The detection of microembolic signals in patients at risk of recurrent cardioembolic stroke: possible therapeutic relevance.

The clinical predictors and potential therapeutic implications of microembolic signals (MES) were investigated in 104 patients with ischemic stroke or transient ischemic attack associated with high-risk (n = 60) or low-risk (n = 44) cardiac emboligenic conditions. Patients with artificial valves and carotid stenosis were excluded. MES counts were based on 30-min bilateral middle cerebral artery transcranial Doppler (TCD) monitoring recordings. MES were detected in 15 subjects (14%). The mean number of MES per hour was 1.9. MES prevalence and counts were influenced neither by age, gender or type of cerebral event, nor by cardiac disease. MES were more frequently detected and greater in number in patients with multiple cerebral ischemic events and in subjects monitored within 1 month of the last event. By multiple logistic regression, TCD recording within 1 month of the last event [Odds ratio (OD) = 13.5; 95% confidence intervals (CI) = 3.3-54.3] and multiple cerebral events (OD = 4.7; 95% CI = 1.3-17.3) were the best MES predictors. MES were detected in 40% (4/10) of patients on heparin, 5% (2/4) of untreated subjects and 13% (5/39) of those on antiplatelet drugs. For patients on warfarin, MES counts and prevalence were similar in subjects with international normalized ratios (INR) below and within/above the therapeutic range. MES were detected in only 2 out of 16 subjects with INR <2 and in 1 with INR >2. MES detection can be potentially relevant to the selection of antithrombotic treatment in acute stroke associated with cardioembolic disease, but further studies are necessary to assess its effectiveness as an additional guide to monitor oral anticoagulant intensity.     

Microembolic signal monitoring in hemispheric acute ischaemic stroke: a prospective study

BACKGROUND AND PURPOSE: There are few data on the occurrence of microembolic signals (MES) in the acute phase of ischaemic stroke. The objective of our work was to systematically study the frequency of MES in non-selected patients with a first-ever hemispheric transient ischemic attack (TIA) or acute cerebral infarction, and to evaluate the clinical usefulness of MES detection. METHODS: 182 consecutive patients with hemispheric TIA or acute cerebral infarction, and 54-age-matched healthy controls were studied. Bilateral transcranial Doppler ultrasound (TCD) monitoring was performed for at least 30 min with a mean time from stroke onset to TCD of 69 h. Stroke severity on admission, early recurrent stroke and dependency on discharge were investigated. RESULTS: MES were detected in 20.5% of patients with arterial sources of embolism, 17. 1% of patients with potential sources of cardioembolism and 5% of patients with cryptogenic stroke. They were not registered, however, in lacunar infarctions (p < 0.001). Stroke severity on admission of patients with MES was greater than that of patients without MES (47. 1 vs. 19.4% with the Canadian Stroke Scale < or =6.5; p = 0.009). Early recurrent stroke was more frequent in patients with MES (11.8%) than in those without MES (4.2%) although the difference was not statistically significant. Multiple logistic regression analysis showed that MES increased the risk of dependency on discharge (odds ratio, 4.2; 95% CI, 1.2-14.9; p = 0.01) independently of age, stroke severity on admission and presence of an arterial or cardiac embolic source. CONCLUSIONS: There is a strong association of MES in the acute phase of stroke with known potential arterial and cardiac embolic sources. MES have an independent predictive value of poor outcome.     

