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Carotid Endarterectomy for Symptomatic Carotid Artery Disease Demonstrated by Duplex Ultrasound With Minimal Arteriographic Findings
Carotid Endarterectomy for Symptomatic Carotid Artery Disease Demonstrated by Duplex Ultrasound With Minimal Arteriographic Findings AE F. AbuRahma, MD, John F. White III, MD, and James P. Boland, AID, Charleston, West Virginia
Ulcerated or irregular heterogeneous carotid plaque as seen by duplex ultrasound can cause hemispheric transient ischemic attacks (TIAs) and/or a cerebrovascular accident, even if only associated with nonsignificant carotid stenosis on arteriography. The purpose of this study was to review our experience in patients who underwent a carotid endarterectomy after medical treatment had failed, based on pathologic findings detected by carotid duplex ultrasound with minimal disease on arteriography. The medical records of 14 patients who underwent carotid endarterectomy for TIA symptoms related to ulcerated or irregular heterogeneous plaques were analyzed. All had had preoperative carotid duplex ultrasound, arteriography, and cardiac and neurologic workups to rule out other causes for their TIAs. Medical treatment had failed in all of them. There were 10 men and four women whose median age was 68 years. Carotid duplex ultrasound showed irregular heterogeneous carotid plaque in all patients associated with 20% to 50% stenosis in 12 and approximately 50% to 60% stenosis in two. All had normal to <20% stenosis on arteriograms. The duplex ultrasound findings were all confirmed at operation. All had an uneventful postoperative course with relief of symptoms. Carotid duplex ultrasound is superior to carotid arteriography in detecting irregular or ulcerative heterogeneous plaque associated with nonsignificant stenosis. Carotid duplex ultrasound can be used to determine the desirability of carotid endarterectomy after failed medical treatment in patients with classical and persistent TIA symptoms despite normal or minimal disease on arteriograms. A successful endarterectomy appears to predict an asymptomatic postoperative course. (Ann Vasc Surg 1996;10:385-389.)
Carotid duplex ultrasound has been shown to present a more satisfactory picture of carotid plaque morphology than arteriography, which is considered the "gold standard. ''~-~ Ulcerated or irregular heterogeneous carotid plaques as seen by duplex ultrasound can cause hemispheric TIA symptoms, amaurosis fugax, or a cerebrovascular
From the Department of Surgery, Section of Vascular Surgery, Charleston Area Medical Center, Robert C. Byrd Health Sciences Center, West Virginia University, Charleston, W. V. Reprint requests: Ali F. AbuRahma, MD, Ste. 603, 3100 MacCorkIe Ave., S.E., Charleston, WV 25304.
accident (CVA), even if only associated with insignificant carotid stenosis by arteriography. The purpose of this study was to review our experience in patients w h o underwent carotid endarterectomy after medical treatment had failed, based on pathologic findings detected by carotid duplex ultrasound, with minimal disease on arteriography. PATIENT POPULATION AND METHODS The records of 14 patients who, after medical treatment had failed, had undergone a carotid endarterectomy within the past 5 years for syrup385
386
Annals of Vascular Surgery
A b u R a h m a et al.
tomatic, ulcerated, or irregular heterogeneous carotid plaques, as demonstrated by carotid duplex ultrasound with minimal disease on preoperative arteriography, were analyzed. Indications for surgery included recurrent hemispheric TIA symptoms in 10 patients similar to the attacks they experienced while receiving medical treatment (four of w h o m had two previous attacks), recurrent amaurosis fugax in two patients (one w h o had a similar attack and one w h o had hemispheric TIAs while receiving medical treatment), and a history of CVA with complete resolution of symptoms in two patients (both of w h o m had prior hemispheric TIAs while receiving medical treatment). A~I 14 patients were initially treated with aspirin; four patients were given ticlopidine and three were given warfarin after the aspirin proved unsuccessful. The duration of the medical treatment ranged from 2 to 15 weeks. The medical treatment was continued until surgery was performed. The workup included color carotid duplex ultrasonography and four-vessel arch aortography with selective carotid arteriography. Preoperative cardiac (including two-dimensional echocardiography in all patients and transesophageal echocardiography in five) and neurologic (including CT scans of the brain) workups were also carried out to rule out other causes of TIA. The diagnosis of carotid plaque ulceration on duplex ultrasound was based on the discovery of irregularities in the wall of the carotid bifurcation or internal carotid artery and/or the presence of irregular heterogeneous plaques. Postoperatively the carotid arteriograms were evaluated by the same radiologist w h o had interpreted the preoperative arteriograms and another independent radiologist.
