Ten-year risk of stroke in patients with previous cerebral infarction and the impact of carotid surgery in the Asymptomatic Carotid Surgery Trial.

BACKGROUND: Silent brain infarcts are common in patients at increased risk of stroke and are associated with a poor prognosis. In patients with asymptomatic carotid stenosis, similar adverse associations were claimed, but the impact of previous infarction or symptoms on the beneficial effects of carotid endarterectomy is not clear. Our aim was to evaluate the impact of prior cerebral infarction in patients enrolled in the Asymptomatic Carotid Surgery Trial, a large trial with 10-year follow-up in which participants whose carotid stenosis had not caused symptoms for at least six months were randomly allocated either immediate or deferred carotid endarterectomy. METHODS: The first Asymptomatic Carotid Surgery Trial included 3120 patients. Of these, 2333 patients with baseline brain imaging were identified and divided into two groups irrespective of treatment assignment, 1331 with evidence of previous cerebral infarction, defined as a history of ischemic stroke or transient ischemic attack > 6 months prior to randomization or radiological evidence of an asymptomatic infarct (group 1) and 1002 with normal imaging and no prior stroke or transient ischemic attack (group 2). Stroke and vascular deaths were compared during follow-up, and the impact of carotid endarterectomy was observed in both groups. RESULTS: Baseline characteristics of patients with and without baseline brain imaging were broadly similar. Of those included in the present report, male gender and hypertension were more common in group 1, while mean ipsilateral stenosis was slightly greater in group 2. At 10 years follow-up, stroke was more common among participants with cerebral infarction before randomization (absolute risk increase 5.8% (1.8-9.8), p = 0.004), and the risk of stroke and vascular death was also higher in this group (absolute risk increase 6.9% (1.9-12.0), p = 0.007). On multivariate analysis, prior cerebral infarction was associated with a greater risk of stroke (hazard ratio = 1.51, 95% confidence interval: 1.17-1.95, p = 0.002) and of stroke or other vascular death (hazard ratio = 1.30, 95% confidence interval: 1.11-1.52, p = 0.001). At 10 years, greater absolute benefits from immediate carotid endarterectomy were seen in those patients with prior cerebral infarction (6.7% strokes immediate carotid endarterectomy vs. 14.7% delayed carotid endarterectomy; hazard ratio 0.47 (0.34-0.65), p = 0.003), compared to those lower risk patients without prior cerebral infarction (6.0% vs. 9.9%, respectively; hazard ratio 0.61 (0.39-0.94), p = 0.005), though it must be emphasized that the first Asymptomatic Carotid Surgery Trial was not designed to test this retrospective and non-randomized comparison. CONCLUSIONS: Asymptomatic carotid stenosis patients with prior cerebral infarction have a higher stroke risk during long-term follow-up than those without prior cerebral infarction. Evidence of prior ischemic events might help identify patients in whom carotid intervention is particularly beneficial.

The Mechanism of Procedural Stroke Following Carotid Endarterectomy within the Asymptomatic Carotid Surgery Trial 1.

INTRODUCTION: Understanding the pathophysiological mechanism of procedural stroke during carotid intervention may help reduce the risk of stroke in those undergoing surgery. We therefore studied the features of procedural strokes within the first Asymptomatic Carotid Surgery Trial-1 (ACST-1) to identify the underlying pathophysiological mechanism. METHODS: In ACST-1, 3,120 patients with severe asymptomatic carotid stenosis thought suitable for surgery were randomized to CEA or indefinite deferral of surgery. Information on procedural (within 30 days) stroke type, laterality, severity and timing was collected. Eight possible mechanisms were defined: embolism from the carotid artery, haemodynamic, thrombosis or occlusion of the carotid artery, hyperperfusion syndrome, cardioembolic, either carotid embolic or haemodynamic, either carotid embolic or thrombotic occlusion, or undetermined. RESULTS: Procedural strokes occurred in 53 patients (2.7%). Strokes were predominantly ischaemic (n = 43; 81%), ipsilateral to the treated artery (n = 42; 79%), often occurred on the day of the operation (n = 32; 60%) and in over half the patients, were disabling or fatal (n = 27; 51%). The identified stroke mechanism was carotid embolic (n = 7), haemodynamic (n = 5), thrombosis or occlusion of the carotid artery (n = 9), hyperperfusion (n = 7), cardioembolic (n = 3), 'probably carotid embolic or haemodynamic' (n = 7), 'probably carotid embolic or thrombotic occlusion' (n = 3) and undetermined in 12 cases. CONCLUSION: In ACST-1, the risk of procedural stroke was low. Most strokes (60%) occurred on the day of the procedure and were caused by thrombosis or thrombotic occlusion of the ipsilateral carotid artery. These findings emphasize the importance of immediate assessment of the treated carotid artery when a stroke occurs after CEA.

