A comparison of risk factors and prognosis for transient ischemic attacks and minor ischemic strokes. The Oxfordshire Community Stroke Project

Identifying risk factors for recurrent mild ischemic stroke and high-risk population characteristics: A 1-year follow-up study

ObjectiveThis observational study examined the risk factors associated with recurrence in patients with mild ischemic stroke and determined the characteristics of high-risk groups.MethodsA total of 656 patients hospitalized for mild ischemic stroke were monitored for 1 year. Statistical analyses, including odds ratio calculations and K-means clustering, were conducted to examine risk factors for recurrence and the characteristics of high-risk groups.ResultsAfter 1 year of follow-up, 99 patients experienced recurrent mild ischemic stroke, resulting in a recurrence rate of 15.09%. The analysis revealed several significant risk factors, including type 2 diabetes mellitus, atrial fibrillation, smoking and alcohol consumption, carotid artery stenosis, cerebral vascular stenosis, and multiple lesions. Propensity score matching confirmed these associations, and K-means clustering revealed that older males with type 2 diabetes mellitus and hypertension were likely to be in the high-risk group.ConclusionsHealthcare professionals should focus on tailored treatment and prevention strategies for high-risk patients, prioritizing the management of the abovementioned risk factors to reduce recurrence and improve outcomes.

Diabetes-induced stimulation of the renin-angiotensin system in the rat brain cortex

Cerebrovascular disease is a threat to people with diabetes and hypertension. Diabetes can damage the brain by stimulating the renin-angiotensin system (RAS), leading to neurological deficits and brain strokes. Diabetes-induced components of the RAS, including angiotensin-converting enzyme (ACE), angiotensin-II (Ang-II), and angiotensin type 1 receptor (AT1R), have been linked to various neurological disorders in the brain. In this study, we investigated how diabetes and high blood pressure affected the regulation of these major RAS components in the frontal cortex of the rat brain. We dissected, homogenized, and processed the brain cortex tissues of control, streptozotocin-induced diabetic, spontaneously hypertensive (SHR), and streptozotocin-induced SHR rats for biochemical and Western blot analyses. We found that systolic blood pressure was elevated in SHR rats, but there was no significant difference between SHR and diabetic-SHR rats. In contrast to SHR rats, the heartbeat of diabetic SHR rats was low. Western blot analysis showed that the frontal cortexes of the brain expressed angiotensinogen, AT1R, and MAS receptor. There were no significant differences in angiotensinogen levels across the rat groups. However, the AT1R level was increased in diabetic and hypertensive rats compared to controls, whereas the MAS receptor was downregulated (p < 0.05). These findings suggest that RAS overactivation caused by diabetes may have negative consequences for the brain's cortex, leading to neurodegeneration and cognitive impairment.

Predictive Role of hsCRP in Recurrent Stroke Differed According to Severity of Cerebrovascular Disease: Analysis from a Prospective Cohort Study

Elevated levels of high-sensitivity C-reactive protein (hsCRP) were associated with an increased risk of recurrent stroke. However, it is still unknown whether the predictive value of hsCRP differed according to the severity of cerebrovascular disease. We used the cohort of the prospective multicenter cohort study of the Third China National Stroke Registry (CNSR-III), in which 10,765 consecutive patients with acute ischemic stroke or transient ischemic attack (TIA) had hsCRP levels measured. Patients were classified into minor stroke, or TIA, and non-minor stroke. The primary outcome was a new stroke within 1 year. Cox proportional hazards models were used to assess the association of hsCRP and its outcome. Elevated levels of hsCRP were associated with an increased risk of recurrent stroke in minor stroke or TIA patients, irrespective of using a National Institutes of Health Stroke Scale (NIHSS) score of ≤3 (the highest quartile vs. the lowest quartile: adjusted hazard ratio, 1.48; 95% CI, 1.12-1.97; p = 0.007) or ≤5 (the highest quartile vs. the lowest quartile: adjusted hazard ratio, 1.45; 95% CI, 1.15-1.84; p = 0.002) to define minor stroke. Such association was more apparent in the large-artery atherosclerosis subtype. However, for the patients with non-minor stroke, the association of hsCRP with recurrent stroke disappeared.

P2Y12 receptor inhibitor plus aspirin versus aspirin treated within 24 hours of acute noncardioembolic ischemic stroke or TIA: Meta-analysis

BACKGROUND/PURPOSE

Antiplatelet therapy is the cornerstone for acute ischemic stroke or transient ischemic attack (TIA). The purpose of this study was to conduct a meta-analysis to assess the efficacy and safety of P2Y12 receptor inhibitor plus aspirin versus aspirin alone treated within 24 h after acute noncardioembolic ischemic stroke or TIA.

METHODS

We search Pubmed, EMBASE, CENTRAL and clinicaltrials.gov from January 1966 to January 2021. We included randomized trials which compared P2Y12 receptor inhibitor plus aspirin versus aspirin alone. Relative risk (RR) with 95% confidence (CI) was used as a measure of P2Y12 receptor inhibitor plus aspirin versus aspirin. The primary efficacy endpoint was recurrent stroke and the primary safety endpoint was severe bleeding.

RESULTS

The search identified 5 randomized trials comparing P2Y12 receptor inhibitor plus aspirin and aspirin with 21,808 individuals enrolled. Pooled results from these trials showed that P2Y12 receptor inhibitor plus aspirin compared with aspirin was associated with a lower risk of recurrent stroke (RR 0.75, 95% CI 0.68 to 0.83). Ticagrelor plus aspirin compared with aspirin was associated with increased risk of severe bleeding (RR 3.98, 95% CI 1.74 to 9.10) and intracranial hemorrhage (RR 3.32, 95% CI 1.33 to 8.25), whereas clopidogrel plus aspirin vs. aspirin had similar hemorrhagic risk.

CONCLUSION

P2Y12 receptor inhibitor plus aspirin vs aspirin given within 24 h after acute noncardioembolic ischemic stroke or TIA reduces the risk of subsequent stroke. However, the risk of severe bleeding, including intracranial hemorrhage, was higher with ticagrelor plus aspirin vs aspirin.

PROSPERO ID

CRD42020203730.

Why are we still debating criteria for carotid artery stenosis?

