Asymptomatic carotid stenosis: a benign lesion?

Carotid, Vertebral, and Brachiocephalic Interventions

Carotid atherosclerosis most frequently manifests in the proximal internal carotid artery and the common carotid artery bifurcations. Subclavian artery atherosclerosis affects the proximal segments with a relatively higher incidence on the left and becomes clinically important in the presence of vertebrobasilar insufficiency or coronary steal. Atherosclerosis of the vertebral artery can lead to posterior circulation stroke. The authors review the major trials on carotid carotid, brachiocephalic and vertebral artery stenosis along with the various available diagnostic and interventional techniques.

Asymptomatic Carotid Stenosis and Risk of Stroke: A Natural History Study

In patients with asymptomatic carotid stenosis >70% diameter, the annual incidence of ipsilateral stroke is 3-4%. Multicentre randomised studies such as the asymptomatic carotid atherosclerosis study (ACAS) in the U.S.A. and the ACST in Europe aim to answer the question whether carotid endarterectomy can reduce the incidence of stroke in such patients. If the surgical risk is too close to benefit or if a high proportion of patients not at risk of stroke are entered into the ACAS or ACST studies, the latter may fail to demonstrate the benefit of carotid endarterectomy (CE). The need to identify a high risk stroke group (ipsilateral stroke >7% per annum) with randomisation of this group to a subsequent study will then become apparent. If the ACAS and ACST studies indicate that the risk of stroke is reduced by 50% (i.e., from 4 to 2%), it has been calculated that the cost of preventing one stroke will be 1.2 million US dollars because of the large number of operations required. It will still be necessary to identify a high-risk group or, better, a low-risk group in order to spare many patients unnecessary operation. A multicentre, natural history study has been set up under the auspices of the International Union of Angiology and monitored from St Mary's Hospital Medical School in London with over 50 centres taking part. Patients with asymptomatic carotid stenosis 50-70% and 70-90% are entered in a ratio of 1 to 2, a number of noninvasive tests are performed, and the patients are followed for 5 years. The tests performed are (a) Grading the degree of internal carotid stenosis using duplex scanning; (b) grading the opposite side; (c) plaque characterisation; (d) presence of ultrasonic ulceration; (e) plaque thickness (mm); (f) cerebral reactivity to CO2using velocity of internal carotid artery and (optional) middle cerebral artery ; (g) CT brain scan for the presence of silent infarction ; (h) intima-media thickness of the common carotid; and (i) identification of conventional risk factors: hypertension, hypercholeterolaemia, smoking, family history, diabetes. The key end points are stroke (including fatal stroke) and ipsilateral stroke. Patients who die from cardiovascular death other than stroke or noncardiovascular death and patients who develop hemispheric transient ischaemic attacks followed by CE are considered to have reached an exit end point. Because this is a natural history study, the clinician in charge of all patients is free to treat them in any way considered appropriate. Patients in the Medical Limb of the ACST study may be entered into the Natural History (ACSRS) study.

What Should We Do with Asymptomatic Carotid Stenosis?

The benefit of prophylactic carotid endarterectomy (CEA) for patients with asymptomatic severe carotid stenosis in the major randomised surgical studies was small, expensive and may now be absorbed by improvements in best practice medical intervention. Strategies to identify patients with high stroke risk are needed. If surgical intervention is to be considered the complication rates of individual surgeons should be available. Clinicians will differ in their interpretation of the same published data. Maintaining professional relationships with clinicians from different disciplines often involves compromise. As such, the management of a patient will, in part, depend on what kind of specialist the patient is referred to. The clinician's discussion with patients about this complex issue must be flexible to accommodate differing patient expectations. Ideally, patients prepared to undergo surgical procedures should be monitored in a trial setting or as part of an audited review process to increase our understanding of current practice outcomes.

Medical (Nonsurgical) Intervention Alone Is Now Best for Prevention of Stroke Associated With Asymptomatic Severe Carotid Stenosis

Significant advances in vascular disease medical intervention since large randomized trials for asymptomatic severe carotid stenosis were conducted (1983–2003) have prompted doubt over current expectations of a surgical benefit. In this systematic review and analysis of published data it was found that rates of ipsilateral and any-territory stroke (+/−TIA), with medical intervention alone, have fallen significantly since the mid-1980s, with recent estimates overlapping those of operated patients in randomized trials. However, current medical intervention alone was estimated at least 3 to 8 times more cost-effective. In conclusion, current vascular disease medical intervention alone is now best for stroke prevention associated with asymptomatic severe carotid stenosis given this new evidence, other cardiovascular benefits, and because high-risk patients who benefit from additional carotid surgery or angioplasty/stenting cannot be identified.

