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1.
Stroke ; : STROKEAHA119025732, 2019 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-31409268

RESUMO

Background and Purpose- In patients with symptomatic intracranial atherosclerotic stenosis, identifying the underlying stroke mechanisms may inform secondary prevention. We aimed to propose reproducible classification criteria for stroke mechanisms based on routine neuroimaging in symptomatic intracranial atherosclerotic stenosis and explore their clinical implications. Methods- We recruited patients with acute ischemic stroke attributed to 50% to 99% intracranial atherosclerotic stenosis in anterior circulation from 2 centers. Two investigators independently classified probable stroke mechanisms as parent artery atherosclerosis occluding penetrating artery, artery-to-artery embolism, hypoperfusion, and mixed mechanisms, with prespecified criteria based on infarct topography and magnetic resonance/computed tomography angiography. These stroke mechanisms were correlated with features of the patients at baseline and recurrent ischemic stroke in the same territory or relevant transient ischemic attack within 1 year. Results- Among 153 patients recruited, the most common stroke mechanisms were isolated hypoperfusion (35.3%) and mixed mechanism of artery-to-artery embolism and hypoperfusion (37.3%) that was associated with higher incidence of dyslipidemia (P=0.045) and hypertension (P=0.033) than patients with other stroke mechanisms. The proposed criteria showed substantial to excellent intrarater and interrater reproducibilities (κ, 0.791-0.908). Overall, 31 patients received interventional treatment of the diseased intracranial artery; 122 received medical treatment, among whom a mixed mechanism of artery-to-artery embolism and hypoperfusion at baseline was associated with higher risk of ischemic stroke in the same territory within 1 year (24.4% versus 7.8%; hazard ratio, 3.40; 95% CI, 1.25-9.20; log-rank P=0.010) than other mechanisms combined. Conclusions- Artery-to-artery embolism and hypoperfusion commonly coexist in ischemic stroke attributed to intracranial atherosclerotic stenosis, which may be associated with higher risk of stroke relapse.

2.
Ann Neurol ; 85(5): 752-764, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30840312

RESUMO

OBJECTIVE: To investigate whether hemodynamic features of symptomatic intracranial atherosclerotic stenosis (sICAS) might correlate with the risk of stroke relapse, using a computational fluid dynamics (CFD) model. METHODS: In a cohort study, we recruited patients with acute ischemic stroke attributed to 50 to 99% ICAS confirmed by computed tomographic angiography (CTA). With CTA-based CFD models, translesional pressure ratio (PR = pressurepoststenotic /pressureprestenotic ) and translesional wall shear stress ratio (WSSR = WSSstenotic - throat /WSSprestenotic ) were obtained in each sICAS lesion. Translesional PR ≤ median was defined as low PR and WSSR ≥4th quartile as high WSSR. All patients received standard medical treatment. The primary outcome was recurrent ischemic stroke in the same territory (SIT) within 1 year. RESULTS: Overall, 245 patients (median age = 61 years, 63.7% males) were analyzed. Median translesional PR was 0.94 (interquartile range [IQR] = 0.87-0.97); median translesional WSSR was 13.3 (IQR = 7.0-26.7). SIT occurred in 20 (8.2%) patients, mostly with multiple infarcts in the border zone and/or cortical regions. In multivariate Cox regression, low PR (adjusted hazard ratio [HR] = 3.16, p = 0.026) and high WSSR (adjusted HR = 3.05, p = 0.014) were independently associated with SIT. Patients with both low PR and high WSSR had significantly higher risk of SIT than those with normal PR and WSSR (risk = 17.5% vs 3.0%, adjusted HR = 7.52, p = 0.004). INTERPRETATION: This work represents a step forward in utilizing computational flow simulation techniques in studying intracranial atherosclerotic disease. It reveals a hemodynamic pattern of sICAS that is more prone to stroke relapse, and supports hypoperfusion and artery-to-artery embolism as common mechanisms of ischemic stroke in such patients. Ann Neurol 2019;85:752-764.