The risk of new or recurrent stroke is high among patients with extracranial carotid artery stenosis and the benefit of carotid revascularization is associated to the degree of luminal stenosis. Catheter-based digital subtraction angiography (DSA) as the diagnostic gold-standard for carotid stenosis (CS) has been replaced by non-invasive techniques including duplex ultrasound, computed-tomography angiography, and magnetic resonance angiography (MRA). Duplex ultrasound is the primary noninvasive diagnostic tool for detecting, grading and monitoring of carotid artery stenosis due to its low cost, high resolution, and widespread availability. However, as discussed in this review, there is a wide range of practice patterns in use of ultrasound diagnostic criteria for carotid artery stenosis. To date, there is no internationally accepted standard for the gradation of CS. Discrepancies in ultrasound criteria may result in clinically relevant misclassification of disease severity leading to inappropriate referral, or lack of it, to revascularization procedures, and potential for consequential adverse outcome. The Society of Radiologists in Ultrasound (SRU), either as originally outlined or in a modified form, are the most common criteria applied. However, such criteria have received criticism for relying primarily on peak systolic velocities, a parameter that when used in isolation could be misleading. Recent proposals rely on a multiparametric approach in which the hemodynamic consequences of carotid narrowing beyond velocity augmentation are considered for an accurate stenosis classification. Consensus criteria would provide standardized parameters for the diagnosis of CS and considerably improve quality of care. Accrediting bodies around the world have called for consensus on unified criteria for diagnosis of CS. A healthy debate between professionals caring for patients with CS regarding optimal CS criteria still continues.

Cardiovascular risk factors and TIA characteristics in 19,872 Swedish TIA patients

BACKGROUND

Transient ischemic attack (TIA) constitutes a major risk factor for stroke, making TIA patients an important group for secondary intervention. The aim of this study was to account for risk factor prevalence in TIA patients and analyze the association between TIA characteristics and risk factors.

METHODS

We included 20,871 TIA events in 19,872 patients who were registered in the Swedish Riksstroke registry during the years 2010 through 2012. Data from other Swedish registers were used for comparison. The following variables were analyzed: age, sex, diabetes mellitus, atrial fibrillation (AF), cigarette smoking, and antihypertensive treatment.

RESULTS

Compared to the general population (based on data retrieved from Sweden's national public health survey 'Health on equal terms'), TIA patients more often had diabetes mellitus (prevalence ratio, PR = 2.3), AF without oral anticoagulants (OAC) (PR = 2.8), and AF on OAC (PR = 1.6). Blood pressure medication was less prevalent among TIA patients than in the general population (PR = 0.57). Increasing age was associated with longer attacks.

CONCLUSIONS

The fact that diabetes mellitus, atrial fibrillation, and smoking are more common in TIA patients than in the general population suggests that these factors are risk factors for TIA, even if causal relations cannot be proven. The relation between increasing age and longer attacks possibly reflects an increased proportion of embolic TIAs, or impaired recovery ability. Our results also suggest a significant proportion of untreated hypertension cases in the population.

Transient monocular blindness and the risk of vascular complications according to subtype: a prospective cohort study

Patients with transient monocular blindness (TMB) can present with many different symptoms, and diagnosis is usually based on the history alone. In this study, we assessed the risk of vascular complications according to different characteristics of TMB. We prospectively studied 341 consecutive patients with TMB. All patients were interviewed by a single investigator with a standardized questionnaire; reported symptoms were classified into predefined categories. We performed Cox regression analyses with adjustment for baseline vascular risk factors. During a mean follow-up of 4.0 years, the primary outcome event of vascular death, stroke, myocardial infarction, or retinal infarction occurred in 60 patients (annual incidence 4.4 %, 95 % confidence interval (CI) 3.4-5.7). An ipsilateral ischemic stroke occurred in 14 patients; an ipsilateral retinal infarct in six. Characteristics of TMB independently associated with subsequent vascular events were: involvement of only the peripheral part of the visual field (hazard ratio (HR) 6.5, 95 % CI 3.0-14.1), constricting onset of loss of vision (HR 3.5, 95 % CI 1.0-12.1), downward onset of loss of vision (HR 1.9, 95 % CI 1.0-3.5), upward resolution of loss of vision (HR 2.0, 95 % CI 1.0-4.0), and the occurrence of more than three attacks (HR 1.7, 95 % CI 1.0-2.9). We could not identify characteristics of TMB that predicted a low risk of vascular complications. In conclusion, careful recording the features of the attack in patients with TMB can provide important information about the risk of future vascular events.

Balance and Gait Impairment in Transient Ischemic Attack and Minor Stroke

BACKGROUND

There has been little research into gait and balance impairment in transient ischemic attack (TIA) and minor stroke, despite these conditions affecting large numbers of people and the potential impact on function. The aim of this study was to determine the impact of TIA and minor stroke on gait and balance.

METHODS

Twelve people with TIA or minor stroke without previous gait/balance problems and 12 age- and sex-matched controls were recruited. Participants (mean age 67 years) underwent a comprehensive assessment including physiological, balance, and gait measures (clinical and computerized [NeuroCom/GAITRite]). Matched-pairs analysis was undertaken.

RESULTS

Groups were similar in body mass index, vision, leg proprioception/strength, and reaction time. Cognition was worse in the TIA/minor stroke group: mean Montreal Cognitive Assessment score 22.2 versus 26.6, P = .001. People with TIA/minor stroke were significantly worse on all but one clinical test. Median scores for TIA/minor stroke versus control were as follows: Timed Up and Go (TUG), 9.4 versus 7.6 seconds, P = .019; TUG dual task, 12.3 versus 8.5 seconds, P = .012; Four Square Step Test, 10.9 versus 7.2 seconds, P = .006. Mean Step Test score for TIA/minor stroke versus control was 14.1 versus 17.7, P = .021. The TIA/minor stroke group also had significantly worse performance on computerized tests: increased turn time/sway, increased step length, slower comfortable/fast gait speeds, and greater proportion of gait cycle spent in double support.

CONCLUSIONS

This study found that people with TIA/minor stroke have gait and balance dysfunction despite having no obvious physiological impairments. Intervention studies aimed at improving balance and gait in this population are needed.

Rehab-let: touchscreen tablet for self-training impaired dexterity post stroke: study protocol for a pilot randomized controlled trial

BACKGROUND

Impaired dexterity of the weaker upper extremity is common post stroke and it is recommended that these individuals practice many repetitions of movement to regain function. However, stroke rehabilitation methods do not achieve the required intensity to be effective. Touchscreen tablet technology may be used as a motivating tool for self-training impaired dexterity of the weaker upper extremity post stroke.