Asymptomatic Carotid Artery Stenosis: Past, Present and Future

BACKGROUND

The role of carotid endarterectomy (CEA) for asymptomatic carotid artery stenosis (aCAS) remains a matter of debate. It seems that not only the degree of stenosis, but also other factors have to be taken in account to improve patient selection and increase the benefit of CEA for aCAS.

METHODS AND RESULTS

The literature pertaining aCAS was reviewed in order to describe the natural history, risk of stroke and benefit of CEA for patients with aCAS in regard to several factors.

CONCLUSION

The benefit of CEA for aCAS is low. Current factors influencing the indication for CEA are severity of stenosis, age, contralateral disease, stenosis progression to >80%, gender, concomitant operations and life expectancy. To improve patient selection investigations will concentrate on plaque characteristics and instability and cerebral hemodynamics and metabolism.

B-mode ultrasonographic characterization of carotid atherosclerotic plaques in symptomatic and asymptomatic patients

OBJECTIVE

To identify features on B-mode ultrasonography (US) prevalent in symptomatic plaques and correlate these findings with histopathologic markers of plaque instability.

METHODS

Carotid endarterectomy (CEA) plaques from symptomatic and asymptomatic patients with critical stenoses (>70%) were qualitatively assessed using preoperative B-mode US for echolucency and calcific acoustic shadowing. US echolucency was quantitated ex vivo using computerized techniques for gray-scale median (GSM) analysis. Histopathologic correlates for US plaque echolucency (percentage of necrotic core area) and acoustic shadowing (percentage of calcification area) were determined.

RESULTS

Fifty CEA plaques were collected from 48 patients (46 unilateral and two bilateral); 26 of these plaques were from symptomatic patients. Age, degree of stenosis, and atherosclerotic risk factors were similar for the symptomatic and asymptomatic patients. Using preoperative B-mode US, 58%, 35%, and 7% of symptomatic plaques and 18%, 41%, and 41% of asymptomatic plaques were found to be echolucent, echogenic, and calcific, respectively (P < .05). Using ex-vivo B-mode US and GSM analysis, symptomatic plaques were more echolucent (41 +/- 19) than asymptomatic plaques (60 +/- 13), P < .03. A strong inverse correlation was found between the percent plaque necrotic area core and GSM (R = -0.9, P < .001). Percentage of calcification area in plaques with acoustic shadowing was 66% and only 27% in those without acoustic shadowing (P < .05).

CONCLUSIONS

Using B-mode US, symptomatic plaques are more echolucent and less calcified than asymptomatic plaques and are associated with a greater degree of histopathologic plaque necrosis. Such features are indicative of plaque instability and should be considered in the decision-making algorithm when selecting patients with high-grade asymptomatic carotid stenosis for intervention.

Evaluation and management of asymptomatic carotid artery stenosis

Internal carotid artery stenosis (ICAS) is responsible for approximately 30% of ischemic strokes. Internal carotid artery stenosis of greater than 50% is present in about 4% to 8% of the population aged 50 to 79 years. Natural history studies and clinical trials have shown a small increase in stroke risk in patients with increasing degrees of ICAS, especially in those with greater than 80% reduction in carotid artery diameter. Randomized, prospective multicenter trials have revealed the superiority of carotid endarterectomy (CEA) over medical therapy in recently symptomatic patients with severe ICAS. However, the evidence from several randomized controlled trials of CEA in asymptomatic patients does not support the use of CEA in most of these patients; also, the role of noninvasive screening in this patient population remains uncertain and controversial. Furthermore, there is considerable uncertainty about whether the statistical benefit of avoiding a nondisabling stroke is worth the overall cost and risk of the procedure. Clinicians continue to struggle with treatment decisions for patients with asymptomatic ICAS. Carotid endarterectomy for asymptomatic ICAS should be considered only for medically stable patients with 80% or greater stenosis who are expected to live at least 5 years, and only in centers with surgeons who have a demonstrated low (<3%) perioperative complication rate. We outline the prevalence and natural history of ICAS, the evidence for CEA in patients with asymptomatic ICAS, the roles of screening and monitoring for ICAS, the methods of evaluating ICAS, and the implications for practicing clinicians.

