Association between factor V Leiden, prothrombin G20210A, and methylenetetrahydrofolate reductase C677T mutations and events of the arterial circulatory system: a meta-analysis of published studies

Association between polymorphism of methylenetetrahydrofolate reductase (MTHFR) C677T and risk of myocardial infarction: a meta-analysis for 8,140 cases and 10,522 controls

BACKGROUND AND AIMS

The methylenetetrahydrofolate reductase (MTHFR) gene C677T polymorphism has been reported to be associated with myocardial infarction (MI), but results from previous studies are conflicting. The present study aimed at investigating the association between this polymorphism and risk of MI using a meta-analysis on the published studies.

METHODS

Medline, EBSCO, BIOSIS, and Cochrane Library were searched to identify eligible studies published in English before August, 2011. Data were extracted using standardized methods. The association was assessed by odds ratio (OR) with 95% confidence intervals (CI). Begg's test was used to measure publication bias.

RESULTS

A total of 30 case-control studies containing 8,140 MI cases and 10,522 controls were involved in this meta-analysis. Overall, significant association was found between MTHFR C677T polymorphism and risk of MI when all studies pooled with fixed-effects model for TT vs. CT (OR = 1.183, 95% CI: 1.076-1.300). In the subgroup analysis, the same association was found in overall Caucasians (OR = 1.139, 95% CI: 1.007-1.288) and young/middle-aged (<50 years) Caucasians (OR = 1.275, 95% CI: 1.077-1.509). No associations were detected between MTHFR C677T and the risk of MI in elderly male or female Caucasians, East Asians, South Asians, and African-Americans.

CONCLUSIONS

Meta-analysis results suggest that the MTHFR C677T polymorphism was associated with risk of MI in young/middle-aged Caucasians. The effect of the variants on the expression levels and the possible functional role of the variants in MI should be addressed in further studies.

Analysis of polymorphisms Leiden Factor V G1691A and prothrombin G20210A as risk factors for acute myocardial infarction

Thrombotic risk increases in elderly, therefore, the understanding of the genetic predisposition of hypercoagulability could make the difference in the prevention of venous and/or arterial thrombotic events. Laboratory evaluation of hyperfibrinogenemia, increased Factor VII levels, antiphospholipid antibodies presence and hyperhomocysteinemia are considered to have a consistent high predictivity for arterial thrombophilic diseases. Anyway, a large debate exists on the validity of testing Leiden Factor V (FV) G1691A and/or prothrombin (FII) G20210A polymorphisms in patients affected by arterial thrombotic diseases, despite of the several observations described. Here we report data strongly suggesting that at least the FII G20210A polymorphism might be considered an important risk factor for acute myocardial infarction in aged patients (55-80 years old). On the other hand, in spite of a not different genotypic and allelic distribution for the Leiden FV G1691A mutation, the presence of one or both the two polymorphisms is significantly higher among cases than in controls. In conclusion, our data suggest that FII G20210A and/or Leiden FV might be involved as risk factor for arterial disorders in about 5% of old subjects, justifying the opportunity of a genetic screening and an eventual preventive treatment, in particular in old subjects in which other and major risk factors, as hypertension and atherosclerosis, are detected.

Free protein S level as a risk factor for coronary heart disease and stroke in a prospective cohort study of healthy United Kingdom men

Plasma protein S (PS) levels are reportedly low in patients with venous thrombosis but high in coronary heart disease (CHD) patients. The authors examined the association between free PS concentration and CHD or stroke risk and assessed risk in combination with C-reactive protein (CRP) levels. Free PS concentration was determined in 6 annual visits among 3,052 middle-aged (49-64 years) United Kingdom men from the Second Northwick Park Heart Study, with 297 CHD events from 1989 to 2005. The highest (vs. first) quintile was associated with a significantly increased CHD risk after adjustment for all other risk factors and correction for regression dilution bias (hazard ratio = 1.85, 95% confidence interval: 1.08, 3.16; P = 0.024). Models that included all well-known risk factors plus PS quintiles improved prediction of CHD (net reclassification improvement (NRI) = 7.0% (P = 0.007), category-less NRI (>0) = 22.1% (P < 0.001)), and the likelihood ratio statistic increased significantly (P = 0.018). The increase in CHD risk was particularly strong when subjects also had high CRP levels. There was no association between free PS level and stroke risk. This study confirms the independent association of elevated free PS levels with future risk of CHD, although elevated PS levels added only modestly to prediction metrics. The novel finding of increased CHD risk, particularly when CRP and PS levels are high, requires further study.