Size of PFO and amount of microembolic signals in patients with ischaemic stroke or TIA

Background and purpose:  The inter-relation between the size of patent foramen ovale (PFO) by transesophageal echocardiography (TEE) and the amount of microembolic signals (MES) on transcranial doppler (TCD) is still not determined.
Methods:  The study group comprised of 104 patients with first-ever ischaemic stroke or transient ischemic attack (TIA). Three groups were formed according to the amount of MES on TCD: a small amount of MES (0–10 MES); a moderate amount of MES (countable MES higher than 10); and multiple MES.
Results:  According to TEE, there were 52 patients (50%) with a small PFO, 37 patients (35.6%) with a moderate PFO, and 15 patients (14.4%) with a large PFO. There were 48 patients (46.1%) with a small amount of MES, 34 patients (32.7%) with a moderate amount of MES, and 22 patients (21.1%) with multiple MES on TCD. A strong relationship between the size of the PFO on TEE and the amount of MES on contrast transcranial Doppler was found ( P  < 0.0001), such that the larger the PFO on TEE, the greater the amount of MES on TCD.
Conclusions:  There is a high correlation between the size of the PFO on TEE and the amount of MES on TCD in stroke and TIA patients.     

以急性多发性脑梗死为首发表现的隐匿性躯体恶性肿瘤12例报告

目的研究以急性多发脑梗死为首发表现的隐匿性躯体恶性肿瘤患者的临床表现、实验室检查、影像学、微栓子监测检查特点,探讨其可能的发病机制。方法纳入以急性多发性脑梗死为首发表现的隐匿性躯体恶性肿瘤患者12例,收集其临床资料,分析其实验室血液学、头颅MRI、微栓子监测结果及其治疗和预后。结果所有患者均以局灶性神经功能缺损为主要表现,包括偏瘫、失语、偏身感觉障碍、构音障碍、眩晕、肢体抽搐等。头颅DWI示急性多发脑梗死,病灶播散性分布,不符合单支动脉供血区,同时累及双侧前循环或前后循环。11例行D-dimer检查者8例升高。7例行微栓子监测有5例阳性。隐匿性躯体恶性肿瘤包括:肺癌5例,胰腺癌3例,胃癌、结肠癌、子宫内膜癌、转移性低分化粘液腺癌原发肿瘤部位不明各1例;诊断时就已有远处转移者10例。病程中缺血性卒中复发者7例,急性心肌梗死4例,住院期间死亡3例,预后差。结论对于不符合单支动脉供血区的多发急性脑梗死,需要考虑可能合并隐匿性躯体恶性肿瘤,凝血功能筛查高凝状态和微栓子阳性可能是诊断提示线索。     

Comparison of a 1-MHz and a 2-MHz probe for microembolus detection using transcranial Doppler ultrasound

OBJECTIVES: Clinically silent microembolic signals (MES) can be detected by transcranial Doppler sonography (TCD). There is theoretical evidence that lower ultrasound emission frequencies may lead to a higher signal intensity and thus sensitivity to detect MES. We compared a 1-MHz probe with a 2-MHz probe regarding sensitivity in the detection of MES. Moreover, embolus detection by transcranial Doppler ultrasound is very time consuming and semi-automated detection is mandatory. Therefore, we studied an on-line algorithm using the bi-gate technique and the two transmission frequencies. METHODS: After defining detection thresholds of > or = 12 dB (1 MHz) and > or = 10 dB (2 MHz) with eight normal subjects as MES-negative controls, taking into account natural fluctuations of the Doppler spectrum, we studied 36 patients with ischaemic events and five asymptomatic patients with incidental embolic sources. All patients subsequently underwent a 1-hour unilateral embolus detection from the middle cerebral artery (MCA) or the posterior cerebral artery (PCA), respectively, using 1 and 2 MHz for 30 minutes each in a randomized order. The software algorithm was compared with a blinded off-line analysis by an experienced observer as a gold standard. RESULTS: The investigator detected 198 MES (range 0-41 MES) in the recordings of 29 patients out of the 41 patients using the 1-MHz probe and 101 MES (range 0-32 MES) in the recordings of 14 patients using the 2-MHz probe (p = 0.0007). Sensitivity of the software to detect MES confirmed by the investigator was 31% using 1 MHz and 41% using 2 MHz. The positive predictive value was 6 and 30%, respectively. DISCUSSION: The sensitivity and positive predictive values of the automated algorithm to detect MES were unacceptably low for clinical practice with both frequencies. The use of 1 MHz instead of 2 MHz may, however, be useful when evaluating the recordings off-line by an experienced blinded observer.     