3.
Atherosclerosis ; 281: 71-77, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30658194

RESUMO

BACKGROUND AND AIMS: Intracranial atherosclerosis (ICAS) is a predictable and preventable condition, but existing evidence concerning its risk factors has not been quantitatively assessed. The aim of this meta-analysis is to identify the non-modifiable and modifiable risk factors for ICAS. METHODS: PubMed and EMBASE were searched (1995-May 15, 2018) for cross-sectional and longitudinal studies exploring risk factors for ICAS. The risk estimates and 95% confidence intervals (CIs) in multivariate analysis were aggregated using random-effect models. RESULTS: Thirty-four studies comprising 59,736 subjects met the inclusion criteria for the systematic review involving thirty-one risk or protective factors. Seven factors were associated with ICAS, as suggested by the meta-analysis, including advanced age (odds ratio (OR) 1.05, 95% CI 1.03-1.08), metabolic syndrome (OR 2.13, 95% CI 1.35-3.37), diabetes mellitus (OR 1.98, 95% CI 1.69-2.31), hypertension (OR 1.97, 95% CI 1.69-2.31), dyslipidemia (OR 1.29, 95% CI 1.04-1.59), high levels of low-density lipoprotein cholesterol (OR 1.06, 95% CI 1.00-1.12) and high levels of apolipoprotein A1 (OR 0.34, 95% CI 0.15-0.75). The subgroup analysis for study populations indicated advanced age, metabolic syndrome, diabetes mellitus and hypertension as an elevated risk of ICAS among community subjects and stroke patients; according to the subgroup analysis for ethnicity, similar associations remained in Asians, but only metabolic syndrome and diabetes mellitus were correlated with ICAS in Caucasians. CONCLUSIONS: Individuals with advanced age, metabolic syndrome, diabetes mellitus, hypertension and dyslipidemia might have a higher risk of ICAS, whereas high levels of apolipoprotein A1 might protect against ICAS.

4.
J Cereb Blood Flow Metab ; : 271678X18805209, 2018 Oct 23.
Artigo em Inglês | MEDLINE | ID: mdl-30351176

RESUMO

We aimed to investigate the roles of antegrade residual flow and leptomeningeal collateral flow in sustaining cerebral perfusion distal to an intracranial atherosclerotic stenosis (ICAS). Patients with apparently normal cerebral perfusion distal to a symptomatic middle cerebral artery (MCA)-M1 stenosis were enrolled. Computational fluid dynamics models were built based on CT angiography to obtain a translesional pressure ratio (PR) to gauge the residual antegrade flow. Leptomeningeal collaterals (LMCs) were scaled on CT angiography. Cerebral perfusion metrics were obtained in CT perfusion maps. Among 83 patients, linear regression analyses revealed that both translesional PR and LMC scale were independently associated with relative ipsilesional mean transit time (rMTT). Subgroup analyses showed that ipsilesional rMTT was significantly associated with translesional PR ( p < 0.001) rather than LMC scale in those with a moderate (50-69%) MCA stenosis, which, however, was only significantly associated with LMC scale ( p = 0.051) in those with a severe (70-99%) stenosis. Antegrade residual flow and leptomeningeal collateral flow have complementary effects in sustaining cerebral perfusion distal to an ICAS, while cerebral perfusion may rely more on the collateral circulation in those with a severe stenosis.

5.
Stroke Vasc Neurol ; 3(3): 117-130, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-30294467

RESUMO

Collateral circulation plays a vital role in sustaining blood flow to the ischaemic areas in acute, subacute or chronic phases after an ischaemic stroke or transient ischaemic attack. Good collateral circulation has shown protective effects towards a favourable functional outcome and a lower risk of recurrence in stroke attributed to different aetiologies or undergoing medical or endovascular treatment. Over the past decade, the importance of collateral circulation has attracted more attention and is becoming a hot spot for research. However, the diversity in imaging methods and criteria to evaluate collateral circulation has hindered comparisons of findings from different cohorts and further studies in exploring the clinical relevance of collateral circulation and possible methods to enhance collateral flow. The statement is aimed to update currently available evidence and provide evidence-based recommendations regarding grading methods for collateral circulation, its significance in patients with stroke and methods under investigation to improve collateral flow.

