- Email: [email protected]
Association between peripheral vascular endothelial dysfunction and livedoid vasculopathy
Association between peripheral vascular endothelial dysfunction and livedoid vasculopathy Chih-Hsun Yang, MD,a Su-Chin Shen, MD,b Rosaline Chung-Yee Hui, PhD,a Yu-Huei Huang, MD,a Pao-Hsien Chu, MD,c and Wan-Jing Ho, MDc Tao-Yuan, Taiwan Background: Livedoid vasculopathy (LV) is a disease characterized by multiple painful and recurrent ulcerations on the feet, accompanied by atrophic scars. Many researchers suggest that a hypercoagulable status is the pathogenetic factor for LV. However, the cause of LV remains elusive. Objective: We sought to determine if endothelial dysfunction is present in patients with LV. Methods: This prospective study included 16 patients with LV and active ulcers and 16 matched control subjects. We reviewed detailed clinical parameters, including antinuclear antibody, high-sensitivity C-reactive protein, protein C, protein S, homocysteine, anti-SSA, anti-SSB, anticardiolipin antibody, and serum lipid profiles. Flow-mediated vasodilation of the brachial artery was used as an indicator of vascular endothelial function using high-resolution 2-dimensional ultrasonic imaging. Results: Blood pressure, blood biochemistry, high-sensitivity C-reactive protein, and homocysteine were not significantly different in patients with LV and control subjects. Nitroglycerin-mediated vasodilation was not significantly different in patients with LV and control subjects. However, flow-mediated vasodilation was much less in patients with LV than in the control group (3.58 6 2.32% vs 7.51 6 2.40%, P \ .001). Limitations: The study was performed at a single site with a limited sample size. Conclusion: Peripheral vascular endothelial dysfunction was demonstrated in patients with LV by reduction of brachial flow-mediated vasodilation. ( J Am Acad Dermatol 2012;67:107-12.) Key words: endothelial dysfunction; endothelium-dependent flow-mediated vasodilation; livedoid vasculopathy.
L
ivedoid vasculopathy (LV) is a disease characterized by multiple, painful, and recurrent ulcerations with atrophic scars involving the lower legs, ankles, and back surfaces of the feet. These necrotic areas tend to be a result of ischemic infarction caused by vascular occlusion of the papillary dermis, although the origin of this remains unclear. Many researchers suggest that a hypercoagulable status contributes to the development of thrombi in the dermal blood vessels.1,2 Patients with LV exhibit various coagulation abnormalities, From the Department of Dermatology,a Department of Ophthalmology,b and First Cardiovascular Division, Department of Cardiology,c Chang Gung Memorial Hospital, College of Medicine, Chang Gung University. Supported by Chang Gung Memorial Hospital grants CMRPG390511 (Drs Yang and Hui), CMRPG370922 (Dr Ho), and CMRPG391241 (Dr Ho). Conflicts of interest: None declared. Accepted for publication July 21, 2011.
Abbreviations used: ACA: FMD: hs-CRP: LV: NMD: NO:
anticardiolipin antibody flow-mediated vasodilation high-sensitivity C-reactive protein livedoid vasculopathy nitroglycerin-mediated vasodilation nitric oxide
including cryoglobulinemia, protein C deficiency, antithrombin III deficiency, factor V Leiden mutation, Reprint requests: Wan-Jing Ho, MD, First Cardiovascular Division, Department of Cardiology, Chang Gung Memorial Hospital, No. 5, Fu-Shin Road, Kwei-Shan, Tao-Yuan, Taiwan 333. E-mail: [email protected]. Published online October 10, 2011. 0190-9622/$36.00 Ó 2011 by the American Academy of Dermatology, Inc. doi:10.1016/j.jaad.2011.07.021
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and hyperhomocysteinemia.3-5 Current treatment diseases, such as hypertension, congestive heart strategies focus on anticoagulant, antiplatelet, and failure, diabetes mellitus, cerebral vascular accifibrinolytic therapies, but these treatments usually dents, or coronary artery disease, were also exproduce slow responses and unsatisfactory results. cluded. Thus, patients were not taking concurrent Impaired endothelial cell function can induce systemic medications, such as antihypertensive vessel inflammation and influence coagulation and drugs, nitrates, or hormone replacement therapy. fibrinolysis, resulting in atherosclerotic and Sixteen gender- and age-matched control subjects several vascular thrombotic from the same hospital were diseases.6 Brachial artery recruited. Control subjects CAPSULE SUMMARY flow-mediated vasodilation were physically healthy with (FMD) measured by highno history of cardiovascular Livedoid vasculopathy is regarded as resolution ultrasound is a diseases on routine medical dysregulation of the coagulation well-established, noninvaexamination and none were pathway because of the presence of sive procedure for the examtaking systemic medications. fibrin thrombi in blood vessels and ination of endothelial Vascular ultrasound was perbecause anticoagulant, antiplatelet, and function.6,7 Reactive hypereformed for both groups after fibrinolytic therapies are effective mia induced by transient isinformed consent was obtreatments. chemia of the forearm can tained. This study was apincrease blood flow and reWe demonstrated peripheral vascular proved by the Chang Gung sult in shear stress of the endothelial dysfunction in patients with Memorial Hospital Instituvessel wall, leading to the livedoid vasculopathy using the flowtional Review Board. release of endothelial nitric mediated vascular dilation test. oxide (NO) and vascular diBlood biochemical Strategies to correct endothelial lation. Assessment of endoanalyses, inflammation dysfunction may be effective in treating thelial function using this markers, and livedoid vasculopathy ulcers. method can be used to preautoimmune antibody dict the development of athmeasurements erosclerosis, hypertension, and cardiovascular Venous blood samples were collected after 12 diseases.8-10 Brachial FMD has also been used to hours of fasting. We performed routine biochemical detect peripheral endothelial dysfunction in patients tests, such as fasting blood glucose (normal range: with Behc¸et disease and ocular glaucomatocyclitic 70-105 mg/dL), serum cholesterol (desired range: crisis.11,12 The presence of endothelial dysfunction in \200 mg/dL), triglycerides (desired range: \150 patients with LV has never been evaluated. mg/dL), low-density lipoprotein (normal range: Therefore, our study assessed vascular endothelial \130 mg/dL), high-density lipoprotein (normal function in patients with LV and matched control range: male [40 mg/dL; female [50 mg/dL), creatsubjects to determine the pathogenesis of this inine (normal range: female, 0.6-1.2 mg/dL; male, disease. 