Heat-induced changes in the mechanical behavior of passive coronary arteries.

We performed in vitro pressure-diameter and axial force-length experiments on nondiseased, passive bovine coronary arteries subjected to bath temperatures from 21 to 80 degrees C for 90 s to 4 hr. Over the strain ranges studied, we found that: (a) vessel behavior remained the same over 20 min of testing at 21 to 55 degrees C, (b) vessels stiffened multiaxially after 5 min of exposure to 60 degrees C and continued to stiffen over 20 min of testing, (c) dramatic multiaxial vessel stiffening and shrinkage occurred after 90 s of exposure to 70 and 80 degrees C, and (d) heat-induced changes at 70 degrees C depended on the intraluminal pressure during heating. Thus, passive bovine coronary arteries exhibit a complex thermomechanical behavior that depends on the temperature, duration of thermal exposure, and the mechanical loads applied during heating.