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Should carotid screening be done?
S38
Ultrasound in Medicine and Biology
Volume 29, Number 5S, 2003
190 for adventitia using linear scaling. This normalisation has enabled us to get reproducible texture measurements when individuals are being scanned by different operators on different equipment. Cross-sectional studies have demonstrated that a number of texture features can be used to characterise and classify plaques. These features were subsequently applied to the ACSRS study, which is an international prospective natural history study of patients with asymptomatic carotid stenosis. Using a Cox proportional hazard model in 1079 patients, it was found that the degree of stenosis, the plaque type after normalisation and the presence of a black area adjacent to the lumen would identify a high-risk group for stroke. This group consists of one-third of the population and has an annual stroke rate of 4.5% and contains 86% of the strokes. The remaining two-thirds of the population have a stroke rate of less than 0.5% per year.
and are likely superior include maximizing sensitivity or specificity and even choosing thresholds based on patient outcome. The relationship between the status of the patient with regard to being neurologically symptomatic versus asymptomatic and Doppler threshold will also be discussed. This lecture will review the pertinent literature and identify reasons for discrepancies. Results of the recent Society of Radiologists in Ultrasound consensus conference on carotid stenosis will be integrated with the above to provide the attendee with reasonable methods and criteria for characterizing carotid stenosis using color and duplex ultrasound.
Should carotid screening be done? Bluth E, Ochsner Clinic Foundation, New Orleans, LA
Carotid endarterectomy (CEA) for stroke prevention in patients with severe atherosclerotic carotid stenosis has been confirmed by the NASCET and ACAS trials, and carotid stent-assisted angioplasty (CAS) is currently being evaluated in the CREST trial. The efficacy of CEA/CAS is highly dependent on a low (⬍5%) periprocedural morbidity and producing a repair with a low incidence of recurrent disease/ occlusion. Duplex ultrasound surveillance after CEA and CAS has shown an incidence of recurrent stenosis (⬎50% DR) in the range of 4 –22%. In the ACAS study, early restenosis (⬎60% DR) was found in 7–11% of cases; late restenosis was found in 2–5% of cases. When intraoperative duplex monitoring of carotid interventions is applied, the restenosis rate can be decreased further (⬍5% early and late combined). The natural history of recurrent stenosis has not been fully elucidated, but lesions in the 50 –75% DR range are associated with low risk of stroke or occlusion, and some (10%) early lesions may demonstrate regression. High-grade (⬎80%, EDV⬎145 cm/s) recurrent ICA stenosis, caused by atherosclerosis or myointimal hyperplasia, has been associated with an increased risk ICA thrombosis and stroke. Duplex scanning is recommended at the completion of CEA/CAS procedure, and then at 3- to 6-month intervals. High-grade ICA stenosis (PSV⬎300 cm/s; EDV⬎125 cm/s; ICA/CCA ratio, ⬎4) should prompt consideration for re-intervention especially if the stenosis is progressing, ⬎1 cm in length, or associated with CAS. In most patients, the reason for duplex surveillance is to identify progression of contralateral ⬎50% ICA stenosis rather than to detect restenosis at the CEA/CAS site. Duplex scanning every 1–2 years may be adequate when a technically precise CEA is achieved, when no restenosis (⬍50%) is detected in the first year, and ⬍50% DR contralateral stenosis is present. More frequent surveillance, i.e., 6 months, is indicated with recurrent or contralateral ⬎50% ICA stenosis. The development of hemispheric symptoms in the presence of ⬎50% ICA stenosis or asymptomatic progression to a high-grade stenosis (⬎80% DR) during follow-up should prompt a recommendation for redo intervention in appropriate patients.
The identification of a screening test to reduce the risk of stroke has been a long-term goal of those interested in public health. The ACAS study has shown that asymptomatic patients with a greater than 60% stenosis would benefit from endarterectomy compared with medical antiplatelet treatment in centers with perioperative morbidity and mortality less than 3%. Over two million people over the age of 50, it is estimated, have asymptomatic carotid artery stenosis of at least 50% of the luminal diameter. Considering the number of individuals at risk for stroke and the significant economic implications associated with providing short- and long-term care for this group, it is no wonder then that there has been considerable attention directed at developing an accurate, low-risk, economical, and rapid stroke screening test. In 1997, Bluth et al reported at the RSNA and subsequently published in Radiology (215:791– 800, 2000) a methodology for rapid screening employing only PDI. This test fits the criteria of being accurate, low risk, economical, and rapid. The test was based on applying the concepts of screening mammography to the carotids. Examinations would be interpreted as either normal or abnormal. If normal, the patient would return for routine screening at intervals to be determined; if abnormal, the patient would be directed for further evaluation at a different time using either a complete duplex Doppler evaluation, MRA, CTA, or angiography as the follow-up test. This test will be described.
