Resistance to activated protein C as a basis for venous thrombosis

The incidence of venous thromboembolism among Factor V Leiden carriers: a community-based cohort study

While Factor V (FV) Leiden is a risk factor for venous thromboembolism (VTE), the incidence of VTE among FV Leiden carriers is uncertain. The objective of the study was to estimate the overall age-specific and pregnancy-related VTE incidence and the relative risk among FV Leiden carriers. In a community-based sample of 3424 south-eastern Minnesota residents, 230 (6.7%) were genotyped as FV Leiden carriers; 220 carriers (mean age = 68 years) could be matched to a non-carrier on age, gender, ethnicity and length of medical history. We performed a retrospective cohort study of carriers and non-carriers by reviewing the complete medical records in the community for demographic and baseline characteristics, pregnancies and live births, and first lifetime VTE. Over 14 722 person-years, 24 (10.9%) carriers developed VTE [overall incidence = 163 (95% CI 104, 242) per 100,000 person-years]. VTE incidence rates for ages 15-29, 30-44, 45-59 and > or = 60 years were 0, 61, 244 and 764 per 100,000 person-years, respectively (cumulative VTE incidence at age 65 years = 6.3%). VTE incidence for carriers did not differ significantly from that for non-carriers except for those > or = 60 years old (relative risk = 3.6; 95% CI 2.0, 6.0). There were 311 live births among 130 women carriers; no VTE events occurred during pregnancy or postpartum [incidence = 0 (95% CI 0, 1186) per 100,000 women-years]. Most FV Leiden carriers do not develop VTE. Among all carriers, those > or = 60 years old are at the highest risk for VTE. The incidence of VTE among asymptomatic women carriers during pregnancy is low and insufficient to warrant prophylaxis.

Factor V Leiden and the prothrombin 20210A gene mutation and osteonecrosis of the knee

INTRODUCTION

The pathogenesis behind osteonecrosis of the knee is still unknown. Circulatory impairment of the bone secondary to thrombosis in the microcirculation has been suggested as a mechanism. The purpose of this study was to examine the association between osteonecrosis of the knee and abnormalities in the thrombotic pathway in the form of factor V Leiden and the prothrombin 20210A gene mutation.

MATERIALS AND METHODS

Thirty-eight consecutive patients (13 men and 25 women) with osteonecrosis of the knee without a history of knee trauma or surgery to the knee were enrolled in this study. Assays for the detection of factor V Leiden and the prothrombin 20210A gene mutation were performed, and the results were compared with those from 282 healthy volunteers.

RESULTS

Six patients were diagnosed with secondary osteonecrosis, four corticosteroid-induced and two alcohol-induced. In 32 patients, no aetiological factor was found, and these patients were diagnosed with primary osteonecrosis of the knee. Twelve patients had 14 gene mutations, 11 factor V Leiden and 3 prothrombin 20210A gene mutations. Factor V Leiden and the prothrombin 20210A gene mutation occurred significantly (p=0.006) more frequently in patients with osteonecrosis than in a population of 282 healthy volunteers (odds ratio 3.1, 95%CI 1.4-6.6).

CONCLUSION

The results of this study suggest that coagulation abnormalities in the form of factor V Leiden and the prothrombin 20210A gene mutation might play a role in osteonecrosis of the knee.

Genetic thrombophilia

The genetic thrombophilias are an important cause of venous thrombotic events. Much has been learned about the natural history of these disorders, their genetics, and, to a lesser degree, their treatment. This article provides an overview of the genetics of thrombophilia. Specific information on the factor V Leiden mutation;the prothrombin G20210A mutation; and protein C, proteinS, and antithrombin deficiency is reviewed. Current testing and treatment options for the genetic thrombophilias also are discussed.

Nonhealing ulcer secondary to factor V Leiden mutation and cryofibrinogenemia

Factor V Leiden is the most common genetic thrombophilia in people of European descent, and is important to recognize as it can have significant implications in dermatology. We report a case of a 30-year-old man who presented for evaluation and treatment of a chronic ulceration on the site of his stump following a below the knee amputation which had been performed for non-healing ulcerations. Despite a variety of treatments, his ulcer persisted. He was referred to a dermatologist who performed a biopsy that was interpreted ass non-specific, and treatment was started for pyoderma gangrenosum. Further investigation revealed a homozygous factor V Leiden mutation and cryofibrinogenemia. He was tapered off of the methylprednisolone and was improving on stanozolol. He healed well after surgery and no new ulcerations have developed. This case highlights the importance of considering this mutation in a non-healing leg ulcer.

Haemophilia and thrombophilia: an unexpected association!

In patients with haemophilia, a close correlation is usually observed between the clinical expression of the disease and plasmatic factor VIII/factor IX clotting activity. However, some patients experience milder bleeding phenotypes than others, although they exhibit a similar biological profile. The high prevalence of some inherited thrombophilia risk factors offers the possibility of a co-inheritance in haemophilic patients which could influence the phenotypic expression of the disease. Rare thrombotic complications occurring in haemophiliacs could also be facilitated by the co-inheritance of modifier genes. The majority of thrombotic events occurring in haemophiliacs are in relation to clotting factor infusions or central venous catheters. Concerning surgical situations, in the absence of therapeutic recommendations, postoperative thromboprophylaxis is not systematically performed in haemophiliacs. However, substitutive treatment more or less completely corrects the coagulation defect and makes the venous thrombosis risk closer to the control population. It should be emphasized that haemophilia does not fully protect against venous thromboembolic disease. Patients with haemophilia very infrequently experience thrombotic events. Thus, the management of thrombotic complications occurring in haemophilic patients should be discussed in each case according to the precipitating risk factors, the clinical context and the thrombo-haemorrhagic balance of the patient with respect to a particular clinical situation.

Mesenteric vein thrombosis in a pregnant patient heterozygous for the factor V (1691 G --> A) Leiden mutation

Factor V Leiden mutation is a risk factor for the development of thromboembolic events in pregnancy. Thrombosis of the mesenteric vein is a fairly infrequent condition complicating pregnancy. In this paper, we described a pregnant patient with mesenteric vein thrombosis who was heterozygous for the factor V Leiden mutation.