METHODS/DESIGN

Rehab-let is a self-training protocol utilizing game apps on a touchscreen for practicing movement of the weaker upper extremity. We will conduct a pilot randomized controlled trial to assess Rehab-let compared to traditional self-training to improve dexterity of the weaker hand, and to increase self-training time and satisfaction in individuals with subacute stroke. Forty individuals with stroke undergoing subacute rehabilitation will be randomly allocated to Rehab-let or a traditional self-training program using therapeutic aids such as balls, blocks and pegs. All participants will be requested to perform self-training for 60 minutes a day, 5 times a week for 4 weeks. Dexterity assessed by The Nine Hole Peg Test is the main outcome measure. Assessments will be administered pre and post the self-training intervention by assessors blind to the group allocation.

DISCUSSION

The outcomes of this study will inform the design of a fully powered randomized controlled trial to evaluate the effectiveness of Rehab-let. If found to be effective, Rehab-let can be used during subacute rehabilitation to increase treatment intensity and improve dexterity. Potentially, Rehab-let can also be used after discharge and might be ideal for individuals with mild stroke who are often not referred to formal rehabilitation.

TRIAL REGISTRATION

Current Controlled Trials NCT02136433 registered on 17 September 2014.

European Stroke Prevention Study 2: A study of low-dose acetylsalicylic acid and of high dose dipyridamole in secondary prevention of cerebro-vascular accidents

In spite of some data being added to our knowledge of the effect of antiplatelets in secondary prevention of brain ischemic lesion in recent years, the main reasons to perform a second European Stroke Prevention Study (ESPS 2), which started in 1987-1988, were: (a) clarify the relative roles of aspirin (ASA) and dipyridamole (DP) alone or in combination; (b) confirm the efficacy of small doses of ASA and, so doing, decrease the number of drop-outs due to ASA side effects; (c) join information to the effect of antiplatelets in complete stroke. General characteristics of the sample of 6602 patients are presented and compared with other major trials and series. The patients in the four treatment arms (aspirin, dipyridamole, aspirin + dipyridamole and placebo) are compared. The more relevant features and risk factors known to influence long term prognosis are described and discussed. The small proportion of patients included with TIA (23.7%) and the comparability among treatment groups are stressed. No relevant differences have been found, among groups, on the sex or age distribution, prevalence of hypertension, diabetes, previous vascular events or atrial fibrillation, nor in the characteristics of the accident leading to the inclusion in trial.

Short-term effects of ambient particulates and gaseous pollutants on the incidence of transient ischaemic attack and minor stroke: a case-crossover study

BACKGROUND

While several studies have investigated the effects of short-term air pollution on cardiovascular disease, less is known about its effects on cerebrovascular disease, including stroke and transient ischaemic attack (TIA). The aim of the study was to assess the effects of short-term variation in air pollutants on the onset of TIA and minor stroke.

METHODS

We performed secondary analyses of data collected prospectively in the North West of England in a multi-centre study (NORTHSTAR) of patients with recent TIA or minor stroke. A case-crossover study was conducted to determine the association between occurrence of TIA and the concentration of ambient PM10 or gaseous pollutants.

RESULTS

A total of 709 cases were recruited from the Manchester (n = 335) and Liverpool (n = 374) areas. Data for the Manchester cohort showed an association between ambient nitric oxide (NO) and risk of occurrence of TIA and minor stroke with a lag of 3 days (odds ratio 1.06, 95% CI: 1.01 - 1.11), whereas negative association was found for the patients from Liverpool. Effects of similar magnitude, although not statistically significant, were generally observed with other pollutants. In a two pollutant model the effect of NO remained stronger and statistically significant when analysed in combination with CO or SO2, but was marginal in combination with NO2 or ozone and non-significant with PM10. There was evidence of effect modification by age, gender and season.

CONCLUSIONS

Our data suggest an association between NO and occurrence of TIA and minor stroke in Greater Manchester.

In vivo imaging of mineral deposition in carotid plaque using 18F-sodium fluoride PET/CT: correlation with atherogenic risk factors

The purpose of this study was to correlate (18)F-sodium fluoride accumulation in the common carotid arteries of neurologically asymptomatic patients with cardiovascular risk factors and carotid calcified plaque burden.

METHODS

Two hundred sixty-nine oncologic patients were examined by (18)F-sodium fluoride PET/CT. Tracer accumulation in the common carotid arteries was analyzed both qualitatively and semiquantitatively by measuring the blood-pool-corrected standardized uptake value (target-to-background ratio) and comparing it with cardiovascular risk factors and calcified plaque burden.

RESULTS

(18)F-sodium fluoride uptake was observed at 141 sites in 94 (34.9%) patients. Radiotracer accumulation was colocalized with calcification in all atherosclerotic lesions. (18)F-sodium fluoride uptake was significantly associated with age (P < 0.0001), male sex (P < 0.0001), hypertension (P < 0.002), and hypercholesterolemia (P < 0.05). The presence of calcified plaque correlated significantly with these risk factors but also with diabetes (P < 0.0001), history of smoking (P = 0.03), and prior cardiovascular events (P < 0.01). There was a highly significant correlation between the presence of (18)F-sodium fluoride uptake and number of present cardiovascular risk factors (r = 0.30, P < 0.0001).

CONCLUSION

Carotid (18)F-sodium fluoride uptake is a surrogate measure of calcifying carotid plaque, correlates with cardiovascular risk factors, and is more frequent in patients with a high-risk profile for atherothrombotic events but demonstrates a weaker correlation with risk factors than does calcified plaque burden. This study provides a rationale to conduct further prospective studies to determine whether (18)F-sodium fluoride uptake can predict vascular events, or if it may be used to monitor pharmacologic therapy.

Does Inflammation Predispose to Recurrent Vascular Events after Recent Transient Ischaemic Attack and Minor Stroke? the North West of England Transient Ischaemic Attack and Minor Stroke (NORTHSTAR) Study

Background and hypothesis

Inflammation is implicated in the pathogenesis and outcome of ischaemic injury. Poststroke inflammation is associated with outcome but it remains unclear whether such inflammation precedes or results from ischaemic injury. We hypothesised that inflammatory markers are associated with an increased risk of recurrent vascular events soon after transient ischaemic attack and minor stroke.

Methods

This was a multicentre, prospective, nested case–control study. Plasma concentrations of C-reactive protein, interleukin-6, interleukin-1-receptor antagonist and fibrinogen, leucocyte counts, erythrocyte sedimentation rate and inflammatory gene allele frequencies were analysed in 711 patients with recent transient ischaemic attack or minor stroke. Cases were defined by the incidence of one or more recurrent vascular events during the three-month follow-up. Association of inflammatory markers with case-status was determined using conditional logistic regression.

