Screening for asymptomatic internal carotid artery stenosis: Duplex criteria for discriminating 60% to 99% stenosis

Purpose: The Asymptomatic Carotid Atherosclerosis Study (ACAS) showed that carotid endarterectomy reduces stroke risk in symptom-free patients with 60% or greater internal carotid artery (ICA) stenosis. This will surely lead to the performance of an increased number of screening duplex examinations. Assuming that positive study results will lead to arteriography or endarterectomy and keeping in mind the modest benefit for prophylactic endarterectomy demonstrated by ACAS (absolute risk reduction for ipsilateral stroke of 5.8% at 5 years), duplex criteria for 60% or greater ICA stenosis must have high positive predictive values (PPV). Determining criteria for 60% or greater stenosis, which emphasized high accuracy and PPV, forms the basis for this study.Methods: Stenoses detected by angiography in 352 ICAs were blindly compared with those detected by duplex scanning. Duplex criteria were determined for highest overall accuracy in detection of 60% or greater ICA stenosis and for 95% or greater PPV.Results: Maximal accuracy for detection of 60% or greater stenosis was 90%. This was achieved by the combination of a peak systolic velocity of 260 cm/sec or greater and an end diastolic velocity of 70 cm/sec or greater (sensitivity 84%, specificity 94%, PPV 92%). The 95% PPV for 60% or greater stenosis results from combining peak systolic velocity of 290 cm/sec or greater and end diastolic velocity of 80 cm/sec or greater.Conclusions: With use of these criteria duplex scanning accurately detects with high PPVs the threshold level of ICA stenosis defined in ACAS as receiving stroke reduction benefit from prophylactic carotid endarterectomy. These criteria should be useful for carotid artery screening and minimizing unneeded intervention. (J VASC SURG 1995;21:989-94.)     

Prospective evaluation of new duplex criteria to identify 70% internal carotid artery stenosis

Purpose: Large multicenter trials (North American Symptomatic Carotid Endarterectomy Trial, European Carotid Surgery Trial) have documented the benefits of carotid endarterectomy for treating symptomatic patients with ≥70% stenosis of the internal carotid artery. Although color-flow duplex scanning has become the preferred method for noninvasive assessment of internal carotid artery disease, no criteria have been generally accepted to identify this subset of patients. We previously reported a retrospective series to establish such criteria. This study details our results when these criteria were applied prospectively.Methods: Carotid color-flow duplex scans were compared with arteriograms in 457 patients who underwent both studies. Criteria for ≥70% internal carotid artery stenosis were peak systolic velocity >130 cm/sec and end-diastolic velocity >100 cm/sec. Internal carotid arteries with peak systolic velocity <40 cm/sec in which only a trickle of flow could be detected were classified as preocclusive lesions (95% to 99% stenosis). Arteriographic stenosis was determined by comparing the diameter of the internal carotid artery at the site of maximal stenosis to the diameter of the normal distal internal carotid artery.Results: Internal carotid artery stenosis of ≥70% was detected with a sensitivity of 87%, specificity of 97%, positive predictive value of 89%, negative predictive value of 96%, and overall accuracy of 95%. Eighty-seven percent of 70% to 99% stenoses were correctly identified. False-positive errors (n = 10) were attributed to contralateral internal carotid artery occlusion or high-grade (>90%) stenosis (n = 5) and to interpreter error (n = 1); no explanation was apparent in the other four. Eleven of 12 false-negative examinations occurred in patients with 70% to 80% internal carotid artery stenosis.Conclusions: In our laboratories, prospective application of the above velocity criteria identified internal carotid artery stenosis of ≥70% with a reasonably high degree of accuracy. Errors occurred when stenoses were borderline and in patients with severe contralateral disease. With suitably modified velocity criteria, color-flow duplex scanning remains the most reliable noninvasive method for identifying symptomatic patients who are candidates for carotid endarterectomy. (J V ASC S URG 1996;23:254-62.)     

