New Duplex Criteria for Threshold Stenoses Used in the Asymptomatic Carotid Atherosclerosis Study

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The current Doppler frequency spectral criteria used to classify internal carotid artery (ICA) stenosis into 1%-15%, 16%-49%, 50%-79%, 80%-99% stenoses may not be applied to stenoses of >60%, which is used by the Asymptomatic Carotid Atherosclerosis Study (ACAS) to justify carotid endarterectomy. Therefore, this study was done to determine the best duplex frequency criteria to identify? 60% stenosis. Three hundred fifty-six carotid arteries were studied in patients who had both carotid color duplex and arteriography. Correlation of duplex and arteriography was done in blind fashion. Four different duplex criteria were analyzed: (1) the peak systolic frequency (PSF) of the ICA, (2) end-diastolic frequency (EDF) of the ICA, (3) PSF times EDF of the ICA, and (4) the ratio of the PSF of the ICA to the PSF of the common carotid artery. Four optimum criteria were noted: (1) PSF of the ICA of >5 kHz with 98% sensitivity, 75% specificity, 83% positive predictive value (PPV), 96% negative predictive value (NPV), and 87% overall accuracy; (2) EDF of ICA of?2.5 kHz with 82% sensitivity, 96% specificity, 96% PPV, 81% NPV, and 89% overall accuracy; (3) PSF x EDF of the ICA of 15 kHz with 84% sensitivity, 96% specificity, 97% PPV, 83% NPV, and 89% overall accuracy; (4) the ratio of the PSF of the ICA/PSF of the common carotid artery of?2.7 with 85% sensitivity, 86% specificity, 89% PPV, 82% NPV, and 86% overall accuracy. There was no statistically significant difference among these four parameters. A PSF of the ICA of?6.5 kHz had a PPV of 95% and an overall accuracy of 87%, which can be used for clinicians who perform carotid endarterectomy without a preoperative arteriogram. A PSF of the ICA of?5.0 kHz, an EDF of the ICA of >2.5 kHz, and a ratio of the PSF of the ICA/PSF of the common carotid artery of?2.7 have the best overall accuracy in identifying?60% carotid stenosis. A PSF of the ICA of?6.5 kHz had a PPV of 95%, which can be used for clinicians who perform a carotid endarterectomy without preoperative arteriography.