RESULTS There were 10 men and four w o m e n whose median age was 68 years (range 48 to 81 years). Nine patients had a history of coronary artery disease, five were diabetic, ten were smokers, and seven had hypertension. Carotid duplex ultrasound showed irregular heterogeneous carotid plaques in all patients associated with 20% to < 50% stenosis (a peak systolic frequency of <4.5 kHz or a peak systolic velocity of < 125 cm/sec) in 12 and approximately 50% to 60% stenosis (a peak systolic frequency of 4.5 kHz and an end-diastolic frequency of <4.5 kHz, or a peak systolic velocity of 125 crn/sec with moderate spectral broadening) in two other patients. All patients were reported to
have had normal to < 20% stenosis on initial arteriography. Preoperative CT scans of the brain were abnormal in the two patients with a history of CVA, one additional patient had an old lacunar infarct, and another patient with hemispheric TIA symptoms had an old CVA contralateral to the symptomatic side. The operative findings confirmed the abnormalities demonstrated by the duplex ultrasound in all patients with stenoses ranging from 20% to 60%, and all plaques showed the irregularity and/or ulceration that was demonstrated on the carotid duplex ultrasound. Figs. 1, 2, and 3 are examples of the findings in one patient in this series. When the carotid arteriograms were evaluated postoperatively with the knowledge of the pathologic findings obtained at operation, only two preoperative interpretations of the arteriograms were changed and described as having 40% to 50% stenosis but with no ulceration. These were the two patients w h o had 50% to 60% stenosis on carotid duplex ultrasound. The postoperative course was uneventful in all patients-specifically, there were no TIA symptoms, strokes, myocardial infarctions, or deaths. At 6-month to 5-year ~o~ovc-ups, a~ patients were still asymptomatic. One patient was followed for 6 months, two patients for 18 months, two patients for 24 months, three patients for 36 months, four patients for 48 months, one patient for 54 months, and one patient for 60 months. Follow-up consisted of completion of a questionnaire and vascular examination in the vascular clinic and the noninvasive vascular laboratory.
DISCUSSION The basis for carotid endarterectomy developed with growing knowledge of the natural history of carotid occlusive disease. In addition, the association of cerebral ischemic events with nonstenotic (ulcerative) lesions has received a fair amount of attention. 2 Several investigators 6'7 have shown that less than one half of patients with documented TIAs have hemodynamically significant carotid stenosis. Others have shown a high incidence of intracarotid plaque hemorrhage in symptomatic patients. 8'9 These observations added support to the commonly held impression that the morphology of carotid plaque may play a more significant role in the etiology of cerebrovascular symptoms than reduction of the arterial lumen by stenosis. Initially arteriography was the sole test used to
Vol. 10, No. 4 1996
Duplex ultrasound in carotid artery disease
A
B
Fig. 1. A, Color carotid duplex ultrasound scan of carotid bifurcation showing multiple irregular heterogeneous plaques of the distal left common carotid artery and carotid bifurcation. 13, Carotid spectrum analysis showing a peak systolic frequency of approximately 4.5 kHz, which is consistent with at least 50% to 60% stenosis.
387
388
A b u R a h m a et al.
Fig. 2. Carotid arteriogram showing minimal disease of < 30%.
Fig. 3. Operative specimen of carotid plaque. Note that the plaque is irregular, ulcerative, and heterogeneous.
