Congenital thrombophilia

Evolving Knowledge on Primary and Secondary Prevention of Venous Thromboembolism in Carriers of Hereditary Thrombophilia: A Narrative Review

The association between heritability of venous thromboembolism (VTE) and thrombophilia was first reported clinically in 1956, later followed by the first description of a congenital cause of hypercoagulability-antithrombin deficiency-in 1965. Since then, our knowledge of hereditary causes of hypercoagulability, which may predispose carriers to VTE has improved greatly. Novel genetic defects responsible for severe thrombophilia have been recently identified and we have learned that a wide range of interactions between thrombophilia and other genetic and acquired risk factors are important determinants of the overall individual risk of developing VTE. Furthermore, therapeutic strategies in thrombophilic patients have benefited significantly from the introduction of direct oral anticoagulants. The present review is an overview of the current knowledge on the mechanisms underlying inherited thrombophilia, with a particular focus on the latest achievements in anticoagulation protocols and prevention strategies for thrombosis in carriers of this prothrombotic condition.

Evolving Knowledge on Primary and Secondary Prevention of Venous Thromboembolism in Carriers of Hereditary Thrombophilia: A Narrative Review

The association between heritability of venous thromboembolism (VTE) and thrombophilia was first reported clinically in 1956, later followed by the first description of a congenital cause of hypercoagulability-antithrombin deficiency-in 1965. Since then, our knowledge of hereditary causes of hypercoagulability, which may predispose carriers to VTE has improved greatly. Novel genetic defects responsible for severe thrombophilia have been recently identified and we have learned that a wide range of interactions between thrombophilia and other genetic and acquired risk factors are important determinants of the overall individual risk of developing VTE. Furthermore, therapeutic strategies in thrombophilic patients have benefited significantly from the introduction of direct oral anticoagulants. The present review is an overview of the current knowledge on the mechanisms underlying inherited thrombophilia, with a particular focus on the latest achievements in anticoagulation protocols and prevention strategies for thrombosis in carriers of this prothrombotic condition.

Risk of and Prophylaxis for Venous Thromboembolism in Hospital Patients

Objective:

To review the published clinical data on prophylaxis for thromboembolism in order to develop general guidelines to encourage the establishment of local protocols for management.

Data sources:

Published papers on thromboembolism over the period 1991–1997 were identified by Medline search and/or from the authors' personal literature collections and reviewed.

Study selection:

A total of 981 studies were identified. Only those papers reporting randomized studies with clearly defined diagnostic methods and clear end-points were included in this review.

Data extraction:

The available evidence for each specialty was summarized and reviewed by the authors responsible for each specialty, prior to presentation and discussion of their findings within the group. Where a consensus opinion was achieved in a speciality, general guidelines for thromboprophylaxis were summarized. Where a consensus could not be agreed, recommendations for further work were made.

Data synthesis:

There is evidence to support the preferred use of low-molecular-weight heparins (LMWHs) over unfractionated heparin (UFH) in orthopaedic surgery, major trauma and general surgery. However, the ideal duration of thromboprophylaxis has yet to be defined. The use of once daily subcutaneous administration of LMWH offers major practical advantages and may have significant cost saving implications. Further work is required to investigate the use of thromboprophylaxis in minimal access surgery, trauma, elective lower limb surgery, hip fracture and pregnancy; to compare the efficacy of LMWH and mechanical prophylaxis; and to investigate extended prophylaxis after discharge.

Conclusions:

There is overwhelming evidence that thromboembolic prophylaxis reduces the incidence of postoperative deep vein thrombosis and pulmonary embolism. Recommendations concerning the management of these patients when stratified into low, moderate and high risk are made with the suggestion that hospitals develop their own guidelines for the treatment of these patients.

Antibodies to serine proteases in the antiphospholipid syndrome

It is generally accepted that the major autoantigen for antiphospholipid antibodies (aPL) in the antiphospholipid syndrome (APS) is beta(2)-glycoprotein I (beta(2)GPI). However, a recent study has revealed that some aPL bind to certain conformational epitope(s) on beta(2)GPI shared by the homologous enzymatic domains of several serine proteases involved in hemostasis and fibrinolysis. Importantly, some serine protease-reactive aPL correspondingly hinder anticoagulant regulation and resolution of clots. These results extend several early findings of aPL binding to other coagulation factors and provide a new perspective about some aPL in terms of binding specificities and related functional properties in promoting thrombosis. Moreover, a recent immunological and pathological study of a panel of human IgG monoclonal aPL showed that aPL with strong binding to thrombin promote in vivo venous thrombosis and leukocyte adherence, suggesting that aPL reactivity with thrombin may be a good predictor for pathogenic potentials of aPL.