Ischaemic stroke following tranexamic acid in young patients carrying heterozygosity of MTHFR C677T

The objective of this study is to report a new manifestation of acute stroke following antifibrinolytic agent administration in young women carrying heterozygosity for methylene-tetrahydrofolate reductase (MTHFR) C677T. The study included two young women who developed an acute ischaemic stroke following three days of tranexamic acid administration for bleeding gynaecological disorders. Case 1, a 44-year-old woman, presented left hemiplegia, mild dysarthria and anosognosia. Brain magnetic resonance imaging showed right ischaemic fronto-temporal lesion due to subocclusion of the right middle cerebral artery. Case 2, a 49-year-old woman, developed aphasia and right hemiplegia. Neuroimaging showed left capsular and periventricular infarcts due to near occlusion of the left internal carotid artery. Thrombophilia screening, coagulation parameters, homocysteine testing, 12-lead electrocardiography, and transthoracic and transoesophageal echocardiography were unremarkable. Genetic assay showed that both patients carried heterozygosity for MTHFR C677T, in which cytosine (C) is replaced by thymidine (T) at base position 677. To our knowledge, this is the first report describing the association between genetic factors and the onset of stroke following antifibrinolytic drugs intake. These data suggest a synergic effect of plasminogen activator inhibitor and heterozygosity for MTHFR C677T on the pathogenetic mechanisms leading to ischaemic stroke in young people.

Prothrombin G20210A and factor V Leiden polymorphisms in stroke

The molecular epidemiology of stroke is critically lacking in the developing world. We explored the relationships between genetics polymorphism and risk for ischemic stroke among the residents of Casablanca, Morocco. Ninety-one stroke patients matched 1:2 for their age, gender, and ethnic background to 182 healthy controls who were genotyped for the prothrombin G20210A mutation and factor V (FV) Leiden and were assessed for conventional risk factors for stroke. No significant association was found between prothrombin gene mutation with stroke (p = .054). Regarding stroke subtypes, significant relationships between patients with a large artery disease subtype of stroke and this mutation was found compared to controls (p = .046). As a genetic risk factor to develop this event, a strong association was observed when adjusted for conventional vascular risk factors (adjusted OR, 4.3; p = .029). No FV Leiden was found. We suggest that prothrombin mutation but not FV Leiden should be considered as a modest genetic risk factor for large artery disease stroke subtype in the Moroccan population.

Recurrent intra-cardiac thrombosis-A unique presentation of prothrombin G20210 mutation

We report a 49-year-old female patient with recurrent large left ventricular thrombus on echocardiogram in an apparently normal heart and insignificant cardiac past medical history. She underwent an excision of the left ventricular mass, final biopsy on which proved it to be a thrombus. Postoperative anti-coagulation was initiated with enoxaparin and warfarin and the patient was followed up at a cardiology clinic 6 weeks later. A repeat trans-thoracic echocardiogram revealed a new mass arising from the left atrium. Considering the increased risk of repeat ventriculostomy, she was treated conservatively with her current management. During this time the patient's pro-thrombotic work-up revealed positive prothrombin G20210 mutation. A follow up trans-thoracic echocardiogram done 2 months later surprisingly revealed complete resolution of the intracardiac mass. Our patient had prothrombin G20210 mutation, an entity primarily known for deep venous thrombosis, which rarely causes intra-arterial thrombus, intra-cardiac being unreported. There are no established protocols for management of these cases. The rate of embolic episodes in mobile pedunculated thrombi is reported as high as 60%. Patients with prior embolism must be offered immediate surgery, especially if the thrombus is large with an irregular surface, pedunculated, and multiple in number. Aggressive anti-coagulation with close monitoring is essential.

