A compliant, banded outflow cannula for decreased after-load sensitivity of rotary right ventricular assist devices
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Biventricular support with dual rotary ventricular assist devices (VADs) has been implemented clinically with restriction of the right VAD (RVAD) outflow cannula to artificially increase afterload and, therefore, operate within recommended design speed ranges. However, the low preload and high afterload sensitivity of these devices increase the susceptibility of suction events. Active control systems are prone to sensor drift or inaccurate inferred (sensor-less) data, therefore an alternative solution may be of benefit. This study presents the in vitro evaluation of a compliant outflow cannula designed to passively decrease the afterload sensitivity of rotary RVADs and minimize left-sided suction events. A one-way fluid-structure interaction model was initially used to produce a design with suitable flow dynamics and radial deformation. The resultant geometry was cast with different initial cross-sectional restrictions and concentrations of a softening diluent before evaluation in a mock circulation loop. Pulmonary vascular resistance (PVR) was increased from 50 dyne s/cm5 until left-sided suction events occurred with each compliant cannula and a rigid, 4.5?mm diameter outflow cannula for comparison. Early suction events (PVR ~ 300 dyne s/cm5) were observed with the rigid outflow cannula. Addition of the compliant section with an initial 3?mm diameter restriction and 10% diluent expanded the outflow restriction as PVR increased, thus increasing RVAD flow rate and preventing left-sided suction events at PVR levels beyond 1000 dyne s/cm5. Therefore, the compliant, restricted outflow cannula provided a passive control system to assist in the prevention of suction events with rotary biventricular support while maintaining pump speeds within normal ranges of operation.
Copyright 2014 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc. This is the peer reviewed version of the following article: A compliant, banded outflow cannula for decreased after-load sensitivity of rotary right ventricular assist devices, Artificial Organs, Vol. 39 (2), pp. 102-109, 2014 which has been published in final form at http://dx.doi.org/10.1111/aor.12338. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving (http://olabout.wiley.com/WileyCDA/Section/id-828039.html)