摘要:

Background and PurposeNormal aging is associated with marked changes in the cardiovascular and cerebrovascular systems. Although cerebral autoregulation (CA) is impaired in certain disease states, the effect of age per se on dynamic CA in humans is unknown and the focus of this study.MethodsTwenty-seven young subjects (≤40 years) and 27 older subjects (≥55 years), matched for sex and systolic blood pressure (BP), underwent measurement of cerebral blood flow velocity by transcranial Doppler ultrasound and noninvasive beat-to-beat arterial BP measurement during induced and spontaneous dynamic BP stimuli. A standard dynamic autoregulatory index (ARI) was derived for each spontaneous and induced dynamic BP stimulus to include the step response, as well as cardiac baroreceptor sensitivity (BRS), for the 2 groups.ResultsThe mean age of the young group was 29±5 years, and that of the older group was 68±5 years. Cardiac BRS was reduced in the older group (8.6±4.5 versus 16.9±8.8 ms/mm Hg;P<0.0001). However, no age-related differences were demonstrated in step response plots or in ARI values for any pressor or depressor dynamic BP stimulus (P=0.62), with mean ARI values for all stimuli combined being 4.9±1.8 for the young group and 5.0±2.3 for the older group.ConclusionsAlthough increasing age is associated with a decrease in cardiac BRS, dynamic CA, as assessed by step response analysis as well as cerebral blood flow responses to transient and induced BP stimuli, is unaffected by aging.

ISSN:0039-2499    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Background and PurposePeri-infarct depolarizations (PIDs) have been demonstrated with diffusion-weighted MRI (DWI) in experimental stroke and are regarded as an important mechanism of ischemic injury. We tested the hypothesis that PIDs are of relevance for the early enlargement of human brain infarcts.MethodsTen stroke patients were investigated by repetitive imaging of the apparent diffusion coefficient (ADC) in the acute phase (7 patients) or subacute phase (3 patients) of developing cortical infarction. In each patient, 20 ADC maps were obtained from serially measured echo-planar DWI (interval of 45 seconds). Data analysis focused on the potential spatial and temporal ADC changes, including structured qualitative analysis, calculation of subtraction images, serial analysis of regions of interest positioned in the infarct core and border, and calculation of hemispheric lesion areas, depending on various ADC thresholds ranging between 0 and 800 &mgr;m2/s.ResultsData analysis was unable to disclose any time-dependent changes in ADC that would resemble PID. In ischemic regions, the ADC reduction significantly progressed from the infarct border (555±96 &mgr;m2/s) to the infarct core (431±104 &mgr;m2/s,P<0.01).ConclusionsBy using an MRI protocol with high temporal resolution and elaborated postprocessing, we were unable to demonstrate a pattern of diffusion changes that would be indicative of PID in human stroke. Experimental infarction and human stroke may differ in the detectability of PID.

ISSN:0039-2499    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Background and PurposeHuman studies have shown that methionine-induced hyperhomocysteinemia impairs brachial artery endothelial function via decreasing nitric oxide activity. However, the effect of homocysteine on cerebrovascular reactivity (CVR), which has been reported to be nitric oxide related in experimental and animal studies, remains unclear in humans. Inhibition of angiotensin-converting enzyme may improve nitric oxide–mediated cerebral as well as peripheral endothelial function. The aim of the present study was to investigate the effect of methionine-induced hyperhomocysteinemia on CVR before and after treatment with quinapril, an angiotensin-converting enzyme inhibitor, in healthy adults.MethodsPlasma homocysteine and CVR were measured at baseline and 4 hours after methionine load (0.1 g/kg body wt) before and after quinapril treatment (10 mg/d for 1 week) in both younger and older groups. CVR was assessed by transcranial Doppler ultrasonography, measuring the percent increase of flow velocity in the middle cerebral artery after brief carotid compression (expressed as transient hyperemic response ratio [THRR]).ResultsHomocysteine levels were significantly increased after methionine load either before or after quinapril treatment in both groups. Before quinapril treatment, postmethionine THRR was preserved in younger adults (24.2±5.3% versus 23.8±6.3% at baseline,P=0.73) and decreased in older adults (12.9±2.2% versus 21.8±4.0% at baseline,P<0.001). After quinapril treatment, postmethionine THRR was preserved in both groups (24.5±5.9% versus 24.0±5.0% at baseline,P=0.42 in younger adults; 20.4±3.9% versus 21.3±3.3% at baseline,P=0.35 in older adults).ConclusionsOur study suggests that methionine-induced hyperhomocysteinemia may be causally associated with impairment of CVR in older normal subjects.

