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Arterial Stenosis (arterial + stenosis)

Distribution by Scientific Domains

Medical Sciences	100%

Kinds of Arterial Stenosis

intracranial arterial stenosis

Selected Abstracts

Natural History of Asymptomatic Intracranial Arterial Stenosis

JOURNAL OF NEUROIMAGING, Issue S1 2009
Robert A. Taylor MD
ABSTRACT The prevalence and natural history of asymptomatic intracranial arterial stenosis are not very well characterized. Existing data suggest that incidentally discovered asymptomatic intracranial stenosis presents a fairly low risk of stroke, though substantial uncertainty remains. Patients may be at greater risk if there are tandem stenoses. Methods to stratify the risk of stroke with asymptomatic intracranial atherosclerotic lesions have yet to be established and validated. In general, aggressive intervention for an asymptomatic intracranial stenosis is not currently recommended. [source]

Symptomatic stenosis of the vertebrobasilar arteries: results of extra- and intracranial stent-PTA

EUROPEAN JOURNAL OF NEUROLOGY, Issue 1 2009
T. Seifert
Background and purpose:, About half of all transient ischaemic attacks (TIAs) or strokes in the posterior circulation are caused by the arterial stenosis. The purposes of this study were to determine the safety of stent-assisted percutaneous transluminal angioplasty (stent-PTA) and its efficacy for the prevention of recurrent stroke in patients with symptomatic artery stenosis in the extra- and intracranial posterior circulation. Methods:, Forty-six patients with a previous stroke or TIA who received balloon-mounted coronary stents for vertebral artery origin stenosis (VAOS; 29 patients) or self-expanding nitinol stents for vertebrobasilar intracranial stenosis (VBIS; 17 patients) were followed-up for a mean of 24.1 (VAOS) and 12.7 (VBIS) months. Results:, When all cause morbidity/mortality within 30 days from stent-PTA and stroke or death from stroke in the treated vascular territory during the first 12 months of follow-up are combined, the incidence of periprocedural complications and disease progression for the first year is 10.3% in VAOS patients and 17.6% in the VBIS group. Vessel restenosis ,50% was found in 52.0% of VAOS and in 32.1% of VBIS patients who completed 6 months follow-up. Conclusions:, We observed a higher periprocedural complication rate for patients with VBIS and a higher rate of restenosis in VAOS patients after stent-PTA for symptomatic artery stenosis. [source]

Reexamining the quantification of perfusion MRI data in the presence of bolus dispersion,

JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 3 2007
Linda Ko BSc
Abstract Purpose To determine the true impact of dispersion upon cerebral blood flow (CBF) quantification by removing an algorithm implementation-induced systematic error. Materials and Methods The impact of dispersion on the arterial input function (AIF) between measurement and entry into the tissue of interest on CBF estimates was simulated assuming: 1) contralateral circulation flow that introduces a true arterial tissue delay (ATD)-related dispersive component; and 2) the presence of an arterial stenosis that disperses and shifts the AIF peak entering the tissue; increasing the apparent ATD relative to the original AIF. Results Previously reported CBF estimates for the stenosis dispersion model were found to be a mixture of true dispersive effects and an algorithm implementation-induced systematic error. The true CBFMEASURED/CBFNO-DISPERSION ratios for short mean transit times (MTT) (normal) and long MTT (infarcted) tissue were similar for both dispersion models evaluated; this was an unanticipated result. The CBF quantification inaccuracies induced through the dispersion model truly related to ATD were lower than for the local stenosis-based dispersion for small ATD values. Conclusion Correcting the systematic error present in a previous deconvolution study removes the reported ATD-related impact on CBF quantification. The impact of dispersion was smaller than half that reported in previous simulation studies. J. Magn. Reson. Imaging 2007;25:639,643. © 2007 Wiley-Liss, Inc. [source]

Natural History of Asymptomatic Intracranial Arterial Stenosis

Screening for Intracranial Stenosis With Transcranial Doppler: The Accuracy of Mean Flow Velocity Thresholds

