Asymptomatic carotid bruit and stenosis: a reappraisal

Effectiveness of carotid endarterectomy for asymptomatic carotid stenosis: design of a clinical trial. Mayo Asymptomatic Carotid Endarterectomy Study Group

A clinical trial, as described in this report, has been designed to compare the effects of carotid endarterectomy and medical treatment with aspirin for prevention of transient ischemic attack, reversible ischemic neurologic deficit, and ischemic stroke in patients with asymptomatic pressure-significant carotid stenosis. A prospective randomized controlled trial design is being used, and selection of patients with asymptomatic pressure-significant carotid stenosis is based on the results of ocular pneumoplethysmography and either duplex ultrasound scanning or digital subtraction angiography. Patients are randomized to either surgical (carotid endarterectomy) or medical (aspirin, 80 mg/day) treatment, and follow-up assessment is accomplished by return visits and patient questionnaires. A total of 945 patient-years of follow-up will accumulated for each of the medical and surgical groups.

Natural history of nonoperated, significant carotid stenosis

One-hundred sixty-seven patients with 190 carotid arteries (109 asymptomatic) demonstrating 50-99% stenosis by arteriography (80), duplex scanning, or other noninvasive techniques were followed from 1-84 months (mean 24.2) for evidence of brain infarct, transient ischemic attacks, or vertebrobasilar symptoms. Thirty-nine arteries (20.5%) were symptomatic at last follow-up, including 13 (6.8%) producing ipsilateral strokes. Twenty-eight sides underwent carotid endarterectomy, 16 for symptomatic lesions at a mean interval of 14.5 months after the initial diagnostic study, with no neurologic deficit. Twenty-seven patients (16.2%) died, eight from stroke (30%), and 12 from cardiac causes (44%). In initially symptomatic sides, the incidence of any subsequent neurologic event (28.7%) or stroke/transient ischemic attack (25%) was significantly greater than in asymptomatic arteries (14.6% and 12%, respectively) (p less than .05). Carotid arteries with greater than 80% stenosis by arteriography and duplex scanning had a 46% incidence of further symptoms and 41.6% stroke/transient ischemic attack rate compared to 19.6% and 15%, respectively, in arteries with less than 80% stenosis (p less than .01). Cumulative life table analysis at 12, 24 and 36 months showed greater than 80% stenosed arteries to have stroke/transient ischemic attack free rates of 69%, 50.5%, and 21.6% compared to 91%, 83.7%, and 76% for arteries with less than 80% stenosis (p less than .05). At a mean follow-up of over two years, nonoperated carotid stenosis (greater than 50%) carries a 20.5% risk of neurologic symptoms and a 6.8% risk of stroke, 61.5% of strokes being fatal. Symptomatic carotid stenosis had a significantly greater incidence of ensuing neurologic events than asymptomatic arteries.(ABSTRACT TRUNCATED AT 250 WORDS)

Noninvasive testing of cerebral perfusion reserve prior to coronary artery bypass graft surgery

Cerebral perfusion reserve testing using fluorine-18-fluoromethane and positron emission tomographic brain scanning to define cerebral blood flow abnormalities was performed in 5 patients being considered for combined coronary and carotid reconstructive surgery. Blood flow testing during normocapnia and following hypercapnia was utilized in these patients to determine the hemodynamic significance of known extracranial carotid artery occlusive lesions. Reserve diminution in 2 of these patients prompted combined surgery, whereas normal reserve values in the other 3 prompted coronary surgery alone. Results obtained in this preliminary series show how preoperative noninvasive testing of cerebral perfusion reserve adds to the diagnostic evaluation of patients with widespread vascular disease.

