- Email: [email protected]
Differences in Endothelial Function between Ischemic Stroke Subtypes
Differences in Endothelial Function between Ischemic Stroke Subtypes Utako Adachi, MD,* Yukiko Tsutsumi, MD,† Mutsumi Iijima, MD,* Satoko Mizuno, MD,* Shinichiro Uchiyama, MD,‡ and Kazuo Kitagawa,
MD*
Background: Endothelial dysfunction plays a key role in the development of ischemic stroke. However, the relationship between endothelial function and stroke subtypes has not been thoroughly examined. Methods: We measured the percentage of brachial flow-mediated vasodilatation (%FMD) in 62 patients with chronic stroke and 13 age- and sex-matched control patients. Patients with stroke included those classified into large artery atherosclerosis (LAA), cardioembolism (CE), and small vessel occlusion (SVO) according to the criteria of the Trial of ORG 10172 in Acute Stroke Treatment classification. Results: %FMD was significantly lower in the patients with any of LAA, CE, and SVO than in the control patients. %FMD was also significantly lower in men than in women as well as in patients with than without hypertension or diabetes mellitus. After adjustment for confounding factors, the patients with LAA and CE but not SVO had lower %FMD compared to the controls. Conclusions: Our results suggest that endothelial function in conduit artery was impaired in patients with LAA and CE regardless with or without concomitant vascular risk factors. Key Words: FMD—stroke subtypes—max-IMT—plaque score. © 2015 National Stroke Association. Published by Elsevier Inc. All rights reserved.
Introduction Endothelial function is crucial for the maintenance of vascular tone, antithrombogenicity and the blood–brain barrier in the cerebral artery.1 Indeed, impairment of endothelial function is the first step toward atherothrombosis.2 Brachial flow-mediated vasodilation (FMD) can be measured using high-resolution ultrasonography (USG) and is an established technique for determining endothelial function From the *Department of Neurology, Tokyo Women’s Medical University School of Medicine, Tokyo, Japan; †Department of Neurology, Tokyo Metropolitan Health and Medical Treatment Corporation Ohkubo Hospital, Tokyo, Japan; and ‡Clinical Research Center for Medicine, Center for Brain and Cerebral Vessels, Sanno Hospital and Sanno Medical Center, International University of Health and Welfare, Tokyo, Japan. Received February 11, 2015; revision received July 29, 2015; accepted August 8, 2015. Address correspondence to Utako Adachi, Department of Neurology, Tokyo Women’s Medical University School of Medicine, 8-1 Kawadacho, Shinjuku-ku, Tokyo, Japan. E-mail: [email protected]. 1052-3057/$ - see front matter © 2015 National Stroke Association. Published by Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jstrokecerebrovasdis.2015.08.009
in the conduit artery.3 Several studies have shown that impaired FMD is associated with cardiovascular risk factors,4 carotid plaque,5 aortic stiffness,6 and cerebral white matter lesions.7 Furthermore, previous studies have supported the notion that FMD is an independent predictor for incident cardiovascular disease, especially coronary artery disease.8-11 Since Chen et al. reported that FMD was impaired in patients with lacunar stroke,12 several subsequent studies have shown a relationship between FMD and cerebral small vessel disease including lacunar infarcts and white matter lesions.13,14 However, FMD reflects endothelial function of the conduit artery as opposed to that of the resistant artery.15 Furthermore, recent findings that atrial fibrillation (AF) is associated with diminished FMD suggested that FMD was impaired in patients with cardiogenic embolism.16 In the present study, we measured capability of FMD in the brachial artery in patients with various subtypes of ischemic stroke at chronic stage.
Materials and Methods Subjects were 62 consecutive patients with chronic ischemic stroke after 4 weeks of the onset, who were diagnosed
Journal of Stroke and Cerebrovascular Diseases, Vol. 24, No. 12 (December), 2015: pp 2781–2786
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using either computerized tomography or magnetic resonance imaging, and they were classified into large artery atherosclerosis (LAA), cardioembolism (CE), or small vessel occlusion (SVO) according to criteria defined by the Trial of ORG 10172 in Acute Stroke Treatment (TOAST) classification.17 Patients with other subtypes of ischemic stroke in the TOAST classification, which were strokes of other determined etiology and stroke of undermined etiology, were excluded. In the present study, the numbers of patients with LAA, CE, and SVO were 18, 11, and 33, respectively. Thirteen age- and sex-matched patients without history of cardiovascular diseases, who visited an outpatient clinic during the study period, served as control subjects. The control subjects consisted of 8 men and 5 women; 7 of the subjects had hypertension, 6 had diabetes mellitus, and 7 had dyslipidemia. Their diagnoses were as follows: 4 patients had mild stenosis of the middle cerebral artery, 1 patient had brain atrophy, 1 patient had hydrocephalus, 1 patient had cerebral angioma, 1 patient had cervical spondylosis, 1 patient had neurally mediated syncope, and 4 patients had no abnormality. Endothelial function was accessed by the measurement of FMD in the brachial artery, and color-coded duplex power USG in the carotid arteries was performed in all patients. The extent of FMD in the brachial artery was measured, as described by Sugano et al.18 Ultrasound systems were used, equipped with vascular software for 2-dimensional (2D) imaging, color Doppler, an internal electrocardiogram monitor and a high-frequency vascular transducer. The subjects were studied in a quiet and temperature-controlled room. They were placed in the supine position with the arm in a comfortable position for imaging the brachial artery. The brachial artery was imaged above the antecubital fossa using a high-resolution ultrasound system (UNEX EF 18G, UNEX Corporation, Nagoya, Japan)
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(Fig 1) equipped with a 10-MHz linear array transducer. A segment with clear anterior and posterior intimal interfaces between the lumen and vessel wall was selected for continuous 2D gray scale imaging. Thereafter, arterial occlusion was created by cuff inflation to at least 50 mmHg above systolic blood pressure for 5 min before release. The resulting increase in shear stress causes the brachial artery to dilate, and the degree of vasodilation of the brachial artery after deflation (percentage of brachial flow-mediated vasodilatation [%FMD]) was measured using USG. Normal %FMD is more than 6%.19 Carotid USG was performed using linear array 7.5-MHz transducers (Hitachi Aloka Prosound α7, Hitachi-Aloka Medical, Ltd. Tokyo, Japan). Initially, the common and internal carotid arteries were scanned axially and longitudinally, whereby distribution of atheromatous plaques was roughly evaluated. During the initial scanning, optimal insonation angles were determined to estimate respective plaque heights, and measurements were performed on the frozen frame perpendicular to the vascular walls. Carotid arteries (common carotid arteries, bifurcations, and internal carotid arteries) were divided into 8 sections (15 mm/section). The plaque score (PS) was calculated using the sum of the maximum thickness of all plaques (local increases in intima–media thickness [IMT] ≥ 1.1 mm) located in both carotid arteries.20 Plaque was defined as a focal protruding structure of 1.1 mm or more that encroaches into the arterial lumen by at least .5 mm or 50% of the surrounding IMT according to the Mannheim Carotid Intima–Media Thickness Consensus.21 The length of individual plaques was not considered for the calculation of this score. The maximum IMT refers to the maximum value of IMT within the common carotid artery. Blood pressure in the supine position was evaluated before USG. Hypertension was defined as casual blood pressure higher than 140/90 mmHg or current use of antihypertensive agents. Levels of fasting blood glucose,
Figure 1. (A) Ultrasound image of the brachial artery. Left panel: a baseline rest image. Right panel: the maximal dilator response occurs. The red line indicates the vessel diameter. (B) The lines indicate echogenicity. The distance between the closest maximum points (d) indicates the diameter of the vascular lumen. (Color version of the figure is available online.)
