Evaluation of the Dynamic Mechanical Properties and Fatigue Resistance of Vascular Grafts Dynamic
The first step in any In Vitro testing program must include a careful analysis of the mechanical and chemical environments that the device being tested will experience once implanted. Once this is done, the next step in the process is to determine the three dimensional properties of the experimental vascular grafts at biologically relevant pressures. These properties should be determined at In Vivo frequencies (ca. 70bpm) and then again at higher frequencies. The evaluation of mechanical property vs. frequency is critically important to allow an investigator to confidently increase the speed of testing of that vascular graft during the fatigue evaluation portion of their protocol. As long as the device is able to respond to the rate of change of loading that a testing instrument is delivering, then reliable and confident data concerning the fatigue resistance of that device can be obtained. The pre-accelerate fatigue testing mechanical evaluation also gives an investigator a starting point of properties that can be re-evaluated at the end of the fatigue testing to determine the change in the graft throughout the fatigue testing program.
Many other considerations need to be addressed when designing a protocol for fatigue resistance evaluation including temperature, number of cycles to test, length of sample, speed of test and number of samples.
Perhaps most important of all is the need to design a test protocol and instrument that can be monitored to give positive proof that the device that is being tested is in fact experiencing the load per cycle that the investigator assumes.
With proper investigation of the In Vivo conditions to be replicated, device frequency response, protocol and instrument design and follow up evaluation, it is possible to gain reliable information on the fatigue resistance of synthetic vascular grafts.