bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of Hemodynamic Cerebral Ischemia and Microembolic Signals Detected During Carotid Endarterectomy and Carotid Angioplasty
Authors: Crawley Francesca , Clifton Andrew , Buckenham Tim , Loosemore Thomas , Taylor Robert S. , Brown Martin M.
Published: June 2011

Background and Purpose
There has been concern about carotid percutaneous transluminal angioplasty (PTA) carrying a greater risk of cerebral ischemia than carotid endarterectomy. We set out to compare cerebral hemodynamics and microembolization during carotid PTA and CEA.

Methods
We used transcranial Doppler to monitor the middle cerebral artery of 28 patients undergoing carotid PTA (n=14) or carotid endarterectomy (CEA) with a shunt (n=14). Each period during which the internal carotid artery was occluded by PTA balloon or by clamp when the shunt was not in place was timed. Individual periods were summated to give a total occlusion time. Ischemic time was defined as the period for which mean middle cerebral artery velocity fell to a third or less of baseline. Microembolic signals were counted during each procedure.

Results
CEA resulted in significantly longer individual and total occlusion time than PTA (mean individual occlusion time, seconds), CEA, 168±51; PTA, 20±7;
P
<.001; mean total occlusion time; CEA, 337±70; PTA, 26±10;
P
<.001. Ischemic time was also significantly longer during CEA than during PTA (CEA, 165±40; PTA, 17±5;
P
=.001). There were significantly more microembolic signals during PTA than during CEA (mean number of microembolic signals during CEA, 52±64; during PTA, 202±119;
P
=.001). There was no correlation between any of the parameters measured and periprocedural stroke, which occurred in one patient in each group.

Conclusion
PTA results in less hemodynamic ischemia but more cerebral microembolism than CEA. In this small series, however, it is not possible to comment on the relations between ischemic time, microembolism, and stroke.
Interobserver Agreement for 10% Categories of Angiographic Carotid Stenosis
Authors: Dippel Diederik W. J. , van Kooten Fop , Bakker Stef L. M. , Koudstaal Peter J.
Published: June 2011

Background and Purpose
Although the reliability of the assessment of severe 70% to 99% carotid stenosis by carotid angiography has been proven excellent, this may not necessarily be the case for a more detailed classification of carotid stenoses by 10% categories.

Methods
Angiograms of the carotid arteries were assessed pairwise by three independent, experienced observers. The measurements of the degree of stenosis of both the carotid bifurcation and the internal carotid artery were made according to the European Carotid Surgery Trial method. Kappa statistics were used to assess the agreement beyond chance for severe (70% to 99%) carotid stenosis (κ
1
) and for 10% categories of carotid stenosis (κ
2
). The penalty scores were adjusted by weights for the relative difference in risk (RDR) of stroke in the ipsilateral carotid distribution between the 10% categories (κ
3
). An adjustment of the RDR method was made by assuming that only patients with a severe carotid stenosis would undergo surgery, and the penalty would be 0 if no disagreement would exist about the indication for surgery (κ
4
). An even further adjustment (κ
5
) was made by assuming that assessment of the rate of carotid stenosis by one or both observers would lead to different treatment recommendations in 50% of the cases, and accordingly the penalty for disagreement (RDR) was halved.

Results
One hundred twenty-one carotid bifurcations in 65 patients with a transient ischemic attack or nondisabling stroke were assessed. The intraclass correlation between the exact estimates of carotid stenosis was .90 (95% confidence interval, .85 to .92). The mean difference in stenosis between the two raters was 0.8% (95% confidence interval, −2.1% to 3.7%). κ
1
to κ
5
equaled 0.80, 0.40, 0.79, 0.91, and 0.92, respectively.

Conclusions
Interobserver agreement for distinct 10% categories of angiographic carotid stenosis is moderate, but when realistic risk- and decision-based weights are used, agreement between experienced observers can be almost perfect.
Asymptomatic Carotid Endarterectomy
Authors: Marcinczyk Michael J. , Nicholas Gary G. , Reed James F. , Nastasee Susan A.
Published: June 2011

Background and Purpose
The applicability of prospective carotid endarterectomy protocols to the general population has been questioned. Outcomes for asymptomatic patients undergoing carotid endarterectomy were compared with the results of the Asymptomatic Carotid Atherosclerosis Study (ACAS) patients treated concurrently at our institution.

Methods
Asymptomatic patients undergoing carotid endarterectomies (n=277) from 1987 to 1993 (ACAS enrollment period) were reviewed. Primary end points were mortality, myocardial infarction, and stroke. Five subgroups were studied: (1) ACAS surgical patients; (2) ACAS-eligible patients not enrolled and ACAS surgeons; (3) ACAS-eligible patients not enrolled and non-ACAS surgeons; (4) ACAS-ineligible patients and ACAS surgeons; and (5) ACAS-ineligible patients and non-ACAS surgeons.

Results
ACAS-eligible patients were younger (
P
=.014), had more severe carotid stenosis (
P
=.001), and had lower incidences of pulmonary (
P
=.015) and renal (
P
=.008) diseases compared with ineligible patients. Patient selection (ACAS eligibility) significantly improved outcomes for mortality (
P
=.014) and myocardial infarction (
P
=.006). Length of stay favored ACAS-eligible patients (
P
=.004). ACAS surgeons operated on more severely stenotic carotid lesions (
P
=.005) and on patients with a lower incidence of coronary artery disease (
P
=.007). There was no difference in outcomes between ACAS and non-ACAS surgeons.