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hemoglobin A1c (HbA1c), serum low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides, and creatinine were determined from blood samples. Information on the patients’ medical histories and medication use was obtained from their clinical records. Diabetes mellitus was defined as fasting blood glucose higher than 126 mg/dL, hemoglobin A1c of more than 5.8%, or use of glucose-lowering agents. Dyslipidemia was defined as fasting serum total cholesterol higher than 220 mg/dL, triglycerides more than 150 mg/dL, highdensity lipoprotein cholesterol higher than 40 mg/dL, or current use of cholesterol-lowering agents. Smoking status was categorically evaluated from self-reports with a smoker defined as currently or previously smoking more than 10 cigarettes per day for more than 1 year. The study protocol was approved by the Academic Research Ethics Committee in Tokyo Women’s Medical University School of Medicine.
Data Analysis Statistical analysis was performed with JMP Pro ver.11.2 SID (SAS Institute Inc. Cary, North Carolina, USA). Data are presented as mean ± SD unless otherwise specified. We used analysis of variance followed by unpaired t-test to investigate the difference of %FMD and risk factors between the control group and each stroke patient group. Next, %FMD was further compared between the control group and each stroke subtype group by adjusting for age, sex, hypertension, and diabetes mellitus, factors showing significant association (P < .05) with %FMD. Linear regression analysis was used to examine the relationship between %FMD and PS. In all tests, P < .05 was considered significant.
Results Patient characteristics are presented in Table 1. In patients with stroke, especially in LAA patients, prevalences of
Table 1. Baseline characteristics of the subjects studied Characteristic
All subjects
No stroke
LAA
SVO
CE
Number Age, mean ± SD Sex, % of men Body mass index (kg/m2) Hypertension (%) Systolic BP (mmHg) Diastolic BP (mmHg) Diabetes mellitus (%) Fasting blood sugar (mg/dL) HbA1c (%) Dyslipidemia (%) LDL-C (mg/dL) Total cholesterol (mg/dL) Triglyceride (mg/dL) HDL-C (mg/dL) Statin use, n (%) Current smoking (%) IHD (%) PAD (%) Anticoagulant use (%) Antiplatelet use (%) Creatinine (mg/dL) Uric acid (mg/dL) eGFR (mL/min/1.73 m2) Proteinuria (%) CRP (mg/dL) Median, interquartile range Max IMT (mm) Plaque score
75 67.7 ± 10.1 68 23.6 ± 3.5 76 131 ± 21 76 ± 12 49 124 ± 39 6.3 ± .8 64 113 ± 30 197 ± 39 149 ± 201 57 ± 16 45 18 33 13 21 72 .97 ± .44 5.6 ± 1.5 63.6 ± 21.3 29 .09 (.05-.18) 1.30 ± .66 6.90 ± 5.73
13 66.2 ± 10.6 62 22.1 ± 2.5 54 123 ± 16 74 ± 11 50 121 ± 42 6.5 ± 1.3 58 113 ± 25 204 ± 48 119 ± 82 62 ± 14 42 0 0 0 0 38 .78 ± .29 5.1 ± 1.6 78.4 ± 28.0 20 .06 (.05-.11) 1.12 ± .38 3.14 ± 2.69
18 65.9 ± 8.1 64 24.8 ± 3.9* 94* 135 ± 24 77 ± 13 61 135 ± 51 6.5 ± .7 78 120 ± 38 207 ± 46 156 ± 101 52 ± 13* 56 28* 50* 28* 11 100* 1.20 ± .69* 5.8 ± 1.0 59.5 ± 24.4* 24 .06 (.05-.12) 1.56 ± .73* 10.21 ± 6.50*
33 69.6 ± 10.9 89 23.7 ± 3.7 82 135 ± 21* 78 ± 12 45 124 ± 33 6.2 ± .8 61 110 ± 26 195 ± 33 114 ± 55 56 ± 18 42 16 15 3 9 85* .94 ± .33 5.8 ± 1.6 60.3 ± 15.8* 31 .12 (.06-.29) 1.32 ± .73 6.79 ± 5.46*
11 66.9 ± 10.0 55 23.2 ± 2.6 73 120 ± 14 73 ± 9 36 108 ± 29 6.1 ± .5 55 114 ± 30 179 ± 29 285 ± 481 62 ± 14 36 27* 100* 36* 100* 27 .91 ± .29 5.1 ± 1.7 61.3 ± 16.5 40 .06 (.05-.10) 1.06 ± .46 6.28 ± 5.34*
Abbreviations: BP, blood pressure; CE, cardioembolism; CRP, C-reactive protein; eGFR, estimated glomerular filtration rate; %FMD, percentage of brachial flow-mediated vasodilatation; HbA1c, hemoglobin A1c; HDL-C, high-density lipoprotein cholesterol; IHD, ischemic heart disease; LAA, large artery atherosclerosis; LDL-C, low-density lipoprotein cholesterol; max IMT, maximum intima–media thickness; PAD, peripheral artery disease; SD, standard deviation; SVO, small vessel occlusion. *P < .05 versus control subjects.
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Table 2. %FMD among control and each stroke subtype
Observed %FMD Adjusted %FMD†
No Stroke
LAA
SVO
CE
8.16 ± 3.39 8.15 ± 1.54
3.75 ± 2.02** 5.05 ± 1.57*
5.68 ± 3.28* 6.28 ± 1.44
4.85 ± 2.98** 5.07 ± 1.58*
Abbreviations: CE, cardioembolism; %FMD, percentage of brachial flow-mediated vasodilatation; LAA, large artery atherosclerosis; SVO, small vessel occlusion. *P < 0.05. **P < 0.01. †%FMD after adjustments for age, sex, hypertension and diabetes mellitus.
hypertension, current smoking, use of antiplatelet drugs or anticoagulants, and levels of serum creatinine were higher than in the control patients. %FMD values in the control, LAA, SVO, and CE groups were 8.16 ± 3.39, 3.75 ± 2.02, 5.68 ± 3.28, and 4.85 ± 2.98%, respectively (Table 2). %FMD in any stroke subtype was significantly lower than that in the control group. The association between %FMD and atherosclerosis risk factors is shown in Table 3. %FMD was significantly lower in men than in women as well as in patients with than without hypertension or diabetes mellitus (Table 3). After adjustments for age, sex, hypertension, and diabetes mellitus, %FMD was significantly lower in the LAA and CE groups than in the control group, whereas no significant difference was observed between the SVO and control groups (Table 2). Carotid maximum IMT was significantly higher in the LAA groups, and PS was significantly higher in patients with all stroke subtypes than in the control groups. The association between %FMD and PS is presented in Figure 2. %FMD was inversely correlated with PS (r = −.36, P = .02).