Annals of Vascular Surgery
"'view" the arterial tree, and as such it became and continues to be the "'gold standard" test prior to carotid endarterectomy despite problems in evaluating stenoses, especially at minimal grades. ~°'~' However, noninvasive vascular studies, particularly carotid duplex ultrasound, have since been advanced to the point where they are being used extensively in the screening of patients with suspected carotid artery disease. Furthermore, there is a growing body of surgeons w h o rely solely on carotid duplex ultrasound for preoperative evaluation of their patients with carotid artery disease. 3"~2~3 Duplex ultrasound has been shown to better delineate the shape of arteriosclerotic plaques and may be used to classify ulcerations. 4 Other investigators have confirmed that arteriography was less than ideal for describing nonstenotic ulcerative lesions. ~4'~ These reports documented that the accuracy of duplex ultrasound in describing the morphology of carotid plaque ranged from 85% to 100%, whereas arteriography was accurate in only 60% to 97%. 4A6A7 This difference in accuracy was more significant in nonstenotic ulcerations where ultrasound was 85% to 97% accurate, in contrast to the 72% accuracy for carotid arteriography w h e n compared to surgical findings. 4"s''s Based on these observations, some authorities have suggested that surgeons can proceed with carotid surgery without a preoperative arteriogram if a good-quality duplex ultrasound scan can confirm the carotid abnormality. 37'~2° With these reports in mind and with these selected 14 cases (i.e., patients with persistent symptoms and heterogeneous irregular or ulcerated plaques on duplex ultrasound), which clearly represent improved diagnostic and prognostic prediction (no postoperative symptoms) of carotid color duplex ultrasound, we propose several alternatives to the current approach to symptomatic patients with carotid disease. In patients with ulcerative lesions or complicated plaque morphology on duplex ultrasound in w h o m other causes for their symptoms have been ruled out by means of scanning and arteriography, carotid endarterectomy may be performed, particularly in those patients in w h o m medical management (antiplatelet therapy or warfarin) has failed, with the anticipation of a good long-term clinical result. It should be emphasized that this study did not compare carotid endarterectomy patients with medically managed patients. Comparative studies such as the North American S~nptomatic Carotid Endarterectomy Trial (NASCET) 2' and the European Carotid Surgery Trial (ECST) 22 both concluded that patients with < 30% carotid stenosis
Vol. 10, No. 4 1996
were equally flee from stroke after surgery and after medical treatment alone. It should be noted that all of our patients had abnormal findings on duplex examination, as well as the persistence of symptoms despite maximal medical therapy. We agree with the preceding comparative studies in that patients initially should be treated with antiplatelet drugs. But if this therapy fails, then carotid endarterectomy can be offered with excellent long-term results.
CONCLUSION Carotid duplex ultrasound is superior to carotid arteriography in detecting irregular or ulcerative heterogeneous plaques associated with mild degrees of stenosis. If medical treatment fails and a minimal but irregular plaque can be demonstrated, endarterectomy is associated with an excellent long-term result. REFERENCES 1. Moore WS, Hall AD. Importance of emboli from carotid bifurcation in pathogenesis of cerebral ischemic attacks. Arch Surg 1970;101:708-716, 2. Moore WS, Clark B, Malone J, et al. Natural history of nonstenotic asymptomatic ulcerative lesions of the carotid artery. Arch Surg 1978; 113:1356-1359. 3. Wagner WH, Treiman RL, Cossman DV, et at. The diminishing role of diagnostic arteriography in carotid artery disease: Duplex scanning as definitive preoperative study. Ann Vasc Surg 1991;5:105-1 i0, 4. Robin JR, Bondi JA, Rhodes RS. Duplex scanning versus conventional arteriography for the evaluation of carotid artery plaque morphology. Surgery 1987;102:749-755. 5. Senkowsky J, Bell WH III, Kerstein MD. Normal angiograms and carotid pathology. Am Surg 1990;56:726-729. 6. Thiele BL, Young JV, Chikos PM, et al. Correlation of arteriographic finding and symptoms in cerebrovascular disease. Neurology 1980;30:1041-1046. 7. O'Donnell TF, Pauker SG, Callow AD, et al. The relative value of carotid noninvasive testing as determined by receiver operator characteristic curves. Surgery 1980;87:9-19.