Thromboembolic events after aortic valve replacement in elderly patients with a Carpentier-Edwards Perimount pericardial bioprosthesis

OBJECTIVES

Thromboembolic events after aortic valve replacement with a bioprosthesis were the most frequently occurring complications in elderly patients. Whether this was valve related or dependent on other factors needed further exploration.

METHODS

Five hundred patients with a median age of 73 years were followed retrospectively after aortic valve replacement with a pericardial prosthesis for occurrence of thromboembolism. Of these, 348 also underwent coronary artery bypass grafting. Twenty-five factors were investigated for their potential effect by using univariate and multivariate analysis.

RESULTS

Univariate analysis revealed 6 significant factors: preoperative endocarditis (P =.0001), preoperative cerebrovascular accident (P =.002), use of postoperative warfarin sodium (Coumadin, DuPont Merck; P =.006), arterial hypertension (P =.023), size of valve prosthesis of 27 mm or larger (P =.023), and hospital thromboembolism (P =.040). There was a trend toward increased fatal thromboembolism in patients without medication. With a multivariate analysis, 4 factors remained significant: preoperative cerebrovascular accident (risk ratio, 4.8; P =.0016), warfarin sodium (risk ratio, 3.0; P =.0028), preoperative endocarditis (risk ratio, 5.6; P =.006), and hospital thromboembolism (risk ratio, 6.1; P =.016). Hypertension had a borderline effect. Age, sex, diabetes, 4 coronary artery factors, 3 other valvular factors, atrial fibrillation, and carotid artery disease had no significant effect.

CONCLUSIONS

Some emboli seemed triggered by the valve prosthesis. A proper anticoagulant protocol but also a treatment of hypertension is important in the prevention of thromboembolism after aortic valve replacement with a bioprosthesis. We did not find a significant role of atrial fibrillation and carotid artery disease.

Natural history of carotid artery stenosis contralateral to endarterectomy: results from two randomized prospective trials

PURPOSE

A few nonrandomized studies have reported the natural history of carotid artery stenosis (CAS) contralateral to carotid endarterectomy (CEA). This study analyzed this condition with data from two randomized prospective trials.

METHODS

The contralateral carotid arteries in 534 patients from two randomized trials that compared CEA with primary closure versus patching were followed up clinically and with duplex ultrasound scanning at 1 month and then every 6 months. CAS was classified as less than 50%, 50% to 79%, 80% to 99%, and occlusion. Late contralateral CEA was performed to treat significant CAS. Progression was defined as progress to a higher category of stenosis. Kaplan-Meier life table analysis was used to estimate freedom from progression of CAS. The correlation of risk factors and CAS progression was also analyzed.

RESULTS

Of 534 patients, 61 had initial contralateral CEA and 53 had contralateral occlusion. Overall, CAS progressed in 109 of 420 patients (26%) at mean follow-up of 41 months. Progression of CAS was noted in 5 of 162 patients (3%) with baseline normal carotid arteries. CAS progressed in 56 of 157 patients (36%) with less than 50% stenosis versus 45 of 95 patients (47%) with 50% to 79% stenosis (P =.003). Median time to progression was 24 months for less than 50% CAS, and 12 months for 50% to 79% CAS (P =.035). At 1, 2, 3, 4, and 5 years, freedom from disease progression in patients with baseline CAS <50% was 95%, 78%, 69%, 61%, 48%, respectively, and in patients with 50% to 79% CAS was 75%, 61%, 51%, 43%, and 33%, respectively (P =.003). Freedom from progression in patients with baseline normal carotid arteries at 1 through 5 years was 99%, 98%, 96%, 96%, and 94%, respectively. Late neurologic events referable to the CCA were infrequent (28 of 420 [6.7%] in the entire series; 28 of 258 [10.9%] patients with contralateral CAS), and included 10 strokes (2.4%) and 18 transient ischemic attacks (4.3%). However, late contralateral CEA was performed in 62 patients (62 of 420 [15%] in the entire series; 62 of 258 [24%] patients with contralateral CAS). Survival rates were 96%, 92%, 90%, 87%, and 82%, respectively, at 1 through 5 years.

CONCLUSIONS

Progression of CCA stenosis was noted in a significant number of patients with baseline contralateral CAS. Serial clinical studies and duplex ultrasound scanning every 6 to 12 months in patients with 50% to 79% CAS, and every 12 to 24 months in patients with 50% or less CAS is adequate.

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.