Conclusions
Patient selection was a significant factor in determining outcome. With strict adherence to ACAS enrollment guidelines, the conclusions of ACAS appear applicable to patients seen at our institution with asymptomatic carotid stenosis.
Correlation of Peak Systolic Velocity and Angiographic Measurement of Carotid Stenosis Revisited
Authors: Alexandrov Andrei V. , Brodie Dianne S. , McLean Arline , Hamilton Paul , Murphy John , Burns Peter N.
Published: June 2011

Background and Purpose
Recent observations from the North American Symptomatic Carotid Endarterectomy Trial (NASCET) questioned the reliability of peak systolic velocity (PSV) criteria for grading carotid stenosis. We compared PSV and angiographic measurements at our center together with known physiological relationships to investigate the accuracy of ultrasound.

Methods
Consecutive patients who underwent both color-coded duplex ultrasound and intra-arterial digital subtraction angiography were studied. PSV was determined with angle correction at the site of the tightest internal carotid artery narrowing. Carotid stenosis was measured on angiograms with the North American (N) and common carotid (C) methods. Variables for the stepwise multiple linear regression analysis were selected from an axisymmetrical flow model.

Results
Eighty bifurcations were imaged in 40 patients. PSV did not exceed 140 cm/s in normal vessels. In diseased arteries, PSV increased proportionally with increasing stenosis and decreased to 0 cm/s at occlusion. In stepwise selection of polynomial terms, the linear, quadratic, and cubic correlations of .38, .17, and .22 for N and .45, .24, and .03 for C were found to be significant (
P
<.02). When only stenosed vessels were evaluated, PSV increase was found with greater scatter for the N measurement:
r
2
=.73 for N and
r
2
=.85 for C (n=50;
P
=.03 for the difference between two correlated correlation coefficients).

Conclusions
At our laboratory PSV consistently correlates well with N and C angiographic measurements, as determined with a simple flow model. The complex nature of these correlations and greater variability of the N measurement should be taken into account when data from different centers are compared.
Effect of Subarachnoid Hemorrhage on Cerebral Vasodilatation in Response to Activation of ATP-Sensitive K
+
Channels in Chronically Hypertensive Rats
Authors: Sobey Christopher G. , Heistad Donald D. , Faraci Frank M.
Published: June 2011

Background and Purpose
Cerebral vasodilatation in response to aprikalim, an opener of ATP-sensitive K
+
channels, is selectively augmented after subarachnoid hemorrhage (SAH). Vasodilatation in response to activation of ATP-sensitive K
+
channels, however, is impaired during chronic hypertension. Hypertension may contribute to a worse outcome after SAH, but the nature of the relationship between hypertension and SAH is uncertain. In the present study we examined responses of the basilar artery to aprikalim after SAH in normotensive Wistar-Kyoto rats (WKY) and stroke-prone spontaneously hypertensive rats (SHRSP).

Methods
In anesthetized WKY and SHRSP, we measured changes in diameter of the basilar artery in response to aprikalim and papaverine using a cranial window 2 days after injection of 0.3 mL saline or autologous blood into the cisterna magna.

Results
Under control conditions, aprikalim (0.1 to 1 μmol/L) and papaverine (10 to 100 μmol/L) produced dilatation of the basilar artery. After SAH, responses to aprikalim were not significantly altered in WKY and were markedly increased in SHRSP compared with saline-injected control rats. In contrast, vasodilator responses to papaverine were not changed by SAH in either WKY or SHRSP, suggesting that augmented vasodilatation in response to aprikalim after SAH was selective.

Conclusions
Responses of the basilar artery to aprikalim were greatly augmented in SHRSP after SAH. Because vasodilator responses to many stimuli are impaired after SAH and cerebral vasodilator responses to several stimuli are impaired by chronic hypertension, augmented responses to activation of K
+
channels despite the presence of hypertension are unusual.
Myxoma in the Carotid Artery
Authors: Robbin N.A. , Landless P. , Cooper K. , Fritz V.U.
Published: June 2011

Background
We describe a patient with an unusual cause of internal carotid artery occlusion resulting in a stroke.

Case Description
A 41-year-old woman presented with a typical acute right middle cerebral artery territory infarct. Her hematological and cardiological status was assessed, including all extracranial vessels. Carotid angiography and a biopsy were performed of the occluded right internal carotid artery and demonstrated a myxoma. Cardiac investigations to determine the source of the myxoma, including transthoracic and transesophageal echocardiograms, CT and yo-yo CT scans, and MRI of the heart, were normal. No residual tumor or potential source of the tumor was found.

Conclusion
The cause of stroke was a myxomatous occlusion of the right internal carotid artery. An entire cardiac tumor may have embolized with no detectable residual tumor in the heart; alternatively, a myxoma may have originated as a primary tumor in the carotid artery. To our knowledge, no primary myxoma has been reported to have originated in a blood vessel.
Comparable Studies of the Incidence of Stroke and its Pathological Types
Authors: Sudlow C.L.M. , Warlow C.P.
Published: June 2011

Background and Purpose
Comparing stroke rates in different parts of the world may increase our understanding of both etiology and prevention. However, comparisons are meaningful only if studies use standard definitions and methods, with comparably presented data. We compared the incidence of stroke and its pathological types (cerebral infarction, primary intracerebral hemorrhage, and subarachnoid hemorrhage) in recent studies from around the world.

Methods
Studies with a midyear of 1984 or later, fulfilling standard criteria for a comparable, community-based study, provided original data for comparative analyses.