Transcranial Doppler detection of microembolic signals in patients with Behçet’s disease

We evaluated the prevalence of microembolic signals (MES) in patients with Behçet’s disease (BD). We also attempted to determine the frequency of MES in BD patients with or without neurological involvement. This study enrolled 55 patients fulfilling the diagnostic criteria of International Study Group for BD. Bilateral transcranial Doppler ultrasound of the middle cerebral arteries was performed. MES were identified based on the criteria of International Consensus group on Microembolus Detection. Patients with BD were divided into two groups in respect of the presence of neurological involvement (n = 10) or not (n = 45), and counts of MES in the two were compared with each other and with normal subjects. We found MES in 16 patients (29%) with BD. The frequency was higher in patients with neurological involvement than in those without (80% vs. 17%, P < 0.001). In patients with neurological involvement there was a positive correlation in regression analysis between the prevalence of MES and disease duration (P = 0.025). There was a significantly higher prevalence of MES in BD patients than in control subjects. The frequency of MES was higher in patients with neurological involvement than in those without. TCD detection of MES may allow the recognition of subset of patients at high risk for the appearance of neurological involvement.     

Prevalence and frequency of microembolic signals in 105 patients with extracranial carotid artery occlusive disease

Besides the established factors "presence of symptoms" and "degree of stenosis", plaque echolucency is considered to be associated with increased risk of stroke in patients with carotid artery disease. An evaluation was carried out as to whether the prevalence and number of microembolic signals (MES) detected by transcranial Doppler ultrasound were higher in patients with echolucent carotid plaques. One hundred and five patients with carotid artery stenosis from 20%-99% or occlusion underwent clinical investigations, duplex ultrasound of the carotid arteries, and a 1 hour recording from the middle cerebral artery downstream to the carotid artery pathology using the four gate technique. The presence of MES was more frequent and the number greater in symptomatic patients (21 out of 64 patients (33%); mean number of MES in all 64 patients 3.1) than in asymptomatic patients (four out of 41 patients (10%); mean number of MES in all 41 patients 0.3) (p=0.007, and p=0.006, respectively). Echogenicity of the lesions did not affect either number or presence of MES. Positivity for MES and the number of MES increased with increasing degree of stenosis (both p=0.002). Four out of 12 patients with carotid artery occlusion showed MES. No MES could be detected in carotid artery stenosis below 80%. There was a decline in positivity of MES and of the number of MES with the time after the ischaemic event. After 80 days or more after the index event, only one patient showed MES. In conclusion, increasing degree of stenosis and presence of symptoms similarly affect macroembolic and microembolic risk. Thus MES may be a surrogate parameter for risk of stroke. The presence of MES in a few asymptomatic patients suggests that clinically silent circulating microemboli may give additional information on the pending embolic potential of carotid artery stenoses. Echolucency of the plaque was not related to an increased number of MES.     

Distribution of cerebral microembolism in the anterior and middle cerebral arteries

BACKGROUND AND PURPOSE: Cerebral infarcts occur more frequently along the middle (MCA) than the anterior cerebral artery (ACA) territory. The reason(s) for this difference remains speculative. The objective of this study was to investigate the distribution of cerebral microemboli as detected by transcranial Doppler ultrasound (TCD) along the MCA and ACA territories. METHODS: Records of consecutive patients examined for the presence of cerebral microembolism during a 32-month period at the Neurovascular Laboratory were reviewed. Of the original 375 TCD studies in 268 patients, 28 studies in 24 patients demonstrated microembolic signals (MES) and monitored the MCA and ACA on the same side. TCD studies were performed on TC-2000 or TC-2020 instruments. MES positive studies were saved and off-line reviewed. MES satisfied previously established criteria. RESULTS: MES were more frequent in the MCA than the ACA in 85.7% (24/28) of studies (P < 0.01). Of the total number of MES (n = 979), 29.6% (n = 290) were detected in the ACA and 70.4% (n=689) in the MCA (P<0.01). The mean (+/- SD) intensity of MCA MES of 12.2 (+/- 2.4) dB was significantly lower than that of ACA MES of 14.8 (+/-3.2) dB (P=0.05). The mean (+/-SD) duration of MCA MES of 38.1 (+/- 45.3) ms was longer than that of ACA MES of 30.7 (+/-34.0) ms (P=0.05). CONCLUSIONS: Cerebral microembolism occurs more frequently in the MCA than the ACA, which may explain the uneven distribution of cerebral infarcts along these arterial territories. Furthermore, there are significant differences in the characteristics of ACA and MCA MES.     