Duplex ultrasound in carotid artery disease
389
8, AbuRahma AE Boland JE Robinson E et al. Antiplatelet therapy and carotid plaque hemorrhage and its clinical implications. J Cardiovasc Surg 1990;31:66-70. 9. Lusby RJ, Ferrel LD, Ehrenfeld WK, et al. Carotid plaque hemorrhage: Its role in production of cerebral ischemia. Arch Surg 1982; 117:1479-1488. 10. Rothwell PM, Gibson RJ, Slattery J, et al, Equivalence of measurements of carotid stenosis: A comparison of three methods on 1001 angiograms. Stroke 1994;25:2435-2439. 11. Rothweil PM, Gibson RJ, Slattery J, et al. Prognostic value and reproducibility of measurements of carotid stenosis: A comparison of three methods on 1001 angiograms. Stroke 1994;25:2440-2444. 12. Horn M, Michelini M, Greister HE et al. Carotid endarterectomy without arteriography: The preeminent role of the vascular laboratory. Ann Vasc Surg 1994;8:221-224. 13. Chervu A, Moore WS. Carotid endarterectomy without arteriography. Ann Vasc Surg 1994;8:296-302. 14. Croft FJ, EUam LD, Harrison MJG. Accuracy of carotid angiography in the assessment of atheroma of the intimal carotid artery. Lancet 1980;1:997-1000. 15. Eihelboum BC, Riles TR, Mintzer N, et al. Inaccuracy of angiography in the diagnosis of carotid ulceration. Stroke 1983; 14:882-885. I6. Johnson JM. Angiography and ultrasound in diagnosis of carotid artery disease: A comparison. Contemp Surg 1982;20: 79-93. 17. O'Donnell TE Erdoes L, Mackey WC, et al. Correlation of B-mode ultrasound imaging and arteriography with pathologic findings at carotid endarterectomy. Arch Surg 1985;120: 443 -449. 18. Johnson JM, Kennely M, O'Holleran L, et al. A comparison angiography ultrasound in the diagnosis of carotid artery disease. Contemp Surg 1985;26:31-86. 19. Blackshear WM, Connar RG. Carotid endarterectomy without angiography. J Cardiovasc Surg 1982;23:477-482. 20. Akers DL Bell WH IlI, Kerstein MD. Does intracranial dye study contribute to evaluation of carotid artery disease? Am J Surg 1988;156:87-90. 21. North American Symptomatic Carotid Endarterectomy Trial Collaborators. Beneficial effect of carotid endarterectomy in symptomatic patients with high-grade carotid stenosis. N Engl J Med 1991;325:445-453. 22. European Carotid Surgery Trialists' Collaborative Group. MRC European Carotid Surgery Trial. Interim results for symptomatic patients with severe (70-99%) or with mild (0-29%) carotid stenosis. Lancet 1991;337:1235-1243,
Ulcerated or irregular heterogeneous carotid plaque as seen by duplex ultrasound can cause hemispheric transient ischemic attacks (TIAs) and/or a cerebrovascular accident, even if only associated with nonsignificant carotid stenosis on arteriography. The purpose of this study was to review our experience in patients who underwent a carotid endarterectomy after medical treatment had failed, based on pathologic findings detected by carotid duplex ultrasound with minimal disease on arteriography. The medical records of 14 patients who underwent carotid endarterectomy for TIA symptoms related to ulcerated or irregular heterogeneous plaques were analyzed. All had had preoperative carotid duplex ultrasound, arteriography, and cardiac and neurologic workups to rule out other causes for their TIAs. Medical treatment had failed in all of them. There were 10 men and four women whose median age was 68 years. Carotid duplex ultrasound showed irregular heterogeneous carotid plaque in all patients associated with 20% to 50% stenosis in 12 and approximately 50% to 60% stenosis in two. All had normal to <20% stenosis on arteriograms. The duplex ultrasound findings were all confirmed at operation. All had an uneventful postoperative course with relief of symptoms. Carotid duplex ultrasound is superior to carotid arteriography in detecting irregular or ulcerative heterogeneous plaque associated with nonsignificant stenosis. Carotid duplex ultrasound can be used to determine the desirability of carotid endarterectomy after failed medical treatment in patients with classical and persistent TIA symptoms despite normal or minimal disease on arteriograms. A successful endarterectomy appears to predict an asymptomatic postoperative course. (Ann Vasc Surg 1996;10:385-389.)
