Biomedical Engineering Reference
In-Depth Information
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5.13 Contegra
Conduit is a pulmonary valved conduit, available under a
Humanitarian Device Exemption fromMedtronic, Inc. The conduit is fabricated
from an isolated bovine jugular vein and preserved in glutaraldehyde. The
conduit is used in certain pediatric applications. (Contegra
Õ
is a registered
trademark of Medtronic, Inc. Reprinted with permission from Medtronic, Inc.
All Rights Reserved.)
isolations, because they are of similar size to the human aortic valve, and bovine
pericardium, because it has tissue properties similar to the aortic valve tissue.
Nonetheless, consideration of other materials and other animal sources has
periodically surfaced. Isolated valves from the bovine jugular vein are used to
treat pediatric congenital defects and are available as a humanitarian-use device
from Medtronic. These devices are used to reconstruct the right ventricular
outflow tract (see Fig. 5.13).
Other tissue sources that have been proposed for use in bioprostheses
include pericardium from cows (Lee et al., 1989a), calves (Gibbons, 2009),
horses (Eckstein et al., 2004), pigs (Naimark et al., 1992), sheep (Naimark et
al., 1992), dogs (Lee and Boughner, 1981), kangaroos (Neethling et al., 2002),
and ostriches (Maestro et al., 2006). Comparative studies documenting the
different properties of these tissues are available. Figure 5.14 shows the
comparative data on tissue thickness, often a design specification for valve
designs. Tissue thickness is a key design parameter for percutaneous valves, as
tissue thickness is essential in determining the smallest packing volume of the
valve (see Fig. 5.15). Except for percutaneous valves, the importance of tissue
thickness is unclear, and in the authors' opinion, narrow thickness
specifications, in the absence of discrete design requirements, are inappropriate
and a burden to manufacturing. Published studies demonstrate that the
mechanical properties of tissues cannot be predicted by tissue thickness, and
that uniform tissue thickness does not ensure uniform mechanical properties
(Mikus et al., 1986).
