09.03 Multi-Axial Mechanical Characteristics of Carotid Plaque in Hypertensives Assessed by Multi-Array Echotracking System

Abstract

The vulnerability to rupture of carotid plaque depends on the various types of mechanical stress including higher circumferential wall stress (CWS) in hypertensives and histological characteristics of plaque.

Objective

determine the multiaxial mechanical deformations of the common carotid artery (CCA) with an echotracking system allowing measurement of thickness, diameter, strain, distensibility, elastic modulus (Einc) and CWS on 4 cm long CCA segments including plaque. This allowed us to determine a longitudinal bending stress (BS) equal to the ratio of strain at the level of plaque to strain of adjacent CCA.

Patients

we included 25 patients with a recent cerebrovascular ischemic event and a plaque on CCA homolateral to stroke territory. We divided patients into two groups according to BS behaviour: pattern A (outward BS, larger strain at plaque site than on CCA), pattern B (inward BS).

Results

16 patients belonged to pattern A and 8 patients to pattern B. Prevalence of dysplipidemia and diabetic were higher in pattern B (100% vs 56%, p = 0.03 and 63% vs 12%, p = 0.04). In pattern B distensibility was significantly lower at the level of plaque than in CCA it was the converse in A patients (13.1±6.5 vs 18.2±3.9, p <0.003 and 22.3±11.2 vs 16.6±12.4 kPa^–1 10^–3, p <0.001). Pattern A patients had lower Einc at the level of the plaque than of CCA (374±173 vs 802±669 kPa, p < 0.01) the opposite was observed in B patients (739±497 vs 543±146 kPa, p < 0.01). CWS in CCA was higher in B than in A patients (83±16 vs 65±15 kPa, p < 0.01), plaque CWS was similar in the two groups (60±7 vs 53±13 kPa, NS).

Conclusion

type 2 diabetes and dyslipidemia were associated with a stiffer plaque than adjacent CCA. These results suggest that the higher risk of plaque complication, reported in patients with diabetes and hypercholesterolemia, may be due to a specific pattern of strain gradient between plaque and adjacent CCA.