Carotid duplex ultrasound has been shown to present a more satisfactory picture of carotid plaque morphology than arteriography, which is considered the "gold standard. ''~-~ Ulcerated or irregular heterogeneous carotid plaques as seen by duplex ultrasound can cause hemispheric TIA symptoms, amaurosis fugax, or a cerebrovascular
From the Department of Surgery, Section of Vascular Surgery, Charleston Area Medical Center, Robert C. Byrd Health Sciences Center, West Virginia University, Charleston, W. V. Reprint requests: Ali F. AbuRahma, MD, Ste. 603, 3100 MacCorkIe Ave., S.E., Charleston, WV 25304.
accident (CVA), even if only associated with insignificant carotid stenosis by arteriography. The purpose of this study was to review our experience in patients w h o underwent carotid endarterectomy after medical treatment had failed, based on pathologic findings detected by carotid duplex ultrasound, with minimal disease on arteriography. PATIENT POPULATION AND METHODS The records of 14 patients who, after medical treatment had failed, had undergone a carotid endarterectomy within the past 5 years for syrup385
386
Annals of Vascular Surgery
A b u R a h m a et al.
tomatic, ulcerated, or irregular heterogeneous carotid plaques, as demonstrated by carotid duplex ultrasound with minimal disease on preoperative arteriography, were analyzed. Indications for surgery included recurrent hemispheric TIA symptoms in 10 patients similar to the attacks they experienced while receiving medical treatment (four of w h o m had two previous attacks), recurrent amaurosis fugax in two patients (one w h o had a similar attack and one w h o had hemispheric TIAs while receiving medical treatment), and a history of CVA with complete resolution of symptoms in two patients (both of w h o m had prior hemispheric TIAs while receiving medical treatment). A~I 14 patients were initially treated with aspirin; four patients were given ticlopidine and three were given warfarin after the aspirin proved unsuccessful. The duration of the medical treatment ranged from 2 to 15 weeks. The medical treatment was continued until surgery was performed. The workup included color carotid duplex ultrasonography and four-vessel arch aortography with selective carotid arteriography. Preoperative cardiac (including two-dimensional echocardiography in all patients and transesophageal echocardiography in five) and neurologic (including CT scans of the brain) workups were also carried out to rule out other causes of TIA. The diagnosis of carotid plaque ulceration on duplex ultrasound was based on the discovery of irregularities in the wall of the carotid bifurcation or internal carotid artery and/or the presence of irregular heterogeneous plaques. Postoperatively the carotid arteriograms were evaluated by the same radiologist w h o had interpreted the preoperative arteriograms and another independent radiologist.
RESULTS There were 10 men and four w o m e n whose median age was 68 years (range 48 to 81 years). Nine patients had a history of coronary artery disease, five were diabetic, ten were smokers, and seven had hypertension. Carotid duplex ultrasound showed irregular heterogeneous carotid plaques in all patients associated with 20% to < 50% stenosis (a peak systolic frequency of <4.5 kHz or a peak systolic velocity of < 125 cm/sec) in 12 and approximately 50% to 60% stenosis (a peak systolic frequency of 4.5 kHz and an end-diastolic frequency of <4.5 kHz, or a peak systolic velocity of 125 crn/sec with moderate spectral broadening) in two other patients. All patients were reported to
have had normal to < 20% stenosis on initial arteriography. Preoperative CT scans of the brain were abnormal in the two patients with a history of CVA, one additional patient had an old lacunar infarct, and another patient with hemispheric TIA symptoms had an old CVA contralateral to the symptomatic side. The operative findings confirmed the abnormalities demonstrated by the duplex ultrasound in all patients with stenoses ranging from 20% to 60%, and all plaques showed the irregularity and/or ulceration that was demonstrated on the carotid duplex ultrasound. Figs. 1, 2, and 3 are examples of the findings in one patient in this series. When the carotid arteriograms were evaluated postoperatively with the knowledge of the pathologic findings obtained at operation, only two preoperative interpretations of the arteriograms were changed and described as having 40% to 50% stenosis but with no ulceration. These were the two patients w h o had 50% to 60% stenosis on carotid duplex ultrasound. The postoperative course was uneventful in all patients-specifically, there were no TIA symptoms, strokes, myocardial infarctions, or deaths. At 6-month to 5-year ~o~ovc-ups, a~ patients were still asymptomatic. One patient was followed for 6 months, two patients for 18 months, two patients for 24 months, three patients for 36 months, four patients for 48 months, one patient for 54 months, and one patient for 60 months. Follow-up consisted of completion of a questionnaire and vascular examination in the vascular clinic and the noninvasive vascular laboratory.
