Carotid Plaque Composition and Mechanism of Behaviour

Introduction: This study determines whether biological plaque composition has any correlation with plaque mechanical behaviour, with particular focus on risk of rupture when undergoing stresses comparable with balloon angioplasty. Methods: Carotid plaques were collected from consecutive patients undergoing endarterectomy to treat carotid artery stenosis. Fourier Transform Infra-Red (FTIR) was carried out on eight locations throughout each of the plaques. Uniaxial mechanical testing was carried out on 23 specimens as a whole to ascertain the global mechanical properties. This study establishes the stress due to a circumferential stretch that the plaque can withstand before rupture. Results: FTIR analysis of each plaque specimen indicated that eight (32 %) of the plaques had a higher calcification as the Calcification to Lipid ratio (Ca:Li) ratio was greater than one. These plaques were noted to have a significantly increased initial rupture stress value (p = 0.003). In plaques with aCal:Li ratio less than one there was rupture at a lower stress and higher stretch value. Conclusions: Carotid plaques with a higher calcium composition are more stable and less likely to rupture in physiological conditions. However, in patients undergoing angioplasty, FTIR can identify calcified plaques that may be more likely to rupture from the circumferential force during angioplasty. The results presented in this study add to debate around the use of minimally invasive techniques to treat carotid artery disease and, in particular the rupture potential due to plaque composition.