Natural history of > or =60% asymptomatic carotid stenosis in patients with contralateral carotid occlusion

OBJECTIVE: Although the Asymptomatic Carotid Atherosclerosis Study (ACAS) reported that carotid endarterectomy (CEA) is beneficial for patients with asymptomatic > or =60% carotid stenosis (ACS), several other studies have reported mixed results. Our prospective study analyzed the natural history of > or =60% ACS in patients with contralateral carotid occlusion (CCO). PATIENT POPULATION AND METHODS: During a 10-year period, patients with 60-<70% ACS with CCO were entered into a protocol of clinical examination and duplex surveillance every 6 months. All patients underwent maximum medical therapy. Late CEAs were considered if lesions became symptomatic or progressed to > or =70% stenosis. A Kaplan-Meier lifetable analysis was performed to estimate the freedom from both ipsilateral strokes and all strokes. RESULTS: Eighty-two patients were enrolled with a mean follow-up of 59.5 months (range, 7-141 months). Late strokes were noted in 27 of 82 patients (33%); 19 (23%) were ipsilateral and 8 (10%) were contralateral (side of CCO). Late transient ischemic attacks (TIAs) were noted in 22 of 82 (27%, 7 ipsilateral and 15 contralateral). The combined neurologic event (TIA/stroke) rate was 60% (49 of 82, 32% ipsilateral and 28% contralateral). Kaplan-Meier lifetable analysis showed that the rates of freedom from ipsilateral strokes, all strokes, and progression to > or =70% stenosis at 1, 2, 3, 4, and 5 years were 94%, 90%, 85%, 80%, 73%; 94%, 89%, 84%, 77%, 67%; and 99%, 96%, 92%, 86%, and 82%, respectively. The ipsilateral stroke-free survival rates at l, 2, 3, 4, and 5 years were 94%, 88%, 78%, 70%, and 63%. Twenty-one late CEAs were performed with no perioperative stroke/deaths (5 for ipsilateral TIAs, 9 for ipsilateral strokes, and 7 for > or =70% ACS). Overall, 20 (24%, 11 with symptoms and 9 asymptomatic) progressed to > or =70% stenosis. CONCLUSIONS: Patients with 60-<70% ACS and CCO with maximal medical therapy carry a higher incidence of ipsilateral strokes and all strokes than what was reported by the ACAS study; therefore, prophylactic CEA may be justified in these patients.     

Carotid endarterectomy in octogenarians with symptomatic high-grade internal carotid artery stenosis: long-term clinical and duplex follow-up

The objective of this study was to evaluate the clinical and duplex outcome after carotid endarterectomy (CEA) in recently symptomatic patients aged 80 years or older. Information was assembled from a prospective data collection of all CEAs performed from January 1986 to December 1999. Included were all patients with recently symptomatic carotid artery stenosis who were aged 80 years or older at time of operation. Thirty-two patients, with a mean age of 82 years, were included. Outcome events were stroke, death, and restenosis (more than 50% diameter reduction) during routine duplex scan follow-up. Conventional surgical technique was used regarding anesthesia and selective shunting or patching. None of the operated-on patients suffered a stroke at any time during follow-up. One patient (3.1%) died in the early postoperative phase (<30 days). An additional 8 patients died during follow-up. None of these deaths were of cerebrovascular origin. Survival at 3 years was 73% (life table analysis). Routine duplex scan follow-up showed 2 patients with a diameter reduction of more than 50%, both 3 months after CEA. Restenosis rate on duplex scan was 7.4% after 1 year. The authors conclude that there seems to be no reason to deny the very elderly the benefits of CEA. Stroke-free survival and survival rates show that carotid surgery is a safe procedure in patients aged 80 and over who are in apparently good health. These findings are supported by a low incidence of restenosis on duplex scan follow-up, indicating a durable repair.     

The natural history of moderate (50% to 79%) internal carotid artery stenosis in symptomatic,nonhemispheric, and asymptomatic patients