The size of juxtaluminal hypoechoic area in ultrasound images of asymptomatic carotid plaques predicts the occurrence of stroke.

OBJECTIVE: To test the hypothesis that the size of a juxtaluminal black (hypoechoic) area (JBA) in ultrasound images of asymptomatic carotid artery plaques predicts future ipsilateral ischemic stroke. METHODS: A JBA was defined as an area of pixels with a grayscale value <25 adjacent to the lumen without a visible echogenic cap after image normalization. The size of a JBA was measured in the carotid plaque images of 1121 patients with asymptomatic carotid stenosis 50% to 99% in relation to the bulb (Asymptomatic Carotid Stenosis and Risk of Stroke study); the patients were followed for up to 8 years. RESULTS: The JBA had a linear association with future stroke rate. The area under the receiver-operating characteristic curve was 0.816. Using Kaplan-Meier curves, the mean annual stroke rate was 0.4% in 706 patients with a JBA <4 mm(2), 1.4% in 171 patients with a JBA 4 to 8 mm(2), 3.2% in 46 patients with a JBA 8 to 10 mm(2), and 5% in 198 patients with a JBA >10 mm(2) (P < .001). In a Cox model with ipsilateral ischemic events (amaurosis fugax, transient ischemic attack [TIA], or stroke) as the dependent variable, the JBA (<4 mm(2), 4-8 mm(2), >8 mm(2)) was still significant after adjusting for other plaque features known to be associated with increased risk, including stenosis, grayscale median, presence of discrete white areas without acoustic shadowing indicating neovascularization, plaque area, and history of contralateral TIA or stroke. Plaque area and grayscale median were not significant. Using the significant variables (stenosis, discrete white areas without acoustic shadowing, JBA, and history of contralateral TIA or stroke), this model predicted the annual risk of stroke for each patient (range, 0.1%-10.0%). The average annual stroke risk was <1% in 734 patients, 1% to 1.9% in 94 patients, 2% to 3.9% in 134 patients, 4% to 5.9% in 125 patients, and 6% to 10% in 34 patients. CONCLUSIONS: The size of a JBA is linearly related to the risk of stroke and can be used in risk stratification models. These findings need to be confirmed in future prospective studies or in the medical arm of randomized controlled studies in the presence of optimal medical therapy. In the meantime, the JBA may be used to select asymptomatic patients at high stroke risk for carotid endarterectomy and spare patients at low risk from an unnecessary operation.

Asymptomatic internal carotid artery stenosis and cerebrovascular risk stratification.

