BACKGROUND

The precise mechanism of carotid calcification formation and its clinical significance including the difference in outcomes compared with coronary artery have not been clearly elucidated yet. We applied the calcium score for analyzing carotid plaque calcification in focus on its relationship with symptoms and discuss the difference in transitional patterns and the clinical outcome in comparison with calcified coronary plaques.

METHODS

Multidetector row computed tomography angiography was performed preoperatively to determine the Agatston calcium score, volume score, and Hounsfield values for a total of 330 carotid arteries from 194 patients. Analysis focused on the relation of "the symptomatic rate" to calcium score, volume score, and Hounsfield value as well as the characteristics of calcified plaques and coexisting diseases. The symptomatic rate of carotid artery plaques in each range of the index was calculated as the percentage of the number of carotid arteries with plaques, which elicited symptoms of the contralateral limbs or the ipsilateral retina to the whole number of carotid arteries with plaques within the range.

RESULTS

Calcified carotids with low symptomatic rate (<40%) tended to have calcification with significantly high calcium scores, high volume scores and mean/maximum Hounsfield values, high circularities, outer positions, positive remodeling, and carotid bulb/common carotid locations by univariate analysis, whereas high maximum Hounsfield value, high circularity, and outer position of calcification were significant independent predictors of low-symptomatic calcified carotid plaques by multivariate logistic regression analysis. When analyzed by calcium score, the rates for symptomatic carotids showed double peaks at calcium scores around 200-400 and 600-800 with a dip at 400-600. Significant independent predictors of low symptomatic carotid artery were high maximum Hounsfield value (odds ratio [OR], 5.70; P = .005), calcification encircling the carotid perimeter (OR, 7.18; P = .005), and the calcium location in the common carotid artery (OR, 6.62; P = .006) in comparing groups with low (0-400) and medium (400-600) calcium scores, whereas a high volume score (OR, .01; P = .003) alone was a significant independent determinant in the comparison between groups with high (600-1000) and medium calcium scores.

CONCLUSIONS

Symptomatic rates of carotid plaque calcification were demonstrated to show double peaks with increasing calcium score and represent different features. Assessment of the 2 calcium-score parts might be helpful for appropriate comprehension of symptomatology and the complex process of carotid plaque calcification. We report a hypothesis for the mechanisms of the 2 different sections.