Discussion Chen et al.12 have previously reported that patients with lacunar stroke, but not atherothrombotic stroke or cardiogenic embolism, exhibited FMD impairment. Subsequently, Table 3. Association between FMD and atherosclerotic risk factors
Age, y Sex, men/women Body mass index (kg/m2) Hypertension, Y/N Diabetes mellitus, Y/N Dislipidemia, Y/N Smoking, Y/N History of IHD, Y/N eGFR
R2 or mean ± SD
P
.016 4.79 ± 2.56/7.08 ± 4.06 .034
.27 .017* .12
4.95 ± 3.19/7.64 ± 2.74 4.45 ± 2.61/6.41 ± 3.51 5.45 ± 3.55/5.46 ± 2.67 5.12 ± 2.27/5.67 ± 3.45 4.62 ± 2.42/5.98 ± 3.56 .047
.001* .006* .670 .782 .162 .082
Abbreviations: FMD, flow-mediated vasodilation; GFR; estimated glomerular filtration rate. *P < 0.05.
Figure 2. Correlation between PS and %FMD. %FMD was inversely correlated with PS. Abbreviations: %FMD, percentage of brachial flowmediated vasodilatation; PS, plaque score.
both Kim et al.13 and Pretnar-Oblak et al.22 also showed that FMD was lower in patients with lacunar stroke than in age- and sex-matched controls. In a systematic review, FMD impairment was shown to be present in patients with lacunar stroke, although it may simply reflect exposure to vascular risk factors.23 The authors concluded that endothelial dysfunction is not specific for small vessel stroke. Indeed, Santos-García et al.24 demonstrated that FMD levels were in fact similar between different stroke subtypes. They also showed that FMD was negatively correlated with stroke severity. The results of the present study suggest that patients with LAA and CE, but not SVO, had endothelial dysfunction in the conduit artery. It remains unknown why the impairment pattern of FMD among stroke subtypes differs between previous studies and our results, but recent studies support the notion that endothelial dysfunction is common in both LAA and CE. The vessel etiology underlying LAA is large vessel atherosclerosis of the cerebral or cervical arteries. FMD primarily reflects endothelial function in the brachial artery, which is a conduit and not a resistant artery. Previous studies have shown a close association between FMD and carotid IMT or aortic stiffness.5,6 Our study also showed an association between %FMD and carotid PS, an index of systemic atherosclerosis. In the Multi-Ethnic Study of
DIFFERENCES IN ENDOTHELIAL FUNCTION 10
Atherosclerosis, FMD was a predictor for all cardiovascular events and coronary heart disease but was not a predictor for stroke. These results suggest that FMD reflects the risk for atherosclerosis of the elastic conduit artery. These findings seem to support the association between FMD and LAA identified in our study. From a viewpoint of noteworthy risk factors, renal function was significantly worse in the LAA group than in the control group (Table 1) In our study, the association between eGFR and %FMD was of borderline significance as shown in Table 3 (P = .082), while the strong association between hypertension and diabetes mellitus and %FMD (P = .001, P = .006) should decrease the influence of eGFR. That is why eGFR could have a tendency to influence %FMD. In 9 cases in our study, the etiology of CE was AF. In a study of 89 patients with ischemic stroke, Chlumský and Charvát25 have previously reported that patients with AF had significantly better FMD results than those without AF. However, Freestone et al.26 showed that FMD was significantly impaired in patients with chronic AF. The causal relationship between AF and endothelial dysfunction is supported by the finding that FMD is improved through maintenance of the sinus rhythm via catheter ablation27 or cardioversion.28 Several factors could be involved in endothelial dysfunction, including an impaired rheology, impaired atrial activity, atrial inflammation, and the renin–angiotensin system.16 These findings could explain the FMD impairment in patients with CE caused by AF observed in the present study. In contrast, the etiology of SVO is mostly arteriosclerosis of the cerebral resistant small artery. Although several previous studies showed that FMD was low in patients with lacunar stroke,12-14 most of these studies did not employ multivariate adjustment with confounding factors for FMD. Our results suggest that the association between FMD and SVO is weak. FMD depends on the endothelial nitric oxide synthase (eNOS) activity at the level of the conduit arteries.29 There are several candidates of vasodilatation factors that can affect FMD. According to plural literatures, these factors are differentially regulated by vessel size. For example, Davis et al.30 reported that the significant role of vasodilational factor in brain microvessels has been attributed to endothelial-derived hyperpolarizing factor (EDHF). Andresen et al.1 have also reported that the influence of endothelium-derived hyperpolarizing factor (EDHF) was stronger than that of nitric oxide in cerebral small vessels. Furthermore, Urakami-Harasawa et al.31 also reported that the EDHF-mediated relaxations are impaired in large arteries but fairly preserved in microvessel, and the contribution of EDHF to endothelium-dependent relaxation is significantly larger in microvessels than in large arteries on the basis of their experimental facts. FMD depends on the eNOS activity at the level of the conduit arteries. Those findings could explain the weak association between %FMD and SVO in this present study.
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In the hereditary form of cerebral small vessel disease (cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy), endotheliumdependent vasodilation in the resistant artery was impaired but FMD was not diminished.32 This is in all likelihood attributable to the fact that FMD reflects endothelial function of the conduit artery as opposed to the resistant artery. No difference in FMD between the SVO and control groups after adjustment by confounding factors was observed in the present study, and this is in line with the findings of cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy. Conflicting results in patients with SVO could be a result of the heterogeneity of the underlying vessel disease, including lipohyalinosis or microatheroma in the perforating artery and branch atheroma in the major proximal cerebral artery. FMD has been shown to be improved by administration of statin,33 cilostazol,34 garlic intake,35 tea consumption,36 and vitamin B supplement.37 Although it remains unclear as to whether FMD change by any treatment reflects a reduction in vascular event risk, FMD could possibly be one of surrogate markers for vascular events. There are some limitations to the present study. FMD depends on the eNOS activity at the level of the conduit arteries.29 We did not measure any of these vasoactive factors in the present study to investigate the mechanism in the impairment of FMD. Second, the sample size was small, and we should increase the number of subjects to obtain a greater statistical power for solid evidence in the future. In conclusion, our results showed that FMD is impaired in all 3 stroke subtypes, but is more specific for LAA and CE. The predictive value of FMD for incident stroke needs to be examined in a large-scale prospective study.
References 1. Andresen J, Shafi NI, Bryan RM Jr. Endothelial influences on cerebrovascular tone. J Appl Physiol 2006;100: 318-327. 2. Hirase T, Node K. Endothelial dysfunction as a cellular mechanism for vascular failure. Am J Physiol Heart Circ Physiol 2012;302:H499-H505. 3. Celermajer DS, Sorensen KE, Gooch VM, et al. Noninvasive detection of endothelial dysfunction in children and adults at risk of atherosclerosis. Lancet 1992;340:11111115. 4. Hasegawa T, Boden-Albala B, Eguchi K, et al. Impaired flow-mediated vasodilatation is associated with increased left ventricular mass in a multiethnic population. The Northern Manhattan Study. Am J Hypertens 2010;23:413419. 5. Lind L. Flow-mediated vasodilation was found to be an independent predictor of changes in the carotid plaque status during a 5-year follow-up. J Atheroscler Thromb 2014;21:161-168.