A negative personal and family history for venous thrombotic events is not sufficient to exclude thrombophilia in patients with cerebral venous thrombosis

A hereditary thrombophilia is found in 20-30% of patients with cerebral venous thrombosis (CVT). These patients might have an increased rate of a positive personal or family history of venous thrombotic events. We investigated the diagnostic value of a structured personal and family history for venous thrombotic events in 56 consecutive cases of CVT. Fourteen of 56 patients (25%) had a hereditary thrombophilia, mostly factor V Leiden. Patients with both CVT and hereditary thrombophilia had more frequently a positive family and personal history than patients affected by CVT only but the difference was not strong enough to differ from the 42 CVT patients without thrombophilia (43% vs. 31%; P = 0.52 and 14% vs. 10 %; P = 0.63). We conclude that a negative personal and family history of venous thrombotic events is not sufficient to exclude thrombophilia and patients with CVT should be tested for inherited thrombophilia regardless of the patient's past personal and family history for venous thrombotic events.

Factor V Leiden and perioperative risk

Factor V Leiden (FVL) is the most common known inherited cause of thrombophilia; it is present in approximately 5% of the Caucasian population. Although the risk of venous thrombosis associated with this polymorphism in various medical settings is well described, its effect on perioperative risk is only beginning to be explored. Specifically, there are few studies addressing the potential risks of FVL in the surgical population, in which both hemorrhagic and thrombotic complications convey substantial clinical and economic significance. There are speculations and unproven hypotheses regarding FVL in this population, and these therefore highlight the need to comprehensively address this issue. This review will describe the physiology of the FVL mutation, briefly clarify its risk in the nonsurgical setting, and assess current data regarding FVL in noncardiac and cardiac surgery. Finally, a summary of current clinical evidence and a plan for more detailed investigation of this potentially significant risk factor will be proposed.

Coagulation abnormalities in patients with hip osteonecrosis

The relatively high frequency of coagulation abnormalities in patients with hip osteonecrosis might represent increased risk factors for the development of bone necrosis by predisposing these patients to thromboembolic phenomena. The recognition of this association may increase as more patients with osteonecrotic lesions are tested for haemostatic abnormalities. Early diagnosis of hypercoagulability in the group of patients at risk may allow pharmacologic intervention that may prevent this devastating process from developing.

Genetic linkage and association studies in bipolar affective disorder: a time for optimism

Genetic research on complex diseases is beginning to bear fruit, with the successful identification of candidate susceptibility genes in diabetes, asthma, and other illnesses. Similar success is on the horizon for bipolar affective disorder (BPAD), but significant challenges remain. In this review, we outline the basic concepts of linkage and association mapping for complex phenotypes. We point out important caveats inherent in both approaches, and review guidelines on the interpretation of linkage statistics and significance thresholds. We then apply these concepts to an evaluation of the present status of genetic linkage and association studies in BPAD. The challenges posed by locus heterogeneity, phenotype definition, and sample size requirements are given a detailed treatment. Despite these challenges, we argue that the way ahead remains firmly rooted in linkage studies, complemented by association studies in linked regions. This is the only truly genome-wide approach currently available; it has succeeded in other complex phenotypes, and it is the surest strategy for mapping susceptibility genes in BPAD. Once these genes are identified, genetic mapping methods will yield to the other methods of 21st-century molecular biology as we begin to elucidate the pathophysiology of BPAD.

Factor V Leiden and prothrombin gene G20210A mutations in Italian patients with Behçet's disease and deep vein thrombosis

OBJECTIVE

To evaluate the frequency and type of vascular lesions and to study the association of factor V gene G1691A (Leiden) and prothrombin gene G20210A polymorphisms with venous thrombosis in Italian patients with Behçet's disease (BD).

METHODS

Included were 118 consecutive Italian BD patients followed over a 3-year period (1997-1999) who satisfied the International Study Group criteria for BD. The control group consisted of 132 healthy Italian blood donors. All BD patients and controls were genotyped by polymerase chain reaction and allele-specific restriction enzyme techniques for factor V Leiden and prothrombin gene G20210A polymorphisms.

RESULTS

Vascular lesions were observed in 37 (31.4%) patients. The 2 most common lesions were subcutaneous thrombophlebitis (10.2%) and deep vein thrombosis (DVT) of the legs (22.8%). No significant demographic and clinical differences between patients with and without DVT were present. The distribution of allele and genotype frequencies of prothrombin gene G20210A and factor V Leiden polymorphisms did not differ significantly between BD patients and healthy controls. The frequencies of carriage rates of prothrombin gene G20210A and factor V Leiden polymorphisms in BD patients with and without DVT were similar. However, the frequency of 20210A allele was significantly higher in BD patients with ocular disease than in those without, particularly in the patients with posterior uveitis/retinal vasculitis.

CONCLUSIONS

The frequency and types of vascular lesions in Italian BD patients were similar to those reported in studies from other countries. No association between factor V Leiden mutation and G20210A mutation in the 3'-untranslated region of the prothrombin gene with DVT was found. However, a prothrombin gene G20210A mutation may influence the development and severity of ocular involvement in BD.

Risk factors for pulmonary emboli after total hip or knee arthroplasty

Because it is difficult to predict which patients may sustain a pulmonary embolism after total hip or knee arthroplasty, we assessed multiple thrombophilic and hypofibrinolytic parameters to identify risk factors. Twenty-nine patients who survived a known pulmonary embolism after total knee or total hip arthroplasty were matched by age, gender, race, arthritic diagnosis, procedure, and surgery date with 29 patient-controls who had a total hip or knee arthroplasty but who did not have a symptomatic known pulmonary embolism or deep vein thrombosis. Twenty-one serologic measures and five genes associated with thrombophilia, hypofibrinolysis, or both were assessed without knowledge of group assignment. All patients with pulmonary embolism had at least one abnormality of plasminogen activator inhibitor activity, dilute Russell's viper venom time, prothrombin time, or total cholesterol versus 13 of 27 (48%) control patients. Forty-seven percent of patients who experienced pulmonary embolism had at least two abnormalities of plasminogen activator inhibitor activity, dilute Russell's viper venom time, prothrombin time, or total cholesterol, versus 7% of control patients. Preoperatively, to identify patients at high risk of pulmonary embolism, plasminogen activator inhibitor activity, dilute Russell's viper venom time, prothrombin time, and cholesterol levels were most predictive. Using at least one abnormality of these four measures as a screening test to detect risk of pulmonary embolism, the test is sensitive (100%), and the predictive value of a negative test is high (100%). After additional prospective study, this may allow identification of patients at low risk (the majority of patients) in whom anticoagulation may not be required and a small group of patients at high risk for pulmonary embolism in whom prophylactic anticoagulation should be provided.