A review of hereditary and acquired coagulation disorders in the aetiology of ischaemic stroke

The diagnostic workup in patients with ischaemic stroke often includes testing for prothrombotic conditions. However, the clinical relevance of coagulation abnormalities in ischaemic stroke is uncertain. Therefore, we reviewed what is presently known about the association between inherited and acquired coagulation disorders and ischaemic stroke, with a special emphasis on the methodological aspects. Good-quality data in this field are scarce, and most studies fall short on epidemiological criteria for causal inference. While inherited coagulation disorders are recognised risk factors for venous thrombosis, there is no substantial evidence for an association with arterial ischaemic stroke. Possible exceptions are the prothrombin G20210A mutation in adults and protein C deficiency in children. There is proof of an association between the antiphospholipid syndrome and ischaemic stroke, but the clinical significance of isolated mildly elevated antiphospholipid antibody titres is unclear. Evidence also suggests significant associations of increased homocysteine and fibrinogen concentrations with ischaemic stroke, but whether these associations are causal is still debated. Data on other acquired coagulation abnormalities are insufficient to allow conclusions regarding causality. For most coagulation disorders, a causal relation with ischaemic stroke has not been definitely established. Hence, at present, there is no valid indication for testing all patients with ischaemic stroke for these conditions. Large prospective population-based studies allowing the evaluation of interactive and subgroup effects are required to appreciate the role of coagulation disorders in the pathophysiology of arterial ischaemic stroke and to guide the management of individual patients.

Frequency of genetic mutations associated with thromboembolism in the Western Black Sea Region

OBJECTIVE

We aimed to determine the prevalences of important genetic causes of thromboembolism for the first time in the western Black Sea Region of Turkey.

PATIENTS AND METHODS

One hundred and eighty-eight patients diagnosed early with thrombophilia were included in the study. The samples were genotyped using real-time LightCycler.

RESULTS

Of the 188 patients, 179 (95.2%) had one or more mutations. The frequencies of Factor V (FV) Leiden (FVL, G1691A), FV H1299R (A1299G), Factor II (FII G20210A), methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C were 11.7%, 5.6%, 2.5%, 30.4% and 39.1%, respectively. FV1691A was commonly represented in deep venous thrombosis (34.2%). The highest frequencies of FV1299G and FII20210A were in the vascular headache and deep venous thrombosis groups (10% and 10.5%, respectively). MTHFR677T was common in the pulmonary embolism (37%). MTHFR1298C frequency was 55.9% in recurrent abortus. Within-group comparisons yielded significant differences in the distributions of the FVL and FV H1299R mutations (p=0.002 and p=0.039, respectively).

CONCLUSION

There were significant positive associations between venous thromboembolism and FVL and FV H1299R. FVL mutation in DVT may be an important predisposing factor that needs to be tested routinely in this population.

Risk factors for ischemic stroke and transient ischemic attack in patients under age 50

To analyze risk factors for ischemic stroke and transient ischemic attack (TIA) in young adults under the age of 50. To make recommendations for additional research and practical consequences. From 97 patients with ischemic stroke or TIA under the age of 50, classical cardiovascular risk factors, coagulation disorders, history of migraine, use of oral contraceptives, cardiac abnormalities on ECG and echocardiography, and the results of duplex ultrasound were retrospectively analyzed. Literature was reviewed and compared to the results. 56.4% of the patients had hypertension, 12.1% increased total cholesterol, 20% hypertriglyceridemia, 31.5% an increased LDL-level, 32.6% a decreased HDL-level and 7.2% a disturbed glucose tolerance. Thrombophilia investigation was abnormal in 21 patients and auto-immune serology was abnormal in 15 patients. Ten of these patients were already known with a systemic disease associated with an increased risk for ischemic stroke (i.e. systemic lupus erythematosus). The ECG was abnormal in 16.7% of the cases, the echocardiography in 12.1% and duplex ultrasound of the carotid arteries was in 31.8% of the cases abnormal. Conventional cardiovascular risk factors are not only important in patients over the age of 50 with ischemic stroke or TIA, but also in this younger population under the age of 50. Thrombophilia investigation and/ or autoimmune serology should be restricted to patients without conventional cardiovascular risk factors and a history or other clinical symptoms associated with hypercoagulability and/ or autoimmune diseases.

Screening for coagulation disorders in patients with ischemic stroke

The role of coagulation disorders in the pathogenesis of (recurrent) ischemic stroke is uncertain. Therefore, the clinical utility of screening patients with ischemic stroke for these conditions and the therapeutic implications of a detected coagulation disorder in a patient who experienced ischemic stroke are uncertain. We reviewed the currently available data on the relationship between various inherited and acquired coagulation abnormalities (factor V Leiden and prothrombin G20210A mutations, deficiencies of protein C, protein S and anti-thrombin, hyperhomocysteinemia, the antiphospholipid syndrome and increased levels of fibrinogen) and ischemic stroke. Based on the existing evidence we discuss the usefulness of screening stroke patients for prothrombotic conditions and current recommendations regarding the optimal management of ischemic stroke patients in whom a coagulation disorder is found.