Results

Plasma concentrations of C-reactive protein, interleukin-1-receptor antagonist and interleukin-6 were not associated with case-status. In secondary analyses, only erythrocyte sedimentation rate was significantly associated with case-status (odds ratio 1·39, 95% confidence interval 1·03–1·85; P=0·03), but this effect did not persist after adjustment for smoking and past history of transient ischaemic attack or stroke. Single nucleotide polymorphisms in four inflammatory genes (interleukin-6, fibrinogen, P-selectin and vascular cell adhesion molecule-1) were nominally associated with case-status.

Conclusions

Circulating inflammatory markers were not associated with recurrent vascular events. Nominally significant associations between genetic markers and case-status will require replication. These data provide little evidence for an inflammatory state predisposing to stroke and other vascular events in a susceptible population.

Rationale and design of a randomized, double-blind trial comparing the effects of a 3-month clopidogrel-aspirin regimen versus aspirin alone for the treatment of high-risk patients with acute nondisabling cerebrovascular event

BACKGROUND

Acute nondisabling cerebrovascular events are common and often portend a disabling stroke. Aspirin is the only antiplatelet agent to have been studied in patients presenting acutely with a cerebrovascular event, but the effect is modest and is reduced by a small increased risk of intracerebral hemorrhage. Treatment with the combination of clopidogrel and aspirin might be beneficial when taken soon after a transient ischemic attack (TIA) or minor stroke. The CHANCE trial is a randomized, double-blind, multicenter, placebo-controlled trial to test an aggressive antiplatelet regimen in acute minor stroke or TIA.

DESIGN

The study will randomize 5,100 Chinese patients with acute TIA or minor stroke to receive a 3-month regimen of clopidogrel initiated with a loading dose of 300 mg followed by 75 mg/d, combined with aspirin 75 mg/d during the first 21 days, or a 3-month regimen of aspirin 75 mg/d alone. The primary efficacy end point is percentage of patients with any stroke (ischemic or hemorrhage) at 3 months. Study visits will be performed on the day of randomization, at day 21, and at day 90.

SUMMARY

CHANCE will determine whether clopidogrel combined with aspirin can prevent more strokes after acute minor stroke or TIA compared with aspirin alone-with an acceptable risk profile.

Decision analysis and carotid endarterectomy

A data base and a framework for clinical decision analysis are provided to enable the clinician to determine the value of carotid endarterectomy in patients with transient ischemic attacks. This approach permits optimal utilization of available data, maximizes the value of informed consent by clearly delineating areas of physician and patient expertise, and permits a quantitative assessment of the impact of uncertainty regarding underlying variables on decision outcome. The results of the analysis indicate that (a) the late nonstroke death rate has little effect on the value of endarterectomy, (b) the patient's relative valuation of stroke and immediate versus delayed death are among the most crucial variables underlying the value of endarterectomy, and (c) endarterectomy may be indicated in certain patients with transient ischemic attacks, but when its utility is measured in terms of value rendered to the patient, its relative cost may be greater than that of certain life-saving operations such as heart or liver transplant.

Predicting recurrent stroke after minor stroke and transient ischemic attack

The risk of a subsequent stroke following an acute transient ischemic attack or minor stroke is high, with 90-day risk at approximately 10%. Identification of those patients at the highest risk for recurrent stroke following a transient ischemic attack or minor stroke may allow risk-specific management strategies to be implemented, such as hospital admission with expedited work-up for those at high risk and emergency room discharge for those at low risk. Predictors of recurrent stroke, including the ABCD2 score, brain imaging and the stroke mechanism, are reviewed in this article, with a focus on recent literature. An emphasis is placed on the importance of early imaging of the brain parenchyma (diffusion-weighted imaging) and vascular imaging to identify patients at high risk for recurrence. The need for identification of the cause of the initial event, allowing therapies to be tailored to the individual patient, is discussed.

The risk of stroke within a week of minor stroke or transient ischemic attack

BACKGROUND

The risk of stroke is highest in the first week following an index stroke or transient ischemic attack (TIA). Recent evidence indicates that prompt pharmacological treatment and evaluation may help mitigate this risk.

OBJECTIVE

To identify risk factors for recurrent stroke 1 week after index cerebrovascular event and review evidence for early and aggressive evaluation and management.

METHODS

We searched the National Library of Medicine Pubmed database to identify studies reporting recurrent or secondary stroke in individuals with identified stroke or TIA.

RESULTS/CONCLUSION

The risk of recurrent stroke in the week after a TIA or minor stroke is up to 10%. Factors identified with risk of early stroke recurrence include age, elevated blood pressure, clinical symptoms of motor weakness or speech disturbance, and large vessel atherothrombotic mechanism. Studies have shown that timely initiation of stroke preventative therapy may reduce the risk of stroke within this early period.

An improved scoring system for identifying patients at high early risk of stroke and functional impairment after an acute transient ischemic attack or minor stroke

BACKGROUND

Risk of a subsequent stroke following an acute transient ischemic attack (TIA) or minor stroke is high. The ABCD(2) tool was proposed as a method to triage these patients using five clinical factors. Modern imaging of the brain was not included. The present study quantified the added value of magnetic resonance imaging (MRI) factors to the ABCD(2) tool.

METHODS

Patients with TIA or minor stroke were examined within 12 h and had a brain MRI within 24 h of symptom onset. Primary outcomes were recurrent stroke and functional impairment at 90 days. A new tool, ABCD(2)+MRI, was created by adding diffusion-weighted imaging lesion and vessel occlusion status to the ABCD(2) tool. The predictive accuracy of both tools was quantified by the area under the curve (AUC).

RESULTS

One hundred and eighty patients were enrolled and 11.1% had a recurrent stroke within 90 days. The predictive accuracy of the ABCD(2)+MRI was significantly higher than ABCD(2) (AUC of 0.88 vs. 0.78, P=0.01). Those with a high score (7-9) had a 90-day recurrent stroke risk of 32.1%, moderate score (5-6) risk of 5.4%, and low score (0-4) risk of 0.0%. The ABCD(2) tool did not predict risk of functional impairment at 90 days (P=0.33), unlike the ABCD(2)+MRI (P=0.02): high score (22.9%), moderate (7.5%), low (7.7%).

CONCLUSIONS

Risk of recurrent stroke and functional impairment after a TIA or minor stroke can be accurately predicted by a scoring system that utilizes both clinical and MRI information. The ABCD(2)+MRI score is simple and its components are commonly available during the time of admission.