0.4-1.4 mg/dL), alanine aminotransferase (normal range: 0-36 U/L), and homocysteine (normal range: METHODS \12 mol/L). Nonspecific markers of immune sysParticipants tem activation and inflammation, including highSixteen patients with confirmed LV were recruited sensitivity C-reactive protein (hs-CRP) levels (\1 from the Department of Dermatology, Chang Gung mg/L, low risk; 1-3 mg/L, average; and [3 mg/L, Memorial Hospital, Tao-Yuan, Taiwan. These pahigh risk) were determined by a high-sensitivity tients had active ulcers with painful erythematouscommercial assay kit (analyzer: Hitachi 7600-210, to-violaceous purpura on the legs in addition to Daiichi Pure Chemicals Co Ltd, Tokyo, Japan). depressed, satellite, ivory-white scarlike skin lesions We evaluated the coagulation profile, which insurrounded by telangiectasia, and hyperpigmentacluded complete blood cell count, prothrombin tion. Skin specimens obtained from all patients were time, partial thromboplastin time, protein C (normal characterized by thrombotic occlusion of the superrange: 70%-140%), and protein S (normal range: ficial vessels and hyalinized vessel walls with mini60%-140%). We also examined the presence of mal perivascular inflammatory cell infiltration. autoantibodies, such as antinuclear antibody (norPatients with venous insufficiency and other specific mal range: \1:80), anticardiolipin antibody (ACA) conditions of the legs, including stasis ulcers, dia(positive [20 GPL /mL), anti-SSA antibody (posibetic foot, deep vein thrombosis, and vasculitis, were tive [130 AU/mL), and anti-SSB antibody (positive excluded from this study. Patients with systemic [130 AU/mL). d
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Measurement of vascular endothelial function All study subjects were referred to the vascular laboratory the morning after overnight fasting for at least 8 hours. Tobacco, alcohol, caffeinated beverages, and any medications including nutritional supplements were prohibited before the examination. Brachial artery FMD was studied using highresolution 2-dimensional ultrasonic imaging as described previously.6,13 All ultrasound images were obtained with a high-resolution linear-array transducer (13 MHz) on an ultrasound system (Aloka Prosound a10, Aloka Co, Tokyo, Japan) coupled with computer-assisted analysis software (e-Tracking System, Aloka Co). Examinations were performed in a dimly lit and quiet room with temperature control. Patients rested in the supine position for at least 10 minutes before the first scan and remained supine until the final recording was acquired with electrocardiogram monitoring. Blood pressure was obtained from the right arm before imaging. The left arm of each patient was fixed on an arm splint and a 7-cm wide blood pressure cuff was placed around the forearm. The brachial artery was scanned longitudinally approximately 3 to 5 cm above the antecubital fossa. The transmit zone was set to the depth of the near wall so that the interface between the media and the adventitia ‘‘m’’ line was clearly visible. When the optimal B-mode image of the anterior and posterior intimal interfaces between the lumen and vessel wall was obtained, the transducer was maintained in an identical position throughout the scan using a micrometer-adjustable stereotactic probe holder (MP-PH0001, Aloka Co) to ensure consistency of the image. The tracking gate was then placed on the intima, the artery diameter was automatically tracked, and the waveform of diameter changes was displayed in real time by using the FMD mode of the ultrasound system. The baseline images and pulsed Doppler blood flow of the brachial artery were acquired for 30 seconds. The blood pressure cuff was inflated to 250 mm Hg to induce hyperemia and arterial occlusion was maintained for 5 minutes. The cuff was then rapidly deflated and pulsed Doppler velocity signals were recorded after deflation for 15 seconds. Longitudinal images of the brachial artery were recorded continuously for 5 minutes after cuff deflation. The response to nitroglycerin was used to assess endothelium-independent nitroglycerin-mediated vasodilation (NMD). Baseline images and arterial blood flow were acquired after a 10-minute rest period to allow re-establishment of brachial artery baseline conditions, followed by administration of sublingual nitroglycerin spray (400 g). Arterial images were recorded continuously for 4 minutes. The
FMD was expressed as the percentage of maximal vessel diameter change induced by hyperemia. Similarly, NMD was expressed as the percentage change of diameter response to nitroglycerin sublingual spray at 4 minutes. The intraobserver and interobserver coefficients of variation for baseline arterial diameter measurements were 1.6% and 2.1%, respectively, in the vascular laboratory (n = 16). Statistical analysis Data are expressed as mean (range) for continuous variables and as a percentage for categorical variables. Continuous variables were compared among the LV and control groups by the nonparametric Mann-Whitney test. Categorical variables were compared between groups using the x2 test; if the number of cases was less than 5, the Fisher exact test was used. P values less than .05 were considered statistically significant. The post hoc power of FMD was calculated because of the small sample size.
RESULTS Clinical and biochemical findings This study included 16 patients with LV (mean age, 32 years; 8 women, 8 men) and 16 control subjects (mean age, 32 years; 8 women, 8 men). Traditional atherosclerosis risk factors, such as body mass index, cigarette smoking, systolic blood pressure, fasting blood glucose, and lipid profile, did not differ significantly between patients with LV and control subjects. Inflammation activity and autoimmune markers and antibodies Homocysteine levels, which are indicative of atherosclerosis, were within normal limits in patients with LV. Levels of hs-CRP, the acute-phase protein that increases during systemic inflammation, were similar in patients with LV and control subjects. In addition, levels of the major physiological anticoagulants, protein C and protein S, were not decreased in patients with LV. All patients with LV had negative findings for antinuclear antibody, anti-SSA antibodies, and anti-SSB antibodies but two patients with LV (12.5%, 2 of 16) had positive findings for ACA. Endothelial function The endothelium-dependent FMD was significantly lower in patients with LV (3.58 6 2.32%) than in control subjects (7.51 6 2.40%, P \ .001) (Fig 1). However, the endothelium-independent NMD did not significantly differ between these two groups (15.22 6 4.69% vs 16.27 6 5.38%, P = .643).
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Fig 1. Endothelium-dependent flow-mediated vasodilation (FMD) and endothelium-independent nitroglycerinmediated vasodilation (NMD) in patients with livedoid vasculopathy (LV) and control subjects (CTL). Values are means 6 SD. *P \ .001.
The post hoc power was calculated to be 99.5% for FMD (a = 0.05).