Testing for Inherited Thrombophilias in Arterial Stroke

Background and Purpose— Despite a paucity of evidence supporting a true association of ischemic stroke and the inherited thrombophilias, it is common practice for many neurologists to order these tests as part of the work-up of ischemic stroke, especially in young patients. Treatment with oral anticoagulation is often used in patients with positive results for the inherited thrombophilias.

Methods— We reviewed the literature focusing on case-control studies of the 5 most commonly inherited disorders of coagulation: protein C deficiency, protein S deficiency, antithrombin deficiency, and the factor V Leiden and prothrombin gene mutations in patients with stroke. We also analyzed the available data on stroke patients with inherited thrombophilia and patent foramen ovale.

Results— Multiple case-control studies have not convincingly shown an association of the inherited thrombophilias with ischemic stroke, even in young patients and patients with patent foramen ovale.

Conclusion— If there is an association between the inherited thrombophilias and arterial stroke, then it is a weak one, likely enhanced by other prothrombotic risk factors. The consequences of ordering these tests and attributing causality to an arterial event can result in significant costs to the health care system and pose a potential risk to patients, because this may lead to inappropriate use of long-term oral anticoagulants, exposing patients to harm without a clearly defined benefit.

Guidelines for the prevention of stroke in patients with stroke or transient ischemic attack: a guideline for healthcare professionals from the american heart association/american stroke association

The aim of this updated statement is to provide comprehensive and timely evidence-based recommendations on the prevention of ischemic stroke among survivors of ischemic stroke or transient ischemic attack. Evidence-based recommendations are included for the control of risk factors, interventional approaches for atherosclerotic disease, antithrombotic treatments for cardioembolism, and the use of antiplatelet agents for noncardioembolic stroke. Further recommendations are provided for the prevention of recurrent stroke in a variety of other specific circumstances, including arterial dissections; patent foramen ovale; hyperhomocysteinemia; hypercoagulable states; sickle cell disease; cerebral venous sinus thrombosis; stroke among women, particularly with regard to pregnancy and the use of postmenopausal hormones; the use of anticoagulation after cerebral hemorrhage; and special approaches to the implementation of guidelines and their use in high-risk populations.

A clinical cardiology perspective of thrombophilias

Thrombophilias, an inherited and/or acquired predisposition to vascular thrombosis beyond hemostatic needs are common in cardiovascular medicine and include systemic disorders such as coronary atherosclerosis, atrial fibrillation, exogenous obesity, metabolic syndrome, collagen vascular disease, human immunodeficiency virus, blood replacement therapy and several commonly used medications. A contemporary approach to patients with suspected thrombophilias, in addition to a very selective investigation for gain-of-function and loss-of-function gene mutations affecting thromboresistance, must consider prevalent diseases and management decisions encountered regularly by cardiologists in clinical practice. An appropriate recognition of common disease states as thrombophilias will also stimulate platforms for much needed scientific investigation.

No early signs of atherosclerotic alterations in carriers of inherited thrombophilia

BACKGROUND

Congenital thrombophilia is a risk factor for venous thromboembolism (VTE). Whether it is associated with increased risk of arterial disease is today a matter of debate. We aimed to look for early signs of atherosclerotic alterations in carriers of inherited thrombophilic alterations (ITA).

METHODS

Between January 2006 and September 2008 ultrasonography assessment of the carotid arteries with measurement of intima-media thickness (IMT), and determination of the ankle/brachial pressure index (ABI), was performed in: a) 161 carriers of ITA (deficiency of antithrombin, protein C or S, factor V Leiden or prothrombin G20210A mutations), 84 of whom with previous VTE, and b) 180 subjects without ITA, matched for age, sex and previous VTE. All subjects were <66 year old.

RESULTS

Carotid plaques were found in 8 subjects [3 (1.9%) with ITA]. Increased IMT values (>1mm) were detected in 6 subjects with and 1 without thrombophilia (p=0.055). The prevalence of IMT values>90(th) percentile was not different in subjects with/without thrombophilia (15.2% vs 11.6%, p=0.416). At multivariate analysis only age was significantly associated with increased odds ratios for IMT values>90(th) percentile. No subjects had abnormal (<0.9) ABI values.

