ISSN:0039-2499    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Background and PurposeWe compared two-dimensional time-of-flight magnetic resonance angiography (MRA) and duplex ultrasonography with arteriography for the detection of 70% to 99% stenoses at the carotid artery bifurcation (ie, surgical disease according to findings of the North American Carotid Endarterectomy Trial).MethodsThree blinded readers independently measured stenoses on MRA in 73 vessels from 38 patients. Duplex ultrasonography was available in 66 vessels from 35 of these patients, and blinded reading was performed by one reader. Comparison was made to arteriography.ResultsMagnetic resonance angiography demonstrated a sensitivity of 92.4%, specificity of 74.5%, and negative predictive value of 95.8% for 70% to 99% stenoses. Interobserver agreement was high (κ=0.91). Absence of signal at stenoses with evidence of distal flow usually, but not always, corresponded to surgical disease. Duplex ultrasonography demonstrated a sensitivity of 81.0%, specificity of 82.2%, and negative predictive value of 90.2% for surgical disease. There was no significant difference between MRA and duplex ultrasonography for the sensitivity or specificity in detecting 70% to 99% stenoses (P>.1, exact form of the McNemar test). MRA had no false positives or false negatives for complete occlusions of the carotid artery, whereas duplex ultrasonography missed one occlusion and falsely called two patent vessels occluded. In seven cases, both MRA and duplex ultrasonography overestimated stenoses to miscategorize them as surgical disease.ConclusionsAlthough the sensitivity and specificity of MRA and duplex ultrasonography are not significantly different for distinguishing surgical and nonsurgical degrees of stenosis at the carotid bifurcation, MRA has some advantages that may make it the screening test of choice. Concordant MRA and duplex ultrasonography for surgical disease does not necessarily obviate the need for catheter arteriography.

ISSN:0039-2499    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Background and PurposeArterial stiffness may indicate early vascular changes that predispose to the development of major vascular disease. The repeatability of a variety of indices of arterial stiffness calculated from a standard carotid arterial M-mode ultrasound image was investigated.MethodsTwenty-six asymptomatic normal subjects were imaged and had blood pressure recordings on each of two separate occasions at least 1 day apart. Using a computer-assisted method, the maximum and minimum internal diameter and average wall thickness of the right common carotid artery were measured over several cardiac cycles, and the following indices of arterial stiffness and distensibility (compliance) were derived: the pressure-strain elastic modulus (Ep), Young's modulus (E), cross-sectional compliance (CC), and the distensibility coefficient (DC).ResultsThe repeatability of these measures, expressed as coefficients of variation, was as follows: Ep, 18%; E, 24%; CC, 14%; and DC, 13%. In another group of 20 subjects, the coefficient of variation for repeat examination by different sonographers was Ep, 19%; E, 20%; CC, 14%; and DC, 17% and for the one sonographer using two ultrasound machines was Ep, 13%; E, 13%; CC, 11%; and DC, 13%. These values indicate a moderate level of repeatability. In a univariate analysis each of these indices was significantly related to increasing age (Ep=1.0+12.9×AGE,r=.80; E=314.5 +13.9×AGE,r=.48; CC=22.6−0.26×AGE,r=−.63; DC=64.0−0.65×AGE,r=−.78) but not to wall thickness (allP> .47). Using multiple regression techniques to adjust for age, wall thickness is a significant predictor of distensibility (P=.017), cross-sectional compliance (P< .001), and the pressure-strain elastic modulus (P=.019). Because Young's modulus is calculated from wall thickness, it could not be included in the multivariate analysis.ConclusionsWe conclude that estimates of carotid artery distensibility and cross-sectional compliance derived from M-mode ultrasound recordings are moderately repeatable and may provide useful additional end points for trials of atherosclerotic progression.

ISSN:0039-2499    

出版商:OVID    

年代:1994

数据来源: OVID

ISSN:0039-2499    

出版商:OVID    

年代:1994

数据来源: OVID

ISSN:0039-2499    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Background and PurposeTransesophageal echocardiography has a high yield for detecting potential cardiac sources of embolism in patients with clinical risk factors for cardioembolism or unexplained stroke. The yield in other stroke subtypes is unknown.MethodsWe classified 145 consecutively admitted patients into stroke subtypes based on clinical findings, brain imaging, and carotid ultrasound. Both transesophageal and transthoracic echocardiography were performed to detect left atrial thrombi, spontaneous echo contrast, atrial septal aneurysm, interatrial shunts, ventricular thrombus or aneurysm, and myxomatous mitral valve.ResultsTransesophageal echocardiography documented at least one of these findings in 46% of the patients compared with an 8% yield on the transthoracic study (P=.002). The yield of transesophageal echocardiography was substantial in all stroke subgroups. Patients with clinical risk factors for cardiac embolism had the highest frequency of spontaneous echo contrast (P=.001). Atrial septal aneurysms were most frequent in patients with lacunar syndromes (P=.012), and interatrial shunts were common in all stroke subtypes.ConclusionsTransesophageal echocardiographic findings vary considerably between stroke subgroups.

