In the United States, 40% of all deaths are caused by cardiovascular disease. More than half of these incidents are a direct result of coronary artery disease.  In an effort to decrease the mortality from coronary heart disease, more than 500,000 coronary artery bypass procedures are performed annually.  The coronary artery lumen diameter (ID) is about 4 mm at most, requiring a similarly small diameter conduit to bypass the blocked artery. The most successful vascular conduit is the patient’s own blood vessel, most commonly the greater saphenous vein in the leg or the internal mammary artery. However, autologous vessels are often unavailable to patients in need of a vascular graft replacement, due to prior harvesting or disease-associated vascular damage.
In search of an alternate vascular replacement, at the beginning of the 20th century allografts were developed as the first valid vascular replacement. However allografts’ limited long-term success due to aneurysm, calcification and thrombosis, in addition to low availability and infectious disease concerns, have hindered their clinical acceptance. [2, 3] The allografts’ shortcomings in small diameter vascular applications led to the development of synthetic substitutes in the 1950’s. Despite the polymers’ thrombogenic surface and lack of compliance, they demonstrated acceptable long-term performance in large diameter vessels (ID > 6 mm inner diameter). However, polymeric grafts are inadequate when used in medium or small diameter applications.
Biology of small diameter vascular grafts - regeneration and failures Although large diameter vessel substitutes are rather successful, small vessel replacement poses a different set of problems that is not encountered in large-caliber arterial substitutes. When blood from native vessels comes into contact with an implanted graft, a number of defense mechanisms are initiated. The most prominent defense mechanism is the coagulation...
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