No association of APC resistance with myocardial infarction

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.

Factor VLeiden and prothrombin G20210A gene polymorphisms in patients with coronary artery disease

PURPOSE

The precise molecular mechanisms culminating in coronary artery disease (CAD) are not well understood, despite a wealth of knowledge on predisposing risk factors and pathomechanisms. CAD and myocardial infarction (MI) are complex genetic diseases; neither the environment alone, nor a single gene, cause disease, rather, a mix of environmental and genetic factors lead to atherosclerosis of the coronary arteries.

MATERIALS AND METHODS

In the present study, our aim was to investigate the roles of prothrombin G20210A mutation and Factor VLeiden mutation in atherosclerotic coronary artery disease. 287 subjects (106 control subjects, who were angiographically normal, and 181 angiographically documented coronary atherosclerotic patients who exhibited coronary artery narrowing to a degree of >or=50%) were included in this study. The mutations were assessed with LightCycler Real-Time PCR mutation detection kits (Roche Diagnostics, GmbH, Germany).

RESULTS

6.6% of control subjects, and 6.1% of patients with (50% coronary artery narrowing were determined to have the Factor VLeiden heterozygote mutation. 6.6% of control subjects had the Prothrombin G20210A heterozygote mutation, while 7.7% of patients with (50% coronary artery narrowing had this mutation. The OR for Factor VLeiden was 1.52 (CI: 0.240-9.602) and for Prothrombin G20210A mutation, the OR was 1.415 (CI: 0.287-6.962).

CONCLUSION

Although both the heterozygote Factor VLeiden and Prothrombin gene mutations were more frequent in patients with CAD than in control subjects, there was no statistical relationship found to exist between coronary artery disease and the Factor VLeiden and Prothrombin G20210A mutations.

Prevalence of resistance against activated protein C resulting from factor V Leiden is significantly increased in myocardial infarction: investigation of 507 patients with myocardial infarction

BACKGROUND

A point mutation in the gene encoding coagulation factor V is a cause of resistance against activated protein C. The presence of factor V Leiden is linked to 50% of congenital defects causing venous thrombosis. Its relationship to arterial thrombosis, particularly to myocardial infarction, has not been defined. Therefore, we performed a study on the role of factor V Leiden in patients with myocardial infarction. The study was carried out in Bavarians of German origin, a relatively homogeneous population.

METHODS AND RESULTS

The study group consisted of 507 patients with documented myocardial infarction (77.5% (393/507) men, 22.5% (114/507) women), with a mean age of 56.1 (range 18-86) years. Strict criteria for patient selection and highly sensitive and specific functional tests for factor V Leiden were used. In addition, all patients with pathological test results were genotyped. The prevalence of factor V Leiden in patients with myocardial infarction was 8.7% (44/507), a significant increase in the prevalence of this mutation compared with the control group (3.7%, P =.0025). The odds ratio was 2.46 (95% CI 1.35-4.50).

CONCLUSIONS

A significantly increased prevalence of factor V Leiden in patients with documented myocardial infarction was seen. Patients with this mutation appear to have a predisposition for myocardial infarction.

The influence of direct and antithrombin-dependent thrombin inhibitors on the procoagulant and anticoagulant effects of thrombin

INTRODUCTION

Clinical trials evaluating direct thrombin inhibitors in unstable coronary artery disease (CAD) have been disappointing. The hypothesis tested in the present study was that these agents may inhibit the anticoagulant effect of thrombin to a further extent than the procoagulant effect of thrombin.

MATERIALS AND METHODS

We studied both reversible and irreversible thrombin inhibitors and compared the effects of each inhibitor on activated protein C (APC) generation vs. the effect on fibrinopeptide A (FPA) generation. A mixture of protein C, thrombin inhibitor, fibrinogen, fibrin polymerisation blocker and thrombin was incubated with thrombomodulin (TM)-expressing human saphenous vein endothelial cells (HSVECs). The inhibitors investigated were melagatran, inogatran, hirudin, hirugen, D-Phe-D-Pro-D-arginyl chloromethyl ketone (PPACK), and antithrombin (AT) alone or in combination with unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH).

RESULTS

All agents, except hirugen, inhibited APC and FPA generation in a dose-dependent manner. FPA inhibition/APC inhibition ratios, based on IC50 for inogatran, melagatran, hirudin, PPACK, AT, AT-UFH and AT-LMWH were 1.73, 0.85, 0.55, 2.1, 0.5, 0.65 and 3.1 respectively.

