Percutaneous Double Lumen Cannula for Right Ventricle Assist Device System: A Computational Fluid Dynamics Study

Abstract

Objectives: Our goal is to develop a double lumen cannula (DLC) for a percutaneous right ventricular assist device (pRVAD) in order to eliminate two open chest surgeries for RVAD installation and removal. The objective of this study was to evaluate the performance, flow pattern, blood hemolysis, and thrombosis potential of the pRVAD DLC.

Methods: Computational fluid dynamics (CFD), using the finite volume method, was performed on the pRVAD DLC. For Reynolds numbers <4000, the laminar model was used to describe the blood flow behavior, while shear-stress transport k-ω model was used for Reynolds numbers >4000. Bench testing with a 27 Fr prototype was performed to validate the CFD calculations.

Results: There was <1.3% difference between the CFD and experimental pressure drop results. The Lagrangian approach revealed a low index of hemolysis (0.012% in drainage lumen and 0.0073% in infusion lumen) at 5 l/min flow rate. Blood stagnancy and recirculation regions were found in the CFD analysis, indicating a potential risk for thrombosis.

Conclusions: The pRVAD DLC can handle up to 5 l/min flow with limited potential hemolysis. Further modification of the pRVAD DLC is needed to address blood stagnancy and recirculation.

Keywords: computational fluid dynamics; double lumen cannula; heart failure; percutaneous; ventricular assist device.

Figure 1

A. Implantation of pRVAD DLC. The drainage lumen is shown in blue and the infusion lumen/extension infusion cannula (EIC) is shown in red. The pRVAD DLC is positioned through the superior vena cava. The drainage lumen withdraws blood from the right atrium (RA), and the EIC perfuses the pulmonary artery (PA). B. The first pRVAD DLC prototype. The pRVAD DLC without rigid introducer allows EIC curvature. C. A rigid introducer straightens the EIC to facilitate insertion. D. The Computer Aided Design Model of pRVAD DLC. Blue arrows show blood flow through the drainage lumen and red arrows indicate blood flow through the infusion lumen (A: inlet infusion lumen; B: outlet drainage lumen; C: outlet infusion lumen; D: inlet drainage lumen; E: infusion main body; F: drainage main body; I and S: outer EIC sections where recirculation was found; L; later drainage inlets).

Figure 2

CFD and Experimental Data Flow-Pressure Comparison. The numerical results were considered validated according to the close fit with experimental pressure data.

Figure 3

Shear Stress Distribution. A. Infusion Lumen. The dashed line shows maximum shear stress region magnified on bottom panel. The maximum shear stress reached 356.9 Pa at the beginning of the EIC of the main section (membrane sleeve lumen). B. Drainage Lumen. The bottom panel shows the maximum shear stress region. The maximum shear stress was 409.1 Pa, located in downstream edge of three side drainage holes, contributing to 37% of the total blood drainage. The numbers reported in parenthesis in the colored scale are used to mark the corresponding value of the shear stress in the different regions of the DLC in Figure 3A and Figure 3B.C. IH% variations along the flow rate. The red line refers to the infusion lumen, and the blue line refers to the drainage lumen. Increasing flow rate resulted in a rise in the index of hemolysis percent (IH%).

Figure 4

A.Highest Velocity Variation. The red line shows the velocity variation for the infusion lumen and the blue line for the drainage lumen. B. Recirculation Volume. Recirculation was defined as a negative x axis velocity.

Figure 5

Velocity Flow Field and Path Lines. A. Infusion Lumen/EIC. At highest flow (5 l/min), the highest velocity was 8.8 m/s, located on main section. The dashed line shows recirculation region magnified on bottom panel. Recirculation was found in outer edge at beginning of EIC and in inner edge at EIC curve due to increased cross-sectional area. B. Drainage Lumen. At 5 l/min flow, the maximum velocity was 6.3 m/s, found on main section. The bottom panel shows recirculation region near outer edge of S-shape outlet drainage.

Figure 6

A. Lowest Velocity Variation. B. Blood Stagnation Volume. C. Wall Shear Rate Volume. Red line shows the variation for the infusion, and the blue line for the drainage lumen. The green line marked the stagnant velocity threshold. Blood stagnation was defined as a velocity < 1mm/s. The shear rate was considered low at values < 250/s.

Figure 7

Velocity Flow Field and Stagnant Flow Volume. A. Infusion Lumen/EIC. At lowest flow (1 l/min), the lowest velocity was 0.16 mm/s. In the magnified bottom panel, the stagnant area was found in the outer edge at beginning of EIC and in the inner edge at EIC curve due to low velocity (red) and low shear stress (green). B. Drainage Lumen. At 1 l/min flow, the minimum velocity was 0.18 mm/s. In the magnified bottom panel, the stagnant area was due to low velocity (red) and low shear stress (green) on cannula outlet.