7.
J Stroke Cerebrovasc Dis ; 27(1): 44-52, 2018 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-29107636

RESUMO

BACKGROUND: Computational fluid dynamics (CFD) allows noninvasive fractional flow (FF) computation in intracranial arterial stenosis. Removal of small artery branches is necessary in CFD simulation. The consequent effects on FF value needs to be judged. METHODS: An idealized vascular model was built with 70% focal luminal stenosis. A branch with one third or one half of the radius of the parent vessel was added at a distance of 5, 10, 15 and 20 mm to the lesion. With pressure and flow rate applied as inlet and outlet boundary conditions, CFD simulations were performed. Flow distribution at bifurcations followed Murray's law. By including or removing side branches, five patient-specific intracranial artery models were simulated. Transient simulation was performed on a patient-specific model, with a larger branch for validation. Branching effect was considered trivial if the FF difference between paired models (branches included or removed) was within 5%. RESULTS: Compared with the control model without a branch, in all idealized models the relative differences of FF was within 2%. In five pairs of cerebral arteries (branches included/removed), FFs were 0.876 and 0.877, 0.853 and 0.858, 0.874 and 0.869, 0.865 and 0.858, 0.952 and 0.948. The relative difference in each pair was less than 1%. In transient model, the relative difference of FF was 3.5%. CONCLUSION: The impact of removing side branches with radius less than 50% of the parent vessel on FF measurement accuracy is negligible in static CFD simulations, and minor in transient CFD simulation.


Assuntos
Artérias Cerebrais/fisiopatologia , Circulação Cerebrovascular , Doenças Arteriais Intracranianas/fisiopatologia , Modelos Cardiovasculares , Modelagem Computacional Específica para o Paciente , Velocidade do Fluxo Sanguíneo , Angiografia Cerebral/métodos , Artérias Cerebrais/diagnóstico por imagem , Angiografia por Tomografia Computadorizada , Constrição Patológica , Humanos , Hidrodinâmica , Doenças Arteriais Intracranianas/diagnóstico por imagem , Interpretação de Imagem Radiográfica Assistida por Computador , Fluxo Sanguíneo Regional
8.
Curr Opin Neurol ; 31(1): 14-22, 2018 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-29084062

RESUMO

PURPOSE OF REVIEW: Reviewing existing evidence regarding well tolerated and effective antiplatelet treatment in patients with acute or chronic, noncardioembolic ischemic stroke and transient ischemic attack (TIA). RECENT FINDINGS: For patients with high-risk stroke or TIA, for instance, minor stroke or high-risk TIA, or stroke of atherosclerotic origin with evidence suggesting risk of artery-to-artery embolism or with high-grade, symptomatic arterial stenosis, early initiated, short-term dual antiplatelet (e.g. aspirin and clopidogrel) is effective in reducing the risk of recurrent stroke and other vascular events which does not increase the risk of severe or fatal bleeding, as compared with mono antiplatelet therapy. However, long-term application of aggressive antiplatelet therapies after a noncardioembolic stroke or TIA increases the bleeding risks. Triple antiplatelet therapy is not appropriate for noncardioembolic stroke or TIA, in view of the high bleeding risk. In addition, emerging antiplatelets such as ticagrelor and cilostazol may work better in certain subgroups of stroke patients, which warrants further investigation. SUMMARY: Antiplatelet therapies should differ in the acute and chronic phases among patients with high-risk stroke or TIA when more aggressive antiplatelet treatment is reasonable in the acute phase, but no solid evidence supports different antiplatelet strategies in acute and chronic phases in patients with low-risk noncardioembolic stroke.


Assuntos
Doença Aguda/terapia , Isquemia Encefálica/tratamento farmacológico , Doença Crônica/tratamento farmacológico , Inibidores da Agregação de Plaquetas/uso terapêutico , Acidente Vascular Cerebral/tratamento farmacológico , Humanos , Inibidores da Agregação de Plaquetas/efeitos adversos
10.
J Stroke Cerebrovasc Dis ; 26(8): 1760-1765, 2017 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-28522230

