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Query: UMLS:C0038454 (stroke)
 147,016 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Atherosclerosis with or without thrombosis superimposed is the most frequent cause of ischemic heart disease (IHD), peripheral arterial disease, and a main cause of stroke. Conflicting results have been reported in genetic, observational, and experimental studies on the relationship between homocysteine and these atherothrombotic diseases. Although cardiovascular complications are common in homocystinuric patients (severe hyperhomocysteinemia), IHD, the most frequent manifestation of atherothrombosis in the general population, appears to be rare. On the basis of findings in individuals with hyperhomocysteinemia of genetic origin, there is in fact no clear evidence for a causal role of homocysteine in the pathogenesis of atherothrombotic disease, and the positive association between plasma homocysteine and IHD observed in many, but not all epidemiologic studies does not prove causality. To infer causality from observational studies, there should be a temporal, consistent, strong, independent, graded (dose-response effect), and duration-dependent relationship between exposure and outcomes, and a biologically plausible mechanism should exist. The relationship between plasma homocysteine levels and IHD does not fulfill these criteria beyond reasonable doubt. In the general population, plasma homocysteine levels are to a great extent determined by dietary habits, and plasma homocysteine could be a marker, or a consequence, of atherothrombosis and/or risk-associated behavior (e.g., a diet low in fruits and vegetables) rather than a cause of atherothrombosis. Experimentally, hyperhomocysteinemia is not in itself atherogenic in normal animals with relatively low plasma cholesterol levels. The homocysteine theory of atherosclerosis should be tested more thoroughly in hypercholesterolemic animals that develop atherosclerosis spontaneously to determine whether elevated plasma homocysteine levels are harmful under atherogenic conditions. A causal role of homocysteine in atherothrombotic disease remains to be established.
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PMID:Homocysteine and atherothrombosis. 1183 89

Atherosclerotic plaques were likened histologically to healing inflammatory lesions by Russell Ross, who proposed a "response to injury" hypothesis for their formation. More recently, intraplaque inflammation has been postulated to play a role in thinning of the fibrous cap, plaque rupture, and superadded thrombosis. Potential causes for vascular injury include mechanical stress, smoke exposure, hypercholesterolemia, hyperhomocysteinemia, and chronic infection (direct, or indirect). Blood levels of inflammatory markers (e.g., C-reactive protein [CRP]; serum amyloid A [SAA]; fibrinogen; plasma viscosity; erythrocyte sedimentation rate [ESR]; leukocyte count, low serum albumin) have been associated with vascular risk factors and with prevalent and incident atherothrombotic cardiovascular disease (CVD) (coronary heart disease, [CHD]; stroke; and peripheral arterial disease). More recently, cytokines (e.g., interleukin-6 [IL-6]) and soluble adhesion molecules (e.g., intercellular adhesion molecule-1, vascular cell adhesion molecule-1) have been associated with both risk factors and disease; and offer potential therapeutic targets for nonspecific "anti-inflammatory" treatment of arterial disease. Infections associated with arterial disease include specific infections (Chlamydia pneumoniae, Helicobacter pylori) and nonspecific infections (periodontal infections, respiratory tract infections). Recent meta-analyses have shown that associations of serum markers of C. pneumoniae and H. pylori with arterial disease, risk factors, or potential intermediary mechanisms for disease are weaker than was first suggested by early reports. Likewise, further studies and meta-analyses are required to evaluate the epidemiologic relationships of CVD to periodontal infection and disease and to chronic pulmonary infections and disease. The weaker the associations between chronic infections and CVD, the larger is the size of randomized controlled trials required to establish (or exclude) a preventive effect of infection treatment. While control of chronic infection in the mouth, stomach or lungs is appropriate for its local effects, proving its efficacy in prevention of CVD presents a continuing challenge to medical science.
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PMID:The relationship between infection, inflammation, and cardiovascular disease: an overview. 1188 52

Plasma homocysteine levels result from the effect of genetic and environmental factors. We investigated the hypothesis of familial association between folates, methylenetetrahydrofolate reductase (MTHFR) and hyperhomocysteinemia with acute events, studying three families through pedigree analysis and log-linear graphical models. In 43 subjects, 13 had homocysteine levels of >15 micromol/l. In Family A, premature venous and arterial events occurred in father and son, respectively. In Family B, several arterial premature events occurred and very high homocysteine level was found in a healthy 18-year-old nephew. In Family C, stroke occurred at the age of 16 in a boy. In all three families, all subjects with premature cardiovascular events had high homocysteine level as well as MTHFR mutation, either homozygous or heterozygous. The present results underline that hyperhomocysteinemia has a direct conditional association with cardiovascular events. Moreover, homocysteine level is a variable that links the indirect association of folates, MTHFR mutation and cardiovascular event.
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PMID:Premature arterial and venous events in three families. Effect of folate levels and MTHFR mutation mediated by family/generation and homocysteine levels. 1195