CONCLUSIONS

All agents, except hirugen, inhibited APC and FPA generation approximately to a similar extent. Thus, it can be inferred that the poor efficacy of thrombin inhibitors in recent clinical trials in patients with unstable CAD is unlikely to be a consequence of their effects on the protein C system.

Inhibition of endothelial cell-mediated generation of activated protein C by direct and antithrombin-dependent thrombin inhibitors

The present study investigated the effect of the thrombin inhibitors antithrombin (AT) (with and without unfractionated heparin or low molecular weight heparin), hirudin, inogatran and melagatran on thrombin-thrombomodulin-mediated generation of activated protein C (APC), in solution and on endothelial cells. Sequential incubation with thrombin, thrombin inhibitors and protein C was followed by measurement of APC by an amidolytic assay. The approximate concentrations resulting in 50% inhibition of endothelial cell-mediated APC generation for AT, AT-unfractionated heparin, AT-low molecular weight heparin, hirudin, melagatran and inogatran were 200, 4, 9, 1, 8 and 60 nmol/l, respectively. The normal plasma level of AT is 2800 nmol/l and relevant therapeutic concentrations from clinical trials are 200 nmol/l for hirudin, 500 nmol/l for melagatran and 1000 nmol/l for inogatran. The present study indicates that clinically relevant concentrations of the tested thrombin inhibitors interfere with endothelial-mediated APC generation, which may offer an explanation for the lack of a dose-response effect in clinical trials with thrombin inhibitors.

Clinical utility of factor V leiden (R506Q) testing for the diagnosis and management of thromboembolic disorders

OBJECTIVE

To review the current state of the art regarding the role of the clinical laboratory in diagnostic testing for the factor V Leiden (FVL) thrombophilic mutation (and other protein C resistance disorders), and to generate, through literature reviews and opinions of recognized thought-leaders, expert consensus recommendations on methodology and diagnostic, prognostic, and management issues pertaining to clinical FVL testing.

DATA SOURCES, EXTRACTION, AND SYNTHESIS

An initial thorough review of the medical literature and of current best clinical practices by a panel of 4 experts followed by a consensus conference review, editing, and ultimate approval by the majority of a panel of 28 additional coagulation laboratory experts.

CONCLUSIONS

Consensus recommendations were generated for topics of direct clinical relevance, including (1) defining those patients (and family members) who should (and should not) be tested for FVL; (2) defining the preferred FVL laboratory testing methods; and (3) defining the therapeutic, prophylactic, and management ramifications of FVL testing in affected individuals and their family members. As FVL is currently the most common recognized familial thrombophilia, it is hoped that these recommendations will assist laboratorians and clinicians caring for patients (and families) with this common mutation.

Prospective cross-sectional study of haemostatic factors in patients with and without coronary artery disease

The role of haemostatic factors for arterial thrombosis, especially the prevalence of activated protein C (APC) resistance in patients with coronary artery disease (CAD), is controversial. Between November 1996 and August 1997, 665 patients were analyzed. Diagnosis of CAD was confirmed by coronary angiography, exclusion of CAD was accepted in the presence of negative stress testing or a negative coronary angiography. CAD was present in 370 (56%) and excluded in 295 (44%) patients. Patients with CAD were older (64 +/- 9.2 versus 57.7 +/- 16 years; P <or= 0.001), more often male [74.1 versus 48.5%; odds ratio (OR) = 3.0, 95% confidence interval (CI) = 2.2-4.2] and had a higher body mass index (27.2 +/- 3.6 versus 26 +/- 4.3; P <or= 0.001). Most conventional risk factors showed a higher prevalence in patients with CAD. An APC ratio < 2.0 showed a tendency towards a higher prevalence in patients with CAD (10.5 versus 6.4%; OR = 1.7, 95% CI = 1.0-3.0). This difference was significant in men (11.7 versus 4.2%; OR = 3.0, 95% CI = 1.3-7.1), but not in women (7.3 versus 8.6%; OR = 0.8, 95% CI = 0.3-2.2). Multiple logistic regression analysis showed an independent association of the presence of CAD with age, male gender, current smoking, arterial hypertension, lipoprotein(a) levels and an APC ratio < 2.0 (OR = 2.87, 95% CI = 1.08-8.12). APC resistance with an APC ratio < 2.0 was the only haemostatic factor that was independently associated with the presence of CAD. This association was significant only for men. It may indicate a contribution of the APC resistance to the development of CAD, which has to be proven by the follow-up.