Risk of stroke early after transient ischaemic attack: a systematic review and meta-analysis

BACKGROUND

Stroke is often preceded by transient ischaemic attack (TIA), but studies of stroke risk after TIA are logistically difficult and have yielded conflicting results. However, reliable estimation of this risk is necessary for planning effective service provision, clinical trials, and public education. We therefore did a systematic review of all studies of stroke risk early after TIA.

METHODS

All studies of stroke risk within 7 days of TIA were identified by use of electronic databases and by hand searches of reference lists, relevant journals, and conference abstracts. Stroke risks at 2 days and 7 days after TIA were calculated overall and analyses for heterogeneity were done, if possible, after categorisation by study method, setting, population, and treatment.

FINDINGS

18 independent cohorts were included, which reported stroke risk in 10 126 TIA patients. The pooled stroke risk was 5.2% (95% CI 3.9-6.5) at 7 days, but there was substantial heterogeneity between studies (p<0.0001), with risks ranging from 0% to 12.8%. However, the risks reported in individual studies over different durations of follow-up were highly correlated (0-7 days vs 8-90 days, r=0.89, p<0.0001), and the heterogeneity between studies was almost fully explained by study method, setting, and treatment. The lowest risks were seen in studies of emergency treatment in specialist stroke services (0.9% [95% CI 0.0-1.9], four studies) and the highest risks in population-based studies without urgent treatment (11.0% [8.6-13.5], three studies). Results were similar for stroke risk at 2 days.

INTERPRETATION

The reported early risks of stroke after TIA were highly heterogeneous, but this could be largely accounted for by differences in study method, setting, and treatment, with lowest risks in studies of emergency treatment in specialist stroke services.

Differential risks of subsequent vascular events for transient ischaemic attack and minor ischaemic stroke

Using a prospective hospital-based registry, 146 patients with transient ischaemic attack (TIA) were compared with 376 patients with minor first-ever ischaemic stroke with respect to the 3-month risk of subsequent vascular events, in order to clarify the distinctions between the disease entities. All patients were enrolled within 48 h of onset. The risk factor distribution for the two groups was comparable, except that the TIA patients had more previous TIAs. Large artery atherosclerosis (34%) and small vessel occlusion (32%) were the main aetiologies in the TIA group, whereas small vessel occlusion (49%) was the major cause in the stroke group. The 3-month risk of combined endpoints of stroke, myocardial infarction, and vascular death for TIA patients was higher than that for the minor stroke group (15.1% vs. 3.2%; hazard ratio 4.6, 95% confidence interval 2.3-9.3 in multivariate analysis). Large artery atherosclerosis and male sex were the other significant predictors. TIA may demand more urgent management than minor stroke. The fact that aetiology is a predictor, highlights the need for rapid diagnostic tests to establish pathogenesis.

Symptome, Risikofaktoren und Ätiologie von transitorisch ischämischer Attacke und Schlaganfall

BACKGROUND

It is unclear whether clinical signs and symptoms differ in the presentation of transient ischemic attack (TIA) and stroke, apart from temporal dynamics.

METHODS

Signs and symptoms of patients diagnosed with TIA or stroke were prospectively collected and compared by means of an age-adjusted logistic regression analysis. Risk factors, prehospital medication, and diagnostic workup were obtained from the charts.

RESULTS

Four hundred five patients diagnosed with stroke (68+/-12 years old, 45% female) and 143 diagnosed with TIA (64+/-14 years old, 48% female) were included. Signs and symptoms of patients with TIA were less often "classic" such as paresis (48% vs 71%, P<0.001) or sensory loss (38% vs 48%, P=0.03). The etiology of TIA was more often classified as "undetermined" (57% vs 46%, P<0.05).

CONCLUSIONS

Transient ischemic attack needs special attention and intensive diagnostic workup, because it bears a considerable risk of death and disability but presents less often with classic signs and symptoms and its etiology often remains undetermined.

Silent ischemia in minor stroke and TIA patients identified on MR imaging

BACKGROUND

In a general population of patients with stroke, the rate of new MRI lesions at 1 week was much higher than expected. With patients with minor stroke and TIA having a higher risk of recurrent clinical events, the authors examined whether patients with minor stroke and TIA also had a high rate of asymptomatic lesions on repeat MRI scanning.

METHODS

Patients with minor stroke and TIA presenting within 12 hours of symptom onset with a NIH Stroke Scale score less than six, who had a baseline MRI and a 1-month follow-up, were enrolled in this study. The follow-up study was examined for new diffusion-weighted imaging lesions as compared to the baseline study. Clinical or MRI factors predicting recurrent lesions were examined.

RESULTS

A total of 143 patients were enrolled and 14 patients (9.8%; 95% CI 5.4, 15.9) had MR evidence of new lesions at 30 days. Six of these new lesions were clinically asymptomatic (42.9%; 95% CI 17.7, 71.1). A trend to increased likelihood of new lesions at 30 days was seen with progressing baseline scan lesion number (none [2.2%], solitary [12.9%], multiple [19.8%]: p = 0.046). Patients whose mechanism of stroke was large artery or cardioembolic were the most likely to have new lesions on follow-up MRI.

CONCLUSION

Minor stroke and TIA are associated with a 10% risk of new lesions on MRI and half of these new lesions are asymptomatic. This risk is lower than seen in more severely affected patients with stroke. Patients with multiple lesions at baseline are at an increased risk for new ischemic lesions.

Epidemiological aspects of isolated systolic hypertension in the elderly population as cerebrovascular risk factor

A large number of studies indicate that isolated systolic hypertension (ISH) is an important cerebrovascular risk factor. This clinical state is very common in elderly people who are the most exposed to stroke risk. Therefore, it is important to know the real prevalence of ISH, in order to predict the possible incidence of cerebrovascular disease in the elderly population. In the Camerano study on hypertension, we have verified the prevalence of ISH in the elderly. ISH has been considered clinically when the systolic arterial pressure (SAP) was higher than 160 mmHg, and the diastolic arterial pressure (DAP) was lower than 90 mmHg. In our study population, an ISH prevalence of 11.9% was found in the elderly (above 60 years of age); whereas in the adult population (between 30 and 60 years), it amounted only to 4.5%.

