Redefined Duplex Ultrasonographic Criteria for Diagnosis of Carotid Artery Stenosis

doi:10.4065/75.11.1133

Mayo Clinic Proceedings

Volume 75, Issue 11, November 2000, Pages 1133-1140

https://doi.org/10.4065/75.11.1133 Get rights and content

OBJECTIVE

To evaluate duplex ultrasongraphic criteria for the determination of 50 % or more and 70% or more stenosis of the diameter of the internal carotid artery based on conventional angiography in order to align ultrasongraphic diagnostic categories with current clinical management schemes.

PATIENTS AND METHODS

Between January 1, 1995, and June 30,1999, 915 patients underwent both carotid duplex ultrasonography and cerebral angiography within 30 days at Mayo Clinic, Rochester, Minn. Of these patients, 294 were excluded from this study because of occlusion of one or both of the internal carotid arteries or atypical Dow characteristics. In the remaining 621 patients (61 % male, 39% female; mean age, 67.7 years [range, 14-88 years]), 1218 vessels were available for correlation. Several Doppler ultrasongraphic velocity variables were compared with the angiographic findings by use of receiver operating characteristic curve analysis. The primary end point was verification of optimal ultrasongraphic criteria to diagnose 70% or more internal carotid artery stenosis. The secondary end point was establishment of threshold values to detect stenosis of 500/0 or more.

RESULTS

At angiography, 382 patients had internal carotid arteries with 70% or more stenosis. Peak systolic and end diastolic velocities of the internal carotid artery and internal carotid artery:common carotid artery peak systolic velocity ratios were measured. For an internal carotid artery stenosis of 70% or more, a peak systolic velocity of 230 cm/s or more resulted in a sensitivity of 86.4%, a specificity of 90.1%, a positive predictive value of 82.7%, a negative predictive value of 92.3%, and an accuracy of 88.8% An end diastolic velocity of 70 cm/s or more and an internal carotid artery:common carotid artery ratio of 3.2 or more yielded similar values. For an internal carotid artery stenosis of 50% or more, a peak systolic velocity of 130 cm/s or more resulted in a sensitivity of 92.1%, a specificity of 89.50/0, a positive predictive value of 90.3%, a negative predictive value of 91.3%, and an overall accuracy of 90.8%. An internal carotid artery:common carotid artery ratio of 1.6 or more yielded similar values.

CONCLUSION

In our ultrasonography laboratory, a carotid artery stenosis of 70% or more (for which carotid endarterectomy is typically recommended in symptomatic patients) is diagnosed reliably with the following duplex ultrasongraphic criteria: a peak systolic velocity of 230 cms or more, an end diastolic velocity of 70 cm/s or more, or an internal carotid artery:common carotid artery ratio of 3.2 or more.

Section snippets

Study Population

Between January 1, 1995, and June 30, 1999, 23,965 carotid ultrasongraphic examinations and 3465 carotid angiographic studies were performed at Mayo Clinic, Rochester, Minn. Among the patients who underwent these tests, 915 had ultrasonography and angiography performed within 30 days. Of these patients, 294 were excluded from the study because of occlusion of 1 ICA or both, atypical flow patterns within the vessels (such as low velocities in a preocclusive state), extensive calcified plaque

RESULTS

At angiography, 382 patients had an ICA stenosis of 70% or more. For an ICA stenosis of 70% or more, a PSV of 230 cm/s or more resulted in a sensitivity of 86.40/0, a specificity of 90.1%, a positive predictive value of 82.70/0, a negative predictive value of 92.3%, and an accuracy of 88.80/0. An EDV of 70 cm/s or more and an ICA:CCA PSV ratio of 3.2 or more yielded similar values. For an ICA stenosis of 50% or more, a PSV of 130 cm/s or more resulted in a sensitivity of 92.1%, a specificity.

DISCUSSION

Symptomatic patients with 70% or more stenosis of the carotid artery have a lower risk of subsequent cerebral infarction if treated with endarterectomy, as demonstrated by the NASCET and the VA trial.^1,² Several different duplex ultrasongraphic criteria based on PSV, EDV, or ratios have been used to quantify this level of ICA stenosis, but the threshold criteria have differed18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 (Table 1). The PSV in the ICA seems to be the best single variable for

CONCLUSION

Duplex ultrasongraphy is an accurate, noninvasive diagnostic method for evaluating carotid artery stenosis. At our institution, the criterion currently used to detect 70% or more stenosis of the carotid artery (for which carotid endarterectomy is typically recommended in symptomatic patients) is a PSV of 230 cm/s or more, an EDV of 70 cm/s or more, or an ICA:CCA PSV ratio of 3.2 or more. For a 50% stenosis threshold, we use a PSV of 130 cm/s or an ICA:CCA ratio of 1.6 (Table 4). Preoperatively,

ACKNOWLEDGMENTS

We gratefully acknowledge Cynthia P. Rausch for assistance with manuscript preparation.