DISCUSSION LV is a thrombo-occlusive vasculopathy characterized by thrombosis of the upper reticular dermal blood vessels, hyalinized vessel walls, and scanty perivascular inflammatory cell infiltration. The underlying pathogenetic processes of this disease remain unclear. Although hereditary and acquired hypercoagulable states are associated with the disease in some patients, these factors do not fully explain dermal vessel thrombosis in LV. According to the Virchow triad theory for thrombogenesis, intravascular thrombus formation is related to endothelial cell injury/dysfunction in addition to coagulation factor dysregulation and turbulent blood flow.14,15 This study showed that patients with LV had decreased FMD of the brachial artery, which indicates systemic endothelial dysfunction. The vascular endothelium actively participates in the balance between blood coagulation and fibrinolysis to maintain the circulation system. Endothelial cells act as a physical barrier by covering the thrombogenic basement membrane. Endothelial cell injury may result in leukocyte adhesion and migration, and exposure of the subendothelium, providing a surface for coagulation. Functional endothelial cells can release vasodilators such as NO, prostaglandins (prostaglandin I2), and endotheliumderived hyperpolarizing factor.16,17 Among these vasodilators, NO is particularly important because it also functions as an endogenous antithrombotic molecule by inhibiting leukocyte-endothelial interactions, platelet aggregation and adhesion, and
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fibrin formation on vessel walls.8,18 NO released by endothelial cells exerts a vasodilator effect by counterbalancing the vasoconstriction produced by the sympathetic nervous system and the reninangiotensin system.19 The mechanism underlying brachial FMD is not completely understood. However, it is generally believed that brachial FMD is mainly mediated by NO.18 When performing the FMD test, the reactive hyperemia induced by transient ischemia of the forearm may increase the blood flow and shear stress of the vessel wall, resulting in the release of endothelial NO and vascular dilatation. A poor brachial FMD response indicates systemically low NO bioavailability.9,20 Therefore, the much lower FMD in patients with LV in the study implies endothelial dysfunction (3.58 6 2.32%) compared with the control group (7.51 6 2.40%, P \ .001). In contrast, the nonendothelium-dependent NMD test, which reflects a direct vasodilation effect by exogenous NO acting on vascular smooth muscle cells, did not significantly differ between the two groups. Decreased production or activity of NO manifested as impaired endothelium-dependent vasodilation has been proposed as a major mechanism of endothelial dysfunction.16,18 However, NO is not only an important mediator of vasodilator to modulate vascular tone, but also plays a pivotal role in antithrombotic activity.21 This may be one possible mechanism of thrombo-occlusive vasculopathy in LV secondary to endothelial dysfunction. Whether other functions of NO such as anti-inflammatory and antiproliferative functions contribute to the development of LV needs further investigation. Nevertheless, the finding of impaired FMD in LV in this study provides some evidence of endothelial dysfunction in the development of the disease. However, the mechanism by which endothelial dysfunction leads to LV may be multifactorial, involving hypercoagulation, thrombosis, endothelial cell injury, vessel constriction, and immune dysregulation; thus, not all diseases with impaired FMD show LV. Impaired FMD has been shown in atherosclerosis, hypertension, diabetes mellitus, and cardiovascular disease, and in autoimmune disease6,22 and antiphospholipid syndrome.23,24 Endothelial dysfunction is one of the earliest stages of atherogenesis, preceding the formation of atherosclerotic plaques, and has been shown to be a risk factor for cardiovascular disease. The high prevalence of atherosclerosis and cardiovascular disease in autoimmune disease supports the hypothesis of an association between these diseases. In addition, high levels of plasma homocysteine5,25 and lipoprotein26 have been associated with LV in some patients. Both are
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also independent risk factors for endothelial dysfunction, thrombosis, and developing cardiovascular diseases. In fact, the association of atherosclerosis with LV was first demonstrated in a review conducted at the Mayo Clinic in 1984, showing 7 of 42 patients with LV had abdominal aortic calcification and atherosclerosis or aneurysm.27 A follow-up 10year retrospective study found that 3 of 45 patients with LV had a cerebrovascular accident or peripheral artery occlusive disease.5 We tried to avoid other factors that may influence the results of brachial FMD in this study. Therefore, the patients enrolled were all younger than 50 years and did not have conventional cardiovascular risk factors such as hypertension, hyperglycemia, or use of systemic medications that might affect endothelial function. A larger clinical study with longer patient follow-up is needed to clarify whether patients with LV are at greater risk than others with atherosclerosis. Hs-CRP is an inflammatory biomarker that reflects the degree of underlying atherosclerosis and independently predicts future vascular events.28 In this study, hs-CRP was not significantly different in patients with LV and control subjects, suggesting that LV is not an inflammatory disease. Homocysteine is a highly reactive amino acid that may produce endothelial cell injury, which plays a major role in the initiation and progression of atherogenesis and/or vessel thrombosis.29 Although hyperhomocysteinemia was found to be present in 14.3% (3 of 21) of patients with LV,5 our study did not detect any cases of hyperhomocysteinemia. This may imply that supplementation of folate or vitamin B12 might be unnecessary, but it could also be related to our small sample size or be a result of selection bias, as we excluded patients with a history of systemic diseases, including cerebral vascular accidents or coronary artery disease. Notably, high homocysteine levels and mutations of the associated methylenetetrahydrofolate reductase gene have been found.30,31 LV has also been associated with autoimmune diseases such as lupus erythematosus and Sj€ ogren syndrome.5 A low antinuclear antibody titer (1:40) was noted in 5 of 16 (31.3%) patients tested but no patients had confirmed lupus erythematosus. Positive serum ACAs were present in two of 16 (12.5%) patients. Individuals positive for ACA have an increased risk of developing arterial and/or venous thrombosis and/or pregnancy morbidity, which is referred to as antiphospholipid syndrome. Although ACAs have been reported in patients with LV, the prevalence of ACAs in our study group was not higher than in the healthy population (5%-12%).32,33
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We observed impaired endothelial function of the brachial artery in patients with LV in this study, indicating that LV is associated with systemic endothelial dysfunction and is therefore more than just a vascular disease localized to the lower extremities. This hypothesis is supported by the frequent observation of chronic purpuric pigmented dermatosislike lesions and livedo reticularis during the acute exacerbation of LV, because systemic endothelial dysfunction might interfere with the physiological regulation of cutaneous blood flow.2 Several therapeutics, such as calcium channel blockers, L-arginine, antioxidant vitamins, and estrogen, have been shown to alleviate endothelial dysfunction.34-36 Among these, danazol and nifedipine have been described as treatments for LV ulcerations.30,37 Hyperbaric oxygen therapy, one of the most effective treatments for LV, has been shown to result in a significant increase in local NO levels in wounds.38,39 The addition of new strategies to reverse endothelial dysfunction might be effective when coupled with core anticoagulant LV management therapies, such as aspirin, heparin, and dipyridamole. Limitations of this study include the small sample size and potential selection bias. It is also possible that our observations are the result of coincidence rather than a true effect as the numbers are too small to demonstrate statistical significance; therefore, further studies with larger numbers are needed. In addition, there is a possibility that brachial FMD is not a reliable marker of vascular endothelial function, although it has become a gold standard for the noninvasive assessment of endothelial function in conduit arteries.7 In conclusion, LV is associated with endothelial dysfunction, and decreased NO bioavailability may be the main reason for this dysfunction. However, more studies are needed to clarify the mechanism underlying the role of endothelial function in the development of LV. REFERENCES 1. Lyde CB. Atrophie blanche: a review from the perspective of a 31 patient cohort. Dermatol Ther 2001;14:111-6. 2. Yang LJ, Chan HL, Chen SY, Kuan YZ, Chen MJ, Wang CN, et al. Atrophie blanche: a clinicopathological study of 27 patients. Changgeng Yi Xue Za Zhi 1991;14:237-45. 3. Baccard M, Vignon-Pennamen MD, Janier M, Scrobohaci ML, Dubertret L. Livedoid vasculitis with protein C system deficiency. Arch Dermatol 1992;128:1410-1. 4. Davis MD, Wysokinski WE. Ulcerations caused by livedoid vasculopathy associated with a prothrombotic state: response to warfarin. J Am Acad Dermatol 2008;58:512-5. 5. Hairston BR, Davis MD, Pittelkow MR, Ahmed I. Livedoid vasculopathy: further evidence for procoagulant pathogenesis. Arch Dermatol 2006;142:1413-8.