ISSN:0039-2499    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Background and PurposeWhen given within 3 hours of symptom onset, recombinant tissue plasminogen activator (rtPA) improves outcome 3 months after ischemic stroke. Prespecified secondary end points of the National Institute of Neurological Disorders and Stroke (NINDS) rt-PA Stroke Trial were CT lesion volumes in the 2 treatment groups (tPA and placebo) at 24 hours, 7 to 10 days, and 3 months after stroke.MethodsThe trial included 2 independent studies, part I and part II, with identical methods of data collection. Before part I, uniform standards were established for CT scanning. CT images were obtained at baseline, 24 hours, 7 to 10 days, and 3 months after stroke onset and were reviewed centrally by reviewers blinded to treatment group and clinical findings. Since the individual studies were not powered to test for lesion volume differences, data from both parts of the trial were combined for all analyses. The primary analysis was conducted with the use of an intention-to-treat algorithm (including patients who died or were lost to follow-up). Measured lesion volume (excluding deaths and those lost to follow-up) was used as a secondary outcome in an exploratory analysis.ResultsAfter tPA treatment, there was a trend toward a reduction in 3-month median lesion volume in the tPA group: 15 cm3(interquartile range, 2 to 87) compared with 24 cm3(interquartile range, 4 to 101) in the placebo group (P=0.06, log model) with a reduction of 11% in cumulative lesion volume, computed with Smirnov’s D statistic. After exclusion of deaths and those lost to follow-up, similar trends toward positive treatment effects were seen at all time points.ConclusionsThe direction of the effect of tPA on CT lesion volume at all time points was consistent with the observed clinical effects at 3 months. CT lesion volume may not be as sensitive a measure of treatment effect as clinical evaluation, at least as used in this study. An intention-to-treat analysis for the radiographic end point in this acute ischemic stroke clinical trial is a less biased approach to account for missing radiographic data than an analysis that uses only measured radiological data.

ISSN:0039-2499    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Background and PurposeIn the United States, tissue plasminogen activator (tPA) was approved for treatment of acute ischemic stroke in 1996. Its use has only recently been approved in Canada. We sought to evaluate the safety, feasibility, and efficacy of treatment in a Canadian hospital setting.MethodsA combined retrospective and prospective review is presented of 46 consecutive patients treated with intravenous tPA at our hospital with a treatment protocol similar to that of the National Institute of Neurological Disorders and Stroke (NINDS) trial.ResultsSymptomatic intracranial hemorrhage at 36 hours occurred in 1 patient (2.2%). The median time to treat was 165 minutes, with a median “door-to-needle” time of 84 minutes. Compared with patients presenting initially at our hospital, patients transferred from another institution for tPA therapy were treated closer to the 3-hour time window (mean 173 versus 148 minutes,P<0.001) but had a shorter door-to-needle time (43 versus 102 minutes,P<0.001). For every 10 minutes closer to the 3-hour time window that any patient arrived at the hospital, 7 minutes was saved in the door-to-needle time (correlation coefficient 0.9,P<0.001). Patient outcome did not differ from that in the NINDS trial (P>0.75).ConclusionsOur safety and patient outcome data compare favorably with NINDS and Phase IV data. Although a 3-hour treatment window was feasible, the median door-to-needle time lengthened as more treatment time was available and the door-to-needle time was beyond recommended standards. This review has prompted changes in our community to improve treatment efficiency.