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2786 6. Kopec´ G, Podolec P, Podolec J, et al. Atherosclerosis progression affects the relationship between endothelial function and aortic stiffness. Atherosclerosis 2009;204:250254. 7. Hoth KF, Tate DF, Poppas A, et al. Endothelial function and white matter hyperintensities in older adults with cardiovascular disease. Stroke 2007;38:308-312. 8. Brevetti G, Silvestro A, Schiano V, et al. Endothelial dysfunction and cardiovascular risk prediction in peripheral arterial disease: additive value of flow-mediated dilation to ankle-brachial pressure index. Circulation 2003;108:2093-2098. 9. Yeboah J, Crouse JR, Hsu FC, et al. Brachial flow-mediated dilation predicts incident cardiovascular events in older adults: the Cardiovascular Health Study. Circulation 2007;115:2390-2397. 10. Yeboah J, Folsom AR, Burke GL, et al. Predictive value of brachial flow-mediated dilation for incident cardiovascular events in a population-based study: the Multi-Ethnic Study of Atherosclerosis. Circulation 2009;120:502-509. 11. Shechter M, Shechter A, Koren-Morag N, et al. Usefulness of brachial artery flow-mediated dilation to predict long-term cardiovascular events in subjects without heart disease. Am J Cardiol 2014;113:162-167. 12. Chen PL1, Wang PY, Sheu WH, et al. Changes of brachial flow-mediated vasodilation in different ischemic stroke subtypes. Neurology 2006;67:1056-1058. 13. Kim JS1, Lee HS, Park HY, et al. Endothelial function in lacunar infarction: a comparison of lacunar infarction, cerebral atherosclerosis and control group. Cerebrovasc Dis 2009;28:166-170. 14. Knottnerus IL, Ten Cate H, Lodder J, et al. Endothelial dysfunction in lacunar stroke: a systematic review. Cerebrovasc Dis 2009;27:519-526. 15. Ghiadoni L1, Versari D, Giannarelli C, et al. Non-invasive diagnostic tools for investigating endothelial dysfunction. Curr Pharm Des 2008;14:3715-3722. 16. Guazzi M, Arena R. Endothelial dysfunction and pathophysiological correlates in atrial fibrillation. Heart 2009;95:102-106. 17. Adams HP Jr, Bendixen BH, Kappelle LJ, et al. Classification of subtypes of acute ischemic stroke. Definitions for use in a multicenter clinical trial. TOAST. Trial of Org 10172 in Acute Stroke Treatment. Stroke 1993;24:35-41. 18. Sugano R1, Matsuoka H, Haramaki N, et al. Polymorphonuclear leukocytes may impair endothelial function: results of crossover randomized study of lipid-lowering therapies. Arterioscler Thromb Vasc Biol 2005;25:1262-1267. 19. Teragawa H, Kato M, Kurokawa J, et al. Usefulness of flow-mediated dilation of the brachial artery and/or the intima-media thickness of the carotid artery in predicting coronary narrowing in patients suspected of having coronary artery disease. Am J Cardiol 2001;88:1147-1151. 20. Handa N, Matsumoto M, Maeda H, et al. Ultrasonic evaluation of early carotid atherosclerosis. Stroke 1990;21:1567-1572. 21. Touboul PJ, Hennerici MG, Meairs S, et al. Mannheim Carotid Intima-Media Thickness and Plaque Consensus (2004-2006-2011). An update on behalf of the advisory board of the 3rd, 4th and 5th watching the risk symposia, at the 13th, 15th and 20th European Stroke Conferences,
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
Mannheim, Germany, 2004, Brussels, Belgium, 2006, and Hamburg, Germany, 2011. Cerebrovasc Dis 2012;34:290296. Pretnar-Oblak J, Sabovic M, Pogacnik T, et al. Flowmediated dilatation and intima-media thickness in patients with lacunar infarctions. Acta Neurol Scand 2006;113:273277. Stevenson SF1, Doubal FN, Shuler K, et al. A systematic review of dynamic cerebral and peripheral endothelial function in lacunar stroke versus controls. Stroke 2010;41:e434-e442. Santos-García D, Blanco M, Serena J, et al. Brachial arterial flow mediated dilation in acute ischemic stroke. Eur J Neurol 2009;16:684-690. Chlumský I, Charvát J. Endothelial dysfunction, distensibility and intima-media thickness and aetiology of stroke. J Int Med Res 2005;33:555-561. Freestone B, Chong AY, Nuttall S, et al. Impaired flow mediated dilatation as evidence of endothelial dysfunction in chronic atrial fibrillation: relationship to plasma von Willebrand factor and soluble E-selectin levels. Thromb Res 2008;122:85-90. Shin SY, Na JO, Lim HE, et al. Improved endothelial function in patients with atrial fibrillation through maintenance of sinus rhythm by successful catheter ablation. J Cardiovasc Electrophysiol 2011;22:376-382. Guazzi M1, Belletti S, Lenatti L, et al. Effects of cardioversion of atrial fibrillation on endothelial function in hypertension or diabetes. Eur J Clin Invest 2007;37:2634. Kelm M. Flow-mediated dilatation in human circulation: diagnostic and therapeutic aspects. Am J Physiol Heart Circ Physiol 2002;282:H1-H5. Davis CM, Siler DA, Alkayed NJ. Endothelium-derived hyperpolarizing factor in the brain: influence of sex, vessel size and disease state. Womens Health (Lond Engl) 2011;7:293-303. Urakami-Harasawa L, Shimokawa H, Nakashima M, et al. Importance of endothelium-derived hyperpolarizing factor in human arteries. J Clin Invest 1997;100:2793-2799. Stenborg A1, Kalimo H, Viitanen M, et al. Impaired endothelial function of forearm resistance arteries in CADASIL patients. Stroke 2007;38:2692-2697. Pretnar-Oblak J, Sabovic M, Sebestjen M, et al. Influence of atorvastatin treatment on L-arginine cerebrovascular reactivity and flow-mediated dilatation in patients with lacunar infarctions. Stroke 2006;37:2540-2545. Takase B, Nagata M, Hattori H, et al. Combined therapeutic effect of probucol and cilostazol on endothelial function in patients with silent cerebral lacunar infarcts and hypercholesterolemia: a preliminary study. Med Princ Pract 2014;23:59-65. Lau KK1, Chan YH, Wong YK, et al. Garlic intake is an independent predictor of endothelial function in patients with ischemic stroke. J Nutr Health Aging 2013;17:600604. Ras RT, Zock PL, Draijer R. Tea consumption enhances endothelial-dependent vasodilation; a meta-analysis. PLoS ONE 2011;6:e16974. Potter K, Hankey GJ, Green DJ, et al. The effect of long-term homocysteine-lowering on carotid intima-media thickness and flow-mediated vasodilation in stroke patients: a randomized controlled trial and meta-analysis. BMC Cardiovasc Disord 2008;8-24.