Management of inherited thrombophilia in pregnancy

PURPOSE OF REVIEW

This review summarizes the currently available data concerning risk and management of venous thromboembolism in pregnant women with inherited thrombophilia.

SUMMARY

Pregnancy is a hypercoagulable state, and inherited thrombophilia increases this risk further. Despite the risks, the actual incidence of venous thromboembolism remains low, and therefore, the widespread use of anticoagulants for pregnant women with inherited thrombophilia is not advised. Although randomized, placebo-controlled trials investigating the risks and benefits of anticoagulation have not been performed, there are data to support the use of low molecular weight heparin for high and intermediate-risk women. We will review these data and treatment recommendations, which are based on retrospective and case-control studies as well as expert opinion and consensus statements.

Novel autoantibodies against the activated coagulation factor IX (FIXa) in the antiphospholipid syndrome that interpose the FIXa regulation by antithrombin

We previously reported that some human antiphospholipid Abs (aPL) in patients with the antiphospholipid syndrome (APS) bind to the homologous enzymatic domains of thrombin and the activated coagulation factor X (FXa). Moreover, some of the reactive Abs are prothrombotic and interfere with inactivation of thrombin and FXa by antithrombin (AT). Considering the enzymatic domain of activated coagulation factor IX (FIXa) is homologous to those of thrombin and FXa, we hypothesized that some aPLs in APS bind to FIXa and hinder AT inactivation of FIXa. To test this hypothesis, we searched for IgG anti-FIXa Abs in APS patients. Once the concerned Abs were found, we studied the effects of the Ab on FIXa inactivation by AT. We found that 10 of 12 patient-derived monoclonal IgG aPLs bound to FIXa and that IgG anti-FIXa Abs in APS patients were significantly higher than those in normal controls (p < 0.0001). Using the mean + 3 SD of 30 normal controls as the cutoff, the IgG anti-FIXa Abs were present in 11 of 38 (28.9%) APS patients. Importantly, 4 of 10 FIXa-reactive monoclonal aPLs (including the B2 mAb generated against beta(2)-glycoprotein I significantly hindered AT inactivation of FIXa. More importantly, IgG from two positive plasma samples were found to interfere with AT inactivation of FIXa. In conclusion, IgG anti-FIXa Ab occurred in approximately 30% of APS patients and could interfere with AT inactivation of FIXa. Because FIXa is an upstream procoagulant factor, impaired AT regulation of FIXa might contribute more toward thrombosis than the dysregulation of the downstream FXa and thrombin.

Some antiphospholipid antibodies bind to hemostasis and fibrinolysis proteases and promote thrombosis

It is generally accepted that the major autoantigen for antiphospholipid antibodies (aPL) is β2glycoprotein I (β2GPI). Interestingly, some aPL bind to β2GPI and the homologous enzymatic domains of several proteases involved in hemostasis and fibrinolysis, and correspondingly hinder anticoagulant regulation and resolution of clots. These findings are consistent with several early findings of aPL and provide a new perspective about some aPL in terms of their binding specificities and related functional properties in promoting thrombosis. In addition, homologous enzymatic domains of the involved proteases share conformation epitope(s) with β2GPI, thus providing a possible structural basis for some non-mutually exclusive mechanisms of aPL-mediated thrombosis.

Thrombophilia and the Risk for Venous Thromboembolism during Pregnancy, Delivery, and Puerperium

The main inherited thrombophilias (antithrombin deficiency, protein C and S deficiency, FVL, the prothrombin gene variant, and MTHFR C677T homozygotes) have a combined prevalence in Western European populations of 15% to 20%. One or more of these inherited thrombophilias is usually found in approximately 50% of women who have a personal history of VTE. Obstetricians must therefore be aware of the interaction between thrombophilias and the procoagulant state of pregnancy and should have an understanding of additional risk factors that may act synergistically with thrombophilias to induce VTE. Such knowledge combined with the appropriate use of thromboprophylaxis and treatment in women who have objectively confirmed VTE continue to improve maternal and perinatal outcomes.