J AM ACAD DERMATOL
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6. Al-Qaisi M, Kharbanda RK, Mittal TK, Donald AE. Measurement of endothelial function and its clinical utility for cardiovascular risk. Vasc Health Risk Manag 2008;4:647-52. 7. Deanfield JE, Halcox JP, Rabelink TJ. Endothelial function and dysfunction: testing and clinical relevance. Circulation 2007; 115:1285-95. 8. Forstermann U, Munzel T. Endothelial nitric oxide synthase in vascular disease: from marvel to menace. Circulation 2006;113: 1708-14. 9. Cooke JP, Dzau VJ. Nitric oxide synthase: role in the genesis of vascular disease. Annu Rev Med 1997;48:489-509. 10. Karatzis EN, Ikonomidis I, Vamvakou GD, Papaioannou TG, Protogerou AD, Andreadou I, et al. Long-term prognostic role of flow-mediated dilatation of the brachial artery after acute coronary syndromes without ST elevation. Am J Cardiol 2006; 98:1424-8. 11. Caliskan M, Yilmaz S, Yildirim E, Gullu H, Erdogan D, Ciftci O, et al. Endothelial functions are more severely impaired during active disease period in patients with Behc¸et’s disease. Clin Rheumatol 2007;26:1074-8. 12. Shen SC, Ho WJ, Wu SC, Yu KH, Lin HC, Lin YS, et al. Peripheral vascular endothelial dysfunction in glaucomatocyclitic crisis: a preliminary study. Invest Ophthalmol Vis Sci 2010;51:272-6. 13. Corretti MC, Anderson TJ, Benjamin EJ, Celermajer D, Charbonneau F, Creager MA, et al. Guidelines for the ultrasound assessment of endothelial-dependent flow-mediated vasodilation of the brachial artery: a report of the International Brachial Artery Reactivity Task Force. J Am Coll Cardiol 2002; 39:257-65. 14. Lowe GD. Virchow’s triad revisited: abnormal flow. Pathophysiol Haemost Thromb 2003;33:455-7. 15. Blann AD, Lip GY. Virchow’s triad revisited: the importance of soluble coagulation factors, the endothelium, and platelets. Thromb Res 2001;101:321-7. 16. Joannides R, Haefeli WE, Linder L, Richard V, Bakkali EH, Thuillez C, et al. Nitric oxide is responsible for flow-dependent dilatation of human peripheral conduit arteries in vivo. Circulation 1995;91:1314-9. 17. Okahara K, Sun B, Kambayashi J. Up-regulation of prostacyclin synthesis-related gene expression by shear stress in vascular endothelial cells. Arterioscler Thromb Vasc Biol 1998;18: 1922-6. 18. Mullen MJ, Kharbanda RK, Cross J, Donald AE, Taylor M, Vallance P, et al. Heterogenous nature of flow-mediated dilatation in human conduit arteries in vivo: relevance to endothelial dysfunction in hypercholesterolemia. Circ Res 2001;88:145-51. 19. Sartori C, Lepori M, Scherrer U. Interaction between nitric oxide and the cholinergic and sympathetic nervous system in cardiovascular control in humans. Pharmacol Ther 2005;106: 209-20. 20. Pyke KE, Tschakovsky ME. The relationship between shear stress and flow-mediated dilatation: implications for the assessment of endothelial function. J Physiol 2005;568:357-69. 21. Radomski MW, Palmer RM, Moncada S. Endogenous nitric oxide inhibits human platelet adhesion to vascular endothelium. Lancet 1987;2:1057-8. 22. Ghiadoni L, Mosca M, Tani C, Virdis A, Taddei S, Bombardieri S. Clinical and methodological aspects of endothelial function in
JULY 2012
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36. 37. 38.
39.
patients with systemic autoimmune diseases. Clin Exp Rheumatol 2008;26:680-7. Charakida M, Besler C, Batuca JR, Sangle S, Marques S, Sousa M, et al. Vascular abnormalities, paraoxonase activity, and dysfunctional HDL in primary antiphospholipid syndrome. JAMA 2009;302:1210-7. Bilora F, Sartori MT, Zanon E, Campagnolo E, Arzenton M, Rossato A. Flow-mediated arterial dilation in primary antiphospholipid syndrome. Angiology 2009;60:104-7. Hairston BR, Davis MD, Gibson LE, Drage LA. Treatment of livedoid vasculopathy with low-molecular-weight heparin: report of 2 cases. Arch Dermatol 2003;139:987-90. Vasconcelos R, Criado PR, Belda W Jr. Livedoid vasculopathy secondary to high levels of lipoprotein(a). Br J Dermatol 2011; 164:1111-3. Schroeter AL, Harris RB. The vasculitis of atrophie blanche (livedoid vasculitis) and abdominal aortic pathology. Cutis 1984;34:298-302. Ridker PM. C-reactive protein: eighty years from discovery to emergence as a major risk marker for cardiovascular disease. Clin Chem 2009;55:209-15. Shai I, Stampfer MJ, Ma J, Manson JE, Hankinson SE, Cannuscio C, et al. Homocysteine as a risk factor for coronary heart diseases and its association with inflammatory biomarkers, lipids and dietary factors. Atherosclerosis 2004;177:375-81. Tsai TF, Yang CH, Chu CY, Liou YH, Hsiao WC, Lin CT, et al. Polymorphisms of MTHFR gene associated with livedoid vasculopathy in Taiwanese population. J Dermatol Sci 2009; 54:214-6. Irani-Hakime NA, Stephan F, Kreidy R, Jureidini I, Almawi WY. Livedoid vasculopathy associated with combined prothrombin G20210A and factor V (Leiden) heterozygosity and MTHFR C677T homozygosity. J Thromb Thrombolysis 2008;26:31-4. Shi W, Krilis SA, Chong BH, Gordon S, Chesterman CN. Prevalence of lupus anticoagulant and anticardiolipin antibodies in a healthy population. Aust N Z J Med 1990;20: 231-6. Manoussakis MN, Tzioufas AG, Silis MP, Pange PJ, Goudevenos J, Moutsopoulos HM. High prevalence of anti-cardiolipin and other autoantibodies in a healthy elderly population. Clin Exp Immunol 1987;69:557-65. Luscher TF, Pieper M, Tendera M, Vrolix M, Rutsch W, van den Branden F, et al. A randomized placebo-controlled study on the effect of nifedipine on coronary endothelial function and plaque formation in patients with coronary artery disease: the ENCORE II study. Eur Heart J 2009;30:1590-7. Fenster BE, Tsao PS, Rockson SG. Endothelial dysfunction: clinical strategies for treating oxidant stress. Am Heart J 2003; 146:218-26. Raitakari OT, Celermajer DS. Flow-mediated dilatation. Br J Clin Pharmacol 2000;50:397-404. Purcell SM. Nifedipine treatment of idiopathic atrophie blanch. J Am Acad Dermatol 1986;14:851-4. Juan WH, Chan YS, Lee JC, Yang LC, Hong HS, Yang CH. Livedoid vasculopathy: long-term follow-up results following hyperbaric oxygen therapy. Br J Dermatol 2006;154:251-5. Saglam M, Bozlar U, Kantarci F, Ay H, Battal B, Coskun U. Effect of hyperbaric oxygen on flow-mediated vasodilation: an ultrasound study. J Ultrasound Med 2008;27:209-14.