Cerebral Microembolization in Left Ventricular Assist Device Associated Ischemic Events

IntroductionThe significance of microembolic signals (MES) detected by transcranial Doppler ultrasound emboli monitoring (TCD-e) in patients supported with left ventricular assist devices (LVAD) remains unclear. We aimed to investigate the relationship between cerebral microembolization detected by TCD-e and acute ischemic events in LVAD patients.MethodsWe reviewed consecutive patients with acute ischemic stroke or transient ischemic attack (TIA) in a prospectively collected database of LVAD patients. TCD-e exams consisted of monitoring the middle cerebral arteries for microembolic signals (MES) over 30 minutes.ResultsOf 515 persons with LVAD, 41 TCD-e studies were performed in 35 patients with acute ischemic stroke or transient ischemic attack (TIA) in a median of 1 day (Interquartile range [IQR]: 0-2) after the event. MES were present in 15 (44%) TCD-e studies with a median MES count of 4 (IQR: 2-15.5). Bloodstream infections were more common in patients with MES (38% versus 8%, P = .039). There were trends for lower international normalized ratio (1.39 versus 1.69, P = .214), lower activated partial thromboplastin (33.2 versus 36.6, P = .577), higher lactate dehydrogenase (531 versus 409, P = .323) and a higher frequency of pump thrombosis (13% versus 8%, P = .637) in patients with MES compared with those without MES.ConclusionsLVAD patients with acute ischemic stroke or TIA have a high prevalence of MES on TCD-e, which may serve as a marker for a prothrombotic state. Further study of MES in LVAD patients is warranted.     

Microembolic signal detection in patients with symptomatic and asymptomatic lone atrial fibrillation

BACKGROUND AND PURPOSE: There are few data on the occurrence of microembolic signals (MES) in patients with lone atrial fibrillation (LAF). The aim of this work was to systematically study the frequency of MES in patients with symptomatic and asymptomatic LAF and to compare it with that of nonvalvular atrial fibrillation (NVAF). METHODS: 37 consecutive acute stroke patients with LAF, 10 asymptomatic patients with LAF and 100 age-matched healthy controls were studied. Another 92 stroke patients with known NVAF were included in the study to compare patients with LAF regarding the presence of MES. Both middle cerebral arteries were monitored by transcranial Doppler ultrasound for at least 30 min at admission and after 1 week in symptomatic and asymptomatic patients with LAF. All patients with LAF were followed up for a mean duration of 18 months, and recurrent strokes were registered. RESULTS: MES was detected in 11 (29%) symptomatic patients with LAF but only in 1 asymptomatic patient with LAF (chi(2) = 11.3; p = 0.0008) and in no control subjects (chi(2) = 106; p = 0.00001). There was no difference in the frequency of MES-positive patients and the number of MES between subjects with symptomatic LAF and known NVAF (29% in both groups; mean count, 16 +/- 4 vs. 17 +/- 6; p = 0.73). In patients with symptomatic LAF and NVAF who underwent anticoagulant therapy, there was no difference in the frequency of MES after 1 week of hospitalization (chi(2) = 1.53; p = 0.2). During a mean follow-up period of 18 months, 1 patient with symptomatic LAF and MES had a recurrent ischemic event 1 year after the first stroke and none of those with asymptomatic LAF had any events. CONCLUSION: Our study suggests that asymptomatic and paroxysmal LAF with a lower frequency of MES is a benign disorder compared to chronic and symptomatic LAF with a higher frequency of MES. Further studies need to justify whether MES has a predictive value in patients with chronic LAF who are prone to ischemic stroke.     