Purpose: This study was undertaken to determine the incidence of disease progression of moderate (50% to 79%) internal carotid artery stenosis in patients with symptoms, patients with nonhemispheric symptoms, and symptom-free patients and to define the risk of development of new neurologic events in each group.Methods: Over a 6-year period, 272 patients with moderate internal carotid artery stenoses were monitored for a mean of 44 months with color-flow duplex scanning (CFS). At the time of the initial scan, 142 patients were symptom free, 87 had experienced transient ischemic attacks, amaurosis fugax, or mild strokes, and 43 had ill-defined nonhemispheric symptoms. The average number of follow-up scans was 2.4 per patient (range 1 to 11).Results: During follow-up, 23 (26%) of the patients with symptoms, 17 (40%) of the patients with nonhemispheric symptoms, and 30 (21%) of the symptom-free patients had development of additional neurologic symptoms. Life-table comparison of ipsilateral ischemic events showed a significantly (p = 0.03) higher cumulative rate in the symptomatic group (20%) than in the asymptomatic group (7%) at 2 years. Mean annual stroke rates were 6% and 2% in patients in the symptomatic and asymptomatic groups, respectively. None of the patients in the nonhemispheric group had a stroke within 4 years of the initial study. Disease progression occurred in 16% of the patients. In the asymptomatic group, ipsilateral stroke occurred more frequently (p = 0.0001) in patients with disease progression (25%) than in patients with stable lesions (1%). CFS detected disease progression in 19 (79%) of 24 patients before the artery occluded or stroke occurred. In patients with symptoms, stroke was more frequent (p = 0.02) in patients with six or more risk factors (29%) than in those with five or fewer risk factors (7%).Conclusion: Although the risk of stroke is less in patients with moderate stenosis than it is in patients with severely stenotic lesions, symptom-free patients with advancing disease and patients with symptoms and multiple risk factors are at increased risk for development of neurologic events. These findings support the use of CFS to monitor patients with carotid artery disease and suggest that a more aggressive surgical approach may be indicated in selected patients with moderate carotid artery stenosis. (J VASC SURG 1995;21:346-57.)     

Effect of carotid endarterectomy on cognitive function in patients with asymptomatic carotid artery stenosis

Background

This study was conducted to determine if patients with asymptomatic carotid artery stenosis show cognitive function decline, and if they experience any changes in cognitive function after carotid endarterectomy (CEA).

Method

Cognitive function was examined in 15 patients (12 males and three females, 70.0?±?6.5 years) with asymptomatic carotid artery stenosis before and 3 months after CEA. Cognitive function was assessed with the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS), two subtests of the Wechsler Adult Intelligence Scale-Revised (WAIS-R 2 subtests), and the Japanese version of National Adult Reading Test (JART). The patients’ average scores were compared with the normal average by one-sample t-tests, and the before and after scores were compared with paired t-tests. Changes in each patient were calculated from difference before and after CEA using 95 % confidence intervals.

Results

Before surgery, patients showed significant cognitive decline in RBANS total scale and immediate memory, language, and attention. At 3 months after CEA, the total scale and the immediate memory were not significantly different from the normal average. The average total scale score, the immediate memory and attention, and the WAIS-R 2 subtests scores were increased after treatment. Changes in each patient were calculated from the scores before and after CEA. At 3 months after CEA, the rate of increase in RBANS scores were 60.0 % of the patients for immediate memory, 26.7 % for visuospatial/constructional, 33.3 % for language and attention, 26.7 % for delayed memory, 47.7 % for total scale and 26.7 % for WAIS-R 2 subtests. Thus, so-called asymptomatic patients exhibit mild cognitive impairment before surgery, but after CEA, patients recover normal memory abilities.

Conclusions

Our findings of mild cognitive dysfunction in asymptomatic patients suggest that they might be symptomatic after all.     

Indications for revascularization in patients with internal carotid artery stenosis

Three different strategies should be associated for ischaemic stroke prevention in patients with internal carotid artery stenosis: vascular risk factors control, anti-thrombotic agents, and carotid revascularization. Patients are selected for carotid revascularization on the basis of the presence of clinical symptoms and degree of stenosis. The optimal indication for carotid surgery is a severe recently symptomatic stenosis, since the benefits are marginal in high-grade asymptomatic stenosis, and in moderate symptomatic stenosis. Angioplasty with endoprothesis is an alternative to surgery, but it must be restricted to symptomatic stenosis either in randomized trials, or in severe stenosis in patients in whom surgery is contra-indicated.     

Management of asymptomatic carotid artery stenosis

No topic in the field of vascular surgery evokes more controversy than the management of the patient with asymptomatic carotid artery stenosis. The fact remains, however, that patients can and do develop stroke without any antecedent TIA, and there is no definite and predictable way to identify the stroke-prone group. Despite considerable differences of opinion in the literature, our evaluation and experience suggest that certain carotid lesions do in fact carry a high risk of stroke without surgical treatment. We continue to recommend prophylactic carotid endarterectomy for selected asymptomatic carotid lesions. A critical review of the published literature reveals that many series which suggest that nonoperative treatment of asymptomatic carotid disease carries a low stroke risk have in fact followed the patients for an inadequate period of time, and frequently do not adequately define the extent of carotid artery disease. It is now clear that studies which use the presence or absence of carotid bruit alone as a marker for subsequent stroke risk, show a relatively low incidence of stroke during brief follow-up periods. If more objective criteria such as non-invasive tests or angiography are used to identify hemodynamically significant stenoses, then the risk of stroke increases with the length of follow-up. The data suggest that high-grade stenoses, particularly preocclusive ones, and deep or compound ulcers have an unfavorable prognosis. The physician who treats patients with asymptomatic carotid stenosis should make every attempt to accurately quantitate the extent of disease. Non-invasive studies, digital subtraction angiography or conventional cerebral arteriography should be performed.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of contralateral disease on duplex measurements of internal carotid artery stenosis