Interaction of hemostatic genetics with hormone therapy: new insights to explain arterial thrombosis in postmenopausal women

Genetic variants of key hemostatic mediators increasingly have been proposed as risk factors for atherothrombosis. The Hormone and Estrogen/Progestin Replacement Study group recently reported that the initiation of estrogen replacement in postmenopausal women with known coronary heart disease is associated with an early increase in cardiovascular events. A putative genetic susceptibility factor has been proposed a potential mediator of this increased event risk. This review outlines the recent literature to support the premise for this important proposal. Genetic profiling has great potential to improve the safety and efficacy of individualized pharmacotherapy in postmenopausal women and other at-risk populations for the prevention of cardiovascular disease.

Genetic thrombophilia in patients with retinal vascular occlusion

BACKGROUND

This study was carried out to determine the prevalence of genetic thrombophilia in patients with retinal vascular occlusion.

METHODS

We investigated 116 consecutive patients with central retinal vein occlusion (CRVO, n = 48), branch retinal vein occlusion (BRVO, n = 33), central retinal artery occlusion (CRAO, n = 21), branch retinal artery occlusion (BRAO, n = 14). All patients underwent comprehensive tests for coagulation disorders including determinations of protein C, protein S, lupus anticoagulants, prothrombin gene mutation (G20210A), resistance to activated protein C (APCR), and were screened for vascular disease risk factors. APC resistance was confirmed by a PCR method to detect the factor V R506Q mutation. A PCR method was also used to detect the G20210A mutation. For comparative purposes, we screened 209 consecutive patients with deep vein thrombosis (DVT) and 581 patients with coronary heart disease (control group) for APC resistance.

RESULTS

13 (27%) of 48 patients with CRVO had the factor V R506Q mutation. The factor V R506Q mutation was detected in six (18%) of 33 patients with BRVO, but in only one patient with CRAO and in two patients with BRAO. Other thrombophilic defects were not detected. The APCR prevalence within the CRVO group was significantly increased when compared to the control group (8%). There was no significant difference in the factor V R506Q mutation prevalence between the CRVO group and the DVT group (19%).

CONCLUSION

The factor V R506Q mutation is the most common cause of genetic thrombophilia in patients with CRVO and has a similar prevalence as in DVT patients.

Thrombin inhibitors suppress the thrombin-thrombomodulin-mediated generation of activated protein C

In the treatment of unstable coronary artery disease, direct thrombin inhibitors have shown no or only limited benefit as compared with heparin, despite theoretical advantages. One explanation may be that the direct thrombin inhibitors to a greater extent than heparin have an inhibiting effect on the generation and activity of activated protein C. In the present study, this hypothesis was tested in an in vitro, "purified" system, where human protein C underwent activation to activated protein C by the thrombin-thrombomodulin complex. Direct thrombin inhibitors, inogatran and hirudin, unfractionated heparin+antithrombin, or dalteparin+antithrombin, were added to the system before activation to evaluate their inhibitory effect on the generation of activated protein C. At inhibitor concentrations well below the achieved plasma levels in major clinical trials, the thrombin-thrombomodulin-mediated activation of protein C was inhibited by all the studied inhibitors in a dose-dependent manner, but, contrary to our hypothesis, to a greater extent by unfractionated heparin+antithrombin and dalteparin+antithrombin than by the direct thrombin inhibitors, hirudin and inogatran. Despite difficulties to draw conclusions for the in vivo situation, the in vitro inhibition, by all studied inhibitors, of the generation of activated protein C, found in this study may be a possible explanation for ongoing cardiovascular events despite adequate treatment with thrombin inhibitors, in patients with unstable coronary artery disease. This inhibition of the generation of activated protein C may also contribute to the rebound in cardiovascular events after withdrawal of effective antithrombotic treatment.

Coagulation factors II, V, VII, and X, prothrombin gene 20210G-->A transition, and factor V Leiden in coronary artery disease: high factor V clotting activity is an independent risk factor for myocardial infarction