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and Purpose: This study proposed a machine learning method for identifying ≥50% stenosis of the extracranial and intracranial arteries.
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Whereas duplex ultrasound parameters for predicting internal carotid artery (ICA) stenosis are well defined, the use of common carotid artery (CCA) Doppler characteristics to predict ICA stenosis when the ICA cannot be insonated directly or accurately because of anatomy, calcification, or tortuosity has not been studied. The objective of this study was to identify CCA Doppler parameters that may predict ICA stenosis.
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CCA EDV and AT are independent predictors of ICA stenosis and may be used in the setting of patients whose ICA cannot be directly insonated or when standard duplex ultrasound parameters of ICA PSV, EDV, or ICA/CCA ratio conflict.
Predictive multivariate regression to increase the specificity of carotid duplex ultrasound for high-grade stenosis in asymptomatic patients
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This resulted in a potential prevention of 15 CTA (16%) with the application of our regression algorithm. Many authors have previously identified and validated CDUS velocity criteria for diagnosing CAS of ≥70%.12–21 Statistical performance of these criteria varies widely, as demonstrated in Table II.
Carotid duplex ultrasound (CDUS) is commonly used to screen for carotid artery stenosis. Specificities of CDUS criteria however are lower than sensitivities, potentially resulting in false-positive examinations with subsequent unnecessary imaging or surgery. Our objective was to establish a multivariate logistic regression to increase the specificity of CDUS for high-grade (≥70%) stenosis.
A retrospective review collected CDUS velocities and radiographic measurements from patients who underwent both CDUS and computed tomography angiography (CTA). After stratification with standard CDUS criteria, a logistic regression was created using peak systolic velocity (PSV), end diastolic velocity (EDV), and PSV ratio (PSV of internal carotid artery [ICA]/PSV of common carotid artery [CCA]) as predictor variables. A receiver operating characteristic curve was generated to test the model's predictive ability. A cutoff probability for unequivocal high-grade stenosis was chosen based on optimal specificity. The regression model was applied to patients with equivocal high-grade stenosis. Probabilities for detection of high-grade stenosis were calculated. Descriptive statistics were generated to quantify the accuracy of the model.
A total of 244 vessels were included. Standardized velocity criteria for ≥70% stenosis yielded a sensitivity of 90.6% (95% confidence interval [CI], 82.3–95.6%), specificity of 63.5% (95% CI, 55.4–70.5%), positive predictive value (PPV) of 57.0% (95% CI, 48.8–65.5%), and negative predictive value (NPV) of 92.7% (95% CI, 85.8–96.5%). Regression analysis produced a model for predicting the probability of high-grade stenosis defined as probability = logit⁻¹ (−4.97 + [0.00938 × PSV] + [0.0135 × EDV] + [0.103 × PSV ICA/CCA ratio]). A cutoff probability of 0.65 for high-grade stenosis yielded a sensitivity of 54.7% (95% CI, 43.9–65.0%), specificity of 94.3% (95% CI, 89.3–97.2%), PPV of 83.9% (95% CI, 71.6–91.9%), and NPV of 79.3% (95% CI, 72.8–84.5%). A cutoff PSV of 400 cm/sec was chosen for unequivocal stenosis of ≥70%. A total of 94 patients were found to meet criteria for high-grade stenosis (PSV ≥ 230 cm/sec) but fall short of criteria for unequivocal high-grade stenosis (PSV < 400 cm/sec). Application of the regression model resulted in identification of 15 patients with probability ≥0.65 for high-grade stenosis and 79 patients with probability <0.65. This resulted in a 16% potential reduction in CTA scans.
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View all citing articles on Scopus

: Dr Lefsrud is now with St Paul Radiology, St Paul, Minn. Dr Robertson is now in Dallas, Tex.

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Original ArticleRedefined Duplex Ultrasonographic Criteria for Diagnosis of Carotid Artery Stenosis

OBJECTIVE

PATIENTS AND METHODS

RESULTS

CONCLUSION

Section snippets

Study Population

RESULTS

DISCUSSION

CONCLUSION

ACKNOWLEDGMENTS

Ann Vasc Surg

Eur J Vase Endovasc Surg

J Vase Surg

J Vase Surg

Ann Vase Surg

J Vasc Surg

J Vase Surg

Beneficial effect of carotid endarterectomy in symptomatic patients with high-grade carotid stenosis

N Engl J Med

Veterans Affairs Cooperative Studies Program 309 Trialist Group. Carotid endarterectomy and prevention of cerebral ischemia in symptomatic carotid stenosis

JMAM

North American Symptomatic Carotid Endarterectomy Trial Collaborators. Benefit of carotid endarterectomy in patients with symptomatic moderate or severe stenosis

N Engl J Med

Doppler evaluation of carotid stenosis

Carotid artery: prospective blinded comparison of two-dimensional lime-of-flight MR angiography with conventional angiography and duplex US

Radiology

Carotid endarterectomy without angiography: the reliability of Doppler ultrasonography and duplex scanning in preoperative assessment

Can J Surg

The role of duplex scanning and arteriography before carotid endarterectomy; a prospective study

J Vase Surg

Colour-coded duplex assessment alone before carotid endartereclomy

Br J Surg

Differentiating subtotal carotid artery stenoses from occlusions by colour-coded duplex sonography

J Neurol

Reevaluation of duplex criteria for diagnosis of high-grade carotid artery stenosis: when do we need angiography and when can we operate without angiography?

Int Angiol

Evaluation of carotid artery stenosis: is duplex ultrasonography sufficient?

Vase Surg

Original Article
Redefined Duplex Ultrasonographic Criteria for Diagnosis of Carotid Artery Stenosis