Potential Confounding by Intermediate Phenotypes in Studies of the Genetics of Ischaemic Stroke

BACKGROUND

Family history (FHx) of stroke is perceived to be an important risk factor for ischaemic stroke. However, there are several intermediate phenotypes that are often involved in the aetiology of ischaemic stroke and that have a substantial genetic component themselves. We studied FHx of ischaemic heart disease (IHD), hypertension (HTN) and diabetes mellitus (DM) as risk factors for ischaemic stroke.

METHODS

We performed a systematic review of case-control and cohort studies reporting on FHx(IHD), FHx(HTN) or FHx(DM) as risk factors for stroke using bibliographic databases, and by hand searching reference lists and journals. Odds ratios of FHx as a risk factor for stroke were calculated within individual studies. We included unpublished data from two Oxfordshire population-based studies to assess effects on subtypes of ischaemic stroke.

RESULTS

We identified 54 studies that investigated the odds of stroke conferred by a positive FHx, 24 of which reported data on FHx of one or more intermediate phenotypes in addition to FHx of stroke. Most studies reported an increased frequency of FHx(IHD) and FHx(HTN) in stroke patients versus controls. The association was significant in 6 out of 14 studies for FHx(IHD) and 4 out of 11 studies for FHx(HTN). In contrast, FHx(DM) was not associated with stroke. FHx(IHD) was particularly associated with large vessel strokes (OR 1.72, CI 1.3-2.2, p = 0.00004).

CONCLUSIONS

FHx(IHD) and FHx(HTN) are both risk factors for stroke. It is likely that the apparent heritability of stroke is partly accounted for by heritability of HTN and large vessel atherosclerosis. Analyses of heritability of stroke and candidate gene studies should be adjusted accordingly.

Triaging transient ischemic attack and minor stroke patients using acute magnetic resonance imaging

We examined whether the presence of diffusion-weighted imaging (DWI) lesions and vessel occlusion on acute brain magnetic resonance images of minor stroke and transient ischemic attack patients predicted the occurrence of subsequent stroke and functional outcome. 120 transient ischemic attack or minor stroke (National Institutes of Health Stroke Scale < or = 3) patients were prospectively enrolled. All were examined within 12 hours and had a magnetic resonance scan within 24 hours. Overall, the 90-day risk for recurrent stroke was 11.7%. Patients with a DWI lesion were at greater risk for having a subsequent stroke than patients without and risk was greatest in the presence of vessel occlusion and a DWI lesion. The 90-day risk rates, adjusted for baseline characteristics, were 4.3% (no DWI lesion), 10.8% (DWI lesion but no vessel occlusion), and 32.6% (DWI lesion and vessel occlusion) (p = 0.02). The percentages of patients who were functionally dependent at 90 days in the three groups were 1.9%, 6.2%, and 21.0%, respectively (p = 0.04). The presence of a DWI lesion and a vessel occlusion on a magnetic resonance image among patients presenting acutely with a transient ischemic attack or minor stroke is predictive of an increased risk for future stroke and functional dependence.

Early risk of stroke after a transient ischemic attack in patients with internal carotid artery disease

BACKGROUND

Transient ischemic attacks (TIAs) often herald a stroke, but little is known about the acute natural history of TIAs. Our objective was to quantify the early risk of stroke after a TIA in patients with internal carotid artery disease.

METHODS

Using patient data from the medical arm of the North American Symptomatic Carotid Endarterectomy Trial, we calculated the risk of ipsilateral stroke in the territory of the symptomatic internal carotid artery within 2 and 90 days after a first-recorded hemispheric TIA. We also studied similar outcomes among patients in the trial who had a first-recorded completed hemispheric stroke.

RESULTS

For patients with a first-recorded hemispheric TIA (n = 603), the 90-day risk of ipsilateral stroke was 20.1% (95% confidence interval [CI] 17.0%-23.2%), higher than the 2.3% risk (95% CI 1.0%-3.6%) for patients with a hemispheric stroke (n = 526). The 2-day risks were 5.5% and 0.0%, respectively. Patients with more severe stenosis of the internal carotid artery (> 70%) appeared to be at no greater risk of stroke than patients with lesser degrees of stenosis (adjusted hazard ratio 1.1, 95% CI 0.7-1.7). Infarct on brain imaging (adjusted hazard ratio 2.1, 95% CI 1.5-3.0) and the presence of intracranial major-artery disease (adjusted hazard ratio 1.9, 95% CI 1.3-2.7) doubled the early risk of stroke in patients with a hemispheric TIA.

INTERPRETATION

Patients who had a hemispheric TIA related to internal carotid artery disease had a high risk of stroke in the first few days after the TIA. Early risk of stroke was not affected by the degree of internal carotid artery stenosis.

Peripheral arterial disease and cognitive function

OBJECTIVE

Peripheral arterial disease (PAD) is associated with comorbid atherosclerosis of the coronary and carotid arteries and is a significant risk factor for stroke. However, cognitive function in PAD patients before clinically evident stroke remains poorly characterized. Here we hypothesized that, on neuropsychological testing, PAD patients would perform more poorly than healthy control subjects, and persons with mild cardiovascular disease (essential hypertension), but better than stroke patients, thus reflecting a continuum of cognitive impairment associated with increased severity of vascular disease.

METHOD

The cognitive performance of 38 PAD patients (mean ankle-brachial index=0.67, Fontaine Class II) was contrasted with that of 23 healthy normotensive controls, 20 essential hypertensives, and 26 anterior ischemic stroke patients on twelve neuropsychological tests.

RESULTS

PAD patients performed significantly more poorly than hypertensives and normotensives, but better than stroke patients, on seven tests of nonverbal memory, concentration, executive function, perceptuo-motor speed, and manual dexterity. Hypertensives displayed poorer performance than normotensives on tests of nonverbal memory and manual dexterity. These findings were independent of age, education, and depression scores. Higher diastolic blood pressure and plasma glucose levels predicted poorer performance of select cognitive tests by PAD patients. Eight to 67% of PAD patients displayed impaired performance (< 5(th) percentile of normotensive controls) on the seven aforementioned cognitive tests.

CONCLUSIONS

PAD patients exhibit diminished performance across a variety of domains of cognitive function. Findings also suggest a continuum of cognitive impairment associated with increasingly severe manifestations of cardiovascular disease, thus emphasizing the need for enhanced preventative measures to avert functional declines.