Dynamics and embolic activity of symptomatic intra-cranial cerebral artery stenoses

OBJECTIVE: To investigate the occurrence of microembolic signals (MES) and hemodynamic features in patients with acute symptomatic intracranial cerebral artery stenoses by transcranial Doppler (TCD). MATERIAL AND METHODS: Twelve patients with acute hemispheric ischemic events and corresponding intracranial cerebral artery stenoses as identified by TCD, and exclusion of extracranial or cardiac emboli sources were repeatedly studied by TCD monitoring of the affected and the contralateral vessel. The occurrence of MES and MES clusters (> or =3 MES per second) and of flow velocity changes was examined. RESULTS: Nine patients presented with MES in the affected artery during the first measurement. In seven patients sudden flow velocity changes could be detected in the affected vessel. In five patients these changes were accompanied by MES clusters. MES and velocity changes disappeared in all patients during follow-up, and the degree of stenosis decreased in nine patients. CONCLUSIONS: The high prevalence of MES and sudden velocity changes in acute intracranial cerebral artery stenoses indicates that acute intracranial stenoses may be formed at least in part by mobile thrombotic material.     

Evaluation of the roles of the Leiden V mutation and ACE I/D polymorphism in subtypes of ischaemic stroke

Objective The Leiden V mutation, which causes activated protein C resistance and thrombophilia, has been found to be a risk factor for venous thrombosis. The angiotensin converting enzyme (ACE) D allele indirectly exerts an unfavourable effect on the vasoregulatory system. In this study, the frequency of these mutations was analysed in different subtypes of ischaemic stroke. Method and material According to the clinical and radiological features 664 Hungarian patients who had suffered acute ischaemic stroke were divided into 3 subtypes: small and large vessel infarcts and a mixed type. In all 664 patients, the Leiden V mutation and ACE I/D polymorphism were examined by means of the PCR technique. The frequencies of the different genotypes for the Leiden V mutation and ACE I/D polymorphism in the 3 subgroups of stroke were compared with 199 stroke-free control subjects whose MRI findings were normal. Results No significant associations were found between the overall group of cerebral infarctions and the Leiden V, ACE I/D and ACE D/D genotypes. The ACE D/D genotype was significantly more common in the patients with small deep infarcts (40.3 %; p < 0.0005; OR 2.31, 95 % CI 1.49–3.57) than in the control group (22.6 %). The Leiden V mutation was significantly more common in patients with large infarcts (13.6 %; p < 0.025; OR 2.25, CI 1.16–4.34) than in the stroke-free control subjects (6.5 %). Conclusions The ACE D/D genotype possibly contributes to the occurrence of small-vessel infarcts rather than large vessel infarcts. The Leiden V mutation might predispose to large brain infarcts. Neither the Leiden V factor nor the ACE D/D genotype has been proved to be a risk factor for ischaemic stroke as a whole. Received: 22 June 2000 / Received in revised form: 5 February 2001 / Accepted: 3 March 2001     

