Objective We sought to evaluate the validity of circumferential carotid artery strain and correlation with other conventional parameters, especially those reflecting mechanical forces such as luminal strain, stiffness and carotid intima-media thickness (IMT).
Methods and Results From April 2007 to July 2008, 1057 patients who had both echocardiography and carotid ultrasonography were consecutively enrolled. Circumferential strain was obtained from ratio of change in circular length during cardiac cycle. Circumferential carotid strain showed positive correlation with luminal strain (r = 0.773), Β-stiffness (r = -0.534), IMT (r = -0.429), and distensibility (r = 0.669). As number of risk factors increased, circumferential strain decreased accordingly (5.1±2.1, 4.4±1.8, 3.8±1.6, 3.3±1.3, 3.1±1.3, p<0.001). In patients with diabetes or atherosclerotic disease, circumferential strain was significantly lower (3.26±1.25% vs 4.28±1.93%, p<0.001). The addition of circumferential carotid strain significantly improved the prognostic power in predicting patients with high Framingham Risk Score on top of IMT (Χ²= 61.0 from 42.4, p<0.001), whereas stiffness did not have additive power.
Conclusion Circumferential strain of carotid artery is highly feasible and well correlated with conventional mechanical forces and IMT. Circumferential strain can be used as a screening tool for subclinical atherosclerosis and may help discriminate between subjects at increased risk for atherosclerotic disease.
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