Ldt. Topoleski et al., COMPOSITION-DEPENDEN AND HISTORY-DEPENDENT RADIAL COMPRESSIVE BEHAVIOR OF HUMAN ATHEROSCLEROTIC PLAQUE, Journal of biomedical materials research, 35(1), 1997, pp. 117-127
Invasive procedures to revascularize occluded blood vessels rely on th
e mechanical response of the diseased tissue. Failure rates associated
with such procedures show the need for improvement. to understand the
associated mechanics, the material properties of atherosclerotic plaq
ue should be known; yet data are scant. The purpose of this study was
to investigate the different mechanical responses exhibited by plaques
with different compositions, focusing specifically on radial compress
ive behavior. A custom-built experimental system was developed that wa
s fully computer controlled with a broad range of loading capabilities
. A temperature-controlled, physiologic specimen bath allowed testing
at 37 degrees C. Monotonically loaded specimens showed that plaque beh
avior was nonlinear under finite deformations. A multiple cycle protoc
ol, executed in two phases, distinguished three types of mechanical re
sponse of different plaques. The differences in behavior were associat
ed with histologic differences in plaque composition, and mechanically
characterized by different ''repeatability'' (the stabilization of th
e cyclic response) and ''recoverability'' (the second loading phase re
tracing the first loading phase behavior). Type 1 behavior was categor
ized by repeatability and recoverability . Type 2 behavior displayed r
epeatability but only partial recovery during the second loading phase
. Recovery was absent in type 3 behavior. The histologic observations
demonstrated that calcified tissue was present only in specimens displ
aying type 1 behavior. Fibrous tissue and part of a modified media (du
e to disease) were present in specimens displaying type 2 behavior. An
atheroma, along with a relatively thin modified media, was present in
specimens displaying type 3 behavior. The differences in the maximum
stretches attained at the end of phase I loading, the stretch offset f
rom the first to the 15th cycle of phase I loading, and the hysteresis
in the first and 15th cycles of phase I loading distinguished the spe
cimen behaviors with statistical significance. These compression data
showed that plaques exhibit composition- and history-dependent nonline
ar and inelastic responses under finite deformations. (C) 1997 John Wi
ley & Sons, Inc.