CONCLUSIONS

The present study, the first to investigate the presence of atherosclerotic markers in relatively young subjects with inherited thrombophilia, did not find a particular prevalence of signs of early atherosclerotic markers in these subjects.

Homocysteine in vascular Behcet disease: a meta-analysis

OBJECTIVE

Behçet disease (BD) is a vasculitis of unknown etiology, characterized by oral or genital aphtosis and uveitis. Homocysteine (hcy) is an independent risk factor for venous and arterial thrombosis. The association between hyperhomocysteinemia and thrombosis has been investigated in some studies in BD patients. However, information on this association is based only on the results of small studies with conflicting results. To overcome such limitations, we performed a metaanalysis comparing the plasma levels of hcy in BD patients with and without history of thrombosis.

METHODS AND RESULTS

We searched for all published studies using the Medline and Embase databases. Two reviewers performed study selection independently. Studies were included if hcy was measured in adult BD patients with and without thrombosis. Two reviewers independently extracted data on study and population characteristics. The mean value of hcy in BD patients and the presence of hyperhomocysteinemia in patients with and without thrombosis were collected. Association between thrombosis and hyperhomocysteinemia, and the mean difference of hcy levels in BD patients with and without thrombosis were calculated. Sixteen studies, for a total of 979 patients, were included. Hyperhomocysteinemia was more prevalent in patients with thrombosis than in those without (odds ratio 3.14; 95% CI 1.26 to 7.80) Mean levels of hcy were significantly higher in patients with thrombosis in comparison with patients without (mean difference 3.30 μmol/L; 95% CI 2.09 to 4.51).

CONCLUSIONS

Our results suggest that hyperhomocysteinemia may be considered to be associated with thrombosis in BD patients.

Meta-analysis of factor V Leiden and ischemic stroke in young adults: the importance of case ascertainment

BACKGROUND AND PURPOSE

The factor V Leiden mutation is associated with ischemic stroke in children but not in adults. Whether it is associated with ischemic stroke in young adults, however, is uncertain.

METHODS

To address this issue, we performed a meta-analysis of 18 case-control studies of ischemic stroke in adults 50 years of age and younger published before June 2009.

RESULTS

Across all studies, factor V Leiden was detected in 154 of 2045 cases (7.5%) and 217 of 5307 controls (4.1%), yielding a fixed-effect odds ratio of 2.00 (95% CI, 1.59-2.51). However, further analyses revealed substantial heterogeneity among these studies (P=0.005 for Q-test of heterogeneity). Hypothesizing that this heterogeneity could be related to differences among studies in case selection criteria, we stratified the meta-analysis into studies for which case samples were enriched or not enriched to include cases having an increased likelihood of prothrombotic genetic involvement ("selected" ischemic stroke studies, n=9) and those that recruited cases from consecutive neurology referrals or hospitalizations ("unselected" ischemic stroke studies, n=8). Among the 9 "selected" ischemic stroke studies, factor V Leiden was more strongly associated with stroke (OR, 2.73; 95% CI, 1.98-3.75), whereas among the 8 "unselected" ischemic stroke studies, the association between factor V Leiden and stroke was substantially weaker (OR, 1.40; 95% CI, 0.998-1.95). This difference was found to be statistically significant (P=0.003 for Woolf test for heterogeneity).

CONCLUSIONS

We conclude that factor V Leiden is associated with ischemic stroke in young adults, particularly in patient populations in which there is an increased clinical suspicion of prothrombotic state.

Atherothrombosis in 2 Vascular Territories in a Young Woman: Importance of Thrombophilia Testing

The diagnosis and management of complex and multiple inherited thrombophilias is still a challenge for the clinicians involved in this field, clinical events being the result of the interaction between genes, environmental or other acquired factors, and age. Moreover, various clinical manifestations as regards severity or type of event (venous or arterial thrombotic event, obstetrical complications) are cited in these patients. We present the case of a 20-year-old woman, with a 2-month history of third-generation contraceptive use and with recently diagnosed hypercholesterolemia, who presented ischemic events in 2 arterial territories: acute left lower limb ischemia and silent myocardial infarction. Screening tests for thrombophilia, including genetic testing, showed moderate hyperhomocysteinemia and 2 inherited thrombophilic defects. Invasive investigation of the coronary arteries showed the presence of advanced atherosclerotic disease. Management of this complex thrombophilia includes lifetime oral anticoagulation as well as a homocysteine-lowering strategy comprising lifestyle modification and group B (folic acid, B6, B12) vitamin supplementing.