RESUMO

BACKGROUND: Cortical microinfarcts (CMIs) have been correlated to cognitive decline and dementia. It was previously considered only visible on microscope, but was recently reported to be visible on 3.0 Tesla magnetic resonance imaging (MRI) and linked to presence of intracranial stenosis. We aimed to investigate CMIs on 3.0 Tesla MRI in patients with M1 middle cerebral artery (MCA-M1) stenosis. METHODS: Patients with a recent non-cardioembolic ischemic stroke or transient ischemic attack and an atherosclerotic MCA-M1 stenosis were recruited. The severity of MCA stenosis was defined as moderate (50%-69%) or severe (70%-99% or focal flow void) on time-of-flight MR angiography (MRA). The distal to proximal signal intensity ratio (SIR) of MCA stenosis was measured on time-of-flight MRA to represent its hemodynamic significance. The presence of CMI(s) in the ipsilateral hemisphere was assessed on axial T1- or T2-weighted images and T2-weighted fluid-attenuated inversion-recovery images. RESULTS: Overall, 86 patients (mean age: 62.8 years; 77.9% males) were analyzed, 66 (76.7%) and 20 (23.3%), respectively, having moderate and severe MCA-M1 stenoses. The median SIR was .91. Forty-five (52.3%) patients had ipsilateral CMI(s). Multivariate logistic regression showed a history of dyslipidemia (odds ratio [OR] = 6.83, P = .008), and an SIR lower than the median (OR = 4.73, P = .014) were independently associated with presence of CMI(s) in ipsilateral hemisphere to an MCA-M1 stenosis. CONCLUSIONS: Patients with stroke and intracranial stenosis had a high burden of CMI. Except for a history of dyslipidemia, the hemodynamic significance of the arterial stenosis may contribute to the presence of ipsilateral CMI(s) in these patients, which warrants further investigation in prospective, longitudinal studies.


Assuntos
Córtex Cerebral/irrigação sanguínea , Córtex Cerebral/diagnóstico por imagem , Infarto da Artéria Cerebral Média/diagnóstico por imagem , Imagem por Ressonância Magnética , Idoso , Velocidade do Fluxo Sanguíneo , Circulação Cerebrovascular , Distribuição de Qui-Quadrado , China/epidemiologia , Estudos Transversais , Dislipidemias/epidemiologia , Feminino , Humanos , Interpretação de Imagem Assistida por Computador , Incidência , Infarto da Artéria Cerebral Média/epidemiologia , Infarto da Artéria Cerebral Média/fisiopatologia , Modelos Logísticos , Angiografia por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Análise Multivariada , Razão de Chances , Valor Preditivo dos Testes , Fatores de Risco , Índice de Gravidade de Doença
11.
Neurol Res ; 39(6): 498-503, 2017 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-28436268

RESUMO

OBJECTIVES: Fractional flow reserve (FFR) accurately predicts the degree of stenosis and is now widely used to identify clinically significant severe coronary artery lesions. In the current study, we utilized a similar indicator, fractional flow (FF), to determine the hemodynamic impact of symptomatic intracranial atherosclerotic stenosis (ICAS) and to assess the correlation of FF with the severity of stenosis and collateral circulation. METHODS: Patients with symptomatic ICAS (70-99% stenosis) confirmed on digital subtraction angiography (DSA) were consecutively recruited. FF was obtained during DSA examination with the use of pressure sensors and was measured as a ratio, comparing measurements distal to an ICAS lesion (Pd) and within the aorta (Pa). The degree of leptomeningeal collateralization was graded from zero (absent) to four (complete compensatory). The correlation between FF, anatomical stenosis, and collateral status was then analyzed. RESULTS: Twenty-five patients with a mean age of 55.6 years were analyzed. The median percentage of stenosis and median FF were 82.3 and 0.68%, respectively. Eleven patients were found to have poor collateralization (grade 0-2), and fourteen patients were identified with good collateral circulation (grade 3-4). Overall, the hemodynamic impact of an atherosclerotic lesions worsened (decreased FF) as the percentage of stenosis increased, although this did not reach statistical significance (r = -0.398, p = 0.06). However, the status of collateralization significantly altered this correlation, worsening the hemodynamic impact in patients with poor collateral circulation (r = -0.677, p = 0.032). There was no difference in patients with good collateral circulation (r = -0.279, p = 0.356). CONCLUSION: An anatomically severe (70-99%) symptomatic ICAS lesion may generate significant hemodynamic stress downstream as assessed by the indicator FF, particularly in patients with poor collateral circulation. Further, good collateralization may mitigate this hemodynamic impact, partially explaining the protective effect of collateral circulation against recurrent stroke in such patients.