Hypertension in older adults

The high prevalence of hypertension in older persons (nearly one of two subjects aged 60 years and older) suggests that the recognition and treatment should be a priority for physicians. Although diastolic blood pressure is regarded as an important risk factor, it is now clear that isolated systolic hypertension and elevated pulse pressure also play an important role in the development of cerebrovascular disease, congestive heart failure, and coronary heart disease, which are the major causes of cardiovascular morbidity and mortality in the population aged older than 65 years. Controlled, randomized trials have shown that treatment of systolic as well as systolodiastolic hypertension decreases the incidence of cardiovascular and cerebrovascular complications in older adults. The question of whether treatment of hypertension should be maintained in very old persons, those older than 80 years, is still undecided.

Management of the first-time transient ischaemic attack

The assessment and management of patients with a suspected transient ischaemic attack of the brain or eye is a daily task in busy emergency departments. They are common, affecting about 50 per 100,000 population each year. Conditions which mimic a transient ischaemic attack are even more common (e.g. migraine aura, partial seizures, benign paroxysmal positional vertigo, hysteria). This comprehensive review outlines an approach to the management of this complex and challenging problem.

Patterns of cerebrovascular symptomatology associated with carotid atheroma

The aim of this study was to identify ultrasonic tissue characteristics and stenosis of carotid plaques that correspond to amaurosis fugax, hemispheric transient ischaemic attack, and stroke. At total of 146 symptomatic carotid plaques (136 patients) associated with amaurosis fugax, hemispheric transient ischaemic attack, stroke, and having 50-99% stenosis on duplex, were studied. These plaques were imaged on duplex, captured in a computer and their grey scale median was evaluated to distinguish the dark (low grey scale median) from the bright (high grey scale median) plaques. Stenosis was assessed on duplex. The amaurosis fugax group corresponded to carotid plaques with low grey scale median and severe stenosis, as contrasted with the other two groups (hemispheric transient ischaemic attack and stroke) (P < 0.05). These results suggested that amaurosis fugax was dependent only on the instability of carotid plaques, whereas hemispheric transient ischaemic attack and stroke were both dependent on carotid plaques and other pathogenetic factors.

Efficacy of antiplatelet treatment in hypertensive patients with TIA or stroke

We performed a subgroup analysis of the first European Stroke Prevention Study including 1,306 patients recruited in a single center, Kuopio, Finland, to investigate whether or not antiplatelet therapy is effective in the secondary prevention of stroke in hypertensive patients with transient ischemic attack (TIA) or stroke. The patients were treated with aspirin, 990 mg/day, plus dipyridamole, 225 mg/day, or placebo for 2 years. The patients with high systolic blood pressure (> or = 140 mm Hg; n = 1.105) or high diastolic blood pressure (> or = 85 mm Hg; n = 1,120) at entry, were classified into subgroups by blood pressure level. The effect of treatment was statistically significant in all subgroups with high systolic (end-point reduction, 55.2-68.2%) and diastolic blood pressure (end-point reduction, 47.3-82.1%). Risk reduction was, however, greatest in patients with the highest diastolic blood pressure. One possible explanation is that platelets are more activated in these patients, and this can be effectively prevented by antiplatelet therapy. Further studies are needed to confirm this hypothesis.

Risk factors and antiplatelet therapy in TIA and stroke patients

Antiplatelet treatment is well established in the secondary prevention of ischemic cerebrovascular events. The reasons for the occurrence of stroke, even though the patient receives drug treatment, have remained unclear. We performed a subgroup analysis of the European Stroke Prevention Study (ESPS 1) to investigate the efficacy of treatment in patients with different cardiovascular risk factors. The ESPS 1 recruited 1306 patients with TIA, RIND or stroke in one single center of Kuopio in Finland. The patients were treated with aspirin 990 mg/day+dipyridamole 225 mg/day or placebo for 2 years or until an endpoint. The endpoints were stroke or death from any cause. The risk factors for endpoints were analyzed by Cox univariate regression analyses. The effect of a single risk factor on the efficacy of antiplatelet therapy was analyzed by Cox proportional hazards model in subgroups according to the significant risk factors found in the univariate analysis. The efficacy of treatment was statistically significant in all subgroups except diabetics and current smokers for the stroke endpoint. When the combined endpoint of stroke or death was used, the treatment failed also to show statistical significance in patients with coronary heart disease. This lack of efficacy might be due to the small sample size. The efficacy of treatment was significantly better in TIA patients than in stroke patients when analyzed with stroke as an end point. This study provides strong evidence that the effectiveness of antiplatelet treatment in ischemic stroke and TIA patients is independent of most cardiovascular risk factors. Furthermore, all patients with TIA and ischemic stroke should receive secondary prevention regardless of whether or not there are risk factors.

Meeting the challenge of stroke

It is the elderly who carry the burden of stroke. Whilst 130,000 people suffer a stroke in the UK every year, nearly three quarters of these cases occur over the age of 65 and nearly half occur over the age of 75. As the proportion of elderly in the population continues to grow, inevitably this burden will increase. With Scotland probably experiencing the highest stroke incidence in the UK and stroke already accounting for 5.5% of total hospital costs, challenges clearly lie ahead for the health service and Scottish society as a whole. The extent to which we are able to meet this challenge is becoming clearer. Thus far, therapeutic advance has been rather "low-tech", with organisation of services and the appropriate use of existing interventions showing modest and, just occasionally, dramatic benefits. In contrast, the high hopes raised by many "high-tech" solutions have largely been dashed or remain promising but unproven.

The effect of treating people with reversible ischaemic attacks of the brain and eye on the incidence of stroke in Australia

BACKGROUND

Reversible ischaemic attacks of the brain or eye (RIA) are a risk factor for stroke. Strategies of stroke prevention include vascular risk factor control, antithrombotic therapy, and carotid surgery.

AIMS

To determine the effectiveness, risks and costs of each stroke prevention strategy for patients with RIA and the Australian community, and the effect of treating people with RIA on the incidence of stroke in Australia.

METHODS

Review of data from prospective community-based studies to determine the prevalence of RIA, the incidence of stroke, and the proportion of stroke patients who report a RIA before their stroke; and data from randomised trials to determine the effectiveness, risks and costs of treatments for RIA.

RESULTS

About 111,000 Australians have had a prior RIA. Each year, about 37,000 Australians suffer a stroke, of whom up to 8000 (22%) have had a prior ('warning') RIA. Targeting effective stroke prevention strategies to RIA patients with relevant treatable conditions may reduce the individual's stroke risk by two-thirds (individual strategies) and possibly further (combination strategies). However, because the attributable risk of RIA for stroke is only about 22% (and may be less, given the role of other causal risk factors for stroke), strategies of stroke prevention in RIA patients can only reduce stroke incidence by up to 15% (from 22% to 7%).

