Introduction: Cap of an atherosclerotic plaque ruptures when mechanical stresses in the cap exceeds local strength. In this study, we investigated influence of plaque geometry on cap stresses.

Methods: Histology images of 30 cross-sections from 10 atherosclerotic human coronary vessels (perfusion fixed at 100 mmHg) were segmented. Mechanical stresses at 140 mmHg blood pressure were computed using finite element analysis after initial stresses were obtained using Backward Incremental Method [1]. Relation between cap stress and six geometric parameters (see Table) were evaluated. For each geometric parameter, two groups were created: the high group containing cross-sections with a value higher than the median value (n=15) and the low group (n=15). Mean values were compared for the two groups (Student’s t-test).

Results: Thin cap cross-sections showed higher stresses than thick cap cross-sections (Table). Plaques with thinner necrotic core (NC) had larger stresses than the plaques with thick NC. Other geometric parameters were statistically insignificant.

Discussion: Higher peak cap stresses for thinner cap cross-sections confirm previous studies [2]. However, higher peak cap stresses for plaques with thin NC contradict an earlier study [2] with idealized geometries. Sharp corners at NC edges in realistic geometries might affect stress distribution in cap. Moreover, not only thickness but shapes of plaque components might influence peak cap stresses. In the near future, the analysis will be extended by incorporating other geometric parameters describing plaque component shapes and multivariate analysis to assess cross correlations between geometric parameters.