Assuntos
Circulação Cerebrovascular/fisiologia , Circulação Colateral/fisiologia , Constrição Patológica/fisiopatologia , Arteriosclerose Intracraniana/etiologia , Estresse Fisiológico , Angiografia Digital/métodos , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estresse Fisiológico/fisiologia
12.
Curr Neurovasc Res ; 14(2): 149-157, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28412909

RESUMO

BACKGROUND: Intracranial arterial stenosis (ICAS) is the dominant cause for ischemic stroke worldwide, with hemodynamic compromise as a crucial contributor. Prolonged perfusion is commonly observed in ICAS patients on CT perfusion (CTP) maps, while the clinical significance of this perfusion pattern has not been elucidated. METHOD: Patients having symptomatic ICAS of 50-99% stenosis with sustained downstream cerebral blood flow (CBF) were enrolled in this study. Prolonged perfusion was defined as increased mean transit time (MTT) in vascular territories of the target ICAS on CTP maps. The primary clinical outcome was recurrence of ipsilateral ischemic stroke, and secondary outcome was any ipsilateral ischemic events at 2 years follow-up. RESULTS: Of the 95 patients (median age 61y; 70% males) with symptomatic ICAS, 29 patients (30.5%) had prolonged perfusion. Such delayed perfusion was persistent in a majority of patients according to the 1-year imaging follow-up. The prolongation of cerebral perfusion was associated with subsequent risk for ipsilateral ischemic stroke (HR 7.01; 95% CI 1.86-26.46; p = 0.004), but not for any ipsilateral ischemic events (HR 1.52; 95% CI 0.63-3.68; p = 0.348). Further comparison of perfusion measures showed lower CBF (p = 0.034) and higher MTT (p = 0.064) in patients with recurrent ischemic stroke, but not in those with recurrent transient ischemic attack (TIA). Among patients with recurrent stroke, a majority had multiple infarcts along the borderzone regions. CONCLUSION: In patients with symptomatic ICAS, persistent prolonged cerebral perfusion might contribute to the relapse of ischemic stroke, but not TIA.


Assuntos
Transtornos Cerebrovasculares/complicações , Ataque Isquêmico Transitório/complicações , Acidente Vascular Cerebral/diagnóstico , Acidente Vascular Cerebral/etiologia , Idoso , Volume Sanguíneo Cerebral/fisiologia , Infarto Cerebral/diagnóstico por imagem , Infarto Cerebral/etiologia , Circulação Cerebrovascular/fisiologia , Transtornos Cerebrovasculares/diagnóstico por imagem , Estudos de Coortes , Constrição Patológica/diagnóstico por imagem , Constrição Patológica/etiologia , Feminino , Lateralidade Funcional , Humanos , Ataque Isquêmico Transitório/diagnóstico por imagem , Estimativa de Kaplan-Meier , Masculino , Pessoa de Meia-Idade , Perfusão , Imagem de Perfusão , Fatores de Risco , Fatores de Tempo
13.
Int J Stroke ; 12(3): 236-245, 2017 04.
Artigo em Inglês | MEDLINE | ID: mdl-28067615

RESUMO

Background Intracranial atherosclerotic stenosis is an important etiology subtype of ischemic stroke. Stenosis severity was thought to be the main reference index for clinical treatment and research. However, stenosis could not reflect the ischemia risk completely, instead the hemodynamic state across the lesion, the extent of collateral circulation, and perfusion impairment downstream the stenosis are more important. Aims We write this review aimed to summarize novel angiographic methods applied in the evaluation of functional severity of ICAS, and commented on their limitations and prospects in future research. Summary of review The main methods to estimate cerebral blood flow including fractional flow assessed by signal intensity ratio, computational fluid dynamics analysis or pressure wire, quantitative magnetic resonance angiography. Fractional flow as a series cerebral hemodynamic parameters may reflect the status of collateral circulation and cerebral blood flow. But the accuracy of the methods was not validated. The method to calculate fractional flow reserve in cardiovascular disease cannot duplicate in cerebrovascular disease. Fractional flow measurement by floating a pressure guidewire across the intracranial stenosis was technically feasible and safe. In the future researches, a non-invasive method should be established to identify high-risk intracranial lesions and may help in decision-making. Conclusions The relationship between stenosis and cerebral blood flow was individualized. Cerebral hemodynamic criteria should be used to screen patients to endovascular treatment, which will optimize the diagnosis and treatment strategies for patients with symptomatic intracranial artery stenosis.