CONCLUSIONS

The potential benefits of the 'high risk' approach to stroke prevention appear to be less than the 'population' approach, but both approaches are necessary and complementary. Indeed, the cost of implementing the 'high risk' approach may be less than the cost of the strokes prevented ($255 million; i.e. 15% of $1.7 billion).

Incidental intracranial vascular pathology in patients investigated for carotid stenosis

The assessment of cervical and cranial carotid arteries for atherosclerotic disease is the second commonest referral for angiography in our neuroradiological department; in 1993 this accounted for approximately 17% of the total cases. This is due to the resurgence of interest in endarterectomy for severe carotid stenosis. Although the degree of stenosis can usually be assessed adequately by duplex Doppler ultrasonography, angiography is still recommended as a preoperative examination. The intracranial vessels are visualised, which we consider important when planning vascular surgery. We present a prospective study of 100 patients referred for angiographic assessment of carotid stenosis. As well as giving information about the carotid bifurcation, angiography showed 9 patients to have aneurysms, 2 arteriovenous malformations and 15 severe intracranial atherosclerosis. We consider these "incidental" findings important for future management and highlight the need for thorough assessment of the intracranial vessels in these patients by angiography.

Prognostic indicators for mortality in transient ischemic attack and minor stroke

In a prospective study, 129 consecutive patients with transient ischemic attacks (TIAs) and 80 consecutive patients with minor ischemic stroke, involving the carotid artery territory in both cases, were followed-up for six years from their inclusion during the period from January 1984 to October 1985. All patients were 40-80 years old at inclusion, the median age being 74 years in the TIA group and 76 years in the minor stroke group. Overall mortality in the TIA group was significantly higher than in the minor stroke group, [44%, (57/129) vs 20% (16/80), p < 0.0006 after correction for age], and that in the general population of Malmö. Pre-existing vascular disease was slightly more prevalent in the TIA than in the minor stroke group [27% (35/129 vs 21% (17/80), NS]. Of the 19 patients with intermittent claudication, who all died [12 (63%) of them due to myocardial infarction (MI)], 18 belonged to the TIA group and only one to the minor stroke group. The respective frequencies of the putative risk factors in the TIA and minor stroke groups were 28% (36/129) vs 9% (7/80) for hypertension (p = 0.016), 9% (12/129) vs 6% (5/80) for diabetes mellitus (NS), and 8% (10/129) vs 9% (7/80) for cardiac arrhythmia (NS). Mortality due to MI was higher in the TIA than in the minor stroke group[24% (31/129) vs 6% (5/80), p = 0.001]. Of the minor stroke patients, none without vascular disease died of MI.(ABSTRACT TRUNCATED AT 250 WORDS)

Transient ischaemic attacks due to meningioma--report of 4 cases

Computed tomography of patients diagnosed as having transient ischaemic attacks has revealed a heterogenous group whose symptoms may be due to completed infarcts or space-occupying lesions (such as neoplasia). Four such cases due to meningioma are presented including one which atypically simulated an infarct on an unenhanced scan. A sign to differentiate this from a true infarct is discussed.

Pathogenetic and prognostic features of lacunar transient ischaemic attack syndromes

Lacunar ischaemic stroke syndromes are a well defined subgroup of ischaemic strokes. To determine whether a similar subgroup can be identified among patients with transient ischaemic attacks (TIAs) we studied prospectively 102 consecutive patients within 24 hours of their first TIA. Based on their history they were classified as lacunar TIA syndromes (LTIAS; n = 45) if isolated motor or sensory symptoms or their combination had involved at least two of three body parts (face, arm, leg), whereas all other subjects were grouped as non-lacunar TIA syndromes (NLTIAS; n = 57). All patients were investigated according to a standardised protocol and followed up for an average of 51.1 months. Cardiac and arterial sources of thromboembolism were more frequent among NLTIAS (p = 0.0001). Survival curve analysis demonstrated that LTIAS had a significantly lower long term mortality and incidence of major vascular events. In a multivariate regression analysis, the type of TIA (that is, NLTIAS) was an independent predictor of stroke or death. LTIAS share the same distinct pathogenetic and prognostic features of lacunar ischaemic stroke syndromes. These findings have implications for management of TIAs and for studies of their natural history and treatment.

Can the long term outcome of individual patients with transient ischaemic attacks be predicted accurately?

The prognosis of individual patients with transient ischaemic attacks (TIAs) is extremely variable; some patients are at high risk and others at low risk of a serious vascular event. Prediction equations of outcome were developed, based on eight clinical prognostic factors, from a cohort of 469 hospital-referred TIA patients ("training" data set), that enable high (and low) risk patients to be identified and for whom costly and risky treatments may (or may not) be targeted. The study aimed to determine whether these equations are externally valid and can predict outcome, with reliability and discrimination, in two independent cohorts of TIA patients ("test" data sets): 1653 TIA patients in the UK-TIA aspirin trial and 107 TIA patients in the Oxfordshire Community Stroke Project. Predicted outcomes agreed closely with the observed outcomes in the "test" data sets (reliability) for all outcome events at low five year risk (< 30%) but the estimates of risk were less precise in groups predicted to have a high five year risk (> 40%). The prediction equations were fairly accurate in discriminating between patients who subsequently suffered the outcome event of interest and those who survived free of the event at five years after the TIA, particularly at lower cut-off levels distinguishing high and low risk (for example, < 30% vs > 30% at five years). It is very difficult to achieve perfect discrimination because there is no single important prognostic factor for TIA patients that indicates whether a patient is going to suffer an event or not. These equations can be used to provide a reliable estimate of the absolute five year risk of a serious vascular event in hospital-referred TIA patients but they cannot, as yet, be used with confidence to distinguish patients at high risk from patients at low risk.

Why is the outcome of transient ischaemic attacks different in different groups of patients?

The outcomes of each of three large cohorts of patients with transient ischaemic attacks, which were studied in the same country at much the same time with the same methods, were compared and found to be quite different from each other. The differences in outcome were related not only to different strategies of treatment but also to differences in the prevalence and level of important prognostic factors (for example, case mix) and other factors such a the time delay from transient ischaemic attack to entry into the study and the play of chance. The implications for purchasers of health care are that they cannot rely solely on non-randomised comparisons of outcome of patients treated in competing units as a measure of the quality of care (which has only rather modest effects) without accounting for other factors that may influence outcome such as the nature of the illness, the case mix, observer bias, and the play of chance.