Flow Analysis of Ventricular Assist Device Inflow and Outflow Cannula Positioning Using a Naturally Shaped Ventricle and Aortic Branch

Abstract

Tip geometry and placement of rotary blood pump inflow and outflow cannulae influence the dynamics of flow within the ventricle and aortic branch. Cannulation, therefore, directly influences the potential for thrombus formation and end-organ perfusion during ventricular assist device (VAD) support or cardiopulmonary bypass (CPB). The purpose of this study was to investigate the effect of various inflow/outflow cannula tip geometries and positions on ventricular and greater vessel flow patterns to evaluate ventricular washout and impact on cerebral perfusion. Transparent models of a dilated cardiomyopathic ventricle and an aortic branch were reconstructed from magnetic resonance imaging data to allow flow measurements using particle image velocimetry (PIV). The contractile function of the failing ventricle was reproduced pneumatically, and supported with a rotary pump. Flow patterns were visualized around VAD inflow cannulae, with various tip geometries placed in three positions in the ventricle. The outflow cannula was placed in the subclavian artery and at several positions in the aorta. Flow patterns were measured using PIV and used to validate an aortic flow computational fluid dynamic study. The PIV technique indicated that locating the inflow tip in the left ventricular outflow tract improved complete ventricular washout while the tip geometry had a smaller influence. However, side holes in the inflow cannula improved washout in all cases. The PIV results confirmed that the positioning and orientation of the outflow cannula in the aortic branch had a high impact on the flow pattern in the vessels, with a negative blood flow in the right carotid artery observed in some cases. Cannula placement within the ventricle had a high influence on chamber washout. The positioning of the outflow cannula directly influences the flow through the greater vessels, and may be responsible for the occasional reduction in cerebral perfusion seen in clinical CPB.

Emerging Trends in CV Flow Visualization

“…These models are mainly reconstructed from either anatomical castings or images acquired from CMR, computed tomography scanning, or echocardiography (29). PIV is commonly used to assess cardiovascular fluid dynamics in vitro, particularly for evaluating new imaging modalities (29,34 -36), heart valves (32,37), and ventricular assist devices (38,39). One important consideration when using PIV to assess a cardiovascular event is the temporal resolution.…”

In vitro flow investigations in the aortic arch during cardiopulmonary bypass with stereo-PIV

“…Stereo-PIV accommodates the three-dimensional character of the flow and offers a high spatial resolution. Herewith, it overcomes limitations of standard PIV, Doppler-US, PC-MRI, or other techniques, which have been applied in recent CPB cannula flow studies (Verdonck et al, 1998, Scharfschwerdt et al, 2004White et al, 2009, Laumen et al 2010. However, data acquisition, data analyses and post processing of the multiple measurement planes can be very time consuming.…”

“…Another applied technique to investigate cannula flow is the Particle Image Velocimetry (PIV) (Laumen et al, 2010;Fukuda et al 2009b). This optical flow measurement technique basically consists of a laser, illuminating a particle seeded flow in a plane and a camera, which captures the particle movement.…”

Application of a meta-analysis of aortic geometry to the generation of a compliant phantom for use in particle image velocimetry experimentation

“…However, PIV is the most common method (Geoghegan et al 2012;Kaufmann et al 2014;Laumen et al 2010;. studied an elastic curved vessel without any branching arteries and a homogenous wall thickness of 1 mm.…”

“…Turbulent flow can also be found when blood velocity increases due to diseases like vascular stenosis or anemia, which causes a reduction in blood viscosity (Schmidt et al 2011). The complex flow dynamics in this process have been the subject of many papers over the last decades (Arzani et al 2012;Benim et al 2011;Gülan et al 2012;Kim et al 2004;Laumen et al 2010;Shahcheraghi et al 2002;Vasava et al 2010). However, these studies were typically based on rigid vessels.…”