Results
By mid-1995, data were available from 11 studies in Europe, Russia, Australasia, and the United States, comprising approximately 3.5 million person-years and 5575 incident strokes. Age- and sex-standardized annual incidence rates for subjects aged 45 to 84 years were similar (between approximately 300/100 000) and 500/100 000) in most places but were significantly lower in Dijon, France (238/100 000), and higher in Novosibirsk, Russia (627/100 000). In subjects aged 75 to 84 years, however, Novosibirsk no longer ranked higher than the other studies. The distribution of pathological types, when these were reliably distinguished, did not differ significantly between studies.

Conclusions
The similarities in stroke incidence and pathological types are perhaps not surprising given that all the populations were westernized and mainly white. The higher rates in Novosibirsk, disappearing in the elderly, and the lower rates in Dijon have several potential explanations. These include methodological artifact and different patterns of population risk factors. Further work is needed to explore these possibilities and to extend our knowledge of stroke incidence to other parts of the world, especially developing countries.
The Canadian Study of Health and Aging
Authors: Lindsay Joan , Hébert Réjean , Rockwood Kenneth
Published: June 2011

Background and Purpose
The Canadian Study of Health and Aging (CSHA) was conducted in communities and institutions in 10 Canadian provinces. One objective of the study was to study risk factors for vascular dementia (VaD).

Methods
This was a population-based case-control study. It included 129 patients clinically diagnosed with VaD with duration of symptoms no more than 3 years and 535 control subjects, frequency matched by age group, study center, and residence in community or institution, who were clinically confirmed to be cognitively normal. Odds ratios (ORs) were calculated using unconditional logistic regression for potential risk factors for VaD.

Results
Risk of VaD was associated with history of arterial hypertension (OR, 2.08; 95% confidence interval, 1.29 to 3.35). Other significantly elevated ORs were seen for history of alcohol abuse (2.45), history of heart condition (1.71), use of aspirin (3.10), and occupational exposure to pesticides and herbicides (2.60), as well as liquid plastic or rubber (2.59). The OR for less than 6 years of education compared with 10 or more years was 4.02.

Conclusions
The study confirmed some previously reported risk factors for VaD, such as history of heart disease. Higher levels of education seemed to lower the risk or delay onset of symptoms of VaD. Use of aspirin may be a predictor of survival rather than a risk factor. The occupational associations, particularly with pesticides and fertilizers, need further study.
Delayed Improvement in Carotid Artery Diameter After Carotid Angioplasty
Authors: Crawley Francesca , Clifton Andrew , Markus Hugh , Brown Martin M.
Published: June 2011

Background and Purpose
Carotid percutaneous transluminal angioplasty (PTA) is a new method of treating carotid artery stenosis. There has been concern about restenosis after carotid PTA. This study was performed to ascertain the change in percent stenosis 1 year after carotid PTA.

Methods
Twelve patients with symptomatic carotid stenosis were treated by PTA, and the anatomic result was studied by digital subtraction angiography at 1 year, supplemented by duplex ultrasound examinations at 1 month and 6 months.

Results
The mean severity of stenosis treated, measured by the common carotid method, was 82% (range, 69% to 98%). The immediate result of PTA was a reduction in the severity of stenosis in all patients to a mean of 51% (
P
<.005). Six of the 12 patients showed a further improvement in lumen diameter of ≥14% at 1-year angiographic follow-up from a mean stenosis of 47% (range, 24% to 76%) immediately after PTA to 28% (range, 0% to 52%) at 1 year. This indicates an active process of remodeling in response to carotid PTA. PTA initially reduced the stenosis by ≥20% in 9 of the 12 arteries, and 8 of these remodeled or remained largely unchanged compared with only 1 of the 3 with a suboptimal initial dilation. In 3 patients the lumen diameter improved by <5%. Three other patients restenosed with an increase in stenosis after PTA of 9%, 16%, and 66% at 1 year, but all were asymptomatic. The duplex findings showed that remodeling occurred at variable times between PTA and 1 year.

Conclusions
Remodeling of the carotid artery after PTA has not been described before. Our results confirm that carotid angioplasty has an acceptable patency rate at 1 year. It has been suggested that endovascular treatment of carotid stenosis should include placement of a stent. Our results indicate that this may not be necessary unless the initial PTA result is a reduction in stenosis of <20%.
Perindopril Reduces Blood Pressure but Not Cerebral Blood Flow in Patients With Recent Cerebral Ischemic Stroke
Authors: Dyker Alexander G. , Grosset Donald G. , Lees Kennedy
Published: June 2011

Background and Purpose
The relationship between high blood pressure and the incidence of stroke is well established. Currently the effects of lowering blood pressure in patients with established cerebrovascular disease is undetermined, and there is continuing concern regarding the treatment of patients soon after a stroke event. Angiotensin-converting enzyme inhibitors maintain cerebral blood flow despite lowering blood pressure in patients with heart failure and otherwise uncomplicated hypertension. We tested the hypothesis that perindopril, an angiotensin-converting enzyme inhibitor with a gradual onset of action and a minimal first-dose hypotensive effect, lowers blood pressure without adversely affecting cerebral blood flow in patients 2 to 7 days after symptoms of cerebral infarction.

Methods
Patients were randomized to receive 15 days of oral perindopril (4 mg) or placebo in a double-blind study. Blood pressure was monitored semiautomatically. Cerebral blood flow was calculated from internal carotid artery and vertebral Doppler ultrasound, supplemented by middle cerebral artery blood velocities.