Evaluation of Factor V Leiden, Prothrombin and Methylenetetrahydrofolate Reductase Gene Mutations in Patients with Severe Pregnancy Complications in Northern Finland

BACKGROUND

Thrombosis in placenta may lead to severe pregnancy complications. Most important inherited thrombophilias are factor V Leiden mutation, prothrombin mutation, and methylenetetrahydrofolate reductase mutation. The aim of our research was to evaluate the prevalence of inherited thrombophilias in severe pregnancy complications and in normal pregnancies.

MATERIAL AND METHODS

The study subjects with severe preeclampsia, intrauterine growth restriction, placental abruption or fetal death were collected during the period 1999-2004 from Oulu University Hospital. We also collected during the same period voluntary parturients with normal pregnancy outcome as the control group. FVL, FII, and MTHFR gene mutations of the patients and controls were analyzed.

RESULTS

We found a significant difference in the prevalence of FVL mutation between the groups. There were 9.5% FVL mutations in the study group compared to 1.8% in the control group; the observed difference between prevalences was 7.7% (95% CI 2.0-13.4). No statistical difference was found in the FII or MTHFR mutations between the groups. All FV and FII mutations were heterozygous and all the MTHFR mutations homozygous.

CONCLUSION

Women with thrombophilia have a risk for severe pregnancy complications. Randomized controlled trials are needed to assess the influence of low-molecular-weight heparin in pregnant women with thrombophilia.

Evidence-based risk factors for postoperative deep vein thrombosis

BACKGROUND

Deep vein thrombosis (DVT) is a common postoperative complication that is associated with significant morbidity and mortality. Thromboprophylaxis has been shown to be underused. In the absence of prophylaxis, rates as high as 50% have been reported following orthopaedic surgery, and 25% following general surgery. Many risk factors have been suggested but there is often little evidence to support these claims.

METHODS

A systematic review was performed to determine the evidence base behind each suggested risk factor, and, where sufficient data were available, a random-effects meta-analysis was performed.

RESULTS

There is evidence to support a significant association between increased age, obesity, a past history of thromboembolism, varicose veins, the oral contraceptive pill, malignancy, Factor V Leiden gene mutation, general anaesthesia and orthopaedic surgery, with higher rates of postoperative DVT, although there remain some variables within the study designs that may lead to overestimation of effect. There is no evidence to support the suggested risk factors of hormone replacement therapy, gender, ethnicity or race, chemotherapy, other thrombophilias, cardiovascular factors, smoking and blood type.

CONCLUSIONS

An accurate knowledge of evidence-based risk factors is important in predicting and preventing postoperative DVT, and can be incorporated into a decision support system for appropriate thromboprophylaxis use.

Inherited thrombophilia and venous thromboembolism

Pulmonary thromboembolism (PTE) is the major cause of maternal death in the UK. Underlying PTE is the problem of deep venous thrombosis (DVT). Inherited thrombophilia will be found in about 50% of women with a personal history of venous thromboembolism (VTE), and screening for thrombophilia should be considered in women with a personal or family history of VTE. There is currently no place for universal screening for thrombophilia in pregnancy. There are particular considerations with regard to the management of thrombophilia in pregnancy. Low-molecular-weight heparins are now the heparin of choice in pregnancy because of a better side-effect profile (substantially reduced risk of heparin-induced osteoporosis and heparin-induced thrombocytopaenia) compared to unfractionated heparin, good safety record for mother and fetus and convenient once-daily dosing for prophylaxis.

Prevention of venous thromboembolism in pregnancy

Pulmonary thromboembolism, rising from deep venous thrombosis (DVT), is a major cause of maternal death in the developed World. DVT is a significant source of morbidity in pregnancy and the puerperium with long-term sequelae such as post-thrombotic syndrome. The major risk factors for venous thromboembolism (VTE) are: increasing age, particularly over 35 years; operative vaginal delivery; Caesarean section, especially emergency Caesarean section in labour; high body mass index; previous VTE, especially if idiopathic or thrombophilia-associated; thrombophilia; and a family history of thrombosis suggestive of an underlying thrombophilia. Thromboprophylaxis centres largely on the use of low-molecular-weight heparin (LMWH). LMWHs, such as enoxaparin and dalteparin, have substantial clinical and practical advantages compared with unfractionated heparin, particularly in terms of improved safety with a significantly lower incidence of heparin-induced osteoporosis and thrombocytopenia. Such agents should be used in women with significant risk factors for VTE both antenatally and post-partum.