Safety concerns and health benefits associated with oral contraception

Since the introduction of hormonal contraceptives in the 1960s, there have been a variety of both health benefits and safety concerns attributed to their use. In most instances, the noncontraceptive benefits of oral contraceptives (OCs) outweigh the potential cardiovascular risks. In fact, the probability of a patient experiencing a cardiovascular event while taking a low-dose OC is very low. However, smoking, hypertension, obesity, and diabetes are risk factors that must be taken into account when prescribing OCs. The neoplastic effects of hormonal contraceptives have been extensively studied, and recent meta-analyses indicate that there is a reduction in the risk of endometrial and ovarian cancer, a possible small increase in the risk for breast and cervical cancer, and an increased risk of liver cancer. Finally, many women will experience noncontraceptive health benefits with OCs that expand far beyond pregnancy prevention. Some of these benefits include reduction in menstrual-related symptoms, fewer ectopic pregnancies, a possible increase in bone density, and possible protection against pelvic inflammatory disease.

Pulmonary thromboembolism in Asians/Pacific Islanders in the United States: analysis of data from the National Hospital Discharge Survey and the United States Bureau of the Census

PURPOSE

To assess the rate of diagnosis of deep venous thrombosis, pulmonary embolism, and venous thromboembolism; the incidence in hospitalized patients; and mortality from pulmonary embolism among Asians/Pacific Islanders in the United States.

METHODS

The number of patients discharged from hospitals with a diagnostic code for pulmonary embolism or deep venous thrombosis from 1990 through 1999 was obtained from the National Hospital Discharge Survey. Population estimates and deaths from pulmonary embolism from 1990 through 1998 were obtained from the United States Bureau of the Census.

RESULTS

Rate ratios of 10-year age-adjusted rates of diagnosis of deep venous thrombosis, pulmonary embolism, and venous thromboembolism comparing Asians/Pacific Islanders with whites and African Americans ranged from 0.16 to 0.21. Rate ratios comparing incidences in hospitalized patients ranged from 0.32 to 0.42. The age-adjusted rate ratio of mortality in "others" (which included Asians/Pacific Islanders) was 0.29 (95% confidence interval [CI]: 0.01 to 0.87) compared with whites and 0.14 (95% CI: 0.0 to 0.58) compared with African Americans.

CONCLUSION

Rates of deep venous thrombosis, pulmonary embolism, and venous thromboembolism; incidences in hospitalized patients; and the mortality rate from pulmonary embolism were markedly lower in Asians/Pacific Islanders than in whites and African Americans. Clinical assessment of the prior probability of venous thromboembolic disease at the bedside should probably be adjusted based on these ethnic differences.

Predictors of left ventricular thrombus formation in patients with dilated cardiomyopathy: role of activated protein C resistance

OBJECTIVES

The aim of this study was to investigate the association between left ventricular thrombus formation and natural anticoagulant systems including the protein C, protein S and antithrombin in patients with dilated cardiomyopathy.

MATERIALS AND METHODS

Sixty patients with dilated cardiomyopathy who met the inclusion criteria were included in the study. Patients were divided into two groups: group I consisted of 22 patients with left ventricular thrombus and group II consisted of 38 patients without left ventricular thrombus. Our main inclusion criteria were ejection fraction </= 35% and left ventricular end-diastolic diameter >/= 6.0 cm. These two groups were compared for clinical and hematologic parameters (activated protein C resistance, protein S and antithrombin).

RESULTS

There were no statistically significant differences between patients with or without left ventricular thrombi with respect to left ventricular end-diastolic and end-systolic dimensions, ejection fraction, fractional shortening and left atrial diameter. There were no statistically significant differences between patients with and without left ventricular thrombus with respect to platelet count (252 +/- 64/mm3 x 10(3) compared with 260 +/- 74/mm3 x 10(3) respectively, P=0.68), prothrombin time (12.94 +/- 1.9 s compared with 12.86 +/- 1.3 s respectively, P=0.82), activated partial thromboplastin time (32 +/- 5 compared with 30 +/- 4 s respectively, P=0.32) and fibrinogen levels (36 +/- 9 mg/dl compared with 34 +/- 8 mg/dl respectively, P=0.41). None of the patients had protein S and antithrombin deficiency. Activated protein C resistance was found in 12 patients (12 out of 22, 54%) in group I and four patients (four out of 38, 9.5%) in group II (P < 0.01). It was also shown to be an independent predictor of left ventricular thrombus (P < 0.05).

CONCLUSION

Activated protein C resistance is found to be an independent predictor of left ventricular thrombus in patients with dilated cardiomyopathy who have ejection fractions less then 35% and left ventricular end-diastolic dimensions > 6.0 cm.