DISCUSSION The basis for carotid endarterectomy developed with growing knowledge of the natural history of carotid occlusive disease. In addition, the association of cerebral ischemic events with nonstenotic (ulcerative) lesions has received a fair amount of attention. 2 Several investigators 6'7 have shown that less than one half of patients with documented TIAs have hemodynamically significant carotid stenosis. Others have shown a high incidence of intracarotid plaque hemorrhage in symptomatic patients. 8'9 These observations added support to the commonly held impression that the morphology of carotid plaque may play a more significant role in the etiology of cerebrovascular symptoms than reduction of the arterial lumen by stenosis. Initially arteriography was the sole test used to
Vol. 10, No. 4 1996
Duplex ultrasound in carotid artery disease
A
B
Fig. 1. A, Color carotid duplex ultrasound scan of carotid bifurcation showing multiple irregular heterogeneous plaques of the distal left common carotid artery and carotid bifurcation. 13, Carotid spectrum analysis showing a peak systolic frequency of approximately 4.5 kHz, which is consistent with at least 50% to 60% stenosis.
387
388
A b u R a h m a et al.
Fig. 2. Carotid arteriogram showing minimal disease of < 30%.
Fig. 3. Operative specimen of carotid plaque. Note that the plaque is irregular, ulcerative, and heterogeneous.
Annals of Vascular Surgery
"'view" the arterial tree, and as such it became and continues to be the "'gold standard" test prior to carotid endarterectomy despite problems in evaluating stenoses, especially at minimal grades. ~°'~' However, noninvasive vascular studies, particularly carotid duplex ultrasound, have since been advanced to the point where they are being used extensively in the screening of patients with suspected carotid artery disease. Furthermore, there is a growing body of surgeons w h o rely solely on carotid duplex ultrasound for preoperative evaluation of their patients with carotid artery disease. 3"~2~3 Duplex ultrasound has been shown to better delineate the shape of arteriosclerotic plaques and may be used to classify ulcerations. 4 Other investigators have confirmed that arteriography was less than ideal for describing nonstenotic ulcerative lesions. ~4'~ These reports documented that the accuracy of duplex ultrasound in describing the morphology of carotid plaque ranged from 85% to 100%, whereas arteriography was accurate in only 60% to 97%. 4A6A7 This difference in accuracy was more significant in nonstenotic ulcerations where ultrasound was 85% to 97% accurate, in contrast to the 72% accuracy for carotid arteriography w h e n compared to surgical findings. 4"s''s Based on these observations, some authorities have suggested that surgeons can proceed with carotid surgery without a preoperative arteriogram if a good-quality duplex ultrasound scan can confirm the carotid abnormality. 37'~2° With these reports in mind and with these selected 14 cases (i.e., patients with persistent symptoms and heterogeneous irregular or ulcerated plaques on duplex ultrasound), which clearly represent improved diagnostic and prognostic prediction (no postoperative symptoms) of carotid color duplex ultrasound, we propose several alternatives to the current approach to symptomatic patients with carotid disease. In patients with ulcerative lesions or complicated plaque morphology on duplex ultrasound in w h o m other causes for their symptoms have been ruled out by means of scanning and arteriography, carotid endarterectomy may be performed, particularly in those patients in w h o m medical management (antiplatelet therapy or warfarin) has failed, with the anticipation of a good long-term clinical result. It should be emphasized that this study did not compare carotid endarterectomy patients with medically managed patients. Comparative studies such as the North American S~nptomatic Carotid Endarterectomy Trial (NASCET) 2' and the European Carotid Surgery Trial (ECST) 22 both concluded that patients with < 30% carotid stenosis
Vol. 10, No. 4 1996
were equally flee from stroke after surgery and after medical treatment alone. It should be noted that all of our patients had abnormal findings on duplex examination, as well as the persistence of symptoms despite maximal medical therapy. We agree with the preceding comparative studies in that patients initially should be treated with antiplatelet drugs. But if this therapy fails, then carotid endarterectomy can be offered with excellent long-term results.
