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Biomedical subjects

S Meairs

Publications and source records attributed to S Meairs.

At least 19 recordsLinked to original sources
PubMed2006

Mannheim carotid intima-media thickness consensus (2004-2006). An update on behalf of the Advisory Board of the 3rd and 4th Watching the Risk Symposium, 13th and 15th European Stroke Conferences, Mannheim, Germany, 2004, and Brussels, Belgium, 2006.

Intima-media thickness (IMT) is increasingly used as a surrogate end point of vascular outcomes in clinical trials aimed at determining the success of interventions that lower risk factors for atherosclerosis and associated diseases (stroke, myocardial infarction and peripheral artery diseases). The necessity to promote further criteria to distinguish early atherosclerotic plaque formation from thickening of IMT and to standardize IMT measurements is expressed through this updated consensus. Plaque is defined as a focal structure that encroaches into the arterial lumen of at least 0.5 mm or 50% of the surrounding IMT value or demonstrates a thickness >1.5 mm as measured from the media-adventitia interface to the intima-lumen interface. Standard use of IMT measurements is based on physics, technical and disease-related principles as well as agreements on how to perform, interpret and document study results. Harmonization of carotid image acquisition and analysis is needed for the comparison of the IMT results obtained from epidemiological and interventional studies around the world. The consensus concludes that there is no need to 'treat IMT values' nor to monitor IMT values in individual patients apart from exceptions named, which emphasize that inside randomized clinical trials should be performed. Although IMT has been suggested to represent an important risk marker, according to the current evidence it does not fulfill the characteristics of an accepted risk factor. Standardized methods recommended in this consensus statement will foster homogenous data collection and analysis. This will help to improve the power of randomized clinical trials incorporating IMT measurements and to facilitate the merging of large databases for meta-analyses.

Adult↗
PubMed2006

[Retrospective analysis of neurological patients on a medical intensive care unit].

OBJECTIVE: The aim of this study was to evaluate number and kind of neurological patients in comparison with other patients on a medical ICU. METHODS: Over a period of one year, all neurological intensive care patients on a medical ICU were evaluated according to age, sex, diagnosis, mortality, diagnostic methods, ventilation and referral to other hospitals and general wards. RESULTS: Comparable to a specialist neurological ICU a wide spectrum of neurological diseases could be observed on an interdisciplinary ICU. In comparison to other patient groups, patients with neurological disease had a higher rate of ventilation, a longer hospital stay and a higher mortality. CONCLUSION: Our data also demonstrate the relevant amount of neurological patients (19 % measured by bed assignment) in comparison to all patients, and the specific neurological procedures were applicable on a medical/interdisciplinary ICU. A higher interest for neurological patient on a medical ICU would therefore be essential.

Adult↗
PubMed2005

Power Doppler evaluation of revascularization in childhood moyamoya.

Moyamoya disease is generally recognized in young children. One potential treatment is direct extra-intracranial bypass combined with indirect revascularization using encephalo-myo-synangiosis. Standard follow-up to assess neoangiogenesis includes repeat cerebral angiography, which is invasive. The authors studied whether noninvasive power Doppler imaging could evaluate the patency of the bypass and the degree of indirect revascularization. They found that transcranial power Doppler imaging is a valid noninvasive alternative to cerebral angiography.

Cerebral Revascularization↗
PubMed2005

[Correlation of duplex sonographic stenosis grading by means of cross-sectional analysis and MR-tomographic blood volume flow quantification in unilateral stenosis of the internal carotid artery].

PURPOSE: Correlation of duplex ultrasonographic grading of unilateral internal carotid artery (ICA) stenosis and ICA blood volume flow (BVF) quantification. MATERIALS AND METHODS: Using a 2D cine phase-contrast MR technique, 62 patients with unilateral ICA stenosis at the level of the bifurcation between 50 % and 98 % and 20 age-matched normal controls were examined. BVF was measured in the stenosed ICA. Ultrasonographic grading of stenoses was based on cross-sectional duplex sonography (color Doppler flow imaging [CDFI], real-time compound imaging) and compared to the changes in BVF in the stenosed ICA. RESULTS: There was no statistically significant difference in BVF in stenoses of the ICA up to 70 % and in normal controls. ICA stenoses greater 70 % began to be hemodynamically relevant. With increasing stenosis, a decrease in BVF in the ipsilateral ICA was determined with a high and linear correlation of r = - 0.83. Normal controls showed a BVF in an ICA of 247.0 +/- 32.0 ml/min, patients with 70 % stenosis a mean BVF of 225.3 +/- 32.2 ml/min (P = 0.4) without significant reduction, patients with 80 % stenosis a significant reduction of BVF to a mean flow of 184.0 +/- 53.8 ml/min (P < 0.005), patients with 90 % stenosis a reduction of the mean BVF in the stenosed ICA to 84.6 +/- 41.9 ml/min (P < 0.0005) and patients with stenoses > 95 % a mean BVF of only 26.0 +/- 4.0 ml/min (P < 0.0005). In patients with unilateral ICA stenosis greater than 81 %, a significant decrease of BVF in the stenosed ICA was documented. CONCLUSION: Comparison of ultrasonographic grading of unilateral ICA stenosis and BVF determination in patients with ICA stenoses demonstrate a high correlation between increase in the stenosis and decrease in the ipsilateral blood flow beginning at 70 % stenosis. ICA stenoses greater than 80 % are significantly hemodynamically relevant.

