Animal Models For The Testing Of Mechanical Devices

Maximizing surgical therapies in end-stage heart failure is a growing biomedical field. Devices (i.e., ventricular assist devices) have become increasingly important because of an increased incidence of patients presenting with end-stage heart failure. Interestingly, mechanical ventricular assist devices are filling a niche in which they are both a "bridge to transplant" as well as a "destination therapy" at centers such as the University of Minnesota. Before any such device can be implanted into a human, the procedure requires years of highlevel animal testing.

8.1. Animal Model Selection for Device Testing

Animal models are useful for both training and research of mechanical devices, such as the ventricular assist device. The justification for use of a particular animal model is primarily based on past and current successes using a particular animal. From careful selection, the right animal model is based on device size and comparative anatomy. This likely will decrease the difficulty of implanting such devices. Obviously, devices designed for human use will require a comparable size research animal for testing. For example, the sizes of in-line axial flow pump have become relatively compact and have been implanted into the dog, sheep, or calf model (54,55). Larger pumps, based on a moving diaphragm, still require a larger animal, such as the sheep or calf, as would be appropriate for human use (56).

8.2. Federal Guidelines for Device Testing

As an example, ventricular assist device technology is a rapidly advancing field, and the FDA has not published official guidance documents for such devices. However, for these devices the FDA does have specific evaluation criteria that are designed to identify possible hazards prior to clinical usage.

Fig. 13. Sedated baboon. Original art by Martin E. Finch.

Long-term reliability is a current issue of concern with such devices because some patients waiting for a transplant survive longer, and destination therapy may become a reality for numerous device recipients. Consequently, long-term biocom-patibility, thrombogenesis (long-term surface-coating anti-thrombogenic integrity), bacterial infection, battery life, hardware reliability, and software reliability have become important parameters for FDA evaluation of devices. Finally, the ease of patient use related to ventricular assist devices is also of central importance. For more information on animal models, see Chapter 5.

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Essentials of Human Physiology

Essentials of Human Physiology

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