Sphingolipids as Bioactive Regulators of Thrombin Generation

Sphingolipids contribute to modulation of two opposing cell processes, cell growth and apoptotic cell death; ceramide and sphingosine promote the latter and sphingosine-1-phosphate triggers the former. Thrombin, a pro-inflammatory protease that is regulated by the blood coagulation cascade, exerts similar effects depending on cell type. Here we report a new mechanism for cross-talk between sphingolipid metabolism and thrombin generation. Sphingosine and sphinganine, but not ceramide or sphingosine-1-phosphate, down-regulated thrombin generation on platelet surfaces (IC(50) = 2.4 and 1.4 microm for sphingosine and sphinganine, respectively) as well as in whole plasma clotting assays. Thrombin generation was also inhibited by glucosylsphingosine, lysosphingomyelin, phytosphingosine, and primary alkylamines with >10 carbons. Acylation of the amino group ablated anticoagulant activities. Factor Va was required for the anticoagulant property of sphingosine because prothrombin activation was inhibited by sphingosine, sphinganine, and stearylamine in the presence but not in the absence of factor Va. Sphingosine did not inhibit thrombin generation when Gla-domainless factor Xa was used in prothrombinase assays, whereas sphingosine inhibited activation of Gla-domainless prothrombin by factor Xa/factor Va in the absence of phospholipids (IC(50) = 0.49 microm). Fluorescence spectroscopy studies showed that sphingosine binds to fluorescein-labeled factor Xa and that this interaction required the Gla domain. These results imply that sphingosine disrupts interactions between factor Va and the Gla domain of factor Xa in the prothrombinase complex. Thus, certain sphingolipids may be bioactive lipid mediators of thrombin generation such that certain sphingolipid metabolites may modulate proteases that affect cell growth and death, blood coagulation, and inflammation.

Impact of environmental and hereditary risk factors on the clinical manifestation of thrombophilia in homozygous carriers of factor V:G1691A

BACKGROUND

Limited data exist on the clinical manifestations of homozygous factor (F)V:G1691A mutation (FV Leiden) and the impact of environmental and genetic risk factors.

OBJECTIVES

To assess the contribution of these factors on the thrombophilic phenotype.

PATIENTS AND METHODS

In a retrospective multicenter cohort study 165 individuals with homozygous FV:G1691A mutation, of whom 129 had previous venous thromboembolism (VTE), were included. To study the role of environmental risk factors, patients were compared by the use of a standardized questionnaire to 165 sex- and age-matched individuals (reference group A); of these, two had previous VTE. To assess the role of genetic risk factors, factor (F)II:G20210A and MTHFR:C677T were determined in individuals homozygous for FV:G1691A and in 177 healthy individuals without previous VTE (reference group B).

RESULTS

The first VTE occurred significantly earlier in women (median age 25 years) than men (35.5 years). In 81% of women and 29% of men an environmental risk factor was present before first VTE. Oral contraceptives increased the risk of thrombosis 4-fold [odds ratio (OR) 4.0, 95% confidence interval (CI) 1.7, 10.4] in women with homozygous FV:G1691A. Postoperative and post-traumatic VTE as first manifestation occurred in 13% and 15% of surgical/traumatic events in patients and in 0.7% and 1.8% in reference group A, respectively (OR 19.7, 95% CI 2.5, 154 and OR 9.2, 95% CI 1.1, 79.4). Heterozygous FII:G20210A was more prevalent in symptomatic patients (11.7%) compared with reference group B (2.8%, OR 4.6, 95% CI 1.6, 13.2). The prevalence of homozygous MTHFR:C677T genotype was similar in patients and reference group B.

CONCLUSIONS

Our study supports the concept of thrombophilia as a multifactorial disorder. The knowledge of coexisting factors predisposing to VTE is useful for medical advice for primary and secondary prophylaxis in these patients.

Impaired APC cofactor activity of factor V plays a major role in the APC resistance associated with the factor V Leiden (R506Q) and R2 (H1299R) mutations

Activated protein C (APC) resistance is a major risk factor for venous thrombosis. Factor V (FV) gene mutations like FV(Leiden) (R506Q) and FV(R2) (H1299R) may cause APC resistance either by reducing the susceptibility of FVa to APC-mediated inactivation or by interfering with the cofactor activity of FV in APC-catalyzed FVIIIa inactivation. We quantified the APC cofactor activity expressed by FV(Leiden) and FV(R2) and determined the relative contributions of reduced susceptibility and impaired APC cofactor activity to the APC resistance associated with these mutations. Plasmas containing varying concentrations of normal FV, FV(Leiden), or FV(R2) were assayed with an APC resistance assay that specifically measures the APC cofactor activity of FV in FVIIIa inactivation, and with the activated partial thromboplastin time (aPTT)-based assay, which probes both the susceptibility and APC cofactor components. FV(R2) expressed 73% of the APC cofactor activity of normal FV, whereas FV(Leiden) exhibited no cofactor activity in FVIIIa inactivation. Poor susceptibility to APC and impaired APC cofactor activity contributed equally to FV(Leiden)-associated APC resistance, whereas FV(R2)-associated APC resistance was entirely due to the reduced APC cofactor activity of FV(R2). Thrombin generation assays confirmed the importance of the anticoagulant activity of FV and indicated that FV(Leiden) homozygotes are exposed to a higher thrombotic risk than heterozygotes because their plasma lacks normal FV acting as an anticoagulant protein.

Genetic testing for cardiovascular disease susceptibility: a useful clinical management tool or possible misinformation?

Genetic susceptibility tests are already advertised on the Internet to identify individuals at above average risk for cardiovascular disease (CVD), such as deep vein thrombosis, hyperlipidemia, or atherosclerosis, whereas other tests claim to predict response to a particular drug treatment. Some kits are available to the public directly, bypassing a doctor. Their value, however, must be considered carefully, because although a genotype may be strongly and consistently associated with an intermediate trait, and because the intermediate trait is a strong predictor of CVD risk, there may be little or no association of genotype with risk over and above that of the measured trait. This is because multigenic effects and environmental modification (context dependency) of genotype effects determine CVD risk. An individual's personal characteristics and plasma risk-trait levels (which reflect both genotype and exposure) at present are the best predictors of clinical outcome. Only when genetic tests surpass this, possibly by the inclusion of many functional common variants, in conjunction with their context-dependent effects on risk, might their usefulness in clinical management be realized. Here we review some of the particular issues and concerns raised by CVD-risk genetic testing, and suggest areas of further research to address these issues.

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

BACKGROUND

The association between the inherited gene mutations of factor V, prothrombin, and homocysteine metabolism and venous thromboembolic events is accepted widely; however, their influence on the arterial circulatory system remains controversial.