Aged↗
PubMed2004

Mannheim intima-media thickness consensus.

Intima-media thickness (IMT) is increasingly used in clinical trials as a surrogate end point for determining the success of interventions that lower risk factors for atherosclerosis. The necessity for unified criteria to distinguish early atherosclerotic plaque formation from thickening of IMT and to standardize IMT measurements is addressed in this consensus statement. Plaque is defined as a focal structure that encroaches into the arterial lumen of at least 0.5 mm or 50% of the surrounding IMT value or demonstrates a thickness of > or =1.5 mm as measured from the media-adventitia interface to the intima-lumen interface. Standard use of IMT measurements is recommended in all epidemiological and interventional trials dealing with vascular diseases to improve characterization of the population investigated. The consensus concludes that there is no need to 'treat IMT values' nor to monitor IMT values in individual patients apart from few exceptions. Although IMT has been suggested to represent an important risk marker, it does not fulfill the characteristics of an accepted risk factor. Standardized methods recommended in this consensus statement will foster homogenous data collection and analysis. This will help to improve the power of studies incorporating IMT measurements and to facilitate the merging of large databases for meta-analyses.

Arteriosclerosis↗
PubMed2000

Pulse-inversion contrast harmonic imaging: ultrasonographic assessment of cerebral perfusion.

Pulse-inversion contrast harmonic imaging is a new ultrasonographic technique that can assess brain perfusion. In an adult with moyamoya disease and multiple recurrent strokes, this method detected subtle hemispheric differences in temporal-lobe perfusion, presumably due to neovascularisation, which were not shown by xenon-computed tomography or magnetic resonance perfusion imaging.

Adult↗
PubMed2000

Traumatic brachiocephalic pseudoaneurysm presenting with delayed stroke: case report.

We report a traumatic pseudoaneurysm of the internal carotid artery bifurcation and subclavian artery with recurrent strokes events in a 19-year-old man. He was admitted with an acute left hemiparesis. His history revealed a similar episode 1 year and a major car accident 3 years previously. Contrast enhanced MR angiography confirmed colour Doppler sonographic findings of a carotid and subclavian artery pseudoaneurysm presumably resulting from seat-belt trauma. The pseudoaneurysm, containing thrombus, was thought to be the source of artery-to-artery embolism.

Accidents, Traffic↗
PubMed2000

Reconstruction and visualization of irregularly sampled three- and four-dimensional ultrasound data for cerebrovascular applications.

Although recent studies have demonstrated the potential value of compounded data for improvement in signal-to-noise ratio and speckle contrast for three-dimensional (3-D) ultrasonography, clinical applications are lacking. We investigated the potential of six degrees-of-freedom (6-DOF) scanhead position and orientation measurement (POM) devices for registration of in vivo multiplanar, irregularly sampled ultrasound (US) images to a regular 3-D volume space. The results demonstrate that accurate spatial and temporal registration of four-dimensional (4-D) US data can be achieved using a 6-DOF scanhead tracking system. For reconstruction of arbitrary, irregularly sampled US data, we introduce a technique based upon a weighted, ellipsoid Gaussian convolution kernel. Volume renderings of 3-D and 4-D compounded in vivo US data are presented. The results, although restricted to the field of cerebrovascular disease, will be of value to other applications of 3-D sonography, particularly those in which compounding of data through irregular sampling may provide superior information on tissue or vessel structure.

Blood Flow Velocity↗
PubMed2000

Imaging arterial wall disease.

Ultrasonographic imaging of the carotid arteries allows assessment of both early and advanced atherosclerotic disease. This noninvasive technique has played a central role in many recent epidemiological studies and is being used increasingly for evaluating the efficacy of atherosclerosis prevention trials. New developments in ultrasound equipment, the use of echocontrast agents, novel applications of three- and four-dimensional sonography and in vivo characterization of plaque constituents with high-resolution MRI have broadened the scope of imaging of arterial walls, providing both enhanced information on disease progression as well as new insights into pathomechanisms of carotid plaque embolization. This article highlights pertinent issues of imaging of arterial wall disease and discusses important areas of current and future research in this field.

Arteries↗
PubMed1999

Four-dimensional ultrasonographic characterization of plaque surface motion in patients with symptomatic and asymptomatic carotid artery stenosis.