Results
Twenty-four patients completed the protocol; four additional patients were withdrawn for reasons unrelated to treatment. Patients on perindopril had a placebo-corrected reduction in blood pressure of 19/11 mm Hg. Blood pressure remained reduced after 2 weeks of treatment. In contrast, total cerebral blood flow was unaffected by perindopril. Neurological symptoms improved similarly in both groups.

Conclusions
Perindopril was well tolerated and effectively reduced blood pressure without reducing carotid territory blood flow in patients with symptoms of recent cerebral ischemia.
Studies on the Influence of Enriched-Environment Housing Combined With Systemic Administration of an α
2
-Adrenergic Antagonist on Spatial Learning and Hyperactivity After Global Ischemia in Rats
Authors: Puurunen Kirsi , Sirviö Jouni , Koistinaho Jari , Miettinen Riitta , Haapalinna Antti , Riekkinen Paavo , Sivenius Juhani
Published: June 2011

Background and Purpose
The purpose of this study was to determine whether an enriched housing environment and/or systemic administration of the α
2
-adrenergic receptor antagonist atipamezole facilitate the rate of spatial learning after global ischemia in rats.

Methods
Carotid arteries were closed for 20 minutes after permanent cauterization of vertebral arteries on the previous day. Enriched-environment housing and drug/saline treatment were begun 3 days after ischemia. For rehabilitation, housing in an enriched environment was combined with exploration in a labyrinth. Behavioral tests (the open-arena test and water-maze learning set task) were performed after 1-week periods of drug/saline treatment three times. In addition, the open-arena test was performed to evaluate the baseline level of animals 2 days after the induction of ischemia and at the end of the experiment, when the water-maze task was assessed in another room.

Results
Rats housed in an enriched environment after ischemia showed better acquisition of the water-maze learning set task after 1 week of housing. The influence of atipamezole treatment on this parameter did not reach statistical significance. In the open-arena test, ischemic animals were slightly hyperactive; however, this symptom was eliminated by housing in an enriched environment.

Conclusions
The present data suggest that housing in an enriched environment facilitates the rate of spatial learning in rats with global ischemia. Rehabilitation also alleviated the hyperactivity observed in ischemic animals.
Transgenic Rats as Models for Studying the Role of Ornithine Decarboxylase Expression in Permanent Middle Cerebral Artery Occlusion
Authors: Lukkarinen Jouko , Gröhn Olli H. J. , Sinervirta Riitta , Järvinen Aki , Kauppinen Risto A. , Jänne Juhani , Alhonen Leena I.
Published: June 2011

Background and Purpose
Cerebral ischemia causes activation of ornithine decarboxylase (ODC) gene and subsequent accumulation of putrescine, which might either directly or indirectly affect the outcome of cerebral infarct. We developed a transgenic rat overexpressing human ODC, which was used to explore the effect of abnormally high putrescine concentration in the brain on the infarct volume after permanent middle cerebral artery (MCA) occlusion.

Methods
The transgenic rats were produced by the pronuclear injection technique with the use of cloned human ODC gene. The right MCA was permanently occluded through craniotomy. ODC activity and polyamines were assayed in the infarcted and contralateral hemispheres. MRI was used to quantify T2 relaxation time, apparent diffusion constant (ADC), and infarct volume, which was also determined by 2,3,5-triphenyltetrazolium chloride.

Results
Permanent MCA occlusion resulted in extensive activation of ODC, which was approximately sevenfold greater than in syngenic animals at 20 hours after occlusion. Consequently, putrescine increased from approximately 10 and 230 pmol/mg to 160 and 410 pmol/mg in the infarcted hemisphere of syngenic and transgenic animals, respectively, but all the other polyamines were unchanged. This high putrescine in the transgenic rats did not influence infarct size evolution, as determined by MRI, T2, ADC, or the infarct volume by 2,3,5-triphenyltetrazolium chloride at 48 hours.

Conclusions
Data from the ODC transgenic rat model show that the development of brain infarct after permanent MCA occlusion was not influenced by extensive levels of putrescine, indicating that this endogenous amine is not involved in maturation and spread of stroke lesion in vivo. Thus, it seems that ODC activation reflects an endogenous adaptation of neural cells to a noxious stimulus that does not directly influence lesion development.
Reproducibility of In Vivo Carotid Intima-Media Thickness Measurements
Authors: Kanters Suzan D.J.M. , Algra Ale , van Leeuwen Maarten S. , Banga Jan-Dirk
Published: June 2011

Background
The early phase of atherosclerosis can be studied by two-dimensional B-mode ultrasonography. Measurements of the combined thickness of the carotid intima and media are currently used as intermediate outcome in clinical trials. Comparison of results between studies is difficult because of the different methods of image acquisition and analysis used. We review these methods and the reported reproducibility of intima-media thickness (IMT) measurements.

Summary of Review
Articles were collected using the MEDLINE literature search system and the references in the selected articles. Literature concerning human in vivo IMT measurements published in the English language in the period 1991 through 1995 was reviewed. A description of the methods of measuring IMT to determine intraobserver and/or interobserver variability was a prerequisite for inclusion. Twenty-three studies were included. Best reproducibility was found when measuring the mean IMT in the common carotid artery in more than one direction.