METHODS

We performed a MEDLINE search to identify published case-control and cohort studies correlating the factor V Leiden, prothrombin (PT) G20210A, and methylenetetrahydrofolate reductase (MTHFR) C677T (TT genotype) mutations with myocardial infarction, ischemic stroke, or peripheral vascular disease. Studies were included only when they adhered to specific diagnostic criteria for ischemic events and met the published methodological criteria. Odds ratios (ORs) with accompanying 95% CIs were calculated for each mutation and clinical end points with a random-effects model (DerSimonian and Laird method).

RESULTS

The association between inherited gene mutations and arterial ischemic events was modest: factor V Leiden mutation (OR, 1.21; 95% CI, 0.99-1.49), PT G20210A mutation (OR, 1.32; 95% CI, 1.03-1.69), and MTHFR TT mutation (OR, 1.20; 95% CI, 1.02-1.41). Subgroup analyses of younger patients (<55 years old) and of women revealed slightly stronger associations overall.

CONCLUSIONS

Genetic abnormalities specific to factor V, prothrombin,and homocysteine metabolism increase the risk for myocardial infarction and ischemic stroke, particularly among younger patients and women. Because the overall association is only modest, screening studies should be limited to carefully selected patient populations. The individual propensity for arterial and venous thrombosis is likely influenced by differing local mechanisms, systemic mechanisms, or both.

Liver transplantation in a patient with Budd-Chiari syndrome secondary to factor V Leiden mutation

A point mutation in the factor V Leiden gene is the most common hereditary thrombophilic state and an important risk factor for Budd-Chiari syndrome. We report on a patient with Budd-Chiari syndrome secondary to factor V Leiden mutation, who underwent successful liver transplantation. Following liver transplantation, his thrombophilic state was corrected and he did not require anticoagulation therapy. There has been no recurrent venous thrombosis for 14 months after transplantation. Although his activated protein C sensitivity was normal, showing the normalization of protein C-factor V interaction, PCR analysis demonstrated that heterozygosity for factor V Leiden mutation was still present. We suggest checking resistance to activated protein C, rather than PCR analysis of factor V Leiden mutation in patients with Budd-Chiari syndrome after liver transplantation; the presence of the second does not effect clinical outcome.

Thrombophilia and pregnancy

Pregnancy is hypercoagulable state. The field of thrombophilia; the tendency to thrombosis, has been developed rapidly and has been linked to many aspects of pregnancy. It is recently that severe pregnancy complications such as severe preeclampsia intrauterine growth retardation abruptio placentae and stillbirth has been shown to be associated with thrombophilia. Recurrent miscarriage and has also been associated with thrombophilia. Finally, thromboembolism in pregnancy as in the non-pregnant state is linked to thrombophilia. In this review all aspects of thrombophilia in pregnancy are discussed, and also all prophylactic and therapeutic implications.

Risk factors for venous thromboembolism

Until the 1990s, venous thromboembolism (VTE) was viewed primarily as a complication of hospitalization for major surgery (or associated with the late stage of terminal illness). However, recent trials in patients hospitalized with a wide variety of acute medical illnesses have demonstrated a risk of VTE in medical patients comparable with that seen after major general surgery. In addition, epidemiologic studies have shown that between one quarter and one half of all clinically recognized symptomatic VTEs occur in individuals who are neither hospitalized nor recovering from a major illness. This expanding understanding of the population at risk challenges physicians to carefully examine risk factors for VTE to identify high-risk patients who could benefit from prophylaxis. Factors sufficient by themselves to prompt physicians to consider VTE prophylaxis include major surgery, multiple trauma, hip fracture, or lower extremity paralysis because of spinal cord injury. Additional risk factors, such as previous VTE, increasing age, cardiac or respiratory failure, prolonged immobility, presence of central venous lines, estrogens, and a wide variety of inherited and acquired hematological conditions contribute to an increased risk for VTE. These predisposing factors are seldom sufficient by themselves to justify the use of prophylaxis. Nevertheless, individual risk factors, or combinations thereof, can have important implications for the type and duration of appropriate prophylaxis and should be carefully reviewed to assess the overall risk of VTE in each patient.

Activated protein C resistance acquired through liver transplantation and associated with recurrent venous thrombosis

We report a new case of recurrent, extra-hepatic, deep vein thrombosis occurring after orthotopic liver transplantation for hepatocellular carcinoma complicating 'mixed' alcoholic and post-hepatitic C cirrhosis. Coagulation tests showed activated protein C resistance. The patient's genomic DNA was negative for the factor V Leiden mutation. Analysis of the grafted liver DNA showed that the donor was a heterozygous carrier of the factor V Leiden mutation and that the recipient's activated protein C resistance was acquired through the transplantation. Screening of candidate liver donors for a prothrombotic tendency is controversial. However, this case suggests that patients who develop venous thrombosis after liver transplantation should be screened for thrombophilic abnormalities, bearing in mind that genetic abnormalities which do not affect clotting test results, such as the G20210A mutation in the factor II gene, can only be diagnosed by testing the donor or graft.

Clinical significance of acquired activated protein C resistance in patients with systemic lupus erythematosus

Antiphospholipid antibodies (aPL) may induce acquired activated protein C resistance (acquired APCR). The role of acquired APCR in patients with systemic lupus erythematosus (SLE) is not well known. To evaluate the prevalence of acquired APCR and its association with clinical manifestations we studied 103 consecutive SLE patients and 103 matched controls. APCR in the undiluted test and after dilution in factor V deficient plasma, factor V Leiden, protein C and S, lupus anticoagulant, and anti-cardiolipin, anti-beta2-glycoprotein I and anti-prothrombin antibodies were determined. Factor V Leiden was found in 4% in both patients and controls. The prevalence of acquired APCR was 22% for the undiluted assay and 17% in the diluted test. In SLE patients, acquired APCR was associated with aPL (39 vs 13% in undiluted assay, P = 0.007; and 33 vs 7% in the diluted test, P = 0.001). Arterial thromboses were found in 24% of patients with acquired APCR and in 6% of patients without (P = 0.04). However, no relationship was found with venous thrombosis. Acquired APCR was also associated with pregnancy losses: miscarriages in 70% of women with acquired APCR vs 32% in those without (P=0.03). Thus, in SLE patients acquired APCR seems to be associated with increased prevalence of arterial thrombosis and pregnancy losses.

