Are biomaterials the limiting factor in the progress of arterial prostheses?

Term paper prepared for the class "BE 512 - Introduction to Biomaterials", handed in at the 9th of April 1995.
Advisor: Prof. Paul Ducheyne from the Department of Bioengineering of the University of Pennsylvania.


As the title suggests this paper tries to answer the question whether biomaterials are the limiting factor in the progress of arterial prostheses. The introduction to the paper gives a brief summary of the history of vascular grafts and introduces some of the concepts of vascular surgery. Then the normal physiological situation of arteries and their relation to the circulatory system of the human body is described in some detail. Of the three different types of arteries the focus is set on the elastic and the muscular arteries, since these are the subjects of vascular surgery. The smaller arterioles are merely mentioned for completeness. The functions of elastic and muscular arteries and the relation between the function and the microscopical structure of these arteries are pointed out. Furthermore the composition and functions of the human blood are described. Special attention is paid to the mechanisms of blood clotting and inflammation, since they are of particular importance for vascular grafts.

The next step in the paper is the description of diseases of arteries, documenting the need for arterial grafts. Basic terms like thrombosis, ischemia, and embolus are defined, leading to the description of the most important form of arterial disease there is: atherosclerosis. The high incidence of atherosclerosis and its fundamental significance for the population of middle age and later life in developed countries is stressed. The less common inflammatory arterial diseases are also mentioned. A short overview over vascular surgery and its possibilities to treat arterial diseases shows that the replacement of the diseased vessel by a graft is often the only applicable solution.

The rest of the paper deals with arterial grafts. The ideal arterial prosthesis is described, followed by the currently used grafts. There are two different types of biological grafts that are in use, the unprocessed autogenous and the processed nonautogenous grafts. The synthetic materials that are in clinical use nowadays for arterial grafts are PTFE and PET. The problems that still exist with all of these possible grafts are then pointed out and compared to the ideal graft. Some of the concepts that are being applied to overcome these problems are described, and a few examples of prospective materials for arterial grafts that are subjects of current research are given.

The conclusion of the paper is, that no material that is in current use matches the requirements for an ideal arterial graft. Furthermore it is shown that the existing problems are clearly problems of the biomaterials. This means that the answer to this paperšs question is definitely a "yes": biomaterials are the limiting factor in the progress of arterial prostheses.

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