Comparison of carotid arterial resistive indices with intima-media thickness as sonographic markers of atherosclerosis

Background and Purpose-The intima-media thickness (IMT) Of the carotid arte ry is a (morphological) sonographic parameter that depends on the degree of atherosclerosis. In the renal arteries, the value of the (hemodynamic) res istive index (RI) is correlated with the severity of atherosclerosis. In co ntrast to the well-known IMT no study has yet applied the carotid RI to est imate generalized atherosclerosis. Methods The SMART atherosclerosis risk score was determined in 157 patients (94 men and 63 women; mean age 63 [range 19 to 80] years) with at least 1 vascular risk factor or a known vascular disease. Duplex sonography of the common carotid (CCA) and internal carotid artery (ICA) was then performed, with determination of IMT and RT. Results-The mean risk score of all patients was 8.8 +/- 3.5 (range 1 to 17) , the mean IMT value in the CCA was 0.727 +/- 0.161 mm, the mean RI in CCA was 0.79 +/- 0.066, and the mean RI in ICA was 0.66 +/- 0.082. Highly signi ficant correlations were found between the score and IMT CCA and the score and RI ICA (r=0.62, P<0.0001 and r=0.55, P<0.0001). The score-RI CCA correl ation was much less marked (r=0.354, P<0.0001). The intraobserver and inter observer agreement was less for IMT than for RI CCA and ICA. The areas unde r the curve of the receiver operating curves to distinguish between low-ris k and high-risk patients resulted in values of 0.86, 0.81, and 0.69 for IMT , RI ICA, and RT CCA, respectively. Conclusions-Although RI reflects the atherosclerotic process in an indirect manner, the correlation between the RI ICA and the SMART atherosclerosis s core as well as the ability to distinguish between low-risk and high-risk p atients are comparable to those of the well-known BI.