Hyperhomocysteinemia is considered to be a risk factor for vascular diseases including ischemic stroke. It has been shown that plasma homocysteine level can be lowered by folic acid supplementation. Vitamin B(12) may be also beneficial when included in the supplement regimen with folic acid. We have examined in Japanese patients with ischemic stroke the homocysteine-lowering potential of a combination therapy with folic acid and vitamin B(12). Patients with ischemic stroke were randomized into three groups and each group received vitamin B(12) (1500 microg/day, n = 63), folic acid (5 mg/day, n = 64), or both vitamin B(12) and folic acid (n = 64) for 8 weeks. Plasma levels of homocysteine and these vitamins were followed. Significant reduction in plasma homocysteine was observed in all three groups, and the combination therapy yielded the most remarkable result, i.e., plasma total homocysteine was reduced by 38.5% and this was significantly larger than the reduction in other two groups (22.4% and 10.9% in the groups received folic acid and vitamin B(12), respectively). Vitamin B(12) synergizes with folic acid in reducing plasma homocysteine in Japanese patients with ischemic stroke and the combined therapy may be particularly effective in the secondary prevention.
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PMID:Hyperhomocysteinemia in Japanese patients with convalescent stage ischemic stroke: effect of combined therapy with folic acid and mecobalamine. 1222 Jun 94

Hereditary prothrombotic states of clinical importance include factor V Leiden, the prothrombin 20210A mutation, deficiencies of protein C, protein S, or antithrombin, sickle cell disease, and hyperhomocysteinemia. Major acquired prothrombotic states include cancer, myeloproliferative disorders, the antiphospholipid syndrome, and heparin-induced thrombocytopenia. Because most of the hereditary prothrombic states are not established risk factors for arterial thrombosis, routine laboratory testing in most patients with ischemic stroke should be limited to complete blood count, lupus anticoagulant, anticardiolipin antibodies, and plasma total homocysteine. Additional testing for factor V Leiden, prothrombin 20210A, antithrombin, protein C, and protein S may be indicated for patients under the age of 50 or those with paradoxical cerebral embolism. The treatment of acute ischemic stroke in patients with prothrombotic states is similar to that in patients without an identifiable prothrombotic condition, and may include antiplatelet agents, anticoagulants, or thrombolytic therapy in patients who otherwise meet eligibility criteria. The potential benefit of chronic anticoagulation therapy for the primary or secondary prevention of stroke in patients with prothrombotic states has not been addressed in controlled clinical trials. Specific therapeutic approaches for the prevention of stroke are established for patients with sickle cell disease, myeloproliferative disorders, and heparin-induced thrombocytopenia, and are under investigation for hyperhomocysteinemia and the antiphospholipid syndrome.
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PMID:Prothrombotic States that Predispose to Stroke. 1235 68

Hyperhomocysteinemia (HHCY) is a consequence of disturbed methionine metabolism. It results from enzyme and/or vitamin deficiency. Epidemiological and clinical studies have proven HHCY to be an independent risk factor for atherosclerotic cardiovascular diseases, stroke, peripheral arterial occlusive disease and venous thrombosis. Trials in progress may clarify the "causality" of high homocysteine (HCY) concentrations and will assess the value of HCY lowering therapy. HHCY is also seen as a risk factor for neurodegenerative diseases such as cognitive impairment, dementia, Alzheimer's disease, and also for depression. There is a high prevalence of HHCY as a syndrome of vitamin shortage in elderly subjects, which strongly increases with advancing age. Elderly people have a high frequency of vitamin B12 deficiency which is more reliably diagnosed by measurement of serum methylmalonic acid and holotranscobalamin II, the metabolically active B12 fraction, than by total serum vitamin B12. Subjects who follow a strict vegetarian diet also have a high prevalence of HHCY caused by vitamin B12 deficiency. For prevention of neurological damages an early diagnosis of vitamin B12 deficiency is important. Furthermore, HHCY is a factor in the pathogenesis of neural tube defects and preeclampsia. HCY should be measured in patients with a history of atherothrombotic vessel diseases, in patients with diabetes or hyperlipidemia, in renal patients, in adipose subjects, in elderly people, in vegetarians, in postmenopausal women, and in early pregnancy.
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PMID:Hyperhomocysteinemia: a new risk factor for degenerative diseases. 1238 6

The role of homocysteine as a risk factor for cardiovascular disease remains controversial because positive reports from case-control studies may be the consequence of reverse causality bias, and positive and negative results have been reported in cohort studies. This is a meta-analysis of published cohort studies. An average relative risk (ARR) was calculated using fixed and random effect models. The likelihood of publication and selection bias, and the impact of each study on the ARR were also evaluated. Fourteen eligible studies were retrieved. We found no evidence of publication bias (P =.62) nor heterogeneity (P =.56). The ARRs from a fixed effect model were 1.49 (95% CI: 1.31-1.70) for cardiac events, and 1.37 (95% CI: 0.99- 1.99) for ischemic stroke. Duration of follow up and age did not significantly change the ARRs. Hyperhomocysteinemia moderately increases the risk of a first cardiovascular event, regardless of age and follow-up duration.
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PMID:Total plasma homocysteine level and risk of cardiovascular disease: a meta-analysis of prospective cohort studies. 1239 75

