Computational stress-deformation analysis of arterial walls including high-pressure response.
BACKGROUND
Changes in the mechanical behavior of arteries after balloon angioplasty cause cell reactions that may be responsible for restenosis. Hence, the study of the stress-deformation changes in arterial walls following supraphysiological tissue loading is an essential task.


METHODS
A normal LAD coronary artery was modeled and computationally analyzed as a two-layer, thick-walled, anisotropic and inelastic circular tube including residual strains. Each layer was treated as a fibre-matrix composite. The tube was subjected to an axial stretch of 1.1 and a transmural pressure of 750 mm Hg. Since overstretch of remnant non-diseased tissue in lesions is a primary mechanism of lumen enlargement this model approach represents a reasonable first step.


RESULTS
At physiological loading, the residual stresses led to a significant reduction of the high circumferential stress values at the inner wall, and the stress gradients. At low pressure level the media was the mechanically relevant layer, while at supraphysiological loading, the adventitia was the predominant load-carrying constituent providing a stiff support for 'redistribution' of soft plaque components by means of radial compression. After unloading to physiological loading conditions the stress state in the arterial wall differed significantly from that before inflation; the stress gradient in the media even changed its sign. Complete unloading indicated lumen enlargement, material softening and energy dissipation, which is in agreement with experimental studies.


CONCLUSIONS
This method may be useful to improve interventional protocols for reducing the dilatational trauma, and thereby the adverse biological reaction in arterial walls following balloon angioplasty.
Holzapfel
Gerhard A
GA
School of Engineering Sciences, Department of Solid Mechanics, Royal Institute of Technology, 100 44 Stockholm Osquars backe 1, Sweden. gh@biomech.tu-graz.ac.at
Gasser
Thomas C
TC
D015906:Angioplasty, Balloon, Coronary; D001794:Blood Pressure; D003331:Coronary Vessels / Q000503:physiopathology*; D004548:Elasticity; D020342:Finite Element Analysis; D006801:Humans; D008955:Models, Cardiovascular; D013314:Stress, Mechanical