Assuntos
Arteriosclerose Intracraniana/diagnóstico por imagem , Arteriosclerose Intracraniana/fisiopatologia , Encéfalo/irrigação sanguínea , Encéfalo/diagnóstico por imagem , Encéfalo/patologia , Encéfalo/fisiopatologia , Hemodinâmica , Humanos , Arteriosclerose Intracraniana/patologia
14.
J Cereb Blood Flow Metab ; 37(7): 2567-2576, 2017 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-27702878

RESUMO

The fractional pressure ratio is introduced to quantitatively assess the hemodynamic significance of severe intracranial stenosis. A computational fluid dynamics-based method is proposed to non-invasively compute the FPRCFD and compared against fractional pressure ratio measured by an invasive technique. Eleven patients with severe intracranial stenosis considered for endovascular intervention were recruited and an invasive procedure was performed to measure the distal and the aortic pressure ( Pd and Pa). The fractional pressure ratio was calculated as [Formula: see text]. The computed tomography angiography was used to reconstruct three-dimensional (3D) arteries for each patient. Cerebral hemodynamics was then computed for the arteries using a mathematical model governed by Navier-Stokes equations and with the outflow conditions imposed by a model of distal resistance and compliance. The non-invasive [Formula: see text], [Formula: see text], and FPRCFD were then obtained from the computational fluid dynamics calculation using a 16-core parallel computer. The invasive and non-invasive parameters were tested by statistical analysis. For this group of patients, the computational fluid dynamics method achieved comparable results with the invasive measurements. The fractional pressure ratio and FPRCFD are very close and highly correlated, but not linearly proportional, with the percentage of stenosis. The proposed computational fluid dynamics method can potentially be useful in assessing the functional alteration of cerebral stenosis.


Assuntos
Pressão Sanguínea/fisiologia , Artérias Cerebrais/diagnóstico por imagem , Angiografia por Tomografia Computadorizada , Arteriosclerose Intracraniana/diagnóstico por imagem , Modelos Teóricos , Acidente Vascular Cerebral/diagnóstico por imagem , Aorta/fisiopatologia , Artérias Cerebrais/patologia , Artérias Cerebrais/fisiopatologia , Circulação Cerebrovascular/fisiologia , Biologia Computacional , Constrição Patológica , Feminino , Humanos , Arteriosclerose Intracraniana/complicações , Arteriosclerose Intracraniana/patologia , Arteriosclerose Intracraniana/fisiopatologia , Masculino , Pessoa de Meia-Idade , Projetos Piloto , Acidente Vascular Cerebral/etiologia , Acidente Vascular Cerebral/patologia , Acidente Vascular Cerebral/fisiopatologia
16.
Interv Neurol ; 5(1-2): 65-75, 2016 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-27610123

RESUMO

PURPOSE: Current studies on endovascular intervention for intracranial atherosclerosis select patients based on luminal stenosis. Coronary studies demonstrated that fractional flow measurements assess ischemia better than anatomical stenosis and can guide patient selection for intervention. We similarly postulated that fractional flow can be used to assess ischemic stroke risk. METHODS: This was a feasibility study to assess the technical use and safety of applying a pressure guidewire to measure fractional flow across intracranial stenoses. Twenty patients with severe intracranial stenosis were recruited. The percentage of luminal stenosis, distal to proximal pressure ratios (fractional flow) and the fractional flow gradients across the stenosis were measured. Procedural success rate and safety outcomes were documented. RESULTS: All 20 patients had successful crossing of stenosis by the pressure guidewire. Ten patients underwent angioplasty, and 5 had stenting performed. There was one perforator stroke, but not related to the use of the pressure wire. For the 13 patients with complete pre- and postintervention data, the mean preintervention stenosis, fractional flow and translesional pressure gradient were 76.2%, 0.66 and 29.9 mm Hg, whilst the corresponding postintervention measurements were 24.7%, 0.88 and 10.9 mm Hg, respectively. Fractional flow (r = -0.530, p = 0.001) and the translesional pressure gradient (r = 0.501, p = 0.002) only had a modest correlation with the luminal stenosis. CONCLUSION: Fractional flow measurement by floating a pressure guidewire across the intracranial stenosis was technically feasible and safe in this study. Further studies are needed to validate its use for ischemic stroke risk assessment.