Conclusions
We conclude that a consensus concerning the assessment of IMT is urgently needed. Variability of IMT measurements is lowest when determining the mean thickness in the common carotid artery in different directions.
Use of a Decibel Threshold in Detecting Doppler Embolic Signals
Authors: Markus Hugh S. , Molloy Jane
Published: June 2011

Background and Purpose
To improve reproducibility and reliability in the identification of embolic signals detected with the use of Doppler ultrasound, many studies have used an intensity threshold. However, variable thresholds between 3 and 12 dB have been used, and often the method of measurement of intensity is not stated. Potentially different methods of measurement could result in different intensity measurements for the same embolic signal. We determined the effect of these differences using commercial transcranial Doppler systems.

Methods
We analyzed 81 embolic signals recorded from the middle cerebral arteries of patients with carotid artery disease using three different methods of measuring intensity that had been previously used in research studies. In method 1 individual time frames of the frequency spectra were analyzed, in method 2 a color-coded intensity scale was used, and in method 3 automated software was used.

Results
There was a highly significant correlation between measurements made by the different techniques (method 1 versus method 2:
r
=.68,
P
<.0001; method 1 versus method 3:
r
=.66,
P
<.0001; method 2 versus method 3:
r
=.70,
P
<.0001). However, the absolute values of intensity for the same embolic signals varied markedly for the different methods. For example, a 4-dB threshold according to method 1 was equivalent to an approximately 7-dB threshold measured by method 2. These differences had major effects on the proportion of embolic signals detected with the use of the same decibel threshold but with intensity measured in the different ways. For example, using a threshold of 7 dB would result in only 4.9% of signals being missed by method 2 but 42.2% and 51.4% being missed by methods 1 and 3, respectively.

Conclusions
Our results demonstrate that the intensities of the same embolic signals, recorded with the same parameters, are markedly different when analyzed in the different ways used in previous studies. This has important implications when a decibel threshold is used and emphasizes that criteria developed by one investigator on one machine cannot be used by another investigator without initial reevaluation. This could account for some of the differences in frequencies of embolic signals reported in previous clinical studies.
Ischemic Stroke After Acute Myocardial Infarction
Authors: Mooe Thomas , Eriksson Peter , Stegmayr Birgitta
Published: June 2011

Background and Purpose
Modern treatment may have influenced the risk of stroke after myocardial infarction (MI). The purpose of this study was to examine the incidence of ischemic stroke during the first month after an acute MI in an unselected population, to identify predictors of MI-related stroke, and to investigate the secular trend in MI-related stroke incidence.

Methods
In this case-control study, from a population of approximately 310 000 25- to 74-year-old inhabitants, case subjects with a stroke within 1 month after an MI were prospectively recorded in the population-based Northern Sweden MONICA (Monitoring of Trends and Determinants in Cardiovascular Disease) study from 1985 to 1994. The same number of control subjects with an MI but without a stroke were matched for age, sex, and year when MI occurred.

Results
One hundred twenty-four case subjects were recorded. Fifty-one percent (63/124) of the strokes occurred within 5 days after onset of MI. The odds ratios (ORs) of an MI-related stroke were for a history of hypertension 1.7 (95% confidence interval [CI], 1.0 to 3.2), previous stroke 2.4 (CI, 1.0 to 6.1), chronic atrial fibrillation 3.0 (CI, 1.1 to 9.2), onset of atrial fibrillation during the hospital stay 3.5 (CI, 1.4 to 10.1), ST-segment elevation 2.4 (CI, 1.4 to 4.6), and anterior infarction 1.5 (CI, 0.9 to 2.6). In a conditional multiple logistic regression model, previous stroke (OR, 2.8; CI, 1.1 to 7.6), chronic atrial fibrillation (OR, 3.8; CI, 1.3 to 11.0), new-onset atrial fibrillation (OR, 4.6; CI, 1.6 to 12.8), and ST-segment elevation (OR, 3.4; CI, 1.6 to 7.4) were independent predictors of stroke. MIs preceding stroke were larger and in 51% were located anteriorly. There was a decrease in the incidence and event rate of MI-related stroke during the study period (
P
<.01 and
P
<.05, respectively).

Conclusions
The risk of stroke is highest the first 5 days after MI. Only approximately half of the strokes occurring the first month after an MI are preceded by an anterior MI. The most important predictors of MI-related stroke are atrial fibrillation (chronic or new onset), ST elevation, and a history of a previous stroke. There is a long-term trend toward a lower incidence of MI-related stroke. These findings have important implications concerning both the pathophysiology and prevention of MI-related stroke.
Role of P-450 Arachidonic Acid Epoxygenase in the Response of Cerebral Blood Flow to Glutamate in Rats
Authors: Alkayed Nabil J. , Birks Eric K. , Narayanan Jayashree , Petrie Kim A. , Kohler-Cabot Anne E. , Harder David R.
Published: June 2011

Background and Purpose
Glutamate, a major excitatory neurotransmitter in the brain, has been implicated in the hyperemic response to increases in the activity of neurons, but the mechanism of glutamate-induced dilation of cerebral blood vessels is unknown. Glutamate has been shown to enhance the release of arachidonic acid (AA) in brain tissue and cultured astrocytes. We have previously shown that astrocytes metabolize AA to vasodilator products, epoxyeicosatrienoic acids (EETs), and express a P-450 AA epoxygenase, P-450 2C11. We tested the hypothesis that glutamate-induced dilation of cerebral arterioles is mediated in part by changes in the formation and release of EETs by perivascular astrocytes.

Methods
Primary astrocyte cultures were prepared from 3-day-old rat pups. The cells were labeled with [
14
C]AA, and the effect of glutamate on the formation of EETs from [
14
C]AA by cultured astrocytes was studied. The expression of P-450 2C11 protein in the microsomal fractions of cultured astrocytes was assessed by Western blot. In vivo cerebral blood flow measurements were made in adult rats by laser-Doppler flowmetry after administration of glutamate into the subdural space of the rat before and after treatment with miconazole.