Computed tomography in reversible ischaemic attacks: clinical and prognostic correlations in a prospective study

Two hundred and nineteen patients admitted with reversible atherothrombotic ischaemic attacks were prospectively evaluated by computed tomography. Of these patients, 122 were diagnosed as suffering from transient ischaemic attacks, 58 from reversible ischaemic neurological deficits and 39 from reversible ischaemic neurological deficits with incomplete resolution. In 133 cases the ischaemic event affected the carotid system, in 63 the vertebrobasilar system and in 23 cases the system could not be determined. Brain infarctions were observed in 64 patients (29.2%), cerebral atrophy in 96 (44.4%) and dilatation of a ventricle in 17 (7.8%). The frequency of brain infarction was related to the duration of the neurological deficit, being 20.5% in those with transient ischaemic attacks, 37.9% in those with reversible ischaemic neurological deficits and 43.6% in patients with reversible ischaemic neurological deficits with incomplete resolution (P = 0.005). Ischaemic lesions were closely correlated with abnormalities on supra-aortic trunk angiography or Doppler ultrasonography. During an average follow-up period of 21 months, a higher percentage of recurrence was found in those patients with CT infarctions, but the difference was not significant.

The relationship between carotid plaque composition and neurologic symptoms

Variations in plaque composition, particularly an increased lipid concentration, could make carotid plaques unstable and prone to embolization. To investigate this hypothesis, 35 carotid bifurcation plaques from 31 patients undergoing carotid endarterectomy (20 symptomatic, 11 asymptomatic) were prospectively analyzed. Plaque total lipid, cholesterol, collagen, and Ca2+ content were determined, and the plaque collagen was fractionated into pepsin-soluble collagen (PSC) (indicative of less crosslinked, more recently synthesized collagen) and pepsin-insoluble collagen. Preoperative serum lipid and plasma lipoprotein levels were also obtained in all patients. Results revealed that plaques removed from symptomatic patients contained significantly more total lipid and cholesterol (P less than 0.001) than those removed from asymptomatic patients. There was also an increased amount of pepsin-soluble collagen in symptomatic plaques, potentially indicating increased metabolic activity (P less than 0.05). In addition, mean plasma low-density lipoprotein cholesterol was higher in symptomatic patients than in asymptomatic patients (P less than 0.05). Since lipid-laden plaques can potentially be identified by B-mode ultrasound, it may be important to remove these plaques in asymptomatic patients or, alternatively, to attempt to lower the plaque cholesterol by lipid-lowering maneuvers.

Carotid endarterectomy without indwelling shunts and intraoperative electrophysiologic monitoring

Although carotid endarterectomy is a common surgical procedure in North America, controversies exist regarding the type of anesthesia, the use of indwelling shunts and the need for intraoperative cerebral monitoring. We present a prospective study of 100 carotid endarterectomies performed over a three year period by a single surgeon without the use of indwelling shunts, patch grafts, or EEG monitoring. The combined stroke and mortality rate was 1%. Our results confirm those of other authors; that indwelling shunts and EEG monitoring are not absolutely essential for a satisfactory outcome in carotid endarterectomies.

Morbidity and mortality of carotid endarterectomy. A literature review of the results reported in the last 10 years

A review of the mortality and morbidity of carotid endarterectomy reported during the last 10 years was made and compared to the risk of carotid stenosis managed by the best medical treatment. For comparison, the patients were classified in asymptomatic patients (grade I), patients with transient ischaemic attacks (grade II), patients with ischaemic neurological deficits operated on acutely (grade III) and into patients with no or incomplete recovery 4-6 weeks after the stroke (grade IV). Based on the results of this literature review, only patients in grade II seem to benefit from carotid endarterectomy.

Complications following carotid endarterectomy for all indications: report of 192 operations

The complications (stroke, myocardial infarction, and death) with 192 endarterectomies performed on 162 patients were evaluated and categorized according to the presenting syndrome: asymptomatic bruit, transient ischemic attack, stroke, stroke in progress, and posterior fossa ischemia. Each group's complication rate was then evaluated over several postoperative periods (0.5 hour to 30 days) and compared with rates in comparable studies. Overall mortality for the entire series was 0.5%. This study points out the need to separate patients having undergone endarterectomy into presenting groups before comparing with other studies having similar postoperative observations.

