Structure-dependent dynamic mechanical behavior of fibrous caps from human atherosclerotic plaques.

Abstract

Background. Although thrombosis associated with a fissured atherosclerotic plaque is believed to be the most common cause of acute coronary syndromes, the underlying factors that trigger plaque rupture are currently unknown. However, the mechanical behavior of the plaque is probably of critical importance.Methods and Results. To test the hypothesis that the mechanical properties of a plaque are dependent on its composition and, in particular, that the stiffness of fibrous caps changes within the range of frequencies carried by a physiological pressure wave, the stress-strain relation was studied in 27 fibrous caps and related to the underlying histological structure of the fibrous cap. Fibrous caps were obtained during 14 autopsies from the abdominal aorta and

Prediction of mechanical properties of human atherosclerotic tissue by high-frequency intravascular ultrasound imaging. An in vitro study.

“…However, biological materials are rarely iso-tropic, 15 and the creep data in this study demonstrate that plaque components are not perfectly elastic. The nonelastic nature of these specimens is also apparent when considering dynamic stiffness described in our previous study with the same experimental apparatus and a separate set of specimens 4 ; dynamic stiffness values at frequencies near physiological heart rates are approximately one order of magnitude greater than static stiffness values referenced to comparable initial equilibrium stress.…”

“…4 The fibrous cap was bathed in room-temperature normal saline and held between an acrylic base that was connected to an actuator mechanism and a 7-mm-diameter cylindrical stainless steel platen that was connected to the spectrometer load cell (Figure 1). An initial uniaxial compressive stress equivalent to 30 mm Hg (-4.0 kPa) was applied normal to the surface of the plaque.…”

“…2 Ultrasonic tissue-characterization methods can differentiate various pathological patterns of atherosclerosis, 3 and these patterns dramatically influence the biomechanical behavior of human plaque compo-nents. 4 Recent advances in high-frequency intravascular ultrasound technology allow reproducible images of arterial structure. 5 " 8 If the tissue appearance of atherosclerotic lesions by intravascular ultrasound can predict the mechanical behavior of plaque components, this technique may be useful for refining interventional mechanical procedures such as percutaneous angioplasty or atherectomy.…”

Elasticity Imaging of Atheroma With Transcutaneous Ultrasound

“…For the plaque in the subjects, soft inclusions of lipid surrounded by fibrous tissue were found. With extrapolation of the results of an in vitro study, 19 we postulated that a thin layer constitutes a fibrous cap surrounding the plaque. Iliac arteries were used to determine the reference parameters, which were then applied to CCAs in the in vivo experiments.…”

Characterizing Vulnerable Plaque Features With Intravascular Elastography

“…Although there is a difference between the static and dynamic mechanical properties of vascular tissue, the ratio between the different plaque components remains similar. 36,37 Nevertheless, in a pulsatile environment, the locations with increased strain may change between static or pulsatile experiments. However, the optimal threshold value (1.26% strain) for detecting a vulnerable plaque cannot be directly transferred from static in vitro experiments to pulsatile in patient recordings.…”