Current status of carotid stenosis grading Grant E, USC University Hospital, Los Angeles, CA Recent literature has produced a wide range of criteria for the characterization of carotid stenosis. This issue has become particularly pertinent in light of recent clinical trails such as the NASCET and ACAS and the current trend away from using contrast angiography to verify sonographic results before proceeding to carotid endarterectomy. Numerous reasons for the discrepancies in the literature exist and include so-called interlaboratory variation (differences in scan technique, equipment, etc., when comparing one facility to another), choice of and inconsistencies in the gold standard, variations in patient population, use of various Doppler parameters, and the choice of statistical methodologies used to arrive at thresholds themselves. This latter area will be explored in detail as our own work shows that wide variations in threshold choice will result from using one or the other method. Most authorities have relied on the highest accuracy of a given Doppler parameter, which is probably the least useful of the commonly used methods as there is minimal change in accuracy over a very wide range of Doppler thresholds. Other statistical techniques that have been used
Follow-up of carotid interventions Bandyk DF, Vascular Surgery, University of South Florida, Tampa, FL
Doppler detection of cerebral emboli: The state-of-the-art Evans DH, Medical Physics, University of Leicester, Leicester, Leicestershire, United Kingdom It is now generally believed that the majority of strokes are caused by emboli from distal sites, rather than by local haemorrhagic or occlusive processes. The discovery that emboli of various types can be detected using Doppler ultrasound as they are carried through the major cerebral arteries has led to a new field of study, which appears to have considerable potential both in research and clinical settings. The basic principle of detection is extremely simple: if an embolus back-scatters more power than the surrounding blood in which it is moving, then the
Ultrasound in Medicine and Biology
Volume 29, Number 5S, 2003
190 for adventitia using linear scaling. This normalisation has enabled us to get reproducible texture measurements when individuals are being scanned by different operators on different equipment. Cross-sectional studies have demonstrated that a number of texture features can be used to characterise and classify plaques. These features were subsequently applied to the ACSRS study, which is an international prospective natural history study of patients with asymptomatic carotid stenosis. Using a Cox proportional hazard model in 1079 patients, it was found that the degree of stenosis, the plaque type after normalisation and the presence of a black area adjacent to the lumen would identify a high-risk group for stroke. This group consists of one-third of the population and has an annual stroke rate of 4.5% and contains 86% of the strokes. The remaining two-thirds of the population have a stroke rate of less than 0.5% per year.
and are likely superior include maximizing sensitivity or specificity and even choosing thresholds based on patient outcome. The relationship between the status of the patient with regard to being neurologically symptomatic versus asymptomatic and Doppler threshold will also be discussed. This lecture will review the pertinent literature and identify reasons for discrepancies. Results of the recent Society of Radiologists in Ultrasound consensus conference on carotid stenosis will be integrated with the above to provide the attendee with reasonable methods and criteria for characterizing carotid stenosis using color and duplex ultrasound.