Genes influencing coagulation and the risk of aneurysmal subarachnoid hemorrhage, and subsequent complications of secondary cerebral ischemia and rebleeding

Background

We investigated whether genes influencing coagulation are associated with the occurrence of aneurysmal subarachnoid hemorrhage (SAH) and with secondary cerebral ischemia and rebleeding in patients with aneurysmal SAH.

Method

Genotyping for factor V Leiden (G1691A), prothrombin G20210A, methylenetetetrahydrofolate reductase (MTHFR) C677T, factor XIII subunit A Val34Leu, Tyr204Phe and Pro564Leu, and factor XIII subunit B His95Arg was performed in 208 patients with aneurysmal SAH and in 925 controls. Secondary cerebral ischemia occurred in 49 (24%) patients and rebleeding in 28 (14%) during their clinical course of 3 months after the aneurysmal SAH. The risk of aneurysmal SAH was assessed as odds ratio (OR) with 95% confidence interval (95% CI). The risk of secondary cerebral ischemia and rebleeding was assessed as hazard ratio (HR) with 95% CI using Cox regression.

Findings

Carriers of the subunit B His95Arg factor XIII polymorphism had an increased risk of aneurysmal SAH with 23% of the patients homozygous or heterozygous for the variant allele compared to 17% of control subjects (OR 1.5, 95% CI 1.0–2.2). For the remaining genetic variants no effect on the risk of aneurysmal SAH could be demonstrated. A clear relation with the risk of secondary cerebral ischemia and of rebleeding could not be established for any of the genetic variants.

Conclusions

We found that aneurysmal SAH patients are more often carriers of the subunit B His95Arg factor XIII polymorphism compared to controls. This suggests that carriers of the subunit B His95Arg factor XIII polymorphism have an increased risk of aneurysmal SAH. Larger studies should confirm our results. As aneurysmal SAH patients who died soon after admission could not be included in the present study, our results only apply to a population of patients who survived the initial hours after the hemorrhage. For the other studied genetic factors involved in coagulation, no association with the occurrence of aneurysmal SAH or with the occurrence of secondary cerebral ischemia or rebleeding after aneurysmal SAH could be demonstrated.

Case-control Study of methylenetetrahydrofolate reductase mutations and hyperhomocysteinemia and risk of stroke

The association of factor V-Leiden and methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C mutations with stroke was investigated in 118 patients with stroke and 120 control subjects. MTHFR 677TT (P < .001) and 1298CC (P < .001), but not factor V-Leiden (P = .179), genotypes were associated with stroke. The C677T but not A1298C MTHFR mutation was associated with elevated homocysteine levels in patients and control subjects. In addition to hypertension, the significant predictors for stroke were MTHFR 677CT and TT and A1298CC genotypes, together with hyperhomocysteinemia, indicating a synergistic effect of MTHFR mutations with elevated homocysteine and other risk factors in pathogenesis of stroke.

Factor V Leiden and the risk of venous thrombosis, myocardial infarction, and stroke: a case-control study in Venezuela

The most common genetic defect associated with deep vein thrombosis (DVT) is a mutation in the Factor V gene (G1691A), known as Factor V Leiden (FVL). We investigated the genotypes for FVL in 571 individuals in Venezuela: 208 patients with DVT, 175 patients with acute myocardial infarction, 54 patients with stroke, and 134 control subjects. Our results showed in the population analyzed here that the FVL was associated with a fourfold increase in the risk for DVT (odds ratio, 4.24; 95% confidence interval, 1.35-14.79); particularly, women carriers showed a 6.5-fold increase in the risk for DVT. No relation was observed between the presence of FVL and the risk for acute myocardial infarction or stroke. In conclusion, a clear association between the FVL mutation and DVT was observed in the population analyzed in Venezuela. These results are in agreement with those found in other populations with different ethnic backgrounds.

