Mock Arterial Compliance: Influence of Hydration, Temperature, Mandril Location, Age and Lot

J.C. Conti1, E.R. Strope and K. Price

Dynatek Dalta Scientific Instruments
1 Southwest Missouri State University

Introduction

The use of latex or other synthetic arterial conduits is vital to the testing programs of intravascular devices that must be flexed for various periods of time. Not only are fairly precise morphological characteristics important but the three-dimensional pressure/volume or compliance characteristics are extremely important when using these mock vessels to evaluate intravascular stents, intra-aortic balloons, stent grafts, etc.

Purpose

It is the purpose of this work to evaluate the influence of a series of typical variables on the resultant three-dimension internal compliance of latex tubes.

Material and Methods

Latex tubing of nominal 4, 8, 11, 16, 19, 23, and 27mm internal diameter were dipped on aluminum mandrils using amber natural latex rubber. These devices were subjected to various pre-testing conditions, including: age when stored at 5° C, position on the mandril (top or bottom), number of days soaked in 37° C distilled water, temperature at testing and lot to lot variation. These devices were all tested on a dynamic internal compliance tester that has been previosly described .1

Results

Table 1 is a summary of the radial compliance obtained by mounting, testing, dismounting, then remounting the same 4.39mm i.d. tube ten times. The results are within 1.5% of the mean. This


establishes the overall reproducibility of the method. Table 2 summarizes the variation in radial compliance with top to bottom of mandril. The compliance follows the variation in wall thickness. In most


cases the results are within 0.5% in compliance of each other. In the worst case the difference is 0.83%.

An aging experiment tested a 3.68mm graft when first dipped and then again after 18 months of storage at 5°C. The % radial compliance was initially 4.20, and then 4.97 after storage.

Finally, the influence of soaking in 37°C distilled water before testing was studied. Four samples were soaked for 24 or 96 hours.

Conclusion

Aging, manufacturing variability, and degree of hydration all effect the mechanical properties of latex mock arteries.

1 Conti, J.C., et. al., “The Effective Measurement of Dynamic Internal Compliance
of Vascular Grafts,” Proceedings AAMl Annual Meeting, Los Angeles, 1990.