Increased levels of hemostatic factors and genetic mutations of proteins involved in coagulation may play a role in the pathogenesis of coronary artery disease. We investigated clotting activity of factors II (FII:C), V (FV:C), VII (FVII:C), and X (FX:C), the prothrombin gene 20210G-->A transition, and the factor V Leiden mutation in 200 survivors of myocardial infarction and in 100 healthy controls. FV:C (P<0.0001) and FVII:C (P<0.0001) were found to be independent risk factors for myocardial infarction. High FV:C or high FVII:C combined with smoking or arterial hypertension increased the relative risk for myocardial infarction up to 50-fold. One of 177 patients (0.6%) and 4 of 89 controls (4.5%) had the prothrombin 20210 AG genotype. Eleven of 177 patients (6.2%) and 6 of 89 controls (6.7%) were heterozygous for the factor V Leiden mutation. No homozygous carrier for these mutations was found. Neither the prothrombin gene 20210G-->A transition (odds ratio [OR], 0.1; 95% confidence interval [CI], 0.01 to 1.1) nor the factor V Leiden mutation (OR, 1.0; 95% CI, 0.4 to 2.8) were associated with an increased relative risk for myocardial infarction. In conclusion, our data indicate that neither the prothrombin gene 20210G-->A transition nor the factor V Leiden mutation are risk factors for myocardial infarction. High FVII:C was confirmed to be an independent risk factor for myocardial infarction. Moreover, we describe for the first time that high FV:C is an independent risk factor for myocardial infarction.

Detection of a common mutation in factor V gene responsible for resistance to activate protein C causing predisposition to thrombosis

Hereditary predisposition to thrombosis due to activated protein C resistance (APCR) has been attributed to a missense mutation in the factor V gene at nucleotide 1691 (G to A), causing replacement of arginine at codon 506 with glutamine. Using an RFLP-PCR assay to detect this mutation, we measured a prevalence of 3.3% in healthy Caucasians and 1.25% in healthy African-Americans. In addition, we evaluated a total of 90 consecutive specimens submitted to the coagulation laboratory at the Medical College of Virginia for the presence of this mutation. We compared our results for 78 of these specimens with the values measured by a modified partial thromboplastin assay, the COATEST. Twelve of the 90 samples could not be tested using the COATEST because the patients were undergoing anticoagulant therapy. One of the latter 12 specimens was positive by the RFLP-PCR test. Using the genetic test as the definitive assay and the cutoff value established for distinguishing between normal and abnormal results by the COATEST, the COATEST had a sensitivity of 50% and specificity of 93% for the detection of factor V mutation. Analysis of the 90 samples stratified by ethnic groups revealed a frequency of mutation of 13.3% for Caucasians and 6.88% for African-Americans, although with the present sample size, the difference was not statistically significant. Although the COATEST is technically simpler to perform than the genetic test for diagnosing the presence of the factor V mutation, its use for this purpose is limited due to low sensitivity. Thus where this disorder is clinically suspected, submission of the specimen directly for genetic testing by RFLP-PCR or equivalent assay should be considered.

Role of factor V Leiden mutation in patients with angiographically demonstrated coronary artery disease

The study sought to determine whether coagulation factor V Leiden (FV Leiden) plays a role in the pathogenesis of coronary artery disease and/or myocardial infarction. Association of FV Leiden with venous thromboembolism is well established in the literature, but the role of the mutation in arterial thrombotic events is controversial. Some studies have documented an association between the mutation and myocardial infarction and stroke in juveniles. Few studies have explored its possible contribution to coronary atherosclerosis. We screened FV genotype in 850 predominantly white coronary angiography patients. Coronary artery disease risk factors and history of myocardial infarction were then analyzed by genotype. The FV Leiden mutation occurred in 54 (6.4%) patients. There was one homozygote; a 37-year-old, white male smoker with a history of myocardial infarction. Gene frequencies for white males and females were similar: 0.965 for the normal allele and 0.035 for FV Leiden. Gene frequencies for both genders were in Hardy-Weinberg equilibrium. FV Leiden was not a useful predictor (p=0.23) of the presence of clinically defined atherosclerosis (> or = 50% stenosis) in a logistic regression model adjusting for age, lipoprotein (a), total cholesterol, triglycerides, high density lipoprotein cholesterol, and fibrinogen. In addition, there was no difference in frequency of FV Leiden among those with and without medical histories of myocardial infarction (p=0.51). Allelic frequencies of FV Leiden in this patient group do not differ significantly from those reported for white populations. The FV Leiden mutation in its heterozygous state is not independently associated with coronary artery disease or myocardial infarction.

Dural puncture and activated protein C resistance: risk factors for cerebral venous sinus thrombosis

OBJECTIVES

Dural puncture is regarded a safe procedure when contraindications are carefully excluded and has so far not been recognised as a risk factor for cerebral venous sinus thrombosis (CVST). Five patients are described with CVST after dural puncture in the presence of additional risk factors.

METHODS

In four out of five patients complete investigations for thrombophilia were performed at least one month after withdrawal of oral anticoagulation.