L
ivedoid vasculopathy (LV) is a disease characterized by multiple, painful, and recurrent ulcerations with atrophic scars involving the lower legs, ankles, and back surfaces of the feet. These necrotic areas tend to be a result of ischemic infarction caused by vascular occlusion of the papillary dermis, although the origin of this remains unclear. Many researchers suggest that a hypercoagulable status contributes to the development of thrombi in the dermal blood vessels.1,2 Patients with LV exhibit various coagulation abnormalities, From the Department of Dermatology,a Department of Ophthalmology,b and First Cardiovascular Division, Department of Cardiology,c Chang Gung Memorial Hospital, College of Medicine, Chang Gung University. Supported by Chang Gung Memorial Hospital grants CMRPG390511 (Drs Yang and Hui), CMRPG370922 (Dr Ho), and CMRPG391241 (Dr Ho). Conflicts of interest: None declared. Accepted for publication July 21, 2011.
Abbreviations used: ACA: FMD: hs-CRP: LV: NMD: NO:
anticardiolipin antibody flow-mediated vasodilation high-sensitivity C-reactive protein livedoid vasculopathy nitroglycerin-mediated vasodilation nitric oxide
including cryoglobulinemia, protein C deficiency, antithrombin III deficiency, factor V Leiden mutation, Reprint requests: Wan-Jing Ho, MD, First Cardiovascular Division, Department of Cardiology, Chang Gung Memorial Hospital, No. 5, Fu-Shin Road, Kwei-Shan, Tao-Yuan, Taiwan 333. E-mail: [email protected]. Published online October 10, 2011. 0190-9622/$36.00 Ó 2011 by the American Academy of Dermatology, Inc. doi:10.1016/j.jaad.2011.07.021
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and hyperhomocysteinemia.3-5 Current treatment diseases, such as hypertension, congestive heart strategies focus on anticoagulant, antiplatelet, and failure, diabetes mellitus, cerebral vascular accifibrinolytic therapies, but these treatments usually dents, or coronary artery disease, were also exproduce slow responses and unsatisfactory results. cluded. Thus, patients were not taking concurrent Impaired endothelial cell function can induce systemic medications, such as antihypertensive vessel inflammation and influence coagulation and drugs, nitrates, or hormone replacement therapy. fibrinolysis, resulting in atherosclerotic and Sixteen gender- and age-matched control subjects several vascular thrombotic from the same hospital were diseases.6 Brachial artery recruited. Control subjects CAPSULE SUMMARY flow-mediated vasodilation were physically healthy with (FMD) measured by highno history of cardiovascular Livedoid vasculopathy is regarded as resolution ultrasound is a diseases on routine medical dysregulation of the coagulation well-established, noninvaexamination and none were pathway because of the presence of sive procedure for the examtaking systemic medications. fibrin thrombi in blood vessels and ination of endothelial Vascular ultrasound was perbecause anticoagulant, antiplatelet, and function.6,7 Reactive hypereformed for both groups after fibrinolytic therapies are effective mia induced by transient isinformed consent was obtreatments. chemia of the forearm can tained. This study was apincrease blood flow and reWe demonstrated peripheral vascular proved by the Chang Gung sult in shear stress of the endothelial dysfunction in patients with Memorial Hospital Instituvessel wall, leading to the livedoid vasculopathy using the flowtional Review Board. release of endothelial nitric mediated vascular dilation test. oxide (NO) and vascular diBlood biochemical Strategies to correct endothelial lation. Assessment of endoanalyses, inflammation dysfunction may be effective in treating thelial function using this markers, and livedoid vasculopathy ulcers. method can be used to preautoimmune antibody dict the development of athmeasurements erosclerosis, hypertension, and cardiovascular Venous blood samples were collected after 12 diseases.8-10 Brachial FMD has also been used to hours of fasting. We performed routine biochemical detect peripheral endothelial dysfunction in patients tests, such as fasting blood glucose (normal range: with Behc¸et disease and ocular glaucomatocyclitic 70-105 mg/dL), serum cholesterol (desired range: crisis.11,12 The presence of endothelial dysfunction in \200 mg/dL), triglycerides (desired range: \150 patients with LV has never been evaluated. mg/dL), low-density lipoprotein (normal range: Therefore, our study assessed vascular endothelial \130 mg/dL), high-density lipoprotein (normal function in patients with LV and matched control range: male [40 mg/dL; female [50 mg/dL), creatsubjects to determine the pathogenesis of this inine (normal range: female, 0.6-1.2 mg/dL; male, disease. 0.4-1.4 mg/dL), alanine aminotransferase (normal range: 0-36 U/L), and homocysteine (normal range: METHODS \12 mol/L). Nonspecific markers of immune sysParticipants tem activation and inflammation, including highSixteen patients with confirmed LV were recruited sensitivity C-reactive protein (hs-CRP) levels (\1 from the Department of Dermatology, Chang Gung mg/L, low risk; 1-3 mg/L, average; and [3 mg/L, Memorial Hospital, Tao-Yuan, Taiwan. These pahigh risk) were determined by a high-sensitivity tients had active ulcers with painful erythematouscommercial assay kit (analyzer: Hitachi 7600-210, to-violaceous purpura on the legs in addition to Daiichi Pure Chemicals Co Ltd, Tokyo, Japan). depressed, satellite, ivory-white scarlike skin lesions We evaluated the coagulation profile, which insurrounded by telangiectasia, and hyperpigmentacluded complete blood cell count, prothrombin tion. Skin specimens obtained from all patients were time, partial thromboplastin time, protein C (normal characterized by thrombotic occlusion of the superrange: 70%-140%), and protein S (normal range: ficial vessels and hyalinized vessel walls with mini60%-140%). We also examined the presence of mal perivascular inflammatory cell infiltration. autoantibodies, such as antinuclear antibody (norPatients with venous insufficiency and other specific mal range: \1:80), anticardiolipin antibody (ACA) conditions of the legs, including stasis ulcers, dia(positive [20 GPL /mL), anti-SSA antibody (posibetic foot, deep vein thrombosis, and vasculitis, were tive [130 AU/mL), and anti-SSB antibody (positive excluded from this study. Patients with systemic [130 AU/mL). d