Gene polymorphisms and risk of adult early-onset ischemic stroke: A meta-analysis

INTRODUCTION

Genetic studies restricted to young adult ischemic stroke patients may help in excluding the potentially confounding variables encountered with advanced age; thus, allowing a more precise risk evaluation derived from the inherited mutations alone. Through meta-analysis, this study was conducted to determine the genetic risk contributed by each susceptibility gene polymorphism, particularly in adult early-onset ischemic stroke patients.

MATERIALS AND METHODS

Electronic databases were searched for all the case-control studies relating to any candidate genes for ischemic stroke. The range of age was 18-50 years for cases. Fixed or random effects model was used depending on the heterogeneity between studies.

RESULTS

Twenty-six studies were finally included in this meta-analysis; these studies focused on 7 candidate genes. A significant but modest association was identified for 2 polymorphisms, namely, methylenetetrahydrofolate reductase (MTHFR) C677T (OR = 1.44, 95% CI = 1.14-1.80) and apolipoprotein E (ApoE) epsilon2-4 (OR = 2.53, 95% CI = 1.71-3.73). Although the pooled analysis for platelet glycoprotein Ia (GPIa) C807T showed a positive association (OR = 1.50, 95% CI=1.10-2.05), the Egger's test indicated the existence of publication bias (t=5.27, P>|t|=0.034).

CONCLUSIONS

Genetic abnormalities specific to homocysteine and lipid metabolism increase the risk for ischemic stroke at an early age. These data may offer important implications for future genetic association studies for stroke.

Investigation of inter-individual variability of the one-carbon folate pathway: a bioinformatic and genetic review

Genetic polymorphisms in the one-carbon folate pathway have been widely studied in association with a number of conditions. Most of the research has focused on the 677C>T polymorphism in the coding region of the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene. However, there are a total of 25 genes in this pathway coding for enzymes, transporters and receptors, which can be investigated using 267 tagging single nucleotide polymorphisms (SNPs); using SNP database (dbSNP), 38 non-synonymous SNPs with a minor allele frequency of >5% are present in these genes. Most of these variants have not been investigated in relation to disease or drug response phenotypes. In addition, their functional consequences are largely unknown. Prediction of the functional effect using six publicly available programs (PolyPhen, SIFT BLink, PMut, SNPs3D, I-Mutant2.0 and LS-SNP) was limited to functionally well-characterized SNPs such as MTHFR c.677C>T and c.1298A>C ranking low. Epigenetic modifications may also be important with some of these genes. In summary, to date, investigation of the one-carbon folate pathway genes has been limited. Future studies should aim for a more comprehensive assessment of this pathway, while further research is also required in determining the functional effects of these genetic variants.

Hereditary thrombophilic factors in stroke due to cerebral infarct

BACKGROUND

The stroke is the third most common cause of all deaths. In new studies, the importance of hereditary thrombophilic factors on stroke is emphasized. The aim of this study is to determine the role of hereditary thrombophilic factors including factor V Leiden A1691G (FVL), prothrombin G20210A, and methylenetetrahydrofolate reductase (MTHFR) C677T gene mutations in patients with stroke because of cerebral infarct.

METHODS

Twenty-four patients with stroke and 53 controls with risk factor for stroke were enrolled. Polymerase chain reaction was used to detect these mutations.

RESULTS

Heterozygote FVL mutation in 2 (8.3%) patients and MTHFR mutation in 10 (41.7%) patients were detected. In the control group, there were 2 (3.8%) patients with heterozygote FVL mutation and 15 (28.3%) patients with MTHR mutation. Both FVL and MTHFR gene mutations were detected in 1 patient and 2 controls, respectively. Prothrombin gene mutation was not found in 2 groups. There were not statistically significant differences for all 3 mutations in-between 2 groups (P > 0.05). Odds ratios were 0.431 (0.074-2.504, 95% CI) for FVL mutation and 0.553 (0.221-1.381, 95% CI) for MTHFR mutation, respectively.

CONCLUSION

Although our study group was small, hereditary thrombophilic factors might not be risk factors for stroke because of cerebral infarct.

Prothrombotic Gene Mutations in Patients with Sudden Sensorineural Hearing Loss and Cardiovascular Thrombotic Disease

Objectives:

Impaired cochlear perfusion seems to be an important event in sudden sensorineural hearing loss. Prothrombotic gene mutations have been related to vascular disorders and sudden hearing loss. We assessed the prothrombotic risk in 10 patients with sudden sensorineural hearing loss who had previously experienced cardiovascular events to support its vascular pathogenesis.