MD*
Background: Endothelial dysfunction plays a key role in the development of ischemic stroke. However, the relationship between endothelial function and stroke subtypes has not been thoroughly examined. Methods: We measured the percentage of brachial flow-mediated vasodilatation (%FMD) in 62 patients with chronic stroke and 13 age- and sex-matched control patients. Patients with stroke included those classified into large artery atherosclerosis (LAA), cardioembolism (CE), and small vessel occlusion (SVO) according to the criteria of the Trial of ORG 10172 in Acute Stroke Treatment classification. Results: %FMD was significantly lower in the patients with any of LAA, CE, and SVO than in the control patients. %FMD was also significantly lower in men than in women as well as in patients with than without hypertension or diabetes mellitus. After adjustment for confounding factors, the patients with LAA and CE but not SVO had lower %FMD compared to the controls. Conclusions: Our results suggest that endothelial function in conduit artery was impaired in patients with LAA and CE regardless with or without concomitant vascular risk factors. Key Words: FMD—stroke subtypes—max-IMT—plaque score. © 2015 National Stroke Association. Published by Elsevier Inc. All rights reserved.
Introduction Endothelial function is crucial for the maintenance of vascular tone, antithrombogenicity and the blood–brain barrier in the cerebral artery.1 Indeed, impairment of endothelial function is the first step toward atherothrombosis.2 Brachial flow-mediated vasodilation (FMD) can be measured using high-resolution ultrasonography (USG) and is an established technique for determining endothelial function From the *Department of Neurology, Tokyo Women’s Medical University School of Medicine, Tokyo, Japan; †Department of Neurology, Tokyo Metropolitan Health and Medical Treatment Corporation Ohkubo Hospital, Tokyo, Japan; and ‡Clinical Research Center for Medicine, Center for Brain and Cerebral Vessels, Sanno Hospital and Sanno Medical Center, International University of Health and Welfare, Tokyo, Japan. Received February 11, 2015; revision received July 29, 2015; accepted August 8, 2015. Address correspondence to Utako Adachi, Department of Neurology, Tokyo Women’s Medical University School of Medicine, 8-1 Kawadacho, Shinjuku-ku, Tokyo, Japan. E-mail: [email protected]. 1052-3057/$ - see front matter © 2015 National Stroke Association. Published by Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jstrokecerebrovasdis.2015.08.009
in the conduit artery.3 Several studies have shown that impaired FMD is associated with cardiovascular risk factors,4 carotid plaque,5 aortic stiffness,6 and cerebral white matter lesions.7 Furthermore, previous studies have supported the notion that FMD is an independent predictor for incident cardiovascular disease, especially coronary artery disease.8-11 Since Chen et al. reported that FMD was impaired in patients with lacunar stroke,12 several subsequent studies have shown a relationship between FMD and cerebral small vessel disease including lacunar infarcts and white matter lesions.13,14 However, FMD reflects endothelial function of the conduit artery as opposed to that of the resistant artery.15 Furthermore, recent findings that atrial fibrillation (AF) is associated with diminished FMD suggested that FMD was impaired in patients with cardiogenic embolism.16 In the present study, we measured capability of FMD in the brachial artery in patients with various subtypes of ischemic stroke at chronic stage.
Materials and Methods Subjects were 62 consecutive patients with chronic ischemic stroke after 4 weeks of the onset, who were diagnosed
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using either computerized tomography or magnetic resonance imaging, and they were classified into large artery atherosclerosis (LAA), cardioembolism (CE), or small vessel occlusion (SVO) according to criteria defined by the Trial of ORG 10172 in Acute Stroke Treatment (TOAST) classification.17 Patients with other subtypes of ischemic stroke in the TOAST classification, which were strokes of other determined etiology and stroke of undermined etiology, were excluded. In the present study, the numbers of patients with LAA, CE, and SVO were 18, 11, and 33, respectively. Thirteen age- and sex-matched patients without history of cardiovascular diseases, who visited an outpatient clinic during the study period, served as control subjects. The control subjects consisted of 8 men and 5 women; 7 of the subjects had hypertension, 6 had diabetes mellitus, and 7 had dyslipidemia. Their diagnoses were as follows: 4 patients had mild stenosis of the middle cerebral artery, 1 patient had brain atrophy, 1 patient had hydrocephalus, 1 patient had cerebral angioma, 1 patient had cervical spondylosis, 1 patient had neurally mediated syncope, and 4 patients had no abnormality. Endothelial function was accessed by the measurement of FMD in the brachial artery, and color-coded duplex power USG in the carotid arteries was performed in all patients. The extent of FMD in the brachial artery was measured, as described by Sugano et al.18 Ultrasound systems were used, equipped with vascular software for 2-dimensional (2D) imaging, color Doppler, an internal electrocardiogram monitor and a high-frequency vascular transducer. The subjects were studied in a quiet and temperature-controlled room. They were placed in the supine position with the arm in a comfortable position for imaging the brachial artery. The brachial artery was imaged above the antecubital fossa using a high-resolution ultrasound system (UNEX EF 18G, UNEX Corporation, Nagoya, Japan)
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(Fig 1) equipped with a 10-MHz linear array transducer. A segment with clear anterior and posterior intimal interfaces between the lumen and vessel wall was selected for continuous 2D gray scale imaging. Thereafter, arterial occlusion was created by cuff inflation to at least 50 mmHg above systolic blood pressure for 5 min before release. The resulting increase in shear stress causes the brachial artery to dilate, and the degree of vasodilation of the brachial artery after deflation (percentage of brachial flow-mediated vasodilatation [%FMD]) was measured using USG. Normal %FMD is more than 6%.19 Carotid USG was performed using linear array 7.5-MHz transducers (Hitachi Aloka Prosound α7, Hitachi-Aloka Medical, Ltd. Tokyo, Japan). Initially, the common and internal carotid arteries were scanned axially and longitudinally, whereby distribution of atheromatous plaques was roughly evaluated. During the initial scanning, optimal insonation angles were determined to estimate respective plaque heights, and measurements were performed on the frozen frame perpendicular to the vascular walls. Carotid arteries (common carotid arteries, bifurcations, and internal carotid arteries) were divided into 8 sections (15 mm/section). The plaque score (PS) was calculated using the sum of the maximum thickness of all plaques (local increases in intima–media thickness [IMT] ≥ 1.1 mm) located in both carotid arteries.20 Plaque was defined as a focal protruding structure of 1.1 mm or more that encroaches into the arterial lumen by at least .5 mm or 50% of the surrounding IMT according to the Mannheim Carotid Intima–Media Thickness Consensus.21 The length of individual plaques was not considered for the calculation of this score. The maximum IMT refers to the maximum value of IMT within the common carotid artery. Blood pressure in the supine position was evaluated before USG. Hypertension was defined as casual blood pressure higher than 140/90 mmHg or current use of antihypertensive agents. Levels of fasting blood glucose,
Figure 1. (A) Ultrasound image of the brachial artery. Left panel: a baseline rest image. Right panel: the maximal dilator response occurs. The red line indicates the vessel diameter. (B) The lines indicate echogenicity. The distance between the closest maximum points (d) indicates the diameter of the vascular lumen. (Color version of the figure is available online.)