Results
Glutamate treatment (100 μmol/L for 30 minutes) induced a threefold increase in the formation of EETs from [
14
C]AA by cultured astrocytes, and the increase was inhibited by miconazole (20 μmol/L), an inhibitor of P-450 AA epoxygenase. Treatment with glutamate (100 μmol/L) for 12 hours increased the expression of P-450 2C11 protein in the microsomal fraction of cultured astrocytes. The response of laser-Doppler cerebral blood flow to administration of glutamate (500 μmol/L) into the subdural space of the rat was significantly attenuated after treatment with miconazole (20 μmol/L for 30 minutes).

Conclusions
These findings suggest a role for a P-450 AA epoxygenase in astrocytes in the coupling between the metabolic activity of neurons and regional blood flow in the brain.
Regional Performance of Carotid Endarterectomy
Authors: Wong John H. , Findlay J. Max , Suarez-Almazor Maria E.
Published: June 2011

Background and Purpose
Guided by the findings of randomized controlled trials evaluating carotid endarterectomy (CEA), we examined the appropriateness of CEAs performed in our city and determined the incidences and risk factors for postoperative stroke, death, and cardiac complications.

Methods
Using health records, we retrospectively reviewed 291 consecutive CEAs performed in our region over 18 months. Based on randomized controlled trial results and standardized remeasurements of angiographic carotid stenoses, indications for CEA were considered appropriate for symptomatic carotid stenoses ≥70%, uncertain for <70% symptomatic or ≥60% asymptomatic stenoses, or inappropriate for <60% asymptomatic stenoses and for patients with preoperative neurological or medical instability.

Results
We found that 41% of patients (118/291) were asymptomatic. Surgical indications were appropriate in 33% of cases (92/281), uncertain in 49% (138/281), and inappropriate in 18% (51/281). Stroke or death occurred within 30 days postoperatively in 5.2% (9/174) of symptomatic patients and 5.1% (6/117) of asymptomatic patients. At least one cardiac complication (angina, congestive heart failure, dysrhythmia, or myocardial infarction) developed in 8.9% (26/291). Independent preoperative risk factors for stroke or death were histories of angina or congestive heart failure and lack of antiplatelet medication; for cardiac complications, risk factors were age >75 years and a history of congestive heart failure.

Conclusions
Almost 1 in 5 patients underwent CEA inappropriately, which was most commonly due to apparent overestimation of stenosis severity, and half had uncertain indications. Our high complication rate possibly negated any overall surgical benefit in the large group of asymptomatic patients.
Stroke Patients’ Knowledge of Stroke
Authors: Williams Linda S. , Bruno Askiel , Rouch Dorinda , Marriott Deanna J. , MAS
Published: June 2011

Background and Purpose
New treatments for acute stroke will likely have to be given soon after stroke onset. Little is known about stroke patients’ general knowledge about stroke, their interpretation of stroke symptoms, and how these factors influence the timing of their decision to seek medical attention.

Methods
We interviewed consecutive stroke patients within 72 hours of stroke onset to define factors influencing time of arrival to the emergency department. Data recorded included demographic information, method of transportation, type of stroke symptoms, the patient’s interpretation of the symptoms, previous stroke, and knowledge of stroke warning signs. Stroke severity was measured with the Barthel Index. Early arrival was defined as within 3 hours of awareness of symptoms.

Results
Sixty-seven patients were interviewed; 96% had an ischemic stroke and 4% a cerebral hemorrhage. Although 38% of patients professed to know the warning signs of stroke, only 25% correctly interpreted their symptoms. Patients with prior stroke were more likely to correctly interpret their symptoms (45% versus 16%;
P
=.03) but were not more likely to present early (19% versus 39%;
P
=.35). Eighty-six percent of patients presenting more than 3 hours after stroke onset thought that their symptoms were not serious. The 24% (n=16) of early arrivals were more likely to arrive by ambulance (81% versus 38%;
P
=.003) and had more severe strokes (Barthel Index score of 49 versus 72;
P
=.01) than late arrivals. Arrival by ambulance was independently associated with early arrival (odds ratio, 5.55; 95% confidence interval, 1.37 to 22.6).

Conclusions
Approximately one quarter of stroke patients correctly interpret their symptoms as representing a stroke. This knowledge is not associated with early presentation to the emergency department. Ambulance transport is independently associated with early arrival at the emergency department. Even when patients know that they are having a stroke, most present late because they perceive their symptoms as “not serious.” Widespread public education of stroke-prone individuals may increase the proportion of patients eligible for new acute stroke treatments.
Sensitivity and Specificity of
99m
Tc-HMPAO SPECT Cerebral Perfusion Measurements During the First 48 Hours for the Localization of Cerebral Infarction
Authors: Baird A.E. , Austin M.C. , McKay W.J. , Donnan G.A.
Published: June 2011

Background and Purpose
There is no routinely used method for imaging the location of the extent and severity of cerebral tissue perfusion changes during the first hours of ischemic stroke, the period during which therapeutic intervention is most likely to be successful. Cerebral perfusion measurements with single-photon emission CT (SPECT) may potentially provide this information rapidly and noninvasively. In this study, the sensitivity and specificity of
99m
Tc–hexamethylpropyleneamine oxime (HMPAO) SPECT cerebral perfusion measurements during the first 48 hours of cerebral ischemia for the localization of cerebral infarction were determined.