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Measurement of vascular endothelial function All study subjects were referred to the vascular laboratory the morning after overnight fasting for at least 8 hours. Tobacco, alcohol, caffeinated beverages, and any medications including nutritional supplements were prohibited before the examination. Brachial artery FMD was studied using highresolution 2-dimensional ultrasonic imaging as described previously.6,13 All ultrasound images were obtained with a high-resolution linear-array transducer (13 MHz) on an ultrasound system (Aloka Prosound a10, Aloka Co, Tokyo, Japan) coupled with computer-assisted analysis software (e-Tracking System, Aloka Co). Examinations were performed in a dimly lit and quiet room with temperature control. Patients rested in the supine position for at least 10 minutes before the first scan and remained supine until the final recording was acquired with electrocardiogram monitoring. Blood pressure was obtained from the right arm before imaging. The left arm of each patient was fixed on an arm splint and a 7-cm wide blood pressure cuff was placed around the forearm. The brachial artery was scanned longitudinally approximately 3 to 5 cm above the antecubital fossa. The transmit zone was set to the depth of the near wall so that the interface between the media and the adventitia ‘‘m’’ line was clearly visible. When the optimal B-mode image of the anterior and posterior intimal interfaces between the lumen and vessel wall was obtained, the transducer was maintained in an identical position throughout the scan using a micrometer-adjustable stereotactic probe holder (MP-PH0001, Aloka Co) to ensure consistency of the image. The tracking gate was then placed on the intima, the artery diameter was automatically tracked, and the waveform of diameter changes was displayed in real time by using the FMD mode of the ultrasound system. The baseline images and pulsed Doppler blood flow of the brachial artery were acquired for 30 seconds. The blood pressure cuff was inflated to 250 mm Hg to induce hyperemia and arterial occlusion was maintained for 5 minutes. The cuff was then rapidly deflated and pulsed Doppler velocity signals were recorded after deflation for 15 seconds. Longitudinal images of the brachial artery were recorded continuously for 5 minutes after cuff deflation. The response to nitroglycerin was used to assess endothelium-independent nitroglycerin-mediated vasodilation (NMD). Baseline images and arterial blood flow were acquired after a 10-minute rest period to allow re-establishment of brachial artery baseline conditions, followed by administration of sublingual nitroglycerin spray (400 g). Arterial images were recorded continuously for 4 minutes. The
FMD was expressed as the percentage of maximal vessel diameter change induced by hyperemia. Similarly, NMD was expressed as the percentage change of diameter response to nitroglycerin sublingual spray at 4 minutes. The intraobserver and interobserver coefficients of variation for baseline arterial diameter measurements were 1.6% and 2.1%, respectively, in the vascular laboratory (n = 16). Statistical analysis Data are expressed as mean (range) for continuous variables and as a percentage for categorical variables. Continuous variables were compared among the LV and control groups by the nonparametric Mann-Whitney test. Categorical variables were compared between groups using the x2 test; if the number of cases was less than 5, the Fisher exact test was used. P values less than .05 were considered statistically significant. The post hoc power of FMD was calculated because of the small sample size.
RESULTS Clinical and biochemical findings This study included 16 patients with LV (mean age, 32 years; 8 women, 8 men) and 16 control subjects (mean age, 32 years; 8 women, 8 men). Traditional atherosclerosis risk factors, such as body mass index, cigarette smoking, systolic blood pressure, fasting blood glucose, and lipid profile, did not differ significantly between patients with LV and control subjects. Inflammation activity and autoimmune markers and antibodies Homocysteine levels, which are indicative of atherosclerosis, were within normal limits in patients with LV. Levels of hs-CRP, the acute-phase protein that increases during systemic inflammation, were similar in patients with LV and control subjects. In addition, levels of the major physiological anticoagulants, protein C and protein S, were not decreased in patients with LV. All patients with LV had negative findings for antinuclear antibody, anti-SSA antibodies, and anti-SSB antibodies but two patients with LV (12.5%, 2 of 16) had positive findings for ACA. Endothelial function The endothelium-dependent FMD was significantly lower in patients with LV (3.58 6 2.32%) than in control subjects (7.51 6 2.40%, P \ .001) (Fig 1). However, the endothelium-independent NMD did not significantly differ between these two groups (15.22 6 4.69% vs 16.27 6 5.38%, P = .643).
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Fig 1. Endothelium-dependent flow-mediated vasodilation (FMD) and endothelium-independent nitroglycerinmediated vasodilation (NMD) in patients with livedoid vasculopathy (LV) and control subjects (CTL). Values are means 6 SD. *P \ .001.
The post hoc power was calculated to be 99.5% for FMD (a = 0.05).
