the VTA yet with a higher risk of left cavity collapse occurrence.

Author Information

From the *Department of Thoracic and Cardiovascular Surgery, Thorax Institut, Nantes Hospital University, Nantes, France; and Department of Thoracic and Cardiovascular Surgery, Papworth Hospital NHS Foundation, Cambridge, United Kingdom.

Submitted for consideration February 2013; accepted for publication in revised form January 2014.

Disclosure: Steven Tsui is a member of Thoratec European Advisory Board and Heartware Scientific Advisory Board. Daniel Duveau is a member of Carmat Advisory Board. Thoratec has provided the Heartmate II pump and DDC console. Ventracor has provided the VentrAssist pump and Syncardia the MOCK circulation. Jean Noel Trochu is a member of Thoratec European Advisory Board. The remaining authors have no conflicts of interest to disclose.

This work received a grant from the French Society of Thoracic and Cardiovascular Surgery.

Reprint Requests: Thomas Sénage, Service de Chirurgie Thoracique et Cardiovasculaire, Hôpital Laënnec, CHU de Nantes, Bd Jacques Monod, 44093 Nantes Cedex 1, France. Email: thomas.senage@chu-nantes.fr.

Copyright © 2014 by the American Society for Artificial Internal Organs