17.
Cerebrovasc Dis ; 42(3-4): 232-9, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27173386

RESUMO

BACKGROUND: Intracranial arterial stenosis (ICAS) is a predominant cause of ischemic stroke in Asia. Changes in the signal intensities (SIs) across ICAS lesions on time-of-flight magnetic resonance angiography (TOF-MRA) have been indicated to partially reflect the hemodynamic significance of the lesions, which we aimed to verify by correlating it with cerebral perfusion features provided by CT perfusion (CTP) imaging. METHODS: Ischemic stroke or transient ischemic attack patients with unilateral symptomatic stenosis (≥50%) of intracranial internal carotid artery or middle cerebral artery (MCA) were included in this study. Change of SIs across an ICAS lesion on TOF-MRA was calculated by the distal and proximal SI ratio (SIR). Cerebral blood volume (CBV), cerebral blood flow (CBF), and mean transit time (MTT) within the MCA territory of ipsilateral and contralateral hemispheres were evaluated on the CTP images at the basal ganglia level. Relative CBV, CBF and MTT were defined as ratios of the values obtained from ipsilateral and contralateral hemispheres. The relationships between SIR and CTP parameters were analyzed. RESULTS: Fifty subjects (74% male, mean age 62) were recruited. Overall, the mean SIR was 0.77 ± 0.17. SIR of ICAS was significantly, linearly and negatively correlated with ipsilateral CBV (r = -0.335, p = 0.017), ipsilateral MTT (r = -0.301, p = 0.034), and ipsilateral/contralateral MTT ratio (r = -0.443, p = 0.001). CONCLUSIONS: Diminished SIs distal to ICAS on TOF-MRA might be associated with delayed ipsilateral cerebral perfusion. Changes of the SIs across ICAS lesions on TOF-MRA may be a simple marker to reflect cerebral perfusion changes in patients with symptomatic ICAS.


Assuntos
Artéria Carótida Interna/diagnóstico por imagem , Estenose das Carótidas/diagnóstico por imagem , Angiografia Cerebral/métodos , Circulação Cerebrovascular , Infarto da Artéria Cerebral Média/diagnóstico por imagem , Ataque Isquêmico Transitório/diagnóstico por imagem , Angiografia por Ressonância Magnética , Artéria Cerebral Média/diagnóstico por imagem , Imagem de Perfusão/métodos , Artéria Carótida Interna/fisiopatologia , Estenose das Carótidas/fisiopatologia , Constrição Patológica , Feminino , Humanos , Infarto da Artéria Cerebral Média/fisiopatologia , Ataque Isquêmico Transitório/fisiopatologia , Masculino , Pessoa de Meia-Idade , Artéria Cerebral Média/fisiopatologia , Valor Preditivo dos Testes , Estudos Prospectivos , Estudos Retrospectivos
18.
Expert Rev Neurother ; 16(6): 701-9, 2016 06.
Artigo em Inglês | MEDLINE | ID: mdl-27082149

RESUMO

Intracranial atherosclerotic disease is the most common cause of cerebral vasculopathy and an important stroke etiology worldwide, with a higher prevalence in Asian, Hispanic and African ethnicities. Symptomatic intracranial atherosclerotic disease portends a recurrent stroke risk as high as 18% at one year. The key to secondary prevention is an understanding of the underlying stroke mechanism and aggressive control of conventional cardiovascular risks. Contemporary treatment includes antiplatelet therapy, optimal glycemic and blood pressure control, statin therapy and lifestyle modifications. For patients with high-grade (70-99%) symptomatic steno-occlusion, short-term dual antiplatelet therapy with aspirin and clopidogrel followed by life-long single antiplatelet therapy may reduce the recurrent risk. Current evidence does not advocate percutaneous transluminal angioplasty and stenting as an initial treatment. External counterpulsation, encephaloduroarteriosynangiosis and remote limb ischemic preconditioning are treatments under investigation. Future studies should aim at predicting patients prone to recurrence despite of medical therapies and testing the efficacy of emerging therapies.


Assuntos
Angioplastia , Fibrinolíticos/uso terapêutico , Arteriosclerose Intracraniana/tratamento farmacológico , Ticlopidina/uso terapêutico , Aspirina/uso terapêutico , Clopidogrel , Humanos , Arteriosclerose Intracraniana/complicações , Acidente Vascular Cerebral/etiologia , Acidente Vascular Cerebral/prevenção & controle , Ticlopidina/análogos & derivados
19.
Cerebrovasc Dis ; 41(1-2): 27-34, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-26579719