Combined carrier status of prothrombin 20210A and factor XIII-A Leu34 alleles as a strong risk factor for myocardial infarction: evidence of a gene-gene interaction

Studies associating the prothrombin 20210G>A (FII 20210A), factor V Leiden (FVL), and factor XIII Leu34 (FXIII-A Leu34) alleles with myocardial infarction (MI) have yielded conflicting results. Complicated gene-gene interactions, small sample sizes, and heterogeneous genetic and environmental backgrounds may contribute to opposing findings. Simultaneous analysis of multiple gene variants in a large sample size from a genetically isolated population may overcome these weaknesses. Genotyping was performed in 500 MI patients and 500 control subjects from the genetically isolated Newfoundland population to determine the prevalence of the FII 20210A, FVL, and FXIII-A Leu34 variants and their association with MI. Gene-gene interactions were also analyzed. The prevalence of the FII 20210A allele was higher in MI patients (3.2%) than in control subjects (1.0%; P =.015). The FII 20210A allele was also 5.6-fold higher in MI patients younger than 51 years than in age-matched control subjects (P =.04). FVL showed 3.9-fold higher prevalence in young patients than in patients older than 50 years (P =.004) and 2.7-fold higher than in age-matched control subjects (P =.007). Furthermore, the prevalence of combined carriers of the FXIII-A L34 and FII 20210A alleles was 12-fold higher in MI patients than in control subjects (P =.002) and with 92% penetrance. There was disequilibrium of the FXIII-A Leu34 allele to MI patients carrying the FII 20210A allele as a genetic background. Based on our data, we determined that (1) the FII 20210A allele is a risk factor for MI, possibly important for early onset; (2) FVL may predispose for early-onset MI; (3) the FXIII-A Leu34 allele predisposes for MI in males only; however, (4) interaction between the FII 20210A and FXIII-A Leu34 alleles forms a synergistic coeffect that strongly predisposes for MI, placing combined carriers at high risk for MI.

Long-term, low-intensity warfarin therapy for the prevention of recurrent venous thromboembolism

BACKGROUND

Standard therapy to prevent recurrent venous thromboembolism includes 3 to 12 months of treatment with full-dose warfarin with a target international normalized ratio (INR) between 2.0 and 3.0. However, for long-term management, no therapeutic agent has shown an acceptable benefit-to-risk ratio.

METHODS

Patients with idiopathic venous thromboembolism who had received full-dose anticoagulation therapy for a median of 6.5 months were randomly assigned to placebo or low-intensity warfarin (target INR, 1.5 to 2.0). Participants were followed for recurrent venous thromboembolism, major hemorrhage, and death.

RESULTS

The trial was terminated early after 508 patients had undergone randomization and had been followed for up to 4.3 years (mean, 2.1). Of 253 patients assigned to placebo, 37 had recurrent venous thromboembolism (7.2 per 100 person-years), as compared with 14 of 255 patients assigned to low-intensity warfarin (2.6 per 100 person-years), a risk reduction of 64 percent (hazard ratio, 0.36 [95 percent confidence interval, 0.19 to 0.67]; P<0.001). Risk reductions were similar for all subgroups, including those with and those without inherited thrombophilia. Major hemorrhage occurred in two patients assigned to placebo and five assigned to low-intensity warfarin (P=0.25). Eight patients in the placebo group and four in the group assigned to low-intensity warfarin died (P=0.26). Low-intensity warfarin was thus associated with a 48 percent reduction in the composite end point of recurrent venous thromboembolism, major hemorrhage, or death. According to per-protocol and as-treated analyses, the reduction in the risk of recurrent venous thromboembolism was between 76 and 81 percent.

CONCLUSIONS

Long-term, low-intensity warfarin therapy is a highly effective method of preventing recurrent venous thromboembolism.

Polymorphisms in coagulation factor genes and their impact on arterial and venous thrombosis

Arterial and venous thromboses, with their clinical manifestations such as stroke, myocardial infarction (MI), or pulmonary embolism, are the major causes of death in developed countries. Several studies in twins and siblings have shown that genetic factors contribute significantly to the development of these diseases. Since the advent of molecular genetics in medicine, it has been a focus of interest to elucidate the role of mutations in various candidate genes and their impact on hemostatic disorders such as arterial and venous thromboses. In this article, we review the current knowledge of the contribution of polymorphisms in coagulation factors to the development of thrombotic diseases. We show that in arterial thrombosis, results are controversial. Only for factor XIII 34Leu a protective effect on the development of myocardial infarction has been demonstrated in several studies. No other single polymorphism in a coagulation factor could be confirmed as a relevant risk factor, although there is evidence for a role of factor V Arg506Gln, factor VII Arg353Gln, and vWF Thr789Ala polymorphisms in patient subgroups. Further studies will be necessary to confirm the value of testing for genetic polymorphisms in arterial thrombosis. A large body of data is available on the role of factor V Arg506Gln and the prothrombin G20210A mutation in venous thrombosis. Some papers already recommend diagnosis and treatment strategies. We will discuss these recent publications on venous thrombosis in our review.

Clinical risk factors for deep venous thrombosis in pregnancy and the puerperium

Thromboembolic events are among the leading causes of maternal mortality. Mutations in the genes for clotting factors are known, but anamnestic factors can be found in a proportion of women with deep venous thromboses (DVT) during pregnancy and the puerperium. We here describe the clinical factors and pregnancy outcomes of such a group of 70 women who were all operated on for DVT. Highest risk is conferred by a familial history of clotting disease and by known mutations of the clotting factors. This might be used to target a high risk group for preventive treatment.

Treatment of recurrent stroke and pulmonary thromboembolism with percutaneous closure of a patent foramen ovale and placement of inferior vena cava filter

The association between recurrent episodes of pulmonary embolism, stroke, and congenital anomalies of the clotting system features a condition of increased risk of recurrences despite anticoagulant therapy. We report the successful management of this association with percutaneous closure of the foramen ovale and placement of an inferior caval vein filter.