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hemoglobin A1c (HbA1c), serum low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides, and creatinine were determined from blood samples. Information on the patients’ medical histories and medication use was obtained from their clinical records. Diabetes mellitus was defined as fasting blood glucose higher than 126 mg/dL, hemoglobin A1c of more than 5.8%, or use of glucose-lowering agents. Dyslipidemia was defined as fasting serum total cholesterol higher than 220 mg/dL, triglycerides more than 150 mg/dL, highdensity lipoprotein cholesterol higher than 40 mg/dL, or current use of cholesterol-lowering agents. Smoking status was categorically evaluated from self-reports with a smoker defined as currently or previously smoking more than 10 cigarettes per day for more than 1 year. The study protocol was approved by the Academic Research Ethics Committee in Tokyo Women’s Medical University School of Medicine.
Data Analysis Statistical analysis was performed with JMP Pro ver.11.2 SID (SAS Institute Inc. Cary, North Carolina, USA). Data are presented as mean ± SD unless otherwise specified. We used analysis of variance followed by unpaired t-test to investigate the difference of %FMD and risk factors between the control group and each stroke patient group. Next, %FMD was further compared between the control group and each stroke subtype group by adjusting for age, sex, hypertension, and diabetes mellitus, factors showing significant association (P < .05) with %FMD. Linear regression analysis was used to examine the relationship between %FMD and PS. In all tests, P < .05 was considered significant.
Results Patient characteristics are presented in Table 1. In patients with stroke, especially in LAA patients, prevalences of
Table 1. Baseline characteristics of the subjects studied Characteristic
All subjects
No stroke
LAA
SVO
CE
Number Age, mean ± SD Sex, % of men Body mass index (kg/m2) Hypertension (%) Systolic BP (mmHg) Diastolic BP (mmHg) Diabetes mellitus (%) Fasting blood sugar (mg/dL) HbA1c (%) Dyslipidemia (%) LDL-C (mg/dL) Total cholesterol (mg/dL) Triglyceride (mg/dL) HDL-C (mg/dL) Statin use, n (%) Current smoking (%) IHD (%) PAD (%) Anticoagulant use (%) Antiplatelet use (%) Creatinine (mg/dL) Uric acid (mg/dL) eGFR (mL/min/1.73 m2) Proteinuria (%) CRP (mg/dL) Median, interquartile range Max IMT (mm) Plaque score
75 67.7 ± 10.1 68 23.6 ± 3.5 76 131 ± 21 76 ± 12 49 124 ± 39 6.3 ± .8 64 113 ± 30 197 ± 39 149 ± 201 57 ± 16 45 18 33 13 21 72 .97 ± .44 5.6 ± 1.5 63.6 ± 21.3 29 .09 (.05-.18) 1.30 ± .66 6.90 ± 5.73
13 66.2 ± 10.6 62 22.1 ± 2.5 54 123 ± 16 74 ± 11 50 121 ± 42 6.5 ± 1.3 58 113 ± 25 204 ± 48 119 ± 82 62 ± 14 42 0 0 0 0 38 .78 ± .29 5.1 ± 1.6 78.4 ± 28.0 20 .06 (.05-.11) 1.12 ± .38 3.14 ± 2.69
18 65.9 ± 8.1 64 24.8 ± 3.9* 94* 135 ± 24 77 ± 13 61 135 ± 51 6.5 ± .7 78 120 ± 38 207 ± 46 156 ± 101 52 ± 13* 56 28* 50* 28* 11 100* 1.20 ± .69* 5.8 ± 1.0 59.5 ± 24.4* 24 .06 (.05-.12) 1.56 ± .73* 10.21 ± 6.50*
33 69.6 ± 10.9 89 23.7 ± 3.7 82 135 ± 21* 78 ± 12 45 124 ± 33 6.2 ± .8 61 110 ± 26 195 ± 33 114 ± 55 56 ± 18 42 16 15 3 9 85* .94 ± .33 5.8 ± 1.6 60.3 ± 15.8* 31 .12 (.06-.29) 1.32 ± .73 6.79 ± 5.46*
11 66.9 ± 10.0 55 23.2 ± 2.6 73 120 ± 14 73 ± 9 36 108 ± 29 6.1 ± .5 55 114 ± 30 179 ± 29 285 ± 481 62 ± 14 36 27* 100* 36* 100* 27 .91 ± .29 5.1 ± 1.7 61.3 ± 16.5 40 .06 (.05-.10) 1.06 ± .46 6.28 ± 5.34*
Abbreviations: BP, blood pressure; CE, cardioembolism; CRP, C-reactive protein; eGFR, estimated glomerular filtration rate; %FMD, percentage of brachial flow-mediated vasodilatation; HbA1c, hemoglobin A1c; HDL-C, high-density lipoprotein cholesterol; IHD, ischemic heart disease; LAA, large artery atherosclerosis; LDL-C, low-density lipoprotein cholesterol; max IMT, maximum intima–media thickness; PAD, peripheral artery disease; SD, standard deviation; SVO, small vessel occlusion. *P < .05 versus control subjects.
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Table 2. %FMD among control and each stroke subtype
Observed %FMD Adjusted %FMD†
No Stroke
LAA
SVO
CE
8.16 ± 3.39 8.15 ± 1.54
3.75 ± 2.02** 5.05 ± 1.57*
5.68 ± 3.28* 6.28 ± 1.44
4.85 ± 2.98** 5.07 ± 1.58*
Abbreviations: CE, cardioembolism; %FMD, percentage of brachial flow-mediated vasodilatation; LAA, large artery atherosclerosis; SVO, small vessel occlusion. *P < 0.05. **P < 0.01. †%FMD after adjustments for age, sex, hypertension and diabetes mellitus.
hypertension, current smoking, use of antiplatelet drugs or anticoagulants, and levels of serum creatinine were higher than in the control patients. %FMD values in the control, LAA, SVO, and CE groups were 8.16 ± 3.39, 3.75 ± 2.02, 5.68 ± 3.28, and 4.85 ± 2.98%, respectively (Table 2). %FMD in any stroke subtype was significantly lower than that in the control group. The association between %FMD and atherosclerosis risk factors is shown in Table 3. %FMD was significantly lower in men than in women as well as in patients with than without hypertension or diabetes mellitus (Table 3). After adjustments for age, sex, hypertension, and diabetes mellitus, %FMD was significantly lower in the LAA and CE groups than in the control group, whereas no significant difference was observed between the SVO and control groups (Table 2). Carotid maximum IMT was significantly higher in the LAA groups, and PS was significantly higher in patients with all stroke subtypes than in the control groups. The association between %FMD and PS is presented in Figure 2. %FMD was inversely correlated with PS (r = −.36, P = .02).
