H. Takekawa, K. Suzuki, T. Nishihira, A. Iwasaki, M. Okamura, Y. Asakawa, M. Yamamoto, R. Okabe, K. Hirata
Dokkyo Medical University – Mibu, Japan

Objective: The Doppler indices, such as systolic acceleration time (AcT) have been used as parameters for peripheral arterial stenosis. However, to our knowledge, the AcT ratio has not routinely been used to evaluate the degree of internal carotid artery (ICA) stenosis. To apply the AcT ratio in the assessment of carotid artery sonography as an additional marker for diagnosing ICA stenosis.

Material and Methods: Carotid artery sonography was performed in 140 consecutive patients with atherothrombotic brain infarction to evaluate extracranial ICA stenosis. The AcT ratio was calculated as the AcT of the internal carotid artery divided by the AcT of ipsilateral common carotid artery and compared with linear stenosis as calculated according to the European Carotid Surgery Trial criteria. Simple regression analysis was used to examine the relationship between the AcT ratio and ICA stenosis. The receiver operating characteristic (ROC) curve was used to calculate the optimal cutoff values of the AcT ratio for ICA stenosis ( > 65%).

Results: There was a significant correlation between linear stenosis and the acceleration time ratio. The ROC curve revealed an AcT ratio cutoff level of 1.5, with 90.0% sensitivity and 93.5% specificity for internal carotid artery stenosis greater than 65%.

Discussion: The peak systolic velocity (PSV) is a useful parameter for determining the severity of stenosis at the origin of the ICA. However, PSV can be unreliable in the presence of acoustic shadow with arterial wall calcification. The presence of a long, calcified lesion and a high degree of bifurcation also cause difficulty with PSV measurement at the ICA when performed with a linear-array probe alone. As in our study, the combined use of a linear-array probe and convex-array probe, which allow us to evaluate distal ICA at a lower frequency than the linear array, may be helpful.

Key words: acceleration time ratio, internal carotid artery, stenosis.

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