BACKGROUND AND PURPOSE: In vitro studies of atherosclerotic plaque fracture mechanics suggest that analysis of local variations in surface deformability may provide information on relative vulnerability to plaque fissuring or rupture. We investigated plaque surface deformations in patients with symptomatic and asymptomatic carotid artery disease using 4-dimensional ultrasonography and techniques for measuring optical flow. METHODS: Four-dimensional ultrasound examinations of carotid artery plaques were performed in 23 asymptomatic and 22 symptomatic patients with 50% to 90% stenosis of the internal carotid artery. Plaque surface motion during 1 cardiac cycle was computed with a hierarchical model-based motion estimator. Results were compared with plaque echogenicity and surface structure. RESULTS: Of the 45 patients examined, plaque surface motion estimates were obtained for 18 asymptomatic and 13 symptomatic patients. There were no significant differences in echogenicity or surface structure of asymptomatic and symptomatic plaques (P>0.05). Results of motion estimation showed that asymptomatic plaques had surface motion vectors of equal orientation and magnitude to those of the internal carotid artery, whereas symptomatic plaques demonstrated evidence of inherent plaque movement. There was no significant difference in maximal plaque velocity between symptomatic and asymptomatic plaques (P<0.14). Maximal discrepant surface velocity (MDSV) in symptomatic plaques was 3.85+/-1.26 mm/s (mean+/-SD), which was significantly higher (P<0.001) than MDSV of asymptomatic plaques with 0.58+/-0.42 mm/s (mean+/-SD). CONCLUSIONS: ++MDSV of carotid artery plaques is significantly different in asymptomatic and symptomatic disease. Further studies are warranted to determine whether plaque surface motion patterns can identify vulnerable plaques in patients with carotid artery stenosis.

Aged↗
PubMed1996

Ischemia-induced migraine from paradoxical cardioembolic stroke.

Although little is known on the pathophysiologic mechanism of migraine-related stroke, the prevailing attitude is that vasoconstriction and activation of clotting factors play a primary role. In 2 female patients presenting with migraine and stroke, risk profiles and history were consistent with this pathophysiologic mechanism. Cerebro- and cardiovascular workup, however, led to a diagnosis of paradoxical cardioembolic stroke through a patent foramen ovale. Since there is hardly any evidence in the literature that migraine acts as a risk factor for stroke on its own, these case reports emphasize the importance of complete cardiovascular evaluation in patients with suspected migrainous stroke.

Adolescent↗
PubMed1996

Sonographic assessment of carotid artery stenosis. Comparison of power Doppler imaging and color Doppler flow imaging.

BACKGROUND AND PURPOSE: Power Doppler imaging (PDI) is a new ultrasound technique that, in contrast to color Doppler flow imaging (CDFI), generates intravascular color signals from the reflected echo amplitude depending mainly on the density of red blood cells. We evaluated the diagnostic significance of PDI compared with CDFI for the measurement of carotid stenosis and characterization of plaque surface. METHODS: In 25 internal carotid artery stenoses, reduction of the intrastenotic lumen contrasted by blood density signals and color Doppler signals on longitudinal and transverse views was assessed for correlative evaluation. In addition, the peak systolic flow velocity of the Doppler spectrum was correlated with PDI and CDFI measurements. RESULTS: PDI provided good visualization of the residual lumen in all stenoses, whereas displays on CDFI were inadequate in two calcified plaques. PDI revealed two ulcerative stenoses classified as smooth on CDFI. The correlation between PDI and CDFI was high for measurement of area stenosis (r = .93) and moderate for diameter stenosis (r = .73). Similarly, cross-sectional reduction on both imaging methods correlated more significantly with peak systolic flow velocity than diameter reduction. CONCLUSIONS: This pilot study suggests that PDI provides additional information for luminal measurement and characterization of plaque surface in complicated high-grade carotid stenosis. Because of the absent visualization of hemodynamics, PDI should be used in combination with CDFI.

Aged↗
PubMed1995

New and future developments in cerebrovascular ultrasound, magnetic resonance angiography, and related techniques.

Four-dimensional (4D) analysis of atherosclerotic plaque and wall motion, the application of 4D ultrasound to the study of atherogenesis, and the incorporation of ultrasound data into flow models for simulation of cerebrovascular hemodynamics are new frontiers in diagnostic ultrasound that use computer vision and optical flow techniques to exploit the full potential of real-time imaging and Doppler studies. New approaches to improve blood vessel delineation with ultrasound include application of contrast agents, harmonic imaging, and red blood cell density imaging. An assessment of the potential clinical utility of these new developments in cerebrovascular ultrasound requires an analysis of comparable trends in magnetic resonance (MR) technology, eg, rapid advances in the fields of MR angiography, dynamic contrast-enhanced MR, and MR diffusion imaging. Likewise, the value of ultrasound techniques for the measurement of blood flow to evaluate cerebrovascular hemodynamics must be compared to related methods in magnetic resonance, such as dynamic MR inflow tracking. This article addresses several new and future developments in cerebrovascular ultrasound and discusses their relative merits in terms of ongoing research in the field of magnetic resonance angiography, imaging, and related techniques.

Blood Flow Velocity↗