Management of preterm infants with intracardiac thrombi: use of thrombolytic agents

Improvement in neonatal care has led to improvements in survival and patient outcome in preterm infants; however, this improved survival has been associated with the development of secondary complications, such as catheter-associated intravascular and intracardiac thrombus formation with a non-negligible morbidity and mortality. The sick preterm infant is at high risk of catheter-related thrombus formation because of the combination of a high prothrombotic activity, low levels of natural anticoagulants, and various imbalances in the fibrinolytic systems. Based on clinical experience in adults and children, and several neonatal case reports demonstrating the efficacy and tolerability of specific thrombolytic treatment, this approach should be recommended as a first choice treatment in the premature infant with intracardiac or intravascular thrombosis. The thrombolytic agents of choice are urokinase or tissue plasminogen activator (tPA); however, none of them have proven to be superior to the other in terms of efficacy or tolerability, either in adult patients or premature infants. In the past, it has been suggested that newborn infants may require higher doses of thrombolytic agents than adults for effective systemic thrombolysis; however, based on more recent in vitro studies, it seems unlikely that this is true. Nevertheless, systemic (high dose) fibrinolysis is of concern as premature neonates present an increased risk of cerebral haemorrhage during the first weeks of life; therefore, low dose treatment has been proposed with, if possible, direct infusion of the fibrinolytic agent into, or close to, the thrombus. This approach has proven to be efficient and well tolerated in several small case series of newborn and preterm infants. Recommended doses are 1000 to 3000 U/kg/h for urokinase or 0.01 to 0.05 mg/kg/h for tPA. A systemic proteolytic state will not be induced by this low dose; however, specific monitoring of fibrinogen plasma levels has to be recommended. Fibrinogen levels should remain above 100 mg/dL during low dose treatment. Lower levels of fibrinogen will indicate the presence of an unwanted systemic fibrinolytic state. After successful thrombolysis, a follow-up treatment, preferentially with low-molecular-weight heparin for neonates at adjusted doses, should be instituted for at least 6 weeks in the absence of any persisting thrombophilic factor. A longer course (3 to 6 months) of anticoagulation therapy is recommended when thrombophilic factors (i.e. hereditary thrombophilia or central venous catheter still in place) are present. Furthermore, it is recommended that any neonate with thrombosis should be evaluated for hereditary thrombophilia later in life.

Management of venous thromboembolism in pregnancy

Pulmonary thromboembolism (PTE) is the major cause of maternal death in the UK, with recent trends showing an increase in the numbers of deaths. Underlying PTE is the problem of deep venous thrombosis (DVT). An appreciation of risk factors, particularly, thrombophilia, and signs or symptoms suggestive of thromboembolism, coupled with objective diagnosis and treatment should reduce mortality and morbidity. There are particular considerations with regard to the management of thrombosis in pregnancy, especially the use of anticoagulants. Low-molecular-weight heparins are now replacing unfractionated heparin for the treatment of DVT and PTE in pregnancy.

Non-haemorrhagic obstetric shock

The causes of non-haemorrhagic obstetric shock (pulmonary thromboembolism, amniotic fluid embolism, acute uterine inversion and sepsis) are uncommon but responsible for the majority of maternal deaths in the developed world. Clinically suspected pulmonary thromboembolism should be treated initially with heparin and objective testing should be performed. If the diagnosis is confirmed, heparin is usually continued until delivery, following which anticoagulation in the puerperium is achieved with either warfarin or heparin. Amniotic fluid embolism is a rare complication of pregnancy, occurring most commonly during labour. The management of amniotic fluid embolism involves maternal oxygenation, the maintenance of cardiac output and blood pressure, and the management of any associated coagulopathy. Acute uterine inversion arises most commonly following mismanagement of the third stage of labour. The shock in uterine inversion is neurogenic in origin, although there may also be profound haemorrhage. The management of this condition includes maternal resuscitation and replacement of the uterus either manually, surgically or by hydrostatic pressure. Genital tract sepsis remains a significant cause of maternal death, the most common predisposing factor being prolonged rupture of the fetal membranes. The management of septic shock in pregnancy includes resuscitation, identification of the source of infection and alteration of the systemic inflammatory response.