血清五聚素3、超敏C反应蛋白、脂蛋白相关磷脂酶A2水平以及微栓子信号与大动脉粥样硬化型急性脑梗死患者颈动脉粥样硬化斑块稳定性的相关研究

目的探讨血清五聚素3(PTX3)、超敏C反应蛋白(hs-CRP)、脂蛋白相关磷脂酶A2(LpPLA2)水平以及微栓子信号(MES)与大动脉粥样硬化型急性脑梗死患者颈动脉粥样硬化斑块稳定性的关系。方法依据中国缺血性卒中亚型分型(CISS),选取起病72 h内大动脉粥样硬化型急性脑梗死患者78例,使用二维彩色多普勒超声检测仪对颈动脉斑块的解剖和病理类型进行分析,将患者分为不稳定斑块组(40例)和稳定斑块组(38例),并同期从体检中心选取健康成人30名作为对照组。测定所有观察对象血清PTX3、hsCRP以及Lp-PLA2水平,分析各组间三种血液学指标水平的差异,并分别对三种血液学指标水平与颈动脉斑块稳定性进行相关性分析。对不稳定斑块组和稳定斑块组患者行TCD监测,分析两组之间MES检出率的差异。结果不稳定斑块组及稳定斑块组血清Hcy、hs-CRP、PTX3、Lp-PLA2水平及高血压的比例均明显高于对照组(均P0.05);不稳定斑块组他汀类用药史的比例明显高于对照组,血清PTX3、Lp-PLA2水平明显高于稳定斑块组(均P0.05)。不稳定斑块组的MES检出率显著高于稳定斑块组(P0.05)。Logistic回归分析显示,血清PTX3、Lp-PLA2水平是与斑块稳定性密切相关的影响因素(均P0.05)。血清PTX3水平预测斑块稳定性的ROC曲线下面积为0.963(P0.05),其临界值为2.57 ng/m L时,灵敏度为78.9%,特异度为84.2%。血清Lp-PLA2水平预测斑块稳定性的ROC曲线下面积为0.927(P0.05),其临界值为54.35μg/L时,灵敏度为72.9%,特异度为81.6%。结论血清PTX3、Lp-PLA2水平可能是预测颈动脉斑块稳定性的生物学指标。MES监测对于颈动脉斑块的稳定性评估具有一定的临床意义。     

Raised plasma oxidised LDL in acute cerebral infarction

BACKGROUND: The association between oxidised low density lipoprotein (OxLDL) and cerebral infarction is suspected but not established. OBJECTIVES: To determine whether plasma OxLDL is a useful marker for monitoring oxidative stress in stroke patients. METHODS: Plasma OxLDL concentrations were determined in 56 stroke patients with cerebral infarction (n = 45) or cerebral haemorrhage (n = 11), and in 19 age matched controls, using a novel sandwich enzyme linked immunosorbent assay. RESULTS: Compared with the controls (0.130 (0.007) ng/ micro g LDL, mean (SEM)), OxLDL was significantly raised in patients with cerebral infarction (0.245 (0.022); p < 0.0001) but not in those with haemorrhage (0.179 (0.023)). Patients with cortical ischaemic infarcts (n = 22) had higher OxLDL levels than either the controls (p < 0.0001) or the patients with non-cortical ischaemic infarcts (n = 23) (p < 0.001). Increased OxLDL concentrations in patients with cortical infarcts persisted until the third day after stroke onset. The National Institutes of Health stroke scales in patients with cortical infarction were higher than in those with non-cortical infarction (p < 0.01). CONCLUSIONS: There is a significant association between raised plasma OxLDL and acute cerebral infarction, especially cortical infarction. Plasma OxLDL may reflect oxidative stress in stroke patients.     

双焦距经颅多普勒在大脑中动脉狭窄患者检测微栓子的研究

目的 研究大脑中动脉（ＭＣＡ）狭窄患者采用ＴＣＤ检测微栓子（ＭＥＳ）的诊断价值。方法 对２１例年龄在３５￣５７岁的单侧ＭＣＡ狭窄患者,经ＣＴ／ＭＲＩ证实为脑梗死。均进行３０分钟的双焦距ＴＣＤ监测。结果 ４例（１９．０％）检测到ＭＥＳ。其中３在狭窄远端检测到,１例近,远端均检测到。均为大面积脑梗死（４／１３,３０．８％）,而腔隙性梗死未发现ＭＥＳ。结论 双焦距ＴＣＤ检测ＭＥＳ对于确定栓子来源有重要价     