RESUMO

BACKGROUND: Pre-treatment collateral status may be associated with the rates of successful revascularization in acute ischemic stroke patients receiving endovascular treatment (EVT). We conducted a systematic review and meta-analysis to synthesize relevant evidence currently available. METHODS: Relevant full-text articles published in English since January 1, 2000, reporting associations between collateral status and successful reperfusion and/or recanalization in acute ischemic stroke patients receiving EVT in cohort or case-control studies, or randomized clinical trials, were retrieved through search of PubMed. Study selection, data extraction and study quality assessment were carried out by 2 investigators. Risk ratios (RR) were pooled for good vs. poor collaterals for the outcomes of successful reperfusion and recanalization, based on random-effects models. Subgroup analyses were conducted to explore for potential factors that might interfere with the effects of pre-treatment collateral status on reperfusion by EVT. RESULTS: In total, 27 studies (2,366 subjects) were included in qualitative analysis, among which 24 studies (2,239 subjects) were quantitatively analyzed. Overall, good pre-treatment collaterals significantly increased the rate of both successful reperfusion (RR 1.28, 95% CI 1.17-1.40; p < 0.001) and recanalization (RR 1.23, 95% CI 1.06-1.42; p = 0.006), as compared with poor collaterals. Subgroup analyses revealed that the effects of collateral status on successful reperfusion by EVT might be different between populations with different ethnicities. CONCLUSIONS: Good pre-treatment collaterals may enhance the rates of successful reperfusion and recanalization in EVT for acute ischemic stroke. This may partly explain the favorable effects of good pre-treatment collaterals on clinical outcomes of stroke patients receiving EVT. Thus, it would be valuable to assess the collateral status prior to EVT in acute ischemic stroke. But studies are needed to further verify if the positive effects of good collaterals on revascularization by EVT are restricted to certain subgroups of patients.


Assuntos
Isquemia Encefálica/terapia , Circulação Cerebrovascular , Circulação Colateral , Procedimentos Endovasculares/métodos , Acidente Vascular Cerebral/terapia , Angioplastia/métodos , Isquemia Encefálica/complicações , Revascularização Cerebral/métodos , Humanos , Prognóstico , Reperfusão , Stents , Acidente Vascular Cerebral/etiologia , Trombectomia/métodos , Terapia Trombolítica/métodos
20.
J Neuroimaging ; 26(3): 331-8, 2016 05.
Artigo em Inglês | MEDLINE | ID: mdl-26598796

RESUMO

OBJECTIVE: Success in clinical trials of intracranial atherosclerosis (ICAS) is related to accurate identification of high-risk patients. Noninvasive computational fluid dynamics (CFD) of stenotic lesions may enhance therapeutic decision-making. We determined whether physiologic parameters change downstream cerebral hemodynamics in patients with ICAS. METHODS: Consecutive ICAS patients who underwent both CT angiography (CTA) and digital subtraction angiography were enrolled. CFD models were made using CTA source images. Inlet boundary conditions were defined using three ranges of systolic blood pressure (BP) (109.2, 158, and 225 mmHg) and hematocrit (27.3, 40.2, and 48.8). Ratios of pressure, shear strain rates (SSR), and flow velocity across the lesion were calculated using CFD simulations. A linear mixed model was used for the statistical analysis of repeated simulations. RESULTS: Among the 56 patients, 32 had moderate stenosis (50-69%) and 24 had severe stenosis (70-99%). A linear mixed model revealed that the ratio of pressure was predicted by systolic BP and stenosis group interaction (P = .036). These pressure decreases were associated with systolic BP (P < .001) and stenosis group (P < .001), but not with hematocrit (P = .337). Post-hoc analysis revealed that pressure decreases were more profound in the severe stenosis than the moderate stenosis group when comparing high and low systolic BP (P = .0108). Ratios of SSR and velocity were only associated in the stenosis group. CONCLUSIONS: Our study showed that systolic BP along with the degree of stenosis was associated with pressure decreases across stenotic lesions. Physiologic conditions may superimpose further changes in post-stenotic or downstream blood flow.


Assuntos
Pressão Sanguínea/fisiologia , Simulação por Computador , Hematócrito , Hemodinâmica/fisiologia , Hidrodinâmica , Arteriosclerose Intracraniana/fisiopatologia , Software , Idoso , Idoso de 80 Anos ou mais , Angiografia Digital , Angiografia por Tomografia Computadorizada , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Acidente Vascular Cerebral/fisiopatologia
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