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Research Papers

The 12cc Penn State Pulsatile Pediatric Ventricular Assist Device: Fluid Dynamics Associated With Valve Selection

[+] Author and Article Information
Benjamin T. Cooper, Breigh N. Roszelle, Tobias C. Long, Steven Deutsch

Department of Bioengineering, The Pennsylvania State University, 205 Hallowell Building, University Park, PA 16802

Keefe B. Manning

Department of Bioengineering, The Pennsylvania State University, 205 Hallowell Building, University Park, PA 16802kbm10@psu.edu

J Biomech Eng 130(4), 041019 (Jun 24, 2008) (14 pages) doi:10.1115/1.2939342 History: Received June 05, 2007; Revised February 07, 2008; Published June 24, 2008

The mortality rate for infants awaiting a heart transplant is 40% because of the extremely limited number of donor organs. Ventricular assist devices (VADs), a common bridge-to-transplant solution in adults, are becoming a viable option for pediatric patients. A major obstacle faced by VAD designers is thromboembolism. Previous studies have shown that the interrelated flow characteristics necessary for the prevention of thrombosis in a pulsatile VAD are a strong inlet jet, a late diastolic recirculating flow, and a wall shear rate greater than 500s1. Particle image velocimetry was used to compare the flow fields in the chamber of the 12cc Penn State pediatric pulsatile VAD using two mechanical heart valves: Björk–Shiley monostrut (BSM) tilting disk valves and CarboMedics (CM) bileaflet valves. In conjunction with the flow evaluation, wall shear data were calculated and analyzed to help quantify wall washing. The major orifice inlet jet of the device containing BSM valves was more intense, which led to better recirculation and wall washing than the three jets produced by the CM valves. Regurgitation through the CM valve served as a significant hindrance to the development of the rotational flow.

Copyright © 2008 by American Society of Mechanical Engineers
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Figures

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Figure 1

The Penn State 12cc pulsatile PVAD

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Figure 2

High speed videography of the model during a typical cardiac cycle. The white arrow represents the direction the diaphragm is moving at (A) 150ms, (B) 300ms, (C) 450ms, and (D) 600ms from the start of diastole.

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Figure 3

Representative driveline and flow (inlet and outlet) wave forms for the mock circulatory flow loop

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Figure 14

Nondimensionalized wall shear maps for the BSM (left column) and CM (right column) valve configurations in the 11mm plane for (A) and (B) Surface 1, (C) and (D) Surface 2, and (E) and (F) Surface 3. Areas of interest are highlighted with ovals. Note that the wall locations are defined in a counterclockwise fashion.

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Figure 12

Surface locations (S1-S7) used in wall shear calculations for both valve configurations

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Figure 11

Mean PIV flow maps in the 11mm plane at (A) 300ms, (B) 400ms, (C) 550ms, and (D) 700ms for the CM valve configuration illustrating the time history of the rotational flow pattern

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Figure 10

Mean PIV flow maps in the 7mm plane at (A) 250ms, (B) 400ms, (C) 550ms, and (D) 700ms for the CM valve configuration illustrating the three distinct jets during diastole, outlet valve regurgitation, (indicated by ovals), and uniform systolic ejection

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Figure 9

Particle traces for the BSM valve configuration at 250ms (left column) and for the CM valve configuration at 350ms (right column) for the 7mm (top row), 8.2mm (middle row), and 11mm (bottom row) planes highlight the first time step that the rotational flow pattern is fully developed

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Figure 8

Mean PIV flow maps in the 11mm plane at (A) 250ms, (B) 400ms, (C) 550ms, and (D) 650ms for the BSM valve configuration showing the time history of the rotational flow pattern

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Figure 7

Mean PIV flow maps in the 7mm plane at (A) 250ms, (B) 400ms, (C) 550ms, and (D) 700ms for the BSM valve configuration with ovals indicating center of rotation (A) and (B) and fluid blockage in (D). Flow separation near the inner wall resulting from converging flow is indicated by a rectangle in (B).

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Figure 6

Mean PIV flow maps in the 7mm plane at (A) 150ms and (B) 200ms, and (C) in the 8.2mm plane at 200ms for the BSM valve configuration demonstrating the formation of the diastolic jet and developing recirculating flow pattern

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Figure 5

(A) An example of diaphragm reflection and valve shadow artifacts in a CCD image, (B) their effect on the amount of images that contribute velocity information within the filtering scheme, and (C) how these artifacts affect the mean velocity flow map

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Figure 4

(A) Schematic illustrating the experimental PIV setup and (B) PVAD acrylic test model highlighting the 7mm, 8.2mm, and 11mm data acquisition planes

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