脑缺血患者微栓子检测与黏附分子的相关性研究

目的研究脑缺血患者微栓子与黏附分子的相关性。方法选择108例研究对象,其中68例为发病72h内颈内动脉或大脑中动脉区域脑梗死或短暂性脑缺血发作患者,经TCD检测微栓子信号(microembolic sig-nals,MES)分为MES阳性组(19例)和MES阴性组(49例);对照组40例,无脑梗死或脑缺血发作病史,且无明显颅内外动脉狭窄。均用双抗体夹心酶联免疫吸附法(enzyme linked immunosorbent assay,ELISA)测定血清可溶性细胞间黏附分子-1(soluble intercellular adhesion molecule-1sICAM-1)、可溶性血管细胞黏附分子-1(soluble vascularcell adhesion molecule-1,sVCAM-1)水平。结果MES阳性组sICAM-1、sVCAM-1水平高于MES阴性组(P<0.05);MES阳性组、MES阴性组sICAM-1、sVCAM-1水平明显高于对照组(P<0.01)。结论黏附分子参与了脑缺血的损伤过程,且与动脉粥样硬化(artherosclerosis,AS)斑块的不稳定性相关。微栓子和黏附分子是...     

大脑中动脉狭窄患者急性脑梗死发病机制:一项弥散加权磁共振和微栓子监测研究

目的我们前瞻性研究了30例经颅多谱勒超声(TCD)和核磁血管成像(MRA)检查证实大脑中动脉(MCA)狭窄,并在该供血区域出现急性缺血性卒中患者,以探讨MCA狭窄的可能机制。方法全部病人均进行微栓子监测以及弥散加权磁共振(DWI)检查。急性梗死分成单发和多发梗死,梗死部位分成皮层梗死(CI)、交界区梗死(BI)和深穿支动脉梗死(PAI)。微栓子信号(MES)和DWI梗死病灶分别由两位不同的医生在不知道对方资料的情况下确认。结果DWI结果发现急性多发脑梗死和单发梗死各15例(50%)。多发梗死病人中,成链状排列的BI最常见(11例,占73%)。单发梗死中只有PAI是最常见的类型(10例,占67%)。10例(33%)病人检测到MES,每30min内MES的中位数为15(3-102)个。MES在多发梗死中的发生频率(9/15,60.0%)明显高于单发梗死(1/15,6.7%)(P=0.002)。MES的数目能预测DWI上脑梗死的数目(线性回归,调整后R2=0.475,P<0.01)。结论MCA狭窄梗死最常见的原因有两个:①穿支动脉闭塞引起的皮层下小的腔隙性梗死;②由动脉-动脉的栓子不能被清除而造成的多发小梗死,尤其是在交界区更明显。     

Transcranial Doppler detection of cerebral microemboli during left heart catheterization.

The role of transcranial Doppler ultrasonography (TCD) in individual risk assessment of embolic complications and the development of prevention strategies during coronary angiography remains to be determined. The purpose of this study was to assess the prevalence, time of occurrence and potential significance of microembolic signals (MES) detected with TCD during femoral left heart catheterization. TCD monitoring of the right and left middle cerebral artery was performed in 51 consecutive patients (36 men, 15 women) who were referred for coronary angiography. Percutaneous coronary angioplasty was performed during the same procedure in 16 patients. MES were counted manually during and after (off-line analysis) the procedure. Two patients were excluded from analysis because of the absence of an adequate acoustic temporal window. No neurological event occurred within 24 h in the 49 included patients. MES were detected in all except 2 patients (mean number 17.1 +/- 12.8 per patient), mainly during left ventriculography (38%) and contrast media injection into the coronary arteries (55%), suggesting their gaseous origin. There was no statistically significant association between the number of MES and patient age, cardiovascular history and risk factors, or catheterization results. The presence of coronary artery disease was inversely related to the number of MES (15.8 +/- 0.3 compared to 21.8 +/- 0.2 per patient when a normal angiogram was present; p < 0.05). In conclusion, although asymptomatic microemboli commonly occur during left heart catheterization, the majority of them are probably of gaseous origin, since they occurred predominantly during contrast media injection in this study, and were not related to cardiovascular history or to atheroma risk factors. Because air embolism has been reported to be harmful, attempts to reduce its occurrence during catheter-based procedures could be pertinent.     