Internal carotid artery stenosis: rate of progression

OBJECTIVES

to assess the incidence and the rate of progression of internal carotid artery (ICA) stenosis and to determine the related risk factors.

DESIGN

open prospective study.

MATERIALS AND METHODS

between 1988-1997, 442 carotid arteries with various degrees of stenosis were followed using colour duplex ultrasonography every 6 months. Of these arteries, 290 (66%) were asymptomatic, 62 (14%) had caused transient ischaemic attack and 90 (20%) a stroke. In 145 cases (33%), there was concomitant coronary artery disease (CAD), in 134 (30%) diabetes mellitus, in 248 (56%) hypertension, in 139 (31%) hypercholesterolaemia and in 370 (84%) history of smoking. Of the plaques, 44 (10%) were uniformly echolucent, 19 (4%) haemorrhagic, 136 (31%) predominantly echolucent, 146 (33%) predominantly echogenic and 97 (22%) uniformly echogenic.

RESULTS

significant progression of stenosis occurred in 82 cases (19%). The mean progression rate in these cases was 15% annually (range: 5-50%). There was no statistically significant correlation between the progression of the ICA stenosis and initial neurological status, age, gender, diabetes mellitus, hypertension, hypercholesterolaemia and smoking habit. Stenosis progression was correlated only with CAD and the ultrasonographic characteristics of the plaques. Patients with CAD as well as those with uniformly echolucent plaques presented a higher incidence and rate of stenosis progression (p<0.05).

CONCLUSIONS

progression of internal carotid artery stenosis occurred in 19% of cases. The mean progression rate in these patients was 15% annually and was correlated with CAD and the ultrasonographic characteristics of the plaque.

Progression of asymptomatic carotid stenosis: a natural history study in 1004 patients

PURPOSE

The purpose of this study was to delineate the natural history of the progression of asymptomatic carotid stenosis.

METHODS

In a 10-year period, 1701 carotid arteries in 1004 patients who were asymptomatic were studied with serial duplex scans (mean follow-up period, 28 months; mean number of scans, 2.9/patient). At each visit, stenoses of the internal carotid artery (ICA) and the external carotid artery (ECA) were categorized as none (0 to 14%), mild (15% to 49%), moderate (50% to 79%), severe (80% to 99%), preocclusive, or occluded. Progression was defined as an increase in ICA stenosis to >/=50% for carotid arteries with a baseline of <50% or as an increase to a higher category of stenosis if the baseline stenosis was >/=50%. The Cox proportional hazards model was used for data analysis.

RESULTS

The risk of progression of ICA stenosis increased steadily with time (annualized risk of progression, 9.3%). With multivariate modeling, the four most important variables that affected the progression (P <.02) were baseline ipsilateral ICA stenosis >/=50% (relative risk [RR], 3.34), baseline ipsilateral ECA stenosis >/=50% (RR, 1.51), baseline contralateral ICA stenosis >/=50% (RR, 1.41), and systolic pressure more than 160 mm Hg (RR, 1. 37). Ipsilateral neurologic ischemic events (stroke/transient ischemic attack) occurred in association with 14.0% of the carotid arteries that were studied. The progression of ICA stenosis correlated with these events (P <.001), but baseline ICA stenosis was not a significant predictor.

CONCLUSION

In contrast to recently published studies, we found that the risk of progression of carotid stenosis is substantial and increases steadily with time. Baseline ICA stenosis was the most important predictor of the progression, but baseline ECA stenosis also was identified as an important independent predictor. Contralateral ICA stenosis and systolic hypertension were additional significant predictors. We found further that the progression of ICA stenosis correlated with ischemic neurologic events but not baseline stenosis. The data provide justification for the use of serial duplex scans to follow carotid stenosis and suggest that different follow-up intervals may be appropriate for different patient subgroups.

Cost-effectiveness of carotid endarterectomy in asymptomatic patients

PURPOSE

The purpose of this study was to determine the cost-effectiveness of carotid endarterectomy for treating asymptomatic patients with > or = 60% internal carotid stenosis, based on outcomes reported in the Asymptomatic Carotid Atherosclerosis Study (ACAS).

METHODS

A cost-effectiveness analysis was performed using a Markov decision model in which the probabilities for base-case analysis (average age, 67 years; 66% male; perioperative stroke plus death rate, 2.3%; ipsilateral stroke rate during medical management, 2.3% per year) were based on ACAS. The model assumed that patients who had TIAs or minor strokes during medical management crossed over to surgical treatment, and used the NASCET data to model the outcome of these now-symptomatic patients. Average cost of surgery ($8500), major stroke ($34,000 plus $18,000 per year), and other costs were based on local cost determinations plus a review of the published literature. Cost-effectiveness was calculated as the incremental cost of surgery per quality-adjusted life year (QALY) saved when compared with medical treatment, discounting at 5% per year. Sensitivity analysis was performed to determine the impact of key variables on cost-effectiveness.