Discussion Chen et al.12 have previously reported that patients with lacunar stroke, but not atherothrombotic stroke or cardiogenic embolism, exhibited FMD impairment. Subsequently, Table 3. Association between FMD and atherosclerotic risk factors
Age, y Sex, men/women Body mass index (kg/m2) Hypertension, Y/N Diabetes mellitus, Y/N Dislipidemia, Y/N Smoking, Y/N History of IHD, Y/N eGFR
R2 or mean ± SD
P
.016 4.79 ± 2.56/7.08 ± 4.06 .034
.27 .017* .12
4.95 ± 3.19/7.64 ± 2.74 4.45 ± 2.61/6.41 ± 3.51 5.45 ± 3.55/5.46 ± 2.67 5.12 ± 2.27/5.67 ± 3.45 4.62 ± 2.42/5.98 ± 3.56 .047
.001* .006* .670 .782 .162 .082
Abbreviations: FMD, flow-mediated vasodilation; GFR; estimated glomerular filtration rate. *P < 0.05.
Figure 2. Correlation between PS and %FMD. %FMD was inversely correlated with PS. Abbreviations: %FMD, percentage of brachial flowmediated vasodilatation; PS, plaque score.
both Kim et al.13 and Pretnar-Oblak et al.22 also showed that FMD was lower in patients with lacunar stroke than in age- and sex-matched controls. In a systematic review, FMD impairment was shown to be present in patients with lacunar stroke, although it may simply reflect exposure to vascular risk factors.23 The authors concluded that endothelial dysfunction is not specific for small vessel stroke. Indeed, Santos-García et al.24 demonstrated that FMD levels were in fact similar between different stroke subtypes. They also showed that FMD was negatively correlated with stroke severity. The results of the present study suggest that patients with LAA and CE, but not SVO, had endothelial dysfunction in the conduit artery. It remains unknown why the impairment pattern of FMD among stroke subtypes differs between previous studies and our results, but recent studies support the notion that endothelial dysfunction is common in both LAA and CE. The vessel etiology underlying LAA is large vessel atherosclerosis of the cerebral or cervical arteries. FMD primarily reflects endothelial function in the brachial artery, which is a conduit and not a resistant artery. Previous studies have shown a close association between FMD and carotid IMT or aortic stiffness.5,6 Our study also showed an association between %FMD and carotid PS, an index of systemic atherosclerosis. In the Multi-Ethnic Study of
DIFFERENCES IN ENDOTHELIAL FUNCTION 10
Atherosclerosis, FMD was a predictor for all cardiovascular events and coronary heart disease but was not a predictor for stroke. These results suggest that FMD reflects the risk for atherosclerosis of the elastic conduit artery. These findings seem to support the association between FMD and LAA identified in our study. From a viewpoint of noteworthy risk factors, renal function was significantly worse in the LAA group than in the control group (Table 1) In our study, the association between eGFR and %FMD was of borderline significance as shown in Table 3 (P = .082), while the strong association between hypertension and diabetes mellitus and %FMD (P = .001, P = .006) should decrease the influence of eGFR. That is why eGFR could have a tendency to influence %FMD. In 9 cases in our study, the etiology of CE was AF. In a study of 89 patients with ischemic stroke, Chlumský and Charvát25 have previously reported that patients with AF had significantly better FMD results than those without AF. However, Freestone et al.26 showed that FMD was significantly impaired in patients with chronic AF. The causal relationship between AF and endothelial dysfunction is supported by the finding that FMD is improved through maintenance of the sinus rhythm via catheter ablation27 or cardioversion.28 Several factors could be involved in endothelial dysfunction, including an impaired rheology, impaired atrial activity, atrial inflammation, and the renin–angiotensin system.16 These findings could explain the FMD impairment in patients with CE caused by AF observed in the present study. In contrast, the etiology of SVO is mostly arteriosclerosis of the cerebral resistant small artery. Although several previous studies showed that FMD was low in patients with lacunar stroke,12-14 most of these studies did not employ multivariate adjustment with confounding factors for FMD. Our results suggest that the association between FMD and SVO is weak. FMD depends on the endothelial nitric oxide synthase (eNOS) activity at the level of the conduit arteries.29 There are several candidates of vasodilatation factors that can affect FMD. According to plural literatures, these factors are differentially regulated by vessel size. For example, Davis et al.30 reported that the significant role of vasodilational factor in brain microvessels has been attributed to endothelial-derived hyperpolarizing factor (EDHF). Andresen et al.1 have also reported that the influence of endothelium-derived hyperpolarizing factor (EDHF) was stronger than that of nitric oxide in cerebral small vessels. Furthermore, Urakami-Harasawa et al.31 also reported that the EDHF-mediated relaxations are impaired in large arteries but fairly preserved in microvessel, and the contribution of EDHF to endothelium-dependent relaxation is significantly larger in microvessels than in large arteries on the basis of their experimental facts. FMD depends on the eNOS activity at the level of the conduit arteries. Those findings could explain the weak association between %FMD and SVO in this present study.
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In the hereditary form of cerebral small vessel disease (cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy), endotheliumdependent vasodilation in the resistant artery was impaired but FMD was not diminished.32 This is in all likelihood attributable to the fact that FMD reflects endothelial function of the conduit artery as opposed to the resistant artery. No difference in FMD between the SVO and control groups after adjustment by confounding factors was observed in the present study, and this is in line with the findings of cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy. Conflicting results in patients with SVO could be a result of the heterogeneity of the underlying vessel disease, including lipohyalinosis or microatheroma in the perforating artery and branch atheroma in the major proximal cerebral artery. FMD has been shown to be improved by administration of statin,33 cilostazol,34 garlic intake,35 tea consumption,36 and vitamin B supplement.37 Although it remains unclear as to whether FMD change by any treatment reflects a reduction in vascular event risk, FMD could possibly be one of surrogate markers for vascular events. There are some limitations to the present study. FMD depends on the eNOS activity at the level of the conduit arteries.29 We did not measure any of these vasoactive factors in the present study to investigate the mechanism in the impairment of FMD. Second, the sample size was small, and we should increase the number of subjects to obtain a greater statistical power for solid evidence in the future. In conclusion, our results showed that FMD is impaired in all 3 stroke subtypes, but is more specific for LAA and CE. The predictive value of FMD for incident stroke needs to be examined in a large-scale prospective study.
References 1. Andresen J, Shafi NI, Bryan RM Jr. Endothelial influences on cerebrovascular tone. J Appl Physiol 2006;100: 318-327. 2. Hirase T, Node K. Endothelial dysfunction as a cellular mechanism for vascular failure. Am J Physiol Heart Circ Physiol 2012;302:H499-H505. 3. Celermajer DS, Sorensen KE, Gooch VM, et al. Noninvasive detection of endothelial dysfunction in children and adults at risk of atherosclerosis. Lancet 1992;340:11111115. 4. Hasegawa T, Boden-Albala B, Eguchi K, et al. Impaired flow-mediated vasodilatation is associated with increased left ventricular mass in a multiethnic population. The Northern Manhattan Study. Am J Hypertens 2010;23:413419. 5. Lind L. Flow-mediated vasodilation was found to be an independent predictor of changes in the carotid plaque status during a 5-year follow-up. J Atheroscler Thromb 2014;21:161-168.