Microembolic signals within 24 hours of stroke onset and diffusion-weighted MRI abnormalities

BACKGROUND: The clinical relevance of the microembolic signals (MES) detected by transcranial Doppler sonography (TCD) in acute stroke remains unclear. In a prospective study the authors analyzed the relationship between MES and the findings on diffusion-weighted magnetic resonance imaging (DWI) in acute stroke patients. METHODS: We performed TCD for a period of 30 min to detect MES in patients within 24 h of stroke onset, and DWI was done within the initial 7 days. MES were assessed from Doppler waves obtained from the middle cerebral artery contralateral to the side of the neurological deficits. The acute ischemic lesions observed on DWI were classified by their diameter (small, medium or large) and by their site (cortical, superficial perforator territory, internal borderzone or deep perforator territory). RESULTS: We obtained Doppler waves from 39 vessels in 37 patients; 2 patients had bilateral deficits. MES were detected in 12 vessels (MES-positive group) and not detected in 27 vessels (MES-negative group). No significant differences in clinical features were observed between the 2 groups. The number of small lesions was significantly higher in the MES-positive group than in the MES-negative group (p = 0.02). The numbers of cortical and superficial perforator infarcts were significantly higher in the MES-positive group than in the MES-negative group (p = 0.002 and 0.02, respectively). CONCLUSION: In acute ischemic stroke, MES detected by TCD in the acute phase may produce small cortical and subcortical lesions found on DWI.     

Mechanisms of acute cerebral infarctions in patients with middle cerebral artery stenosis: a diffusion-weighted imaging and microemboli monitoring study

Although most therapeutic efforts and experimental stroke models focus on the concept of complete occlusion of the middle cerebral artery as a result of embolism from the carotid artery or cardiac chamber, relatively little is known about the stroke mechanism of intrinsic middle cerebral artery stenosis. Differences in stroke pathophysiology may require different strategies for prevention and treatment. We prospectively studied 30 consecutive acute ischemic stroke patients with middle cerebral artery stenosis detected by transcranial Doppler and magnetic resonance angiography. Patients underwent microembolic signal monitoring by transcranial Doppler and diffusion-weighted magnetic resonance imaging. Characteristics of acute infarct on diffusion-weighted magnetic resonance imaging were categorized according to the number (single or multiple infarcts) and the pattern of cerebral infarcts (cortical, border zone, or perforating artery territory infarcts). The data of microembolic signals and diffusion-weighted magnetic resonance imaging were assessed blindly and independently by separate observers. Diffusion-weighted magnetic resonance imaging showed that 15 patients (50%) had single acute cerebral infarcts and 15 patients had multiple acute cerebral infarcts. Among patients with multiple acute infarcts, unilateral, deep, chainlike border zone infarcts were the most common pattern (11 patients, 73%), and for single infarcts, penetrating artery infarcts were the most common (10 patients, 67%). Microembolic signals were detected in 10 patients (33%). The median number of microembolic signals per 30 minutes was 15 (range, 3-102). Microembolic signals were found in 9 patients with multiple infarcts and in 1 patient with a single infarct (p = 0.002, chi(2)). The number of microembolic signals predicted the number of acute infarcts on diffusion-weighted magnetic resonance imaging (linear regression, adjusted R(2) =0.475, p < 0.001). Common stroke mechanisms in patients with middle cerebral artery stenosis are the occlusion of a single penetrating artery to produce a small subcortical lacuna-like infarct and an artery-to-artery embolism with impaired clearance of emboli that produces multiple small cerebral infarcts, especially along the border zone region.