We examined effects of hyperhomocysteinemia on structure and mechanics of cerebral arterioles. We measured plasma total homocysteine (tHcy) and pressure, diameter, and cross-sectional area of the vessel wall in maximally dilated cerebral arterioles in heterozygous cystathionine beta-synthase-deficient (CBS(+/-)) mice and wild-type (CBS(+/+)) littermates that were provided with drinking water that was unsupplemented (control diet) or supplemented with 0.5% L-methionine (high-methionine diet). Plasma tHcy was 5.0+/-1.1 micro mol/L in CBS(+/+) mice and 8.3+/-0.9 micro mol/L in CBS(+/-) mice (P<0.05 versus CBS(+/+) mice) fed the control diet. Plasma tHcy was 17.2+/-4.6 micro mol/L in CBS(+/+) mice and 21.2+/-3.9 micro mol/L in CBS(+/-) mice (P<0.05) fed the high-methionine diet. Cross-sectional area of the vessel wall was significantly increased in CBS(+/-) (437+/-22 micro m(2)) mice fed control diet and CBS(+/+) (442+/-36 micro m(2)) and CBS(+/-) (471+/-46 micro m(2)) mice fed high-methionine diet relative to CBS(+/+) (324+/-18 micro m(2)) mice fed control diet (P<0.05). During maximal dilatation, the stress-strain curves in cerebral arterioles of CBS(+/-) mice on control diet and CBS(+/+) and CBS(+/-) mice on high-methionine diet were shifted to the right of the curve in cerebral arterioles of CBS(+/+) mice on control diet, an indication that distensibility of cerebral arterioles was increased in mice with elevated levels of plasma tHcy. Thus, hyperhomocysteinemia in mice was associated with hypertrophy and an increase in distensibility of cerebral arterioles. These findings suggest that hyperhomocysteinemia promotes cerebral vascular hypertrophy and altered cerebral vascular mechanics, both of which may contribute to the increased incidence of stroke associated with hyperhomocysteinemia.
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PMID:Structure of cerebral arterioles in cystathionine beta-synthase-deficient mice. 1243 38

Thromboembolism is the most important complication in patients with atrial fibrilation (AF). Homocysteine is a toxic amino acid that has been recently accepted as a risk factor for atherosclerosis and stroke. The aim of the present study is to show whether there is a relation between hyperhomocysteinemia and thromboembolic complications in patients with non-valvular AF. We admitted 38 patients with non-valvular AF. The patients were divided into two groups: group A (n = 20; mean age, 75.7 +/- 10.4 years; three males/17 females), and group B (n = 18; mean age, 68.0 +/- 10.6 years; 11 males/seven females). While group A consisted of the patients with AF and stroke, group B was composed of the patients with AF but without stroke. The patients having sinus rhythm (15 subjects) were used as the reference group to obtain the cut-off value. Homocysteine was measured by the immunoassay method. The means of the homocysteine levels were 12.4 +/- 3.3 micromol/l in group A, 8.3 +/- 2.3 micromol/l in group B and 9.3 +/- 1.8 micromol/l in the reference group. The cut-off value was 10.6 micromol/l. Group A had a statistically higher homocysteine level than not only group B, but also the reference group (P < 0.05). While 60% of group A (n = 12) had the elevated homocysteine level, the rate was only 22% for group B (n = 4). In conclusion, hyperhomocysteinemia may be one of the explanations for the increased rate of thromboembolic complications in older patients with AF.
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PMID:Role of homocysteine for thromboembolic complication in patients with non-valvular atrial fibrilation. 1285 41

Spontaneous cervical artery dissections are produced by the penetration of circulating blood into the vessel wall of one or more cervical arteries, without a preceding major trauma. Dissection is one of the most frequent etiologies of ischemic stroke in young patients. Its annual incidence is about 3 per 100,000. Pathophysiology of cervical artery dissection remains misunderstood. Triggering factors such as minor trauma and infection have been identified. However, they are too trivial to explain alone the occurrence of a mural hematoma. Several abnormalities suggesting an underlying arteriopathy related to an extracellular matrix defect which could predispose to dissection have been reported: arterial redundancies, intracranial aneurysms, aortic root dilatation, common carotid artery distensibility increase, fibromuscular dysplasia, inherited connective tissue disorders, ultrastructural dermal connective tissue abnormalities. Other factors associated with dissection, such as migraine, hyperhomocysteinemia and alpha-1 antitrypsin deficiency, suggest arterial wall fragility secondary to hyperactivity of some proteases. If an underlying arteriopathy is likely, its nature remains unidentified to date and does not seem to be unique.
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PMID:[Epidemiology and pathophysiology of spontaneous cervical artery dissection]. 1253 41


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