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The Effect of Inflow Cannula Angle on the Intraventricular Flow Field of the Left Ventricular Assist Device–Assisted Heart

An In Vitro Flow Visualization Study

May-Newman, Karen; Marquez-Maya, Nikolas; Montes, Ricardo; Salim, Saniya

doi: 10.1097/MAT.0000000000000790
Adult Circulatory Support
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Abstract: Previous studies have identified left ventricular assist device (LVAD) inflow cannula (IC) malposition as a significant risk for pump thrombosis. Thrombus development is a consequence of altered flow dynamics, which can produce areas of flow stasis or high shear that promote coagulation. The goal of this study was to measure the effect of IC orientation on the left ventricle (LV) flow field using a mock circulatory loop, and identify flow-based indices that are sensitive measures of cannula malposition. Experimental studies were performed with a customized silicone model of the dilated LV and the EVAHEART Centrifugal LVAS (Evaheart, Inc.; Houston TX). The velocity field of the LV midplane was measured for a transparent IC oriented parallel to and rotated 15° toward the septum under matched hemodynamic conditions. Vortex structures were analyzed and localized stasis calculated within the IC and combined with a map of normalized pulsatile velocity. The velocity fields revealed increased apical stasis and lower pulsatility with a small angulation of the IC. A significant change in vortex dynamics with the angled IC was observed, doubling the size of the counterclockwise (CCW) vortex while reducing the kinetic energy provided by LVAD support. A significant decrease in average and systolic velocities within the IC was found with cannula angulation, suggesting an increased resistance that affects primarily systolic flow and is worsened with increased LVAD support. These common echocardiographic indices offer the opportunity for immediate clinical application during ramp study assessment. Optimized IC positioning may be determined preoperatively using imaging techniques to develop patient-specific surgical recommendations.

From the Bioengineering Program, Department of Mechanical Engineering, San Diego State University (SDSU), San Diego, California.

Submitted for consideration October 2017; accepted for publication in revised form February 2018.

Disclosure: Karen May-Newman is a consultant for B-Squared Medical Device Solutions. The other authors have no conflicts of interest to report.

Project funding was obtained as part of a research experience for undergraduates at SDSU (Principal Investigator (PI): K.M.-N.).

Correspondence: Karen May-Newman, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182. E-mail: kmaynewm@mail.sdsu.edu.

Copyright © 2019 by the American Society for Artificial Internal Organs