RESULTS

In the base-case analysis, surgical treatment improved quality-adjusted life expectancy from 7.87 to 8.12 QALYs, at an incremental lifetime cost of $2041. This yielded an incremental cost-effectiveness ratio of $8,000 per QALY saved by surgical compared with medical treatment. The high cost of care after major stroke during medical management largely offset the initial cost of endarterectomy in the surgical group. Furthermore, 26% of medically managed patients eventually underwent endarterectomy because of symptom development, which also decreased the cost differential. Sensitivity analysis demonstrated that the relative cost of surgical treatment increased substantially with increasing age, increasing perioperative stroke rate, and decreasing stroke rate during medical management.

CONCLUSION

For the typical asymptomatic patient in ACAS with > or = 60% carotid stenosis, our results indicate that carotid endarterectomy is cost-effective when compared with other commonly accepted health care practices. Surgery does not appear cost-effective in very elderly patients, in settings where the operative stroke risk is high, or in patients with very low stroke risk without surgery.

Carotid endarterectomy contralateral to an occluded carotid artery: a retrospective case-control study

OBJECTIVES

To analyse whether contralateral occlusion represents an additional perioperative risk factor in carotid endarterectomy (CEA), and whether long-term survival after surgery in patients with contralateral occlusion differs from that of patients without.

DESIGN

Retrospective clinical study.

SETTING

Vascular Surgery Unit, Department of Surgery, University of Perugia, Perugia, Italy.

MATERIALS

Fifty-five patients with carotid stenosis and contralateral occlusion undergoing CEA (Group 1) were compared with 110 patients (Group II), without contralateral occlusion selected from a cohort of 367 patients with a patent contralateral artery, matched for gender, age and ipsilateral symptoms.

CHIEF OUTCOME MEASURES

Perioperative stroke/death rate at 30 days and minor complications in Group I vs. Group II over a mean follow-up of 38 months.

MAIN RESULTS

The perioperative stroke/death rate at 30 days was 0% in Group I and 2.7% in Group II (p = 0.6) while minor complications amounted to 11% in Group I and 5% in Group II (p = 0.2). Survival rates of patients free from stroke, using Kaplan Meier curves, were 79.4% in Group I and 83.3% in Group II (p = 0.4); stroke free rates were 92.8% and 94.3% in Groups I and II, respectively. The incidence of late stroke, fatal or not, in patients who had undergone CEA with contralateral obstruction was the same as in similarly operated patients without contralateral obstruction (7% vs. 6%). However, the incidence of late vascular death, exemplified by a crude rate of 14% vs. 6% (p = 0.1; O.R. = 2.50; C.I. = 0.77-8.25) was greater in patients with contralateral occlusion.

CONCLUSIONS

In this study, CEA in patients with contralateral occlusion was not associated with an increased perioperative morbidity/mortality rate. The higher incidence of vascular death in the late follow-up of patients with contralateral carotid occlusion, although not statistically significant, could indicate the presence of more severe systemic vascular disease.

Clinical outcome in patients with mild and moderate carotid artery stenosis

PURPOSE

The natural history of incidentally discovered asymptomatic mild (< 50%) and moderate (50% to 79%) carotid artery stenosis is not known. The carotid artery duplex ultrasound surveillance program at the University of Washington Department of Vascular Surgery has serially evaluated patients with carotid artery disease for more than a decade and provides data on the progress and management of this disease.

METHODS

Patients with asymptomatic carotid artery bruits who had carotid artery disease causing less than 80% lumen diameter narrowing at their initial visit were identified. At each return visit (6 months, 1 year, and annually thereafter) a clinical questionnaire was completed, and bilateral carotid artery duplex sonography was performed.

RESULTS

Two hundred thirty-two patients (136 men and 96 women) were monitored for up to 10 years with sufficient data for a 7-year life-table analysis. Progression in the degree of stenosis was noted in 23% of patients during follow-up, and nearly half of these progressed to severe stenosis (80% to 99%) or occlusion. The risk of progression to severe stenosis and occlusion was significantly greater for those patients with moderate initial stenosis than mild initial stenosis (p < 0.01). The cumulative stroke risk for patients with mild initial stenosis (6%) was half of that for patients with moderate initial stenosis (11%) after 7 years. Carotid endarterectomy was performed in 27 patients during follow-up; in 13 the indication was an event ipsilateral to the stenosis, and in 14 there was asymptomatic progression to high-grade stenosis.