Noninvasive assessment of stroke risk in asymptomatic and nonhemispheric patients with suspected carotid disease. Five-year follow-up of 294 unoperated and 81 operated patients

Based on the assumption that greater than or equal to 50% stenosis of the internal carotid artery increases stroke risk, noninvasive tests are being used to screen patients for prophylactic carotid endarterectomy. To assess the validity of this concept, 104 asymptomatic and 190 nonhemispheric patients referred for cerebrovascular tests were reviewed after 5 years. Carotid stenosis greater than or equal to 50% predicted a 15% stroke incidence at 2 years compared to a 3% incidence with 1-49% stenosis (p less than or equal to 0.05). Five-year cumulative stroke incidence was 21% with greater than 50% stenosis, 14% with 1-49% stenosis (NS), and 9% with 0% stenosis (p less than 0.05). Stenosis greater than or equal to 50% predicted increased cardiac mortality (p less than 0.025). Hypertensive patients, greater than 70 years, with greater than or equal to 50% stenosis had a 37% incidence of stroke; normotensive patients, less than 70 years, with or without stenosis, had few strokes. In patients with greater than or equal to 50% disease, surgery reduced the 5-year stroke rate from 21 to 8% (p less than 0.05), mitigated the effects of age and hypertension, and improved survival. Noninvasive test results must be considered in conjunction with age and hypertension in predicting stroke risk.

Prevalence of atherosclerotic lesions at the carotid bifurcation in patients with asymptomatic bruits: an echo-Doppler (duplex) study

The prevalence of atherosclerotic lesions at the carotid bifurcation with asymptomatic Meck bruits has been evaluated in 71 patients, 42 males, ages ranging from 19 to 84 yrs, referred to our non-invasive vascular laboratory for an echo-Doppler (duplex) scan, associated with spectral analysis (Mark V ATL with Flow analyzer 459). Fifty-nine patients had mid-neck or high-neck bruits (30 bilateral), 12 had low-neck bruits (4 bilateral). The internal carotid arteries were classified as normal, minimal stenosis (diameter reduction 20%), moderate stenosis (20-49%), severe stenosis greater than or equal to 50%), total occlusion. Twenty-four of the internal carotid arteries homolateral to a mid- or high-neck bruit were normal, 84% had stenosis of various degree (16% severe), 2% were occluded. Stenoses of various degree were also present on the contralateral side of the bruit. No lesions above a diameter reduction of 20% were present in the internal carotid arteries corresponding to a low-neck bruit. The echo-Doppler (duplex) system, being capable of spanning the whole spectrum of the internal carotid occlusive disease, allows us to limit the number of the invasive diagnostic procedures in asymptomatic patients.

[Spontaneous clinical course of asymptomatic vascular processes of the extracranial cerebral arteries. Further results of a long-term prospective study]

The natural history of a prospectively selected group of neurologically asymptomatic patients with extracranial arterial disease (EAD) was studied. 35 of 184 patients died over a period of follow-up of four years (mean = 21 months). Only four of them had a stroke, while coronary artery disease was the far more common cause of death (n = 19). Among those patients still alive 12 reported transient ischaemic attacks, two a stroke, and 116 remained asymptomatic--only two patients could not be followed. Thus by life-table analysis, the cumulative stroke rate was only 6%, irrespective of death or survival, about the same as the average risk of death in a normal population (5%). However, the probability of EAD progression was 88% as revealed by subsequent continuous-wave Doppler analysis of both the carotid and vertebral arteries in the neck. Neither the degree of initial EAD nor its progression during follow-up were found to represent significant indicators of the patient's cerebrovascular risk. Since the majority of symptomatic patients did not proceed to frank strokes but presented with TIAs, prophylactic surgical treatment may reasonably be delayed.

Noninvasive carotid testing in threatened stroke. 2. Predictive performance

The various noninvasive tests have different inherent limitations, and expectations of the tests must take these limitations into account. The tests' main value lies in cases where indications do not clearly favor surgical management nor do they contraindicate it for prophylaxis of threatened stroke. In such cases, test results may help sway the clinician's decision. Intravenous digital subtraction angiography may affect the application of the traditional noninvasive technologies in the future.