Methods:

Ten patients underwent hematologic tests (MTHFR C677T/A1298C, prothrombin G20210A, platelet GlyIIIaA1/A2, and V Leiden G1691A genotyping; fibrinogenemia; cholesterolemia; homocysteinemia; folatemia). The results were compared with those of 100 previously investigated patients with sudden hearing loss alone and those of 200 healthy controls. DNA was isolated from peripheral blood leukocytes, and the gene mutations were investigated by polymerase chain reaction and a LightCycler DNA analyzer.

Results:

Two patients had 2 mutant alleles, 6 had 3, and 2 had 4. The mean homocysteine, cholesterol, and fibrinogen levels were above the upper limit of normal; the mean folate levels were slightly above the lower limit of normal. Multiple mutations were more frequent in the patient group than in the previously analyzed patients and healthy controls.

Conclusions:

The association between inherited and acquired prothrombotic factors in patients with sudden sensorineural hearing loss and thrombotic diseases in other sites suggests that a multifactorial mechanism may underlie microvascular cochlear impairment. Hematologic investigation, including MTHFR, prothrombin, platelet, and V Leiden genotyping, may help to detect patients at potential risk of recurrent hearing loss and multiple microvascular diseases, and could be usefully performed in otherwise idiopathic sudden sensorineural hearing loss.

Venous and arterial thrombosis: different sides of the same coin?

Until recently venous and arterial thrombosis were considered mechanistically distinct entities. However, their separate nature has been challenged by several studies showing that these conditions share a number of risk factors such as age, obesity, infections and the metabolic syndrome. The existence of an association is further supported by the finding that patients with venous thromboembolism are at higher risk of arterial events and vice versa. This review article addresses the association between venous and arterial thrombosis and its clinical and therapeutic implications. We conclude that arterial and venous thrombosis are mechanistically different, but that common risk factors are more relevant and frequent than previously thought.

[Thrombophilias and peripheral arterial occlusive disease]

Peripheral arterial occlusive disease is a frequent disease due to the classical vascular risk factors such as smoking, diabetes mellitus, dyslipidemia, and hypertension. Despite these risk factors, many thrombophilias (physiological inhibitors defects, Factor V Leiden and 20210A prothrombin gene variant, antiphospholipid antibodies, mild hyperhomocysteinemia 15-30micromol/l) can be evoked in some clinical forms of peripheral arterial occlusive disease. This paper provides a synthesis of the published data about this topic. Screening for these thrombophilias is justified in patients with venous thromboembolic disease, or signs of antiphospholipid syndrome and possibly in different situations such as premature atheroma of lower limbs, chronic ischaemia, evolutive disease despite adapted treatment and revascularisation failures without evident technical explanation. Except for the antiphospholipid syndrome, there is currently no consensus for systematic screening of thrombophilia and treatment in patients with peripheral arterial occlusive disease.

Are patients with thrombophilia and previous venous thromboembolism at higher risk to arterial thrombosis?

INTRODUCTION

Whether thrombophilic disorders, which are established risk factors for venous thromboembolism (VTE), also increase the risk of arterial thrombosis is still unknown.

MATERIALS AND METHODS

We analyzed data from 1081 consecutive patients (649 F/432 M, 16-93 years of age) with previous VTE registered in the MAISTHRO (MAin-ISar-THROmbosis) database with regard to arterial thrombotic events and contributing risk factors. Screening for thrombophilia included testing for factor V Leiden and prothrombin G20210A mutation, antiphospholipid antibodies and activities of factor VIII, protein C, protein S and antithrombin.

RESULTS

Of the entire study cohort, 40 patients (3.7%) had a prior myocardial infarction (MI), and 41 (3.8%) suffered a stroke. Other arterial thrombotic events were rare. Elevated factor VIII levels were more prevalent in MI patients than in controls (44.4 vs. 25.9%, p=0.044), but after adjusting for the traditional cardiovascular risk factors, this relationship was no longer significant. We observed a higher rate of lupus anticoagulant in MI patients with an adjusted odds ratio of 3.3 (95%CI 0.84-12.8, p=0.090). No difference in any other tested thrombophilia was observed in patients with MI or stroke relative to those without.

CONCLUSION

The cumulative incidence of arterial thrombotic events in VTE patients is low, and the inherited thrombophilias do not seem to substantially increase the risk of arterial thrombosis.