RESULTS

In three out of four patients tested, activated protein C (APC) resistance due to heterozygous coagulation factor V R506Q mutation (factor V Leiden) was found. One patient was using oral contraceptives as a circumstantial risk factor and three had had spinal anaesthesia for surgical procedures. Family history of venous thromboembolism was negative in all patients. Retrospective evaluation of 66 patients with CVST disclosed that dural puncture was the fourth most common risk factor (8%) possibly contributing to thrombosis.

CONCLUSION

Dural puncture may constitute an additional risk factor for CVST especially in patients with APC resistance or surgery. In such patients a thrombophilia screen is indicated.

Activated protein C resistance, factor V Leiden and peripheral vascular disease

Activated protein C resistance caused by factor V Leiden is an important thrombophilia disorder which predisposes to venous thromboembolism. Some studies also suggest a role in the pathogenesis of arterial thrombosis and atherosclerosis. The authors have investigated the prevalence of activated protein C resistance and factor V Leiden in a series of 45 patients with peripheral vascular disease. Twelve patients were receiving warfarin. The activated protein C resistance ratios were significantly lower in the group of 33 non-warfarinized patients with peripheral vascular disease (median 2.82 (range 1.36-3.83)) compared with 33 age- and sex-matched controls (median 2.97 range 2.24-4.11); P<0.005; Wilcoxon rank sum). Eight patients (24%) had activated protein C resistance (ratio <2.2). The prevalence of factor V Leiden in patients with peripheral vascular disease was 17.8% (8/45). This is significantly increased compared with the local population and UK published frequency of 3.5% for this genotype. The presence of factor V Leiden did not affect the late outcome of arterial reconstructive surgery in terms of graft patency (P=0.5, Fisher's Exact test).

Activated protein C resistance due to a common factor V gene mutation is a major risk factor for venous thrombosis

Inherited resistance to activated protein C (APC) was recently discovered to be a cause of familial thrombophilia and is now known to be the most common genetic risk factor for venous thrombosis. It is caused by a single point mutation in the gene for factor V, which predicts substitution or arginine (R) at position 506 with a glutamine (Q). Accordingly, the activated form of mutated factor V (FVa:Q506) is more slowly degraded by activated protein C than normal FVa (FVa:R506) is, resulting in hypercoagulability and a lifelong 5- to 10-fold increased risk of venous thrombosis. Previously known inherited hypercoagulable states, i.e. deficiencies of the anticoagulant proteins antithrombin III, protein S, and protein C, are found fewer than 10-15% of thrombosis patients in western countries, whereas inherited APC resistance is present in 20-60% of such patients. The FV mutation is common in populations of Caucasian origin, with prevalences ranging from 1-15%, whereas it is not found in certain other ethnic groups such as Japanese and Chinese. The high prevalence of APC resistance, in combination with the availability of simple laboratory tests, will have a profound influence on the development of therapeutic and prophylactic regimens for thrombosis and will, it is hoped, result in a decreased incidence of thromboembolic events.

Familial thrombophilia: clinical and molecular analysis of Swedish families with inherited resistance to activated protein C or protein S deficiency

This report describes the characterization of Swedish families with inherited resistance to activated protein C (APC resistance) and/or protein S deficiency, two genetic disorders associated with functional impairment of the protein C anticoagulant pathway. The APC resistance phenotype was linked to the factor V gene locus in a kindred with independent inheritance of APC resistance and protein S deficiency. A point mutation changing Arg506 to a Gln (FV:Q506) in the factor V gene was the cause of APC resistance. In studies of 50 families with hereditary APC resistance, the FV:Q506 mutation was identified in 94% (47/50) of the families, and the thrombotic risk was found to be dependent on the factor V genotype. Moreover, 18 families with hereditary deficiency of free protein S were investigated. Type I protein S deficiency (low free and total protein S) and type III deficiency (low free but normal total protein S) coexisted in 78% (14/18) of the families, suggesting the two types to be phenotypic variants of the same genetic disorder. Deficiency of free protein S was caused by equimolar relationship between protein S and beta-chain containing isoforms of C4BP. Though protein S deficiency was a strong risk factor for thrombosis, the FV:Q506 mutation was identified as an additional genetic risk factor in 39% of the families. Thus, familial thrombophilia is a multiple gene disorder. The thrombophilic tendency associated with APC resistance or protein S deficiency was related to increased levels of prothrombin fragment 1 + 2, reflecting increased activation of the common coagulation pathway.