ISSN:0039-2499    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Background and PurposeMagnetic resonance imaging should have the potential to replace angiography in the diagnosis of dural sinus thrombosis. Concerning time-dependent signal changes of the thrombus, we intended to develop a standardized examination protocol for routine use in suspected dural sinus thrombosis.MethodsThe time-dependent signal changes of thrombosed dural sinuses were studied in 23 consecutive patients by multiplanar spin-echo and flow-sensitive sequences. Signal intensities and thrombus homogeneity were graded and related to the time after clinical onset and the results of the magnetic resonance angiography.ResultsFour stages of the thrombus evolution could be observed. The acute thrombosis (days 1 to 5) appeared strongly hypointense in T2-weighted images and isointense in spin density- and T1-weighted images. In the subacute stage (up to day 15) the thrombus signal was strongly hyperintense in T1- and T2-weighted images. The third stage began in the third week after clinical onset. The thrombus signal was decreased in all sequences and showed an increasing inhomogeneity. The fourth (late) stage was characterized by either the restitution of blood flow or the persistence of a residual thrombus.ConclusionsEach stage requires a different diagnostic approach. With the combined use of spin-echo and gradient-echo sequences, it is possible to make the diagnosis of acute thrombosis; in the second stage, multiplanar spin-echo sequences are sufficient. Diagnosis of dural sinus thrombosis can be established accurately with magnetic resonance imaging in the first two stages. However, the diagnosis of the later stages is difficult because of inhomogeneous signs of recanalization and flow phenomena. Therefore, a suspected older dural sinus thrombus still requires intra-arterial angiography as the primary diagnostic tool.

ISSN:0039-2499    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Background and PurposeTo assess the feasibility of intravascular ultrasound imaging during carotid endarterectomy.MethodsIntravascular ultrasound imaging was performed during carotid endarterectomy in eight patients using an over-the-wire catheter system with a 30-MHz ultrasound probe. In vitro studies were carried out before the intraoperative application, paying special attention to visualization of the wall layers of normal carotid arteries, structures of more or less diseased vessels, and surgically placed materials such as patch, suture material, and fibrin glue. Although intravascular ultrasound failed to distinguish between intima and media in areas of normal intima, fibrotic and calcified plaques were detected clearly. Dacron patch as well as sutures were identified as highly reflective structures.ResultsIn seven of the eight patients studied, intravascular ultrasound yielded cross-sectional images of good quality allowing identification of the vessel layers and the structures at the endarterectomy site. In all patients the three layers of the vessel wall were clearly differentiated and the transition zone between the site of endarterectomy and the genuine vessel appeared smooth without intimal flaps or residual arteriosclerotic plaques. In one patient severe eccentric thickening of the media was detected in the distal internal carotid artery. Neither damage of the vessel layers by the shunt nor thrombus formation in the operating area and the internal carotid artery were detected.ConclusionsIntravascular ultrasound lends itself as a potentially valuable method of quality control during carotid endarterectomy. The method seems to enable an accurate evaluation of the endarterectomy site and the search for residual plaques.

ISSN:0039-2499    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Background and PurposeWe sought to modify existing sex-specific health risk appraisal functions (profile functions) for the prediction of first stroke that better assess the effects of the use of antihypertensive medication.MethodsHealth risk appraisal functions were previously developed from the Framingham Study cohort. These functions were Cox proportional hazards regression models relating age, systolic blood pressure, diabetes mellitus, cigarette smoking, prior cardiovascular disease, atrial fibrillation, left ventricular hypertrophy by electrocardiogram, and the use of antihypertensive medication to the occurrence of stroke. Closer examination of the data indicated that antihypertensive therapy effect is present only for systolic blood pressures between 110 and 200 mm Hg. Adjustments to the regressions to better fit the observed data were developed and tested for statistical significance and goodness-of-fit of the model residuals.ResultsModified functions more consistent with the data were developed, and, from these, tables to evaluate 10-year risk of first stroke were computed.ConclusionsThe stroke profile can be used for evaluation of the risk of stroke and suggestion of risk factor modification to reduce risk. The effect of antihypertensive therapy in the evaluation of stroke risk can now be better evaluated.

ISSN:0039-2499    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Background and PurposeThe Systolic Hypertension in the Elderly Program (SHEP) was a randomized trial testing the efficacy of treating systolic hypertension in older adults. A significant reduction in stroke risk was observed among participants assigned to active treatment. Serial carotid duplex scans were performed on 129 participants at the University of Pittsburgh center, and rates of progression and regression of carotid stenosis were observed.MethodsChanges in blood flow velocity ratios were used to detect progression because they can be reliably measured and their relation to degree of residual lumen is known. Progression required the development of a 40% to 50% diameter stenosis when stenosis was not initially present or, if already present, further reduction in the lumen diameter. Regression required the absence of a 40% to 50% diameter stenosis when stenosis was initially present or a stenosis significantly less severe than that initially seen.ResultsProgression occurred in 22% (28/129) of participants and regression in 16% (8/49). Progression of carotid stenosis occurred more often among participants randomized to placebo as compared with active treatment (31% versus 14%,P=.020). All eight patients exhibiting regression were randomized to active treatment. In multivariate analysis, participants assigned to placebo had 4.3 times greater odds of progressing than participants assigned to active treatment. Other factors significantly related to progression were higher degree of plaque at baseline, low high-density lipoprotein-3, high lipoprotein(a), and younger age.ConclusionsTreating systolic hypertension appears to slow progression of carotid stenosis. Similar effects occurring in the intracranial vessels may be one reason for the substantial decrease in stroke among SHEP participants assigned to active treatment.

ISSN:0039-2499    

出版商:OVID    

年代:1994

数据来源: OVID