BACKGROUND: Duplex ultrasonography is increasingly used as the sole method of imaging before carotid endarterectomy. This study investigated the measured degree of stenosis in the contralateral carotid artery before and after operation. METHODS: Duplex-derived peak systolic velocity (PSV), end-diastolic velocity (EDV) and internal carotid artery/common carotid artery (ICA/CCA) velocity ratios were measured in the contralateral unoperated ICA before 131 consecutive unilateral endarterectomies and compared with preoperative angiographic findings. Three months later duplex scans were repeated to assess whether there had been any alteration in the severity of the stenosis in the contralateral unoperated artery. RESULTS: Bilateral ICA disease (greater than 50 per cent stenosis) was present in 50 patients (38 per cent). Three months after operation, ultrasonography of the 105 unoperated, patent, contralateral arteries showed a decrease in mean(s.d.) PSV (1.21(0. 83) versus 1.07(0.69) m/s; P < 0.01) and EDV (0.41(0.29) versus 0. 35(0.24) m/s; P < 0.01). This resulted in 14 (42 per cent) of 33 patients with contralateral disease being downgraded to a less severe category of stenosis. Use of the ICA/CCA velocity ratio prevented overestimation in eight of the 14 patients, while preoperative angiography correctly classified 13 of the 14 patients. CONCLUSION: Bilateral carotid artery disease can cause overestimation of the severity of stenosis by duplex ultrasonography if absolute velocity is used as the main criterion.     

Long-term results of surgical treatment of patients with asymptomatic carotid artery stenosis

Results of treatment of 148 patients with asymptomatic carotid stenosis were analyzed in terms from 5 to 180 months. 75 (51%) patients were operated, 73 (49%)--were not operated. Non-operated asymptomatic patients with more than 90% stenosis and patients with prolonged (more than 18 mm) stenosis have the highest risk of cerebral events (4% annually and more). In long-term period (from the 70th month of follow-up) patients with the 70-90% stenosis are the group of high risk of cerebro-vascular symptoms.     

Outcome of moderate carotid artery stenosis in patients who are asymptomatic

Purpose: The incidence rate of disease progression and stroke after the diagnosis of a moderate (50% to 79%) carotid stenosis was determined by means of color-flow duplex scanning. Methods: During a 4-year period, 344 male veterans with moderate internal carotid artery stenoses, on one or both sides, were examined at regular intervals for a mean period of 25 months. Carotid color-flow scans were obtained semiannually. Clinical follow-up was performed to determine the incidence rate of amaurosis fugax, transient ischemic attacks, nonhemispheric symptoms, and strokes. Results: New neurologic symptoms developed in 75 patients (21.8%). Fifty-one (14.8%) had ipsilateral symptoms during follow-up: 18 amaurosis fugax (5.2%), 14 transient ischemic attacks (4%), 5 nonhemispheric symptoms (1.4%), and 14 strokes (4%). Twenty-four patients (6.9%) had contralateral symptoms: 20 strokes (5.8%) and 4 transient ischemic attacks (1.2%). Life-table analysis showed that the annual rate of ipsilateral neurologic events was 8.1%, and the annual rate of stroke was 2.1%. Seventy-five patients (22%) died in the follow-up period. Disease progression to 80% to 99% stenosis or occlusion occurred in 71 of 458 vessels (15.5%). The internal carotid arteries that showed evidence of disease progression had a significantly higher initial peak systolic velocity (251 vs 190 cm/s; P < .0001) and end diastolic velocity (74 vs 52 cm/s; P < 0.0001). Black patients and patients with ischemic heart disease were at a higher risk for disease progression. We could not identify any atherosclerotic risk factors that reliably predicted patients in whom future ipsilateral neurologic symptoms were more likely to develop. However, there was an increased risk of stroke associated with progression of disease. Conclusion: Patients who are asymptomatic and who have moderate carotid stenoses are at significant risk for neurologic symptoms and death, but have a relatively low incidence rate of ipsilateral events. The initial flow characteristics in the stenotic vessel are predictive of future disease progression, but they are not helpful in identifying patients in whom symptoms will develop. (J Vasc Surg 1999;29:217-27.)     

