AAWSAP DIRD, Biomaterials, January 2010

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A problem most materials cause when in blood contact is that they trigger the rapid
formation of thrombus (an aggregation of blood cells) . The formation of a thrombus is
dangerous, as the thrombus could either adhere to the surface of the biomaterial or be
detached. If a thrombus is detached, it can travel in the blood stream and occlude
smaller vessels in the brain (called a stroke) or lungs (called an embolism). Some
small-diameter vascular grafts ( < 5-millimeter internal diameter) and prostheses for
reconstruction of diseased veins are "safe" only when anticoagulant drugs are used.
In addition to thrombus formation, biomaterials can become colonized with infection­
causing bacteria. Some microorganisms found in hospitals are extremely resistant to
antibiotic therapy, and infections cannot be fully resolved until the biomaterial is
removed. This is particularly a problem with hip and knee implants, where there is poor
blood flow near the joint and the body's immune system has limited access. Methicillin­
resistant staphylococcus aureus infections are dangerous in these situations.
The high tolerance of the body for woven and formed Teflon allows it to be used as a
flexible patch material for other blood-contacting surfaces, in addition to blood vessels.
For example, Gore, Inc., makes a Teflon-based material that is used to patch holes in
the heart of infants born with atrial septal defects. Figure 23 is an artist's conception of
how the patch is inserted into the hole in the atrial wall using a catheter.
Figure 23. Illustration of Treatment of an Atrial Septal Defect Using a Teflon-Based Product
Manufactured by Gore, Inc.
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