ISSN:0039-2499    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Background and PurposeWith the exception of atrial fibrillation (AF), little scientific attention has been given the associations between cardiac arrhythmias and incidence of stroke. We sought to study whether atrial and ventricular arrhythmias assessed during a 24-hour ambulatory ECG registration are associated with incidence of stroke.MethodsThe population-based cohort “Men Born in 1914” was examined with 24-hour ambulatory ECG registrations at 68 years of age. Four hundred two men without previous myocardial infarction or stroke were included, and 236 of them had hypertension (≥160/95 mm Hg or treatment). Fourteen-year rates of stroke (fatal and nonfatal) and all-cause mortality were updated from national and regional registers. Frequent or complex ventricular arrhythmias was defined as Lown class 2 to 5. A high frequency of atrial ectopic beats (AEB) was defined as the fifth quintile (ie, ≥218 AEB per 24 hours).ResultsFifty-eight men suffered a first stroke during the follow-up. Stroke rates (per 1000 person-years) among men with AF (n=14), with frequent AEB (n=77), and without AF or frequent AEB (n=311) were 34.5, 19.5, and 11.6, respectively. The corresponding values among men with hypertension were 40.7, 32.3, and 14.7, respectively. Frequent AEB (compared with absence of AF and frequent AEB) was significantly associated with stroke among all men (relative risk=1.9; 95% CI, 1.02 to 3.4; P=0.04) and among hypertensive men (relative risk=2.5; 95% CI, 1.3 to 4.8; P=0.009) after adjustments for potential confounders. The increased stroke rates among men with Lown class 2 to 5 did not reach statistical significance.ConclusionsA high frequency of AEB is associated with an increased incidence of stroke.

ISSN:0039-2499    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Background and PurposeResearch for infectious agents in the etiology of atherosclerosis has identifiedChlamydia pneumoniaeas a possible candidate. While there is evidence of an association between presence of this microorganism and atherosclerosis, it is unclear whether infection has a genuinely etiologic role in this disease, whether its presence influences clinical outcomes, and, if so, at which stages of disease this occurs. We have approached this issue in patients with advanced carotid artery atherosclerosis using molecular biological detection methods and clinically relevant indicators of pathology in carotid artery atheroma to determine whether the presence ofC pneumoniaecorrelates with plaque instability.MethodsC pneumoniaewas detected with the use of a sensitive nested polymerase chain reaction. Preoperative embolization and preoperative infarcts were recorded with the use of transcranial Doppler insonation of the middle cerebral artery and cerebral CT, respectively.ResultsC pneumoniaeDNA was detected in 25.5% of a cohort of 98 symptomatic patients. There was no significant difference in plaque stability as measured by embolization rates between the chlamydial-positive and -negative specimens. There was also no correlation between the number of ipsilateral hemispheric infarcts in the territory of the middle cerebral artery and chlamydial status.ConclusionsThis study confirms thatC pneumoniaeis a common finding in atherosclerotic plaques of the carotid artery but suggests that the presence of the infectious organism has little detectable impact on plaque instability when measured by clinically significant markers. This raises important questions for the rationale of antibiotic therapy in atherosclerosis.

ISSN:0039-2499    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Background and PurposeDiabetic subjects have a 3- to 6-fold increased risk for stroke compared with nondiabetic subjects, and hyperinsulinemia shows strong and consistent associations with a cluster of cardiovascular risk factors. Methods separating proinsulin from (true) insulin have demonstrated proinsulin to be more strongly associated with cardiovascular disease than insulin. The present study evaluates the associations between first-ever stroke, proinsulin, and insulin.MethodsIn this incident case-referent study of a nondiabetic population, 94 cases of first-ever stroke (59 men and 35 women) were individually age- and sex-matched to 178 referents. Blood sampling was collected before the stroke event. Proinsulin and insulin were measured with highly sensitive 2-site sandwich enzyme-linked immunosorbent assays.ResultsIn the study population, high proinsulin concentration more than tripled the risk for first-ever stroke after adjustments for total cholesterol, systolic blood pressure, smoking, body mass index, and insulin, with an odds ratio of 3.4 (95% CI, 1.4 to 8.4). In women the risk was even more pronounced, with an odds ratio of 13.7 (95% CI, 1.3 to 146). Synergy was found between proinsulin and systolic blood pressure. In women, synergy was also found between proinsulin and diastolic blood pressure as well as between insulin and both blood pressures.ConclusionsHigh levels of proinsulin may predict later occurrence of first-ever stroke in a nondiabetic population.