The cytokines within the carotid plaque in symptomatic patients with internal carotid artery stenosis

Occurrence of acute aortic dissection after aortic valve replacement is rare, however, it is associated with high mortality and morbidity rates. We report two Asian cases in which acute aortic dissection occurred after urgent aortic valve replacement for infective endocarditis. Successful graft replacement was carried out with preservation of the prosthetic valves in both cases. Our experience with these cases suggests that, even in urgent or emergent situations, surgical intervention for associated aortic dilatation should be considered when aortic valve replacement is performed.     

Magnetic resonance angiography of collateral compensation in asymptomatic and symptomatic internal carotid artery stenosis

OBJECTIVE: In patients with stenosis of the internal carotid artery (ICA), the presence of collateral circulatory pathways may be crucial to maintain cerebral perfusion pressure, metabolism, and function. The purpose of the present study was to determine whether patients with asymptomatic stenosis of the ICA have a better collateral ability of the circle of Willis when compared with patients with symptomatic ICA stenosis. METHOD: Magnetic resonance angiography consisting of the circle of Willis was performed in 19 patients with severe asymptomatic ICA stenosis and in 21 patients with severe symptomatic ICA stenosis prior to carotid endarterectomy and in 53 control subjects. Between group comparisons were made for function (directional flow) and anatomy (diameter). RESULTS: In patients with asymptomatic ICA stenosis, the prevalence of collateral flow via the anterior communicating artery was significantly increased (37%, 7 of 19) compared with symptomatic patients (10%, 2 of 21) and control subjects (0%; P <.001). Patients with asymptomatic ICA stenosis demonstrated the largest mean diameter of the anterior communicating artery (1.33 +/- 0.18 mm) compared with patients with symptomatic ICA stenosis (1.22 +/- 0.18 mm) and control subjects (1.06 +/- 0.10 mm, P <.05). No differences in collateral flow pattern or diameter were found for the posterior communicating artery between the groups. CONCLUSIONS: The present cross-sectional study demonstrates the importance of an adequate hemodynamic compensation via the circle of Willis in patients with ICA stenosis. Whether differences in collateral compensation can be used to select patients for CEA has yet to be determined.     

Cerebral hemodynamics in patients with carotid artery occlusion and contralateral moderate or severe internal carotid artery stenosis

OBJECT: The purpose of this study was to evaluate cerebral hemodynamics in patients suffering from occlusion of the carotid artery (CA) and contralateral CA stenosis. METHODS: Using transcranial Doppler ultrasonography, the cerebrovascular reactivity to hypercapnia in the middle cerebral arteries was evaluated by calculating the breath-holding index (BHI) of 69 symptomatic patients suffering from internal CA (ICA) occlusion and moderate or severe contralateral ICA stenosis. To evaluate which variables influenced BHIs ipsilateral to the site of ICA occlusion, a multiple stepwise linear regression analysis was performed that included the following factors: patient age, percentage of contralateral ICA stenosis, contralateral BHI, number of collateral pathways, and presence of hypertension, diabetes, smoking, and hyperlipidemia. An analysis of variance was conducted to evaluate the impact of the type of collateral vessels on the BHI. A regression analysis showed that the BHI ipsilateral to the site of ICA occlusion could be accounted for by the contralateral BHI (which was entered at the first step of the analysis, p < 0.001) and by the number of collateral pathways (which was entered at the second step, p = 0.033). Neither the degree of contralateral ICA stenosis nor the other variables could be added to improve the model. The analysis demonstrated that the absence of collateral pathways and the presence of the anterior communicating artery (ACoA) alone were associated with lower BHI values than those found in the presence of two or three collateral vessels, regardless of the presence of an anterior collateral pathway. CONCLUSIONS: On the basis of these data one can infer that the cerebral hemodynamic status of patients with occlusive disease of the CA is influenced by individual anatomical and functional characteristics. Because improvement in contralateral hemodynamics after surgical correction of an ICA stenosis can only be expected in the presence of an ACoA, the planning of strategies for influencing cerebral blood flow distal to an ICA occlusion and, in particular, the consideration of a contralateral carotid endarterectomy, should be preceded by a careful evaluation of the intracranial hemodynamic adaptive status of the patient. Particular attention should be paid to cerebrovascular reactivity and the number and type of collateral vessels that are present.