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2786 6. Kopec´ G, Podolec P, Podolec J, et al. Atherosclerosis progression affects the relationship between endothelial function and aortic stiffness. Atherosclerosis 2009;204:250254. 7. Hoth KF, Tate DF, Poppas A, et al. Endothelial function and white matter hyperintensities in older adults with cardiovascular disease. Stroke 2007;38:308-312. 8. Brevetti G, Silvestro A, Schiano V, et al. Endothelial dysfunction and cardiovascular risk prediction in peripheral arterial disease: additive value of flow-mediated dilation to ankle-brachial pressure index. Circulation 2003;108:2093-2098. 9. Yeboah J, Crouse JR, Hsu FC, et al. Brachial flow-mediated dilation predicts incident cardiovascular events in older adults: the Cardiovascular Health Study. Circulation 2007;115:2390-2397. 10. Yeboah J, Folsom AR, Burke GL, et al. Predictive value of brachial flow-mediated dilation for incident cardiovascular events in a population-based study: the Multi-Ethnic Study of Atherosclerosis. Circulation 2009;120:502-509. 11. Shechter M, Shechter A, Koren-Morag N, et al. Usefulness of brachial artery flow-mediated dilation to predict long-term cardiovascular events in subjects without heart disease. Am J Cardiol 2014;113:162-167. 12. Chen PL1, Wang PY, Sheu WH, et al. Changes of brachial flow-mediated vasodilation in different ischemic stroke subtypes. Neurology 2006;67:1056-1058. 13. Kim JS1, Lee HS, Park HY, et al. Endothelial function in lacunar infarction: a comparison of lacunar infarction, cerebral atherosclerosis and control group. Cerebrovasc Dis 2009;28:166-170. 14. Knottnerus IL, Ten Cate H, Lodder J, et al. Endothelial dysfunction in lacunar stroke: a systematic review. Cerebrovasc Dis 2009;27:519-526. 15. Ghiadoni L1, Versari D, Giannarelli C, et al. Non-invasive diagnostic tools for investigating endothelial dysfunction. Curr Pharm Des 2008;14:3715-3722. 16. Guazzi M, Arena R. Endothelial dysfunction and pathophysiological correlates in atrial fibrillation. Heart 2009;95:102-106. 17. Adams HP Jr, Bendixen BH, Kappelle LJ, et al. Classification of subtypes of acute ischemic stroke. Definitions for use in a multicenter clinical trial. TOAST. Trial of Org 10172 in Acute Stroke Treatment. Stroke 1993;24:35-41. 18. Sugano R1, Matsuoka H, Haramaki N, et al. Polymorphonuclear leukocytes may impair endothelial function: results of crossover randomized study of lipid-lowering therapies. Arterioscler Thromb Vasc Biol 2005;25:1262-1267. 19. Teragawa H, Kato M, Kurokawa J, et al. Usefulness of flow-mediated dilation of the brachial artery and/or the intima-media thickness of the carotid artery in predicting coronary narrowing in patients suspected of having coronary artery disease. Am J Cardiol 2001;88:1147-1151. 20. Handa N, Matsumoto M, Maeda H, et al. Ultrasonic evaluation of early carotid atherosclerosis. Stroke 1990;21:1567-1572. 21. Touboul PJ, Hennerici MG, Meairs S, et al. Mannheim Carotid Intima-Media Thickness and Plaque Consensus (2004-2006-2011). An update on behalf of the advisory board of the 3rd, 4th and 5th watching the risk symposia, at the 13th, 15th and 20th European Stroke Conferences,
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
Mannheim, Germany, 2004, Brussels, Belgium, 2006, and Hamburg, Germany, 2011. Cerebrovasc Dis 2012;34:290296. Pretnar-Oblak J, Sabovic M, Pogacnik T, et al. Flowmediated dilatation and intima-media thickness in patients with lacunar infarctions. Acta Neurol Scand 2006;113:273277. Stevenson SF1, Doubal FN, Shuler K, et al. A systematic review of dynamic cerebral and peripheral endothelial function in lacunar stroke versus controls. Stroke 2010;41:e434-e442. Santos-García D, Blanco M, Serena J, et al. Brachial arterial flow mediated dilation in acute ischemic stroke. Eur J Neurol 2009;16:684-690. Chlumský I, Charvát J. Endothelial dysfunction, distensibility and intima-media thickness and aetiology of stroke. J Int Med Res 2005;33:555-561. Freestone B, Chong AY, Nuttall S, et al. Impaired flow mediated dilatation as evidence of endothelial dysfunction in chronic atrial fibrillation: relationship to plasma von Willebrand factor and soluble E-selectin levels. Thromb Res 2008;122:85-90. Shin SY, Na JO, Lim HE, et al. Improved endothelial function in patients with atrial fibrillation through maintenance of sinus rhythm by successful catheter ablation. J Cardiovasc Electrophysiol 2011;22:376-382. Guazzi M1, Belletti S, Lenatti L, et al. Effects of cardioversion of atrial fibrillation on endothelial function in hypertension or diabetes. Eur J Clin Invest 2007;37:2634. Kelm M. Flow-mediated dilatation in human circulation: diagnostic and therapeutic aspects. Am J Physiol Heart Circ Physiol 2002;282:H1-H5. Davis CM, Siler DA, Alkayed NJ. Endothelium-derived hyperpolarizing factor in the brain: influence of sex, vessel size and disease state. Womens Health (Lond Engl) 2011;7:293-303. Urakami-Harasawa L, Shimokawa H, Nakashima M, et al. Importance of endothelium-derived hyperpolarizing factor in human arteries. J Clin Invest 1997;100:2793-2799. Stenborg A1, Kalimo H, Viitanen M, et al. Impaired endothelial function of forearm resistance arteries in CADASIL patients. Stroke 2007;38:2692-2697. Pretnar-Oblak J, Sabovic M, Sebestjen M, et al. Influence of atorvastatin treatment on L-arginine cerebrovascular reactivity and flow-mediated dilatation in patients with lacunar infarctions. Stroke 2006;37:2540-2545. Takase B, Nagata M, Hattori H, et al. Combined therapeutic effect of probucol and cilostazol on endothelial function in patients with silent cerebral lacunar infarcts and hypercholesterolemia: a preliminary study. Med Princ Pract 2014;23:59-65. Lau KK1, Chan YH, Wong YK, et al. Garlic intake is an independent predictor of endothelial function in patients with ischemic stroke. J Nutr Health Aging 2013;17:600604. Ras RT, Zock PL, Draijer R. Tea consumption enhances endothelial-dependent vasodilation; a meta-analysis. PLoS ONE 2011;6:e16974. Potter K, Hankey GJ, Green DJ, et al. The effect of long-term homocysteine-lowering on carotid intima-media thickness and flow-mediated vasodilation in stroke patients: a randomized controlled trial and meta-analysis. BMC Cardiovasc Disord 2008;8-24.