Should carotid screening be done? Bluth E, Ochsner Clinic Foundation, New Orleans, LA
Carotid endarterectomy (CEA) for stroke prevention in patients with severe atherosclerotic carotid stenosis has been confirmed by the NASCET and ACAS trials, and carotid stent-assisted angioplasty (CAS) is currently being evaluated in the CREST trial. The efficacy of CEA/CAS is highly dependent on a low (⬍5%) periprocedural morbidity and producing a repair with a low incidence of recurrent disease/ occlusion. Duplex ultrasound surveillance after CEA and CAS has shown an incidence of recurrent stenosis (⬎50% DR) in the range of 4 –22%. In the ACAS study, early restenosis (⬎60% DR) was found in 7–11% of cases; late restenosis was found in 2–5% of cases. When intraoperative duplex monitoring of carotid interventions is applied, the restenosis rate can be decreased further (⬍5% early and late combined). The natural history of recurrent stenosis has not been fully elucidated, but lesions in the 50 –75% DR range are associated with low risk of stroke or occlusion, and some (10%) early lesions may demonstrate regression. High-grade (⬎80%, EDV⬎145 cm/s) recurrent ICA stenosis, caused by atherosclerosis or myointimal hyperplasia, has been associated with an increased risk ICA thrombosis and stroke. Duplex scanning is recommended at the completion of CEA/CAS procedure, and then at 3- to 6-month intervals. High-grade ICA stenosis (PSV⬎300 cm/s; EDV⬎125 cm/s; ICA/CCA ratio, ⬎4) should prompt consideration for re-intervention especially if the stenosis is progressing, ⬎1 cm in length, or associated with CAS. In most patients, the reason for duplex surveillance is to identify progression of contralateral ⬎50% ICA stenosis rather than to detect restenosis at the CEA/CAS site. Duplex scanning every 1–2 years may be adequate when a technically precise CEA is achieved, when no restenosis (⬍50%) is detected in the first year, and ⬍50% DR contralateral stenosis is present. More frequent surveillance, i.e., 6 months, is indicated with recurrent or contralateral ⬎50% ICA stenosis. The development of hemispheric symptoms in the presence of ⬎50% ICA stenosis or asymptomatic progression to a high-grade stenosis (⬎80% DR) during follow-up should prompt a recommendation for redo intervention in appropriate patients.
The identification of a screening test to reduce the risk of stroke has been a long-term goal of those interested in public health. The ACAS study has shown that asymptomatic patients with a greater than 60% stenosis would benefit from endarterectomy compared with medical antiplatelet treatment in centers with perioperative morbidity and mortality less than 3%. Over two million people over the age of 50, it is estimated, have asymptomatic carotid artery stenosis of at least 50% of the luminal diameter. Considering the number of individuals at risk for stroke and the significant economic implications associated with providing short- and long-term care for this group, it is no wonder then that there has been considerable attention directed at developing an accurate, low-risk, economical, and rapid stroke screening test. In 1997, Bluth et al reported at the RSNA and subsequently published in Radiology (215:791– 800, 2000) a methodology for rapid screening employing only PDI. This test fits the criteria of being accurate, low risk, economical, and rapid. The test was based on applying the concepts of screening mammography to the carotids. Examinations would be interpreted as either normal or abnormal. If normal, the patient would return for routine screening at intervals to be determined; if abnormal, the patient would be directed for further evaluation at a different time using either a complete duplex Doppler evaluation, MRA, CTA, or angiography as the follow-up test. This test will be described.
Current status of carotid stenosis grading Grant E, USC University Hospital, Los Angeles, CA Recent literature has produced a wide range of criteria for the characterization of carotid stenosis. This issue has become particularly pertinent in light of recent clinical trails such as the NASCET and ACAS and the current trend away from using contrast angiography to verify sonographic results before proceeding to carotid endarterectomy. Numerous reasons for the discrepancies in the literature exist and include so-called interlaboratory variation (differences in scan technique, equipment, etc., when comparing one facility to another), choice of and inconsistencies in the gold standard, variations in patient population, use of various Doppler parameters, and the choice of statistical methodologies used to arrive at thresholds themselves. This latter area will be explored in detail as our own work shows that wide variations in threshold choice will result from using one or the other method. Most authorities have relied on the highest accuracy of a given Doppler parameter, which is probably the least useful of the commonly used methods as there is minimal change in accuracy over a very wide range of Doppler thresholds. Other statistical techniques that have been used
Follow-up of carotid interventions Bandyk DF, Vascular Surgery, University of South Florida, Tampa, FL
Doppler detection of cerebral emboli: The state-of-the-art Evans DH, Medical Physics, University of Leicester, Leicester, Leicestershire, United Kingdom It is now generally believed that the majority of strokes are caused by emboli from distal sites, rather than by local haemorrhagic or occlusive processes. The discovery that emboli of various types can be detected using Doppler ultrasound as they are carried through the major cerebral arteries has led to a new field of study, which appears to have considerable potential both in research and clinical settings. The basic principle of detection is extremely simple: if an embolus back-scatters more power than the surrounding blood in which it is moving, then the