BACKGROUND: The purpose of this study was to determine the cerebrovascular risk stratification potential of baseline degree of stenosis, clinical features, and ultrasonic plaque characteristics in patients with asymptomatic internal carotid artery (ICA) stenosis. METHODS: This was a prospective, multicenter, cohort study of patients undergoing medical intervention for vascular disease. Hazard ratios for ICA stenosis, clinical features, and plaque texture features associated with ipsilateral cerebrovascular or retinal ischemic (CORI) events were calculated using proportional hazards models. RESULTS: A total of 1121 patients with 50% to 99% asymptomatic ICA stenosis in relation to the bulb (European Carotid Surgery Trial [ECST] method) were followed-up for 6 to 96 months (mean, 48). A total of 130 ipsilateral CORI events occurred. Severity of stenosis, age, systolic blood pressure, increased serum creatinine, smoking history of more than 10 pack-years, history of contralateral transient ischemic attacks (TIAs) or stroke, low grayscale median (GSM), increased plaque area, plaque types 1, 2, and 3, and the presence of discrete white areas (DWAs) without acoustic shadowing were associated with increased risk. Receiver operating characteristic (ROC) curves were constructed for predicted risk versus observed CORI events as a measure of model validity. The areas under the ROC curves for a model of stenosis alone, a model of stenosis combined with clinical features and a model of stenosis combined with clinical, and plaque features were 0.59 (95% confidence interval [CI] 0.54-0.64), 0.66 (0.62-0.72), and 0.82 (0.78-0.86), respectively. In the last model, stenosis, history of contralateral TIAs or stroke, GSM, plaque area, and DWAs were independent predictors of ipsilateral CORI events. Combinations of these could stratify patients into different levels of risk for ipsilateral CORI and stroke, with predicted risk close to observed risk. Of the 923 patients with ≥ 70% stenosis, the predicted cumulative 5-year stroke rate was <5% in 495, 5% to 9.9% in 202, 10% to 19.9% in 142, and ≥ 20% in 84 patients. CONCLUSION: Cerebrovascular risk stratification is possible using a combination of clinical and ultrasonic plaque features. These findings need to be validated in additional prospective studies of patients receiving optimal medical intervention alone.

Kuru in the 21st century--an acquired human prion disease with very long incubation periods.

BACKGROUND: Kuru provides the principal experience of epidemic human prion disease. Its incidence has steadily fallen after the abrupt cessation of its route of transmission (endocannibalism) in Papua New Guinea in the 1950s. The onset of variant Creutzfeldt-Jakob disease (vCJD), and the unknown prevalence of infection after the extensive dietary exposure to bovine spongiform encephalopathy (BSE) prions in the UK, has led to renewed interest in kuru. We investigated possible incubation periods, pathogenesis, and genetic susceptibility factors in kuru patients in Papua New Guinea. METHODS: We strengthened active kuru surveillance in 1996 with an expanded field team to investigate all suspected patients. Detailed histories of residence and exposure to mortuary feasts were obtained together with serial neurological examination, if possible. FINDINGS: We identified 11 patients with kuru from July, 1996, to June, 2004, all living in the South Fore. All patients were born before the cessation of cannibalism in the late 1950s. The minimum estimated incubation periods ranged from 34 to 41 years. However, likely incubation periods in men ranged from 39 to 56 years and could have been up to 7 years longer. PRNP analysis showed that most patients with kuru were heterozygous at polymorphic codon 129, a genotype associated with extended incubation periods and resistance to prion disease. INTERPRETATION: Incubation periods of infection with human prions can exceed 50 years. In human infection with BSE prions, species-barrier effects, which are characteristic of cross-species transmission, would be expected to further increase the mean and range of incubation periods, compared with recycling of prions within species. These data should inform attempts to model variant CJD epidemiology.

Markers of endothelial dysfunction in lacunar infarction and ischaemic leukoaraiosis.

Patients with cerebral small vessel disease (SVD) can present as isolated lacunar infarction or with diffuse white matter changes, with the imaging appearance of leukoaraiosis. Endothelial dysfunction, which can lead to breakdown of the blood-brain barrier, impaired cerebral autoregulation and prothrombotic changes, is believed to be important in mediating disease. Circulating levels of intercellular adhesion molecule 1 (ICAM1), thrombomodulin (TM), tissue factor (TF) and tissue factor pathway inhibitor (TFPI) are markers of endothelial activation and damage, and may provide insights into disease pathogenesis or differences between phenotypes. We therefore measured these markers in a prospective series of patients with lacunar stroke. One hundred and ten white Caucasian patients with previous lacunar stroke and 50 community control subjects were studied. Markers of endothelial function were measured on venous blood samples. Patients were classified on brain imaging into two groups: isolated lacunar infarction (n = 47) and ischaemic leukoaraiosis, defined as a clinical lacunar stroke and leukoaraiosis on brain imaging (n = 63). The number of lacunes and severity of leukoaraiosis were also scored on MRI. ICAM1, TM and TFPI were elevated in cerebral SVD subjects compared with controls (P