DISCUSSION LV is a thrombo-occlusive vasculopathy characterized by thrombosis of the upper reticular dermal blood vessels, hyalinized vessel walls, and scanty perivascular inflammatory cell infiltration. The underlying pathogenetic processes of this disease remain unclear. Although hereditary and acquired hypercoagulable states are associated with the disease in some patients, these factors do not fully explain dermal vessel thrombosis in LV. According to the Virchow triad theory for thrombogenesis, intravascular thrombus formation is related to endothelial cell injury/dysfunction in addition to coagulation factor dysregulation and turbulent blood flow.14,15 This study showed that patients with LV had decreased FMD of the brachial artery, which indicates systemic endothelial dysfunction. The vascular endothelium actively participates in the balance between blood coagulation and fibrinolysis to maintain the circulation system. Endothelial cells act as a physical barrier by covering the thrombogenic basement membrane. Endothelial cell injury may result in leukocyte adhesion and migration, and exposure of the subendothelium, providing a surface for coagulation. Functional endothelial cells can release vasodilators such as NO, prostaglandins (prostaglandin I2), and endotheliumderived hyperpolarizing factor.16,17 Among these vasodilators, NO is particularly important because it also functions as an endogenous antithrombotic molecule by inhibiting leukocyte-endothelial interactions, platelet aggregation and adhesion, and
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fibrin formation on vessel walls.8,18 NO released by endothelial cells exerts a vasodilator effect by counterbalancing the vasoconstriction produced by the sympathetic nervous system and the reninangiotensin system.19 The mechanism underlying brachial FMD is not completely understood. However, it is generally believed that brachial FMD is mainly mediated by NO.18 When performing the FMD test, the reactive hyperemia induced by transient ischemia of the forearm may increase the blood flow and shear stress of the vessel wall, resulting in the release of endothelial NO and vascular dilatation. A poor brachial FMD response indicates systemically low NO bioavailability.9,20 Therefore, the much lower FMD in patients with LV in the study implies endothelial dysfunction (3.58 6 2.32%) compared with the control group (7.51 6 2.40%, P \ .001). In contrast, the nonendothelium-dependent NMD test, which reflects a direct vasodilation effect by exogenous NO acting on vascular smooth muscle cells, did not significantly differ between the two groups. Decreased production or activity of NO manifested as impaired endothelium-dependent vasodilation has been proposed as a major mechanism of endothelial dysfunction.16,18 However, NO is not only an important mediator of vasodilator to modulate vascular tone, but also plays a pivotal role in antithrombotic activity.21 This may be one possible mechanism of thrombo-occlusive vasculopathy in LV secondary to endothelial dysfunction. Whether other functions of NO such as anti-inflammatory and antiproliferative functions contribute to the development of LV needs further investigation. Nevertheless, the finding of impaired FMD in LV in this study provides some evidence of endothelial dysfunction in the development of the disease. However, the mechanism by which endothelial dysfunction leads to LV may be multifactorial, involving hypercoagulation, thrombosis, endothelial cell injury, vessel constriction, and immune dysregulation; thus, not all diseases with impaired FMD show LV. Impaired FMD has been shown in atherosclerosis, hypertension, diabetes mellitus, and cardiovascular disease, and in autoimmune disease6,22 and antiphospholipid syndrome.23,24 Endothelial dysfunction is one of the earliest stages of atherogenesis, preceding the formation of atherosclerotic plaques, and has been shown to be a risk factor for cardiovascular disease. The high prevalence of atherosclerosis and cardiovascular disease in autoimmune disease supports the hypothesis of an association between these diseases. In addition, high levels of plasma homocysteine5,25 and lipoprotein26 have been associated with LV in some patients. Both are
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also independent risk factors for endothelial dysfunction, thrombosis, and developing cardiovascular diseases. In fact, the association of atherosclerosis with LV was first demonstrated in a review conducted at the Mayo Clinic in 1984, showing 7 of 42 patients with LV had abdominal aortic calcification and atherosclerosis or aneurysm.27 A follow-up 10year retrospective study found that 3 of 45 patients with LV had a cerebrovascular accident or peripheral artery occlusive disease.5 We tried to avoid other factors that may influence the results of brachial FMD in this study. Therefore, the patients enrolled were all younger than 50 years and did not have conventional cardiovascular risk factors such as hypertension, hyperglycemia, or use of systemic medications that might affect endothelial function. A larger clinical study with longer patient follow-up is needed to clarify whether patients with LV are at greater risk than others with atherosclerosis. Hs-CRP is an inflammatory biomarker that reflects the degree of underlying atherosclerosis and independently predicts future vascular events.28 In this study, hs-CRP was not significantly different in patients with LV and control subjects, suggesting that LV is not an inflammatory disease. Homocysteine is a highly reactive amino acid that may produce endothelial cell injury, which plays a major role in the initiation and progression of atherogenesis and/or vessel thrombosis.29 Although hyperhomocysteinemia was found to be present in 14.3% (3 of 21) of patients with LV,5 our study did not detect any cases of hyperhomocysteinemia. This may imply that supplementation of folate or vitamin B12 might be unnecessary, but it could also be related to our small sample size or be a result of selection bias, as we excluded patients with a history of systemic diseases, including cerebral vascular accidents or coronary artery disease. Notably, high homocysteine levels and mutations of the associated methylenetetrahydrofolate reductase gene have been found.30,31 LV has also been associated with autoimmune diseases such as lupus erythematosus and Sj€ ogren syndrome.5 A low antinuclear antibody titer (1:40) was noted in 5 of 16 (31.3%) patients tested but no patients had confirmed lupus erythematosus. Positive serum ACAs were present in two of 16 (12.5%) patients. Individuals positive for ACA have an increased risk of developing arterial and/or venous thrombosis and/or pregnancy morbidity, which is referred to as antiphospholipid syndrome. Although ACAs have been reported in patients with LV, the prevalence of ACAs in our study group was not higher than in the healthy population (5%-12%).32,33
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We observed impaired endothelial function of the brachial artery in patients with LV in this study, indicating that LV is associated with systemic endothelial dysfunction and is therefore more than just a vascular disease localized to the lower extremities. This hypothesis is supported by the frequent observation of chronic purpuric pigmented dermatosislike lesions and livedo reticularis during the acute exacerbation of LV, because systemic endothelial dysfunction might interfere with the physiological regulation of cutaneous blood flow.2 Several therapeutics, such as calcium channel blockers, L-arginine, antioxidant vitamins, and estrogen, have been shown to alleviate endothelial dysfunction.34-36 Among these, danazol and nifedipine have been described as treatments for LV ulcerations.30,37 Hyperbaric oxygen therapy, one of the most effective treatments for LV, has been shown to result in a significant increase in local NO levels in wounds.38,39 The addition of new strategies to reverse endothelial dysfunction might be effective when coupled with core anticoagulant LV management therapies, such as aspirin, heparin, and dipyridamole. Limitations of this study include the small sample size and potential selection bias. It is also possible that our observations are the result of coincidence rather than a true effect as the numbers are too small to demonstrate statistical significance; therefore, further studies with larger numbers are needed. In addition, there is a possibility that brachial FMD is not a reliable marker of vascular endothelial function, although it has become a gold standard for the noninvasive assessment of endothelial function in conduit arteries.7 In conclusion, LV is associated with endothelial dysfunction, and decreased NO bioavailability may be the main reason for this dysfunction. However, more studies are needed to clarify the mechanism underlying the role of endothelial function in the development of LV. REFERENCES 1. Lyde CB. Atrophie blanche: a review from the perspective of a 31 patient cohort. Dermatol Ther 2001;14:111-6. 2. Yang LJ, Chan HL, Chen SY, Kuan YZ, Chen MJ, Wang CN, et al. Atrophie blanche: a clinicopathological study of 27 patients. Changgeng Yi Xue Za Zhi 1991;14:237-45. 3. Baccard M, Vignon-Pennamen MD, Janier M, Scrobohaci ML, Dubertret L. Livedoid vasculitis with protein C system deficiency. Arch Dermatol 1992;128:1410-1. 4. Davis MD, Wysokinski WE. Ulcerations caused by livedoid vasculopathy associated with a prothrombotic state: response to warfarin. J Am Acad Dermatol 2008;58:512-5. 5. Hairston BR, Davis MD, Pittelkow MR, Ahmed I. Livedoid vasculopathy: further evidence for procoagulant pathogenesis. Arch Dermatol 2006;142:1413-8.