JOURNAL OF NEUROIMAGING, Issue 1 2002
Robert A. Felberg MD
ABSTRACT Background. Patients with 50% intracranial arterial stenosis may require more intensive therapies for stroke prevention. Transcranial Doppler (TCD) is a convenient noninvasive screen for intracranial stenosis. The accuracy of different mean flow velocity (MFV) thresholds for determining the degree of stenosis remains uncertain. Methods. The authors prospectively compared the accuracy of TCD criteria and MFV thresholds to magnetic resonance, computed tomography, and digital subtraction angiography in patients with symptoms of recent or remote stroke or transient ischemic attack. Stenosis on angiography was measured as 0%, <50%, or ,50% diameter reduction. Results. Of 136 consecutive patients, 33 (24%) had distal internal carotid artery (ICA), middle cerebral artery (MCA), posterior cerebral artery, or basilar artery stenosis on angiography (14 patients [10%] were excluded due to incomplete TCD examinations, mainly from a lack of temporal windows). TCD showed 31 true-positive, 9 false-positive, 2 false-negative, and 94 true-negative studies. For all vessels, TCD had a sensitivity of 93.9% (confidence interval [CI] = 89%-98%), a specificity of 91.2% (CI = 87%-96%), a positive predictive value (PPV) of 77.5%, and a negative predictive value (NPV) of 97.9%. The trade-off in sensitivity and specificity for MCA MFV thresholds was as follows: MFV ,80 cm/s had a sensitivity of 100%, a specificity of 96.9% (CI = 94%-99%), a PPV of 84%, and an NPV of 100%. MFV,100 cm/s had a sensitivity of 100%, a specificity of 97.9% (CI = 96%-99%), a PPV of 88.8%, and an NPV of 94.9%. MFV,120 cm/s had a sensitivity of 68.7% (CI = 61%-78%), a specificity of 100%, a PPV of 100%, and an NPV of 94.9%. Reasons for false-positive findings include collateralization of flow in the presence of proximal ICA stenosis and prestenotic to stenotic MCA velocity ratios of 1:,2. Conclusion. TCD is both sensitive and specific in identifying ,50% intracranial arterial stenosis. A MFV threshold cutoff of 100 cm/s has an optimal sensitivity and specificity trade-off for ,50% MCA stenosis. To help avoid false-positive results, a prestenotic to stenotic MCA velocity ratio of 1:,2 should be used in addition to the MFV threshold. [source]

Comparison of Transcranial Color-Coded Sonography and Magnetic Resonance Angiography in Acute Ischemic Stroke

JOURNAL OF NEUROIMAGING, Issue 4 2001
Li-Ming Lien MD
ABSTRACT Background and Purpose. This study was designed to assess the accuracy of transcranial color-coded sonography (TCCS) as compared to magnetic resonance angiography (MRA) for detecting intracranial arterial stenosis in patients with acute cerebral ischemia. Methods. The authors prospectively identified 120 consecutive patients admitted with acute ischemic stroke and performed both TCCS and MRA with a mean interval of 1 day. TCCS data (sampling depth, peak systolic and end diastolic angle-corrected velocity, mean angle-corrected velocity, and pulsatility index) for middle cerebral arteries (MCAs) were compared to MRA data and classified into 4 grades: normal (grade 1): normal caliber and signal; mild stenosis (grade 2): irregular lumen with reduced signal; severe stenosis (grade 3): absent signal in the stenotic segment (flow gap) and reconstituted distal signal; and possible occlusion (grade 4): absent signal. The cutoffs were chosen to maximize diagnostic accuracy. Results. Interobserver agreement for MRA grading resulted in a weighted-kappa value of 0.776. The rate of poor temporal window was 37% (89/240). Doppler signals were obtained in 135 vessels, and the angle-corrected velocities (peak systolic, end diastolic, mean) were significantly different (P= .001, P= .006, P < .001) among the MRA grades: grade 1 (100, 47, 68 cm/s), grade 2 (171, 72, 110 cm/s), grade 3 (226, 79, 134 cm/s), grade 4 (61, 26, 39 cm/s). Additionally, an angle-corrected MCA peak systolic velocity ,120 cm/s correlates with intracranial stenosis on MRA (grade 2 or worse) with high specificity (90.5%; 95% confidence interval = 78.5%,96.8%) and positive predictive value (93.9%) but relatively low sensitivity (66.7%; 95% confidence interval = 61.2%,69.5%) and negative predictive value (55.1%). Conclusion. Elevated MCA velocities on TCCS correlate with intracranial stenosis detected on MRA. An angle-corrected peak systolic velocity ,120 cm/s is highly specific for detecting intracranial stenosis as defined by significant MRA abnormality. [source]

Ex vivo inhibition of thrombus formation by an anti-glycoprotein VI Fab fragment in non-human primates without modification of glycoprotein VI expression

JOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 6 2008
P. OHLMANN
Summary.,Objectives:,Glycoprotein (GP)VI is an attractive target for the development of new antithrombotic drugs. Its deficiency protects animals in several models of thrombosis, arterial stenosis and ischemia-,reperfusion while inducing no major bleeding tendency. The Fab fragment of one anti-GPVI monoclonal antibody (9O12.2) inhibits all GPVI functions in vitro. The aim of this study was to determine the ex vivo effects of 9O12.2 Fab on hemostasis, coagulation and thrombosis in non-human primates. Methods and results:,Blood samples were collected from cynomolgus monkeys before and after (30, 90 and 150 min, 1 and 7 days) a bolus injection of 9O12.2 Fab (4 mg kg,1) or vehicle. Platelet counts and coagulation tests (prothrombin time, activated partial thromboplastin time) were not modified following Fab injection. The PFA-100 closure time increased during the first hours and returned to initial values on day + 1. Platelet-bound Fab was detected from 30 min to 24 h after Fab injection without GPVI depletion at any time. Collagen-induced platelet aggregation was selectively and fully inhibited at 30 min. Thrombus formation on collagen in flowing whole blood (1500 s,1) was delayed and decreased, and collagen-induced or tissue factor-induced thrombin generation in platelet-rich plasma was profoundly inhibited. Conclusion:,The anti-GPVI 9O12.2 Fab inhibits thrombus formation ex vivo in non-human primates with a composite effect on platelet activation and thrombin generation in the absence of GPVI depletion. [source]

Circulating endothelial microparticles as a marker of cerebrovascular disease,

ANNALS OF NEUROLOGY, Issue 2 2009
Keun-Hwa Jung MD
Objective Circulating endothelial microparticles (EMPs) have been reported to reflect vascular damage. Detailed profiling of these blood endothelial markers may adumbrate the pathogenesis of stroke or enable determination of the risk for stroke. We investigated EMP profiles in patients at risk for cerebrovascular disease. Methods We prospectively examined 348 consecutive patients: 73 patients with acute stroke and 275 patients with vascular risk factors but no stroke events. We quantified various types of EMPs by flow cytometry using CD31, CD42b, annexin V (AV), and CD62E antibodies in the peripheral blood of patients. This method allowed fractionation of CD31+/CD42b,, CD31+/AV+, and CD62E+ EMPs. Clinical and laboratory factors associated with EMPs were assessed. Results Recent ischemic episodes were found to be more strongly associated with greater CD62E+ EMP levels than with levels of other phenotypes. Increased National Institutes of Health Stroke Scale scores and infarct volumes in acute stroke patients were significantly associated with greater CD62E+ EMP levels. In the risk factor group, patients with extracranial arterial stenosis had greater CD62E+ EMP levels, whereas those with intracranial arterial stenosis had greater CD31+/CD42b, and CD31+/AV+ EMP levels. The ratio of CD62E+ to CD31+/CD42b, or CD31+/AV+ EMP level significantly discriminated extracranial and intracranial arterial stenosis. Interpretation Circulating EMP phenotypic profiles reflect distinct phenotypes of cerebrovascular disease and are markers of vascular pathology and an increased risk for ischemic stroke. Ann Neurol 2009;66:191,199 [source]

Subcutaneous Transposition of the Superficial Femoral Artery for Arterioarterial Hemodialysis: Technique and Results

ARTIFICIAL ORGANS, Issue 12 2008
Octavio J. Salgado
Abstract We report the use of subcutaneous transposition of the femoral artery (STFA) for placement of both inflow and outflow needles in 14 hemodialysis (HD) adult patients with difficult access. Follow-up time was 318 months during which a total of 3215 arterioarterial HD sessions were done. Kt/V values ranged between 0.71 and 1.59. Elevated access recirculation and dialysis outflow pressures were common findings to all patients. Complications were: (i) two episodes of bleeding secondary to puncture-related arterial wall laceration, repaired by stitching; (ii) three episodes of thrombosis in two patients, all successfully declotted; (iii) three puncture-related complications needing placement of a vein interposition graft, namely, aneurysm, pseudoaneurysm, and arterial stenosis; and (iv) one case of arterial ligation because of suppurative puncture site infection, without subsequent distal ischemia signs or claudication. The use of STFA should only be reserved for patients in urgent need for vascular access with no remaining options. [source]