CONCLUSIONS

Regular monitoring of mild to moderate carotid artery stenosis shows how these lesions progress over time, permitting a realistic appraisal of their potential for producing an ischemic cerebrovascular event.

Symptoms, stenosis and carotid plaque morphology. Is plaque morphology relevant?

OBJECTIVES

To study the relationship between carotid plaque morphology and the degree of stenosis on Duplex ultrasonography and symptoms.

DESIGN

Prospective open clinical study.

METHODS

2,590 patients with 5,180 carotid arteries were scanned, 4,560 were initially analysed in terms of symptoms but 54 were excluded, leaving a total of 4,258.

RESULTS

Localising symptoms were present with respect to 1,342 vessels (29.4%). Two-thirds of symptomatic patients had normal carotid arteries. Tight stenosis (80-99%) was more likely to be associated with symptoms than low-grade (20-79%) stenosis (chi 2 = 28.0, p < 0.0001). Plaque type was identified in 1,558 bifurcations (36.6%). Heterogeneous type I & II plaques accounted for one third of plaques. There was a relationship between plaque morphology and degree of stenosis. At < 20% stenosis only 4.4% of plaques were heterogeneous whereas at 80-99% stenosis 84.5% of plaques were heterogeneous. Amaurosis fugax was the only symptom that had any association with a particular plaque morphology. Seventy-two percent of plaques associated with this symptom were heterogeneous in nature.

CONCLUSIONS

Carotid plaque morphology and degree of internal carotid stenosis are mutually dependent factors and both reflect the severity of atherosclerotic disease. Plaque morphology does not add to the sensitivity of stenosis in predicting the presence of symptoms.

Characterization of symptomatic and asymptomatic carotid plaques using high-resolution real-time ultrasonography

High-resolution ultrasonography was used to classify carotid plaques into five different types in 72 patients with symptoms and in 49 without, and with stenosis of the origin of the internal carotid artery > 70 per cent. There were 72 plaques in the symptomatic group and 75 in the asymptomatic group. Type 1 plaques were uniformly echolucent, type 2 predominantly echolucent, type 3 predominantly echogenic, type 4 uniformly echogenic and type 5 consisted of plaques that could not be classified owing to heavy calcification and acoustic shadows. Type 1 plaque was found in 90 per cent of patients with symptoms and in 10 per cent of those without, type 2 plaque was found in 53 and 47 per cent, type 3 in 34 and 66 per cent, and type 4 in 5 and 95 per cent, respectively. The preponderance of echolucent plaques in symptomatic patients with stenosis > 70 per cent supports the hypothesis that this type of plaque is unstable and tends to embolize. In contrast, in patients without symptoms there is preponderance of echogenic plaques.

Natural history of patients with unoperated atherosclerotic carotid artery disease--results from a retrospective study

The natural history of carotid artery disease was studied in a retrospective study of 609 angiograms performed during 1969-1979 on patients who had subsequently not been operated on. The indication for angiography differed, but was aimed at clarifying suspected cerebrovascular events. 578 patients could be followed-up after a median time of 10.4 years (0-22). The median survival time after angiography was 9.7 years for the 355 men and 12.8 years for the 223 women (p = 0.0099). Internal carotid stenosis of > 50% was seen in 9.0% (bilaterally in 2.2%), a stenosis > 75% in 4.5% (bilaterally in 0.9%) and occlusion in 9% (bilaterally in 0.7%). Ulceration was present in 10.7% (bilaterally in 1.6%). 26.5% of the patients had a cerebrovascular event during follow-up, of which 31.4% had transient ischaemic attack or amaurosis fugax. Survival was not influenced by the degree of stenosis, but presence of arteriosclerotic carotid artery disease significantly reduced the median survival time from 11 to 3 years. The main cause of death for men was myocardial infarction (27.7%) and for women a cerebrovascular event (27.8%), a significant difference. From this study, in selected patients it can be concluded that the annual frequency of cerebrovascular events was low, approaching frequencies reported in asymptomatic patients. The cause of death differed between men and women, with more cardiac deaths among men and more cerebrovascular deaths among women.