J AM ACAD DERMATOL
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6. Al-Qaisi M, Kharbanda RK, Mittal TK, Donald AE. Measurement of endothelial function and its clinical utility for cardiovascular risk. Vasc Health Risk Manag 2008;4:647-52. 7. Deanfield JE, Halcox JP, Rabelink TJ. Endothelial function and dysfunction: testing and clinical relevance. Circulation 2007; 115:1285-95. 8. Forstermann U, Munzel T. Endothelial nitric oxide synthase in vascular disease: from marvel to menace. Circulation 2006;113: 1708-14. 9. Cooke JP, Dzau VJ. Nitric oxide synthase: role in the genesis of vascular disease. Annu Rev Med 1997;48:489-509. 10. Karatzis EN, Ikonomidis I, Vamvakou GD, Papaioannou TG, Protogerou AD, Andreadou I, et al. Long-term prognostic role of flow-mediated dilatation of the brachial artery after acute coronary syndromes without ST elevation. Am J Cardiol 2006; 98:1424-8. 11. Caliskan M, Yilmaz S, Yildirim E, Gullu H, Erdogan D, Ciftci O, et al. Endothelial functions are more severely impaired during active disease period in patients with Behc¸et’s disease. Clin Rheumatol 2007;26:1074-8. 12. Shen SC, Ho WJ, Wu SC, Yu KH, Lin HC, Lin YS, et al. Peripheral vascular endothelial dysfunction in glaucomatocyclitic crisis: a preliminary study. Invest Ophthalmol Vis Sci 2010;51:272-6. 13. Corretti MC, Anderson TJ, Benjamin EJ, Celermajer D, Charbonneau F, Creager MA, et al. Guidelines for the ultrasound assessment of endothelial-dependent flow-mediated vasodilation of the brachial artery: a report of the International Brachial Artery Reactivity Task Force. J Am Coll Cardiol 2002; 39:257-65. 14. Lowe GD. Virchow’s triad revisited: abnormal flow. Pathophysiol Haemost Thromb 2003;33:455-7. 15. Blann AD, Lip GY. Virchow’s triad revisited: the importance of soluble coagulation factors, the endothelium, and platelets. Thromb Res 2001;101:321-7. 16. Joannides R, Haefeli WE, Linder L, Richard V, Bakkali EH, Thuillez C, et al. Nitric oxide is responsible for flow-dependent dilatation of human peripheral conduit arteries in vivo. Circulation 1995;91:1314-9. 17. Okahara K, Sun B, Kambayashi J. Up-regulation of prostacyclin synthesis-related gene expression by shear stress in vascular endothelial cells. Arterioscler Thromb Vasc Biol 1998;18: 1922-6. 18. Mullen MJ, Kharbanda RK, Cross J, Donald AE, Taylor M, Vallance P, et al. Heterogenous nature of flow-mediated dilatation in human conduit arteries in vivo: relevance to endothelial dysfunction in hypercholesterolemia. Circ Res 2001;88:145-51. 19. Sartori C, Lepori M, Scherrer U. Interaction between nitric oxide and the cholinergic and sympathetic nervous system in cardiovascular control in humans. Pharmacol Ther 2005;106: 209-20. 20. Pyke KE, Tschakovsky ME. The relationship between shear stress and flow-mediated dilatation: implications for the assessment of endothelial function. J Physiol 2005;568:357-69. 21. Radomski MW, Palmer RM, Moncada S. Endogenous nitric oxide inhibits human platelet adhesion to vascular endothelium. Lancet 1987;2:1057-8. 22. Ghiadoni L, Mosca M, Tani C, Virdis A, Taddei S, Bombardieri S. Clinical and methodological aspects of endothelial function in
JULY 2012
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36. 37. 38.
39.
patients with systemic autoimmune diseases. Clin Exp Rheumatol 2008;26:680-7. Charakida M, Besler C, Batuca JR, Sangle S, Marques S, Sousa M, et al. Vascular abnormalities, paraoxonase activity, and dysfunctional HDL in primary antiphospholipid syndrome. JAMA 2009;302:1210-7. Bilora F, Sartori MT, Zanon E, Campagnolo E, Arzenton M, Rossato A. Flow-mediated arterial dilation in primary antiphospholipid syndrome. Angiology 2009;60:104-7. Hairston BR, Davis MD, Gibson LE, Drage LA. Treatment of livedoid vasculopathy with low-molecular-weight heparin: report of 2 cases. Arch Dermatol 2003;139:987-90. Vasconcelos R, Criado PR, Belda W Jr. Livedoid vasculopathy secondary to high levels of lipoprotein(a). Br J Dermatol 2011; 164:1111-3. Schroeter AL, Harris RB. The vasculitis of atrophie blanche (livedoid vasculitis) and abdominal aortic pathology. Cutis 1984;34:298-302. Ridker PM. C-reactive protein: eighty years from discovery to emergence as a major risk marker for cardiovascular disease. Clin Chem 2009;55:209-15. Shai I, Stampfer MJ, Ma J, Manson JE, Hankinson SE, Cannuscio C, et al. Homocysteine as a risk factor for coronary heart diseases and its association with inflammatory biomarkers, lipids and dietary factors. Atherosclerosis 2004;177:375-81. Tsai TF, Yang CH, Chu CY, Liou YH, Hsiao WC, Lin CT, et al. Polymorphisms of MTHFR gene associated with livedoid vasculopathy in Taiwanese population. J Dermatol Sci 2009; 54:214-6. Irani-Hakime NA, Stephan F, Kreidy R, Jureidini I, Almawi WY. Livedoid vasculopathy associated with combined prothrombin G20210A and factor V (Leiden) heterozygosity and MTHFR C677T homozygosity. J Thromb Thrombolysis 2008;26:31-4. Shi W, Krilis SA, Chong BH, Gordon S, Chesterman CN. Prevalence of lupus anticoagulant and anticardiolipin antibodies in a healthy population. Aust N Z J Med 1990;20: 231-6. Manoussakis MN, Tzioufas AG, Silis MP, Pange PJ, Goudevenos J, Moutsopoulos HM. High prevalence of anti-cardiolipin and other autoantibodies in a healthy elderly population. Clin Exp Immunol 1987;69:557-65. Luscher TF, Pieper M, Tendera M, Vrolix M, Rutsch W, van den Branden F, et al. A randomized placebo-controlled study on the effect of nifedipine on coronary endothelial function and plaque formation in patients with coronary artery disease: the ENCORE II study. Eur Heart J 2009;30:1590-7. Fenster BE, Tsao PS, Rockson SG. Endothelial dysfunction: clinical strategies for treating oxidant stress. Am Heart J 2003; 146:218-26. Raitakari OT, Celermajer DS. Flow-mediated dilatation. Br J Clin Pharmacol 2000;50:397-404. Purcell SM. Nifedipine treatment of idiopathic atrophie blanch. J Am Acad Dermatol 1986;14:851-4. Juan WH, Chan YS, Lee JC, Yang LC, Hong HS, Yang CH. Livedoid vasculopathy: long-term follow-up results following hyperbaric oxygen therapy. Br J Dermatol 2006;154:251-5. Saglam M, Bozlar U, Kantarci F, Ay H, Battal B, Coskun U. Effect of hyperbaric oxygen on flow-mediated vasodilation: an ultrasound study. J Ultrasound Med 2008;27:209-14.