Methods
One hundred and four patients with acute ischemic stroke underwent
99m
Tc-HMPAO SPECT and CT scanning during the first 48 hours. In each patient, the location of the SPECT perfusion abnormality was compared with the location of infarction on a second brain CT acquired at a mean of 8 days after stroke.

Results
During the first 48 hours of ischemic stroke, the sensitivity of
99m
Tc-HMPAO SPECT in locating the site of infarction was 79% (110/139), and the specificity was 95% (362/381). SPECT was more sensitive in the localization of the vascular territory of cortical infarction (sensitivity, 93%) than pure subcortical infarcts (sensitivity, 47%). During the first 48 hours, SPECT was significantly more sensitive than brain CT (sensitivity of brain CT during the first 48 hours, 35%;
P
<.001, Mann-Whitney
U
test).

Conclusions
HMPAO SPECT measurement provides a widely available and practical technique of locating cerebral ischemia acutely and demonstrates high sensitivity and specificity within the first 48 hours for the localization of the vascular territory of cerebral infarction. It is most sensitive for cortical ischemia but is limited by its resolution in the subcortex, particularly of white matter perfusion changes.
Epidemiology and Costs of Acute Hospital Care for Cerebrovascular Disease in Diabetic and Nondiabetic Populations
Authors: Currie Craig J. , Morgan Christopher L. , Gill Leicester , Stott Nigel C. H. , Peters John R.
Published: June 2011

Background and Purpose
Little is known about the pattern of cerebrovascular disease (CVD) for diabetic and nondiabetic patients or about the cost of treatment for CVD in the United Kingdom. The purpose of this study was to extend previous work to describe the epidemiology and cost of acute care of CVD as a frequent comorbidity of diabetes in a UK population (408 000 people).

Methods
Routine data describing inpatient care for a 4-year period were analyzed (financial years 1991/1992 to 1994/1995). These data had undergone record linkage to draw together records from the same patients. Cost estimates were determined by attributing a diagnosis-related group cost weight to each record. Mortality data from an overlapping period were supplied by the Office of Population Censuses and Surveys.

Results
There were 11 196 CVD admissions (3.1% of all admissions). Of these, 7351 (66%) were primary diagnoses. These admissions were generated by 5358 patients (3904 primary diagnosis). For people with diabetes, the incidence rate was between 23 and 32.8 per 1000 per year compared with 2.4 to 3.3 per 1000 for the population as a whole, depending on the use of primary and subsidiary codes. The age-adjusted relative risk of stroke in diabetic men versus nondiabetic men was 3.70 (95% confidence interval, 3.53 to 3.88) and in women was 4.35 (95% confidence interval, 4.37 to 4.76). We describe other epidemiological relationships. The cost of CVD is between £1.1 and £1.6 million per 100 000 population—at least £0.7 million per 100 000 for CVD alone. Approximately 15% of this value is related to diabetes, and an estimated 94% of this diabetes-related expenditure is potentially avoidable.

Conclusions
CVD represents a major source of expenditure for health services, and diabetes is confirmed as a major risk factor within this disease group. Differences between diabetic and nondiabetic inpatient patterns of CVD may reflect greater incidence of comorbidities in the former.
STAR MR Angiography for Rapid Detection of Vascular Abnormalities in Patients With Acute Cerebrovascular Disease
Authors: Siewert Bettina , Wielopolski Piotr A. , Schlaug Gottfried , Edelman Robert R. , Warach Steven
Published: June 2011

Background and Purpose
We undertook to investigate the usefulness of signal targeting with alternating radiofrequency magnetic resonance angiography (STAR MRA) in the diagnosis of acute cerebrovascular disease. The potential advantage of the technique is that angiographic images can be acquired in less than 1 minute.

Methods
We studied 19 patients (11 men and 8 women, ranging in age from 36 to 84 years [mean age, 66 years]) presenting with signs and symptoms of acute stroke. Patients underwent STAR MRA and three-dimensional fast imaging with steady-state precession (3D FISP) MRA. The MRAs were analyzed as to image quality and vascular abnormalities in the vascular territory of stroke as defined by diffusion-weighted imaging abnormalities and compared using a Wilcoxon signed-rank test.

Results
STAR MRAs had slightly inferior image quality compared with 3D FISP MRA (
P
<.05). STAR MRA and 3D FISP MRA agreed in 18 of 19 cases regarding vascular abnormalities in the territory of the infarct (occlusion, n=8; stenosis, n=4; no abnormality, n=6). In one patient, the techniques disagreed, when 3D FISP MRA was normal and STAR MRA demonstrated a vessel occlusion in the vascular territory of a stroke as defined by diffusion-weighted imaging abnormalities (
P
>.05).

Conclusions
Despite slightly inferior image quality compared with 3D FISP MRA, STAR MRA is comparable with 3D FISP MRA in depicting abnormalities in the proximal parts of the cerebral arteries corresponding to ischemic regions on diffusion-weighted imaging, in a strikingly shorter acquisition time. Further studies are necessary to confirm that the smaller branches are better shown by using longer inversion times.
Kainate-Induced Cerebrovascular Dilation Is Resistant to Ischemia in Piglets
Authors: Bari Ferenc , Louis Thomas M. , Busija David W.
Published: June 2011

Background and Purpose
Cerebral arteriolar dilation to
N
-methyl-
d
-aspartate (NMDA) is drastically reduced by anoxic stress. The effects of anoxic stress on cerebrovascular dilation to activation of other types of glutamate receptors are unknown. The purpose of this study was to examine the effects of ischemia on cerebral arteriolar responses to kainate in anesthetized piglets.