Hormone therapy and venous thromboembolism

Convincing data from randomized trials and observational studies have demonstrated a two- to threefold increased risk of venous thromboembolism (VTE) with the use of hormone replacement therapy (HRT) in post-menopausal women. This risk is highest in the first year of use, but an increased risk persists after the first year if HRT use is ongoing. The risk of VTE is increased for oral oestrogen alone, oral oestrogen combined with progestin and probably for transdermal HRT. There is an increase in both idiopathic and non-idiopathic VTE with HRT. Early evidence suggests an interaction of HRT with thrombophilic states such as the factor V Leiden mutation, resulting in a synergistic increase in the risk of VTE. There is also an increased risk of VTE with raloxifene and tamoxifen, but the effects of low-dose HRT and tibolone on VTE risk are less clear.

Factor V Leiden protects against blood loss and transfusion after cardiac surgery

BACKGROUND

The outcome of cardiac surgery is influenced by several factors, but the impact of specific genetic variants has not been systematically explored. Because blood conservation is a pressing issue in cardiac surgery, we tested the hypothesis that factor V Leiden (FVL), a common coagulation factor polymorphism, may protect against blood loss and transfusion in patients undergoing cardiac surgery.

METHODS AND RESULTS

We enrolled 517 patients undergoing cardiac surgery, including 26 heterozygous FVL carriers, and evaluated the impact of FVL on chest tube output and transfusion by using univariate and multivariate techniques. For patients with FVL, blood loss at 6 (238+/-131 mL) and 24 hours (522+/-302 mL) was significantly lower than that for noncarriers (358+/-259 mL and 730+/-452 mL; P<0.001 and P=0.001, respectively). In a multivariate regression analysis, controlling for ethnicity and factors known to affect blood loss, FVL was a significant independent contributor at both time points. Using a similar regression approach, FVL did not have a significant effect on the number of units transfused. However, logistic regression of the risk of receiving any transfusion during hospitalization demonstrated a significant independent protective effect of FVL on overall transfusion risk.

CONCLUSIONS

FVL represents a common genetic trait that may protect against blood loss and transfusion in this population. This study demonstrates that genetic variability can affect the outcome of cardiac surgery.

Acquired activated protein C resistance, high tissue factor expression, and hyper-homocysteinemia in systemic lupus erythematosus

Activated protein C resistance (APCR), high tissue factor (TF) expression, and hyper-homocysteinemia are associated with thromboembolic diseases. Thromboembolism is a frequent complication of systemic lupus erythematosus (SLE). In this study, we evaluated the prevalence of APCR, high TF, and homocysteine with correlation of the thrombotic tendency in SLE. Ninety-four SLE patients and 28 normal controls were included. APC ratio and TF antigen were measured using commercial kits. Plasma homocysteine level was measured using HPLC. The prevalence of APCR, high TF antigen level, and hyper-homocysteinemia in our SLE patients were 21.3%, 66.0%, and 23.4%, respectively. The median plasma level of TF antigen in SLE patients was 145.23 pg/mL (range, 31.00-778.50 pg/mL), which was significantly higher than the control value of 39.83 pg/mL (range, 1.55-168.50 pg/mL). The median APC ratio in SLE patients was 2.76 (range, 1.48-13.47), which was significantly lower than the control value of 3.59 (range, 0.26-5.66). The plasma level of homocysteine was not significantly different from that of control. A significant association was observed between the presence of APCR (OR = 8.59, P < 0.0001) but not with the presence of high plasma TF antigen level (OR = 1.24, P = 0.67) and thrombotic complications in SLE patients. In conclusion, APCR and high plasma TF levels are common in SLE, but a significant association was observed only between the presence of APCR and thrombosis in SLE patients.

Incidence of thrombophilia detected in southern Taiwanese patients with venous thrombosis

In order to analyze the incidence of thrombophilia in southern Taiwan, we studied the prevalence of antithrombin (AT), protein C (PC), and protein S (PS) deficiencies, the prevalence of factor V Leiden mutation, and the presence of acquired lupus anticoagulant (LA) and anticardiolipin antibody (ACA) in 56 patients < or =65 years old with deep venous thrombosis (DVT). Of 56 patients, 30 were male, 26 female, and the mean age of the patients was 43 years (18-65 years). None had factor V mutation or activated PC resistance; 21 patients (37.5%) showed abnormal results: 4 (7.1%) had AT deficiencies, 6 (10.7%) PC deficiencies, 6 (10.7%) PS deficiencies, 2 (3.6%) a combined PC and PS deficiency, and 3 (5.4%) LA and ACA. Only PC and PS deficiencies were significantly associated with increased risk for the development of thrombosis with an odds ratio of 4.2 (95% confidence interval: 1.2-15.0, P=0.018) and 8.1 (95% confidence interval: 1.6-40.6, P=0.003), respectively. We concluded that the prevalence of heritable thrombophilia (34.0%) in Taiwan is higher than that in Western countries, but that it is lower than previously reported in Hong Kong and Taiwan. We attribute this to selection bias.

Activated protein C resistance (FV(Leiden)) and thrombosis: factor V mutations causing hypercoagulable states

The integrity of the vascular system is of prime importance for survival. Therefore, several emergency and repair systems safeguard the circulatory system. Multiple processes jointly limit vascular damage and blood loss. In this article, the authors focus on the protein C anticoagulant pathway and the role of activated protein C resistance in thrombotic disease, and they discuss the involvement in thrombosis of mutations other than the Arg506Gln mutation in the gene encoding for factor V.

A prospective cohort study determining the prevalence of thrombotic events in children with acute lymphoblastic leukemia and a central venous line who are treated with L-asparaginase: results of the Prophylactic Antithrombin Replacement in Kids with Acute Lymphoblastic Leukemia Treated with Asparaginase (PARKAA) Study

BACKGROUND

Thrombotic events (TEs) are serious secondary complications in children with acute lymphoblastic leukemia (ALL) who receive L-asparaginase (ASP) therapy; however, the prevalence of TEs has not been established. The primary objective of the Prophylactic Antithrombin Replacement in Kids with Acute Lymphoblastic Leukemia Treated with Asparaginase (PARKAA) Study was to determine the prevalence of TEs. The secondary objective was to detect any association of TEs with the presence of congenital or acquired prothrombotic disorders.

