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Session: Poster session I
Session starts: Thursday 24 January, 15:00

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Ali Akyildiz ()
Lambert Speelman ()
Harm Nieuwstadt ()
Ton van der Steen ()
Jolanda Wentzel ()
Frank Gijsen ()

Abstract:
Background: More than 70% of fatal heart attacks are caused by rupture of vulnerable plaque caps in atherosclerotic coronary arteries. From a mechanical point of view, a plaque cap ruptures when stress exceeds strength at a certain location in the cap. Plaque morphology is an important determinant of cap stresses [1]. Previously developed models based on idealized geometries have provided very valuable insight to geometrical risk factors in atherosclerotic plaques; however, they were not able to incorporate the complex geometry of plaques completely. The aim of this study is to investigate the effects of plaque morphology on cap stresses using realistic geometries and to search for a statistical model based on geometric plaque features to predict cap stresses in human coronary plaques. Methods: We included 77 atherosclerotic lesions from 13 human coronary arteries. Histology was applied to identify the relevant plaque components: adventicia, media, and the intima containing the lesions with the necrotic core and fibrous cap. Peak cap stresses were computed by using finite element method, including initial stress computations [2] and anisotropic material models. Measures of geometric plaque features for all lesions were determined and their relations to peak cap stress were examined. Results and discussion: The study showed that peak cap stress is highly heterogeneous and is mainly affected by minimum cap thickness and maximum lumen radius. Additionally, large lumen curvature increased peak cap stresses locally. A statistical model (R=0.79), employing minimum cap thickness and maximum lumen radius, was employed to estimate peak cap stress in coronary plaques based on geometrical plaque features. Furthermore, the ratio of maximum lumen radius to minimum cap thickness enabled us to stratify coronary plaques based on peak cap stress: a ratio of 2.5 correctly identified all plaques with peak cap stress below 140 kPa, which is generally assumed to be the lower threshold value for cap strength. This ratio can be determined by intravascular imaging techniques and can possibly improve clinical rupture risk assessment for human coronary plaques. REFERENCES [1] Akyildiz et al.,Biomedical Engineering Online, doi: 10.1186/1475-925X-10-25, (2011). [2] Speelman et al., Journal of Biomechannics, vol. 44(13), pp. 2376-582, (2011).