ISSN:0039-2499    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Background and PurposeThe present study aimed at evaluating the prognostic value of transcranial Doppler ultrasonography (TCD) in the acute phase of ischemic stroke, when major therapeutic decisions must be made.MethodsSeventy-three patients with a first-ever ischemic hemispheric stroke underwent neurological assessment according to the Unified Neurological Stroke Scale, clinical subgrouping according to the criteria of Bamford, CT scan, cervical duplex sonography, and TCD, all within 12 hours from stroke onset. TCD was repeated on days 2 and 7. Patients were followed for 90 days, during which we calculated the fatality rate and then assessed clinical outcome.ResultsEmergency TCD revealed middle cerebral artery (MCA) no-flow in 24 cases and MCA asymmetry in 30 subjects. Serial TCD showed early (<24 hours) MCA recanalization in 6 patients. After 90 days, no patient with MCA occlusion at admission was autonomous, while 17 of 19 patients (89.5%) with a normal baseline TCD were independent. The fatality rate at 3 months was 21% but was 46% in patients with MCA occlusion and 61% in patients without signs of early MCA recanalization. Total anterior circulation infarct and abnormal TCD were significantly correlated (P<0.001) with higher mortality rate and worse outcome (Barthel Index score ≤60), whereas early CT ischemic signs and severe carotid disease were not. Furthermore, TCD identified within the total anterior circulation infarct subgroup 2 prognostic clusters according to MCA patency at admission (P<0.001). Logistic regression selected normal baseline TCD as an independent predictor of good long-term outcome and MCA no-flow as an independent predictor of disability or death.ConclusionsTCD findings play an important role in the early prognosis of anterior circulation stroke, providing possible guidance for therapeutic interventions.

ISSN:0039-2499    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Background and PurposeWe sought to characterize the subtypes of stroke associated with pregnancy and the puerperium, with emphasis on timing, etiology, risk factors, and outcome.MethodsWe conducted a retrospective analysis of patients admitted to the Toronto Hospital between January 1, 1980, and June 30, 1997, with a diagnosis of stroke during pregnancy or within 6 weeks postpartum. Strokes were classified as ischemic (arterial or venous) or hemorrhagic (subarachnoid or intracerebral). All patients were investigated with at least a CT scan of the head, and most had MRI and/or cerebral angiography.ResultsOf approximately 50 700 admissions for delivery, 34 patients with a diagnosis of stroke were identified (21 infarctions and 13 hemorrhages). Of patients with infarction, 13 were arterial and 8 were venous. Nine of 13 arterial events occurred in the third trimester or puerperium. Seven of 8 venous occlusions occurred postpartum. An etiologic diagnosis was made in 7 of 13 patients with arterial territory infarction, including cardiac emboli, coagulopathies, and carotid artery dissection. Of patients with hemorrhage, 7 were subarachnoid and 6 were intracerebral. The etiology was identified in 10 patients: 3 were due to ruptured aneurysms, 5 were associated with arteriovenous malformations, and 2 were associated with disseminated intravascular coagulation. All patients with infarction survived, but 3 patients with hemorrhage died.ConclusionsThe majority of strokes associated with pregnancy were arterial occlusions. Most presented during the third trimester and puerperium.

ISSN:0039-2499    

出版商:OVID    

年代:2000

数据来源: OVID