METHODS

Children with ALL were screened for TEs at the end of ASP treatment using bilateral venograms, ultrasound, magnetic resonance imaging, and echocardiography. Symptomatic TEs were confirmed by appropriate radiographic tests. All tests were read by a blinded central adjudication committee.

RESULTS

Twenty-two of 60 children had TEs, a prevalence of 36.7% (95% confidence interval, 24.4-48.8%). TEs were located in the sinovenous system of the brain in 1 patient, the right atrium in 3 patients, and the upper central venous system in 19 patients. TEs detected by venography resulted in 1) 25-100% occlusion, with 1 in 3 patients showing occlusion of > 75% of the greatest vessel dimension, and 2) the presence of collaterals in 60% of patients, with 40% categorized as major. No children with TEs were positive for factor V Leiden or prothrombin gene 20201A, and four of eight children with antiphospholipid antibodies had a TE.

CONCLUSIONS

The prevalence of TEs is exceedingly high in this population, and it is likely that the extent of occlusion is likely clinically significant. No trend was seen toward an association between TEs and the presence of congenital prothrombotic disorders. A trend was seen toward an association between TEs and antiphospholipid antibodies. Carefully designed clinical trials of primary prophylaxis for the prevention of TEs are required in this patient population.

Molecular epidemiology of preeclampsia

Numerous articles have been published that address the possible genetic influences on the development of preeclampsia (PE). However, to our knowledge, a complete review of the results has not yet been completed. We undertook a MEDLINE search to identify English-language articles published after January 1, 1990 that examined the possible role of specific genes in the etiology of PE. After a brief introduction and a concise review of the prevailing etiologic hypotheses, we have categorized the candidate genes into six categories, based on their hypothesized role in PE etiology. The purpose of this paper is to review the literature, comment on its quality, and provide a reference for researchers interested in the molecular epidemiology of preeclampsia.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians.

LEARNING OBJECTIVES

After completion of this article, the reader will be able to list the prevailing etiologic hypotheses of preeclampsia, to outline the published data on possible genetic influence on the development of preeclampsia, and to clearly state the definition of preeclampsia.

Hemostatic markers with bolus versus prolonged heparin after carotid artery stenting

BACKGROUND

The evolving technique of carotid stenting (CS) requires optimal antithrombotic strategies to reduce periinterventional thromboembolic risk. In animal models of balloon injury, tissue factor (TF) was shown to be the major procoagulant of the atherosclerotic plaque mediating prolonged procoagulant activity.

METHODS

We analyzed TF and TF-dependent hemostatic markers before and 2, 6 and 24 h after CS with two antithrombotic drug regimens. Group A (n=20) received prolonged unfractionated heparin (UFH) for 18-20 h starting at intervention next to aspirin and thienopyridine. In group B (n=16), single bolus UFH was administered next to combined antiplatelet therapy. Natural anticoagulants were determined at baseline.

RESULTS

Patients with symptomatic and asymptomatic cerebrovascular disease did not differ in plasma TF levels. Furthermore, no statistically significant difference for TF, TFPI/Xa-complex and prothrombin fragment F1.2 was observed between bolus and prolonged heparin treatment. No significant change was found in time course for these parameters. Two patients (5.5%; one in each treatment group) suffered periinterventional minor stroke associated with increased levels of F1.2 and TFPI/Xa-complex. Both were resistant to activated protein C (APC ratio<1.9) due to heterozygous factor V Leiden mutation.

CONCLUSIONS

No significant activation of the TF pathway was seen with both antithrombotic regimens suggesting that single bolus UFH combined with antiplatelet therapy is generally sufficient to control TF-dependent procoagulant activity after CS. However, patients with resistance to activated protein C may be at increased periinterventional stroke risk.

Arterial embolism to the upper extremity in a patient with factor V Leiden mutation (APC resistance)--a case report and review of the literature

Factor V Leiden mutation has emerged as one of the leading abnormalities in inherited blood coagulation disorders, resulting in a markedly increased risk for deep leg vein thrombosis. A 24-year-old woman presented with acute onset of critical ischemia of her left thumb and index finger. Intraarterial angiography revealed an embolus in the distal radial artery and a thrombotic occlusion of the digital artery of the thumb and index finger. Immediate therapy encompassed a selective surgical embolectomy of the distal radial artery followed by a local intraarterial lysis that was continued for 3 days. Additionally, therapeutic anticoagulation and vasodilating drugs (prostaglandin E) were administered. Within 2 days, capillary refill reappeared and the initial loss of sensory function at the tip of the thumb and index finger diminished. A screening test for thrombophilic disorders led to the diagnosis of a heterozygous mutation of factor V (Leiden mutation). Arterial thromboembolic events of factor V Leiden mutation are rare and have to date been described only in the supraaortic and coronary circulation. Therefore, the arterial embolism to the left hand presented in this report constitutes a rarity that could be successfully salvaged by the combined use of a vascular surgical procedure and intensified medical management.

The discovery of activated protein C resistance

Venous thrombosis is a multifactorial disease, with the pathogenesis involving genetic and environmental risk factors. The most common genetic risk factor known to date is a single point mutation in the gene of coagulation factor V (FV), which results in the replacement of Arg506 with Gln (FV Leiden). Arg506 is one of several cleavage sites in FV for anticoagulant activated protein C (APC) and the mutation results in the loss of the cleavage site. Via a complicated series of reactions, this results in impaired APC-mediated degradation of both FVa and FVIIIa. The associated hypercoagulable condition, which causes a lifelong increased risk of thrombosis, is known as APC resistance. APC resistance was discovered in my laboratory in the late 1980s and we published the first report almost exactly 10 years ago. This started an avalanche of research activities and several thousand articles have since been published on this topic. Analyses for APC resistance and FV Leiden have made their way into clinical medicine and are now performed routinely all over the world. I have been asked to write a personal historical annotation about the discovery of APC resistance, the early research activities and the rapid progress in this field.