Methods
Arteriolar responses to 5×10
−5
mol/L and 10
−4
mol/L kainate were evaluated before and 10 minutes after total, global ischemia. Ischemia was induced by increasing intracranial pressure. We measured pial arteriolar diameters (≈100 μm) using a cranial window and intravital microscopy.

Results
Before ischemia, kainate dilated arterioles by 16±2% at 5×10
−5
mol/L and 30±2% at 10
−4
mol/L (mean±SEM; n=6). After ischemia, the diameter of arterioles increased by 17±3% and 26±3% to 5×10
−5
and 10
−4
mol/L kainate, respectively (
P
>.05). We also investigated the mechanisms involved in mediating arteriolar dilation to kainate. Intravenous administration of
N
ω
-nitro-
l
-arginine methyl ester (L-NAME) (15 mg/kg) (n=7) or indomethacin (10 mg/kg) (n=6) individually reduced arteriolar dilation to kainate by approximately one half. Coadministration of L-NAME and indomethacin almost completely eliminated arteriolar dilation to kainate (n=10). Administration of theophylline (20 mg/kg IV) did not affect dilator responses to kainate (n=7). Blockade of NMDA receptors by MK801 had minimal effects on arteriolar dilation to kainate (n=6).

Conclusions
There are three main findings from this study: (1) kainate is a potent dilator agent in the neonatal cerebral circulation; (2) nitric oxide and prostaglandins both participate in the vasodilator response to kainate; and (3) in contrast to NMDA, cerebral arteriolar dilator responses to kainate are resistant to ischemic stress.
Nitric Oxide Synthase in Models of Focal Ischemia
Authors: Samdani Amer F. , Dawson Ted M. , Dawson Valina L.
Published: June 2011

Background and Purpose
Cessation of blood flow to the brain, for even a few minutes, sets in motion a potential reversible cascade of events resulting in neuronal cell death. Oxygen free radicals and oxidants appear to play an important role in central nervous system injury after cerebral ischemia and reperfusion. Recently, divergent roles for the newly identified neuronal messenger molecule and oxygen radical, nitric oxide (NO), have been identified in various models of cerebral ischemia. Because of the chemical and physical properties of NO, the numerous physiological activities it mediates, and the lack of specific agents to modulate the activity of the different isoforms of NO synthase (NOS), reports regarding the role of NO in focal cerebral ischemia have been confounding and often conflicting. Recent advances in pharmacology and the development of transgenic knockout mice specific for the different isoforms of NOS have advanced our knowledge and clarified the role of NO in cerebral ischemia.

Methods
Animal models of focal ischemia employ occlusion of nutrient cerebral vessels, most commonly the middle cerebral artery. Primary cortical cultures are exposed to excitotoxic or ischemic conditions, and the activities of NOS isoforms or NO production are evaluated. Transgenic mice lacking expression of either the neuronal isoform of NOS (nNOS), the endothelial isoform of NOS (eNOS), or the immunologic isoform of NOS (iNOS) have been examined in models of excitotoxic injury and ischemia.

Results
Excitotoxic or ischemic conditions excessively activate nNOS, resulting in concentrations of NO that are toxic to surrounding neurons. Conversely, NO generated from eNOS is critical in maintaining cerebral blood flow and reducing infarct volume. iNOS, which is not normally present in healthy tissue, is induced shortly after ischemia and contributes to secondary late-phase damage.

Conclusions
Pharmacological and genetic approaches have significantly advanced our knowledge regarding the role of NO and the different NOS isoforms in focal cerebral ischemia. nNOS and iNOS play key roles in neurodegeneration, while eNOS plays a prominent role in maintaining cerebral blood flow and preventing neuronal injury.
Impaired Dynamic Cerebral Autoregulation in Carotid Artery Stenosis
Authors: White Richard P. , Markus Hugh S.
Published: June 2011

Background and Purpose
If it could be determined whether cerebral blood flow can be maintained (autoregulated) during transient falls in arterial blood pressure, we might be able to identify patients with carotid stenosis who are at risk of stroke. However, conventional methods of determining autoregulation in such patients are invasive and/or expensive.

Methods
We used a new noninvasive method to estimate dynamic cerebral autoregulation in 27 patients with carotid stenosis and 21 age-matched normal controls. After a stepwise fall in arterial blood pressure, we determined the rate of rise of middle cerebral artery blood flow velocity compared with that of arterial blood pressure. We compared the method with a conventional method of determining cerebral hemodynamics, CO
2
reactivity.

Results
Autoregulatory index (ARI) was significantly reduced in middle cerebral arteries ipsilateral to a stenosed/occluded carotid artery: mean±SD 3.3±2.2 compared with normal controls (6.3±1.1;
P
<.0001) and nonstenosed carotid arteries in patients (5.9±2.1;
P
<.002). A subgroup of patients with severe impairment was identified. ARI returned to normal after carotid endarterectomy was performed. In a number of cases, ARI was impaired in the presence of CO
2
reactivity.

Conclusions
This simple technique allows identification of impaired autoregulation in patients with carotid artery disease. It may allow identification of patients at risk from transient falls of blood pressure as may occur at the onset of antihypertensive therapy and during surgery. It may allow a subgroup of patients with asymptomatic carotid stenosis who are at risk of hemodynamic stroke to be identified.