CONCLUSION Carotid duplex ultrasound is superior to carotid arteriography in detecting irregular or ulcerative heterogeneous plaques associated with mild degrees of stenosis. If medical treatment fails and a minimal but irregular plaque can be demonstrated, endarterectomy is associated with an excellent long-term result. REFERENCES 1. Moore WS, Hall AD. Importance of emboli from carotid bifurcation in pathogenesis of cerebral ischemic attacks. Arch Surg 1970;101:708-716, 2. Moore WS, Clark B, Malone J, et al. Natural history of nonstenotic asymptomatic ulcerative lesions of the carotid artery. Arch Surg 1978; 113:1356-1359. 3. Wagner WH, Treiman RL, Cossman DV, et at. The diminishing role of diagnostic arteriography in carotid artery disease: Duplex scanning as definitive preoperative study. Ann Vasc Surg 1991;5:105-1 i0, 4. Robin JR, Bondi JA, Rhodes RS. Duplex scanning versus conventional arteriography for the evaluation of carotid artery plaque morphology. Surgery 1987;102:749-755. 5. Senkowsky J, Bell WH III, Kerstein MD. Normal angiograms and carotid pathology. Am Surg 1990;56:726-729. 6. Thiele BL, Young JV, Chikos PM, et al. Correlation of arteriographic finding and symptoms in cerebrovascular disease. Neurology 1980;30:1041-1046. 7. O'Donnell TF, Pauker SG, Callow AD, et al. The relative value of carotid noninvasive testing as determined by receiver operator characteristic curves. Surgery 1980;87:9-19.
Duplex ultrasound in carotid artery disease
389
8, AbuRahma AE Boland JE Robinson E et al. Antiplatelet therapy and carotid plaque hemorrhage and its clinical implications. J Cardiovasc Surg 1990;31:66-70. 9. Lusby RJ, Ferrel LD, Ehrenfeld WK, et al. Carotid plaque hemorrhage: Its role in production of cerebral ischemia. Arch Surg 1982; 117:1479-1488. 10. Rothwell PM, Gibson RJ, Slattery J, et al, Equivalence of measurements of carotid stenosis: A comparison of three methods on 1001 angiograms. Stroke 1994;25:2435-2439. 11. Rothweil PM, Gibson RJ, Slattery J, et al. Prognostic value and reproducibility of measurements of carotid stenosis: A comparison of three methods on 1001 angiograms. Stroke 1994;25:2440-2444. 12. Horn M, Michelini M, Greister HE et al. Carotid endarterectomy without arteriography: The preeminent role of the vascular laboratory. Ann Vasc Surg 1994;8:221-224. 13. Chervu A, Moore WS. Carotid endarterectomy without arteriography. Ann Vasc Surg 1994;8:296-302. 14. Croft FJ, EUam LD, Harrison MJG. Accuracy of carotid angiography in the assessment of atheroma of the intimal carotid artery. Lancet 1980;1:997-1000. 15. Eihelboum BC, Riles TR, Mintzer N, et al. Inaccuracy of angiography in the diagnosis of carotid ulceration. Stroke 1983; 14:882-885. I6. Johnson JM. Angiography and ultrasound in diagnosis of carotid artery disease: A comparison. Contemp Surg 1982;20: 79-93. 17. O'Donnell TE Erdoes L, Mackey WC, et al. Correlation of B-mode ultrasound imaging and arteriography with pathologic findings at carotid endarterectomy. Arch Surg 1985;120: 443 -449. 18. Johnson JM, Kennely M, O'Holleran L, et al. A comparison angiography ultrasound in the diagnosis of carotid artery disease. Contemp Surg 1985;26:31-86. 19. Blackshear WM, Connar RG. Carotid endarterectomy without angiography. J Cardiovasc Surg 1982;23:477-482. 20. Akers DL Bell WH IlI, Kerstein MD. Does intracranial dye study contribute to evaluation of carotid artery disease? Am J Surg 1988;156:87-90. 21. North American Symptomatic Carotid Endarterectomy Trial Collaborators. Beneficial effect of carotid endarterectomy in symptomatic patients with high-grade carotid stenosis. N Engl J Med 1991;325:445-453. 22. European Carotid Surgery Trialists' Collaborative Group. MRC European Carotid Surgery Trial. Interim results for symptomatic patients with severe (70-99%) or with mild (0-29%) carotid stenosis. Lancet 1991;337:1235-1243,