Antithrombin III Deficiency and Thromboembolism

A phenome-wide approach to identify causal risk factors for deep vein thrombosis

Deep vein thrombosis (DVT) is the formation of a blood clot in a deep vein. DVT can lead to a venous thromboembolism (VTE), the combined term for DVT and pulmonary embolism, a leading cause of death and disability worldwide. Despite the prevalence and associated morbidity of DVT, the underlying causes are not well understood. Our aim was to leverage publicly available genetic summary association statistics to identify causal risk factors for DVT. We conducted a Mendelian randomization phenome-wide association study (MR-PheWAS) using genetic summary association statistics for 973 exposures and DVT (6,767 cases and 330,392 controls in UK Biobank). There was evidence for a causal effect of 57 exposures on DVT risk, including previously reported risk factors (e.g. body mass index-BMI and height) and novel risk factors (e.g. hyperthyroidism and varicose veins). As the majority of identified risk factors were adiposity-related, we explored the molecular link with DVT by undertaking a two-sample MR mediation analysis of BMI-associated circulating proteins on DVT risk. Our results indicate that circulating neurogenic locus notch homolog protein 1 (NOTCH1), inhibin beta C chain (INHBC) and plasminogen activator inhibitor 1 (PAI-1) influence DVT risk, with PAI-1 mediating the BMI-DVT relationship. Using a phenome-wide approach, we provide putative causal evidence that hyperthyroidism, varicose veins and BMI enhance the risk of DVT. Furthermore, the circulating protein PAI-1 has a causal role in DVT aetiology and is involved in mediating the BMI-DVT relationship.

Efficacy of Serum Antithrombin III Test in Patients With Severe Traumatic Brain Injury

Objective

Immune reactions following traumatic brain injury (TBI) cause many complications, including intravascular dissemination. Antithrombin III (AT-III) plays an important role in suppressing abnormal clot formation and ensuring hemostasis. Therefore, we investigated the efficacy of serum AT-III in patients with severe TBI.

Methods

This retrospective study included 224 patients with severe TBI who visited a single regional trauma center between 2018 and 2020. AT-III levels were measured immediately after the TBI diagnosis. AT-III deficiency was defined as an AT-III serum level <70%. Patient characteristics, injury severity, and procedures were also investigated. Patient outcomes included Glasgow Outcome Scale scores at discharge and mortality.

Results

AT-III levels were significantly lower in the AT-III deficient group (n=89; 48.27% ± 1.91%) than in the AT-III sufficient group (n = 135, 78.90% ± 1.52%) (p < 0.001). Mortality occurred in 72 of the 224 patients (33.04%), indicating that there were significantly more patients in the AT-III-deficient group (45/89, 50.6%) than in the AT-III-sufficient group (27/135, 20%). Significant risk factors for mortality included the Glasgow Coma Scale score (P = 0.003), pupil dilatation (P = 0.031), disseminated intravascular coagulopathy (P = 0.012), serum AT-III level (P = 0.033), and procedures including barbiturate coma therapy (P = 0.010). Serum AT-III levels were significantly correlated with Glasgow Outcome Scale scores at discharge (correlation coefficient = 0.455, p < 0.001).

Conclusion

Patients with AT-III deficiency after severe TBI may require more intensive care during treatment, because AT-III levels reflect injury severity and correlate with mortality.

Impact of SERPINC1 mutation on thrombotic phenotype in children with congenital antithrombin deficiency-first analysis of the International Society on Thrombosis and Haemostasis pediatric antithrombin deficiency database and biorepository

BACKGROUND

The natural history and genotype-phenotype correlation of congenital antithrombin (AT) deficiency in children are unknown.

OBJECTIVES

To describe the clinical presentation of congenital AT deficiency in children and evaluate its correlation to specific mutations in SERPINC1.

METHODS

In 2017, a prospective pediatric database and DNA biorepository for congenital AT deficiency was established. During the pilot phase, the database was opened at 4 tertiary care centers in Canada and US. Approval from research ethics board was obtained at each participating center. Written consent/assent was obtained from guardians/subjects who met eligibility. Demographic/clinical data were uploaded into a database. DNA extraction and SERPINC1 sequencing were centralized for US centers. Standard statistical methods were used to summarize parameters. Probability of VTE-free survival was assessed using the Kaplan-Meier method.

RESULTS

Overall, 43 participants (25 females) from 31 unique kindreds were enrolled. Median age (range) at enrollment was 14.8 years (1-21 years). Median AT activity was 52% (24%-87%), and median AT antigen (n = 20) was 55% (38%-110%). Nineteen (44%) participants had a history of venous thromboembolism (VTE). Median age at VTE diagnosis was 12.8 years (0.1-19.2 years). SERPINC1 sequencing was completed for 31 participants and 21 unique mutations were identified, including 5 novel variants. Probability of 5-year VTE-free survival (95% CI) for carriers of missense mutations (92.0% [95% CI: 71.6%-97.9%]) was significantly higher compared with carriers of null mutations (66.7% [95% CI: 19.5%-90.4%]); p = .0012.

CONCLUSION

To our knowledge, this is the first pediatric study to document a severe thrombotic phenotype in carriers of null mutations in SERPINC1, when compared with carriers of missense mutations; underscoring the importance of genetic testing.

Antithrombin Therapy: Current State and Future Outlook

Antithrombin (AT) is a natural anticoagulant pivotal in inactivating serine protease enzymes in the coagulation cascade, making it a potent inhibitor of blood clot formation. AT also possesses anti-inflammatory properties by influencing anticoagulation and directly interacting with endothelial cells. Hereditary AT deficiency is one of the most severe inherited thrombophilias, with up to 85% lifetime risk of venous thromboembolism. Acquired AT deficiency arises during heparin therapy or states of hypercoagulability like sepsis and premature infancy. Optimization of AT levels in individuals with AT deficiency is an important treatment consideration, particularly during high-risk situations such as surgery, trauma, pregnancy, and postpartum. Here, we integrate the existing evidence surrounding the approved uses of AT therapy, as well as potential additional patient populations where AT therapy has been considered by the medical community, including any available consensus statements and guidelines. We also describe current knowledge regarding cost-effectiveness of AT concentrate in different contexts. Future work should seek to identify specific patient populations for whom targeted AT therapy is likely to provide the strongest clinical benefit.

Platelet and Thrombophilia-Related Risk Factors of Retinal Vein Occlusion

Retinal vein occlusion (RVO) is a heterogenous disorder in which the formation of a thrombus results in the retinal venous system narrowing and obstructing venous return from the retinal circulation. The pathogenesis of RVO remains uncertain, but it is believed to be multifactorial and to depend on both local and systemic factors, which can be divided into vascular, platelet, and hypercoagulable factors. The vascular factors include dyslipidaemia, high blood pressure, and diabetes mellitus. Regarding the platelet factors, platelet function, mean platelet volume (MPV), platelet distribution width (PDW), and platelet large cell ratio (PLCR) play key roles in the diagnosis of retinal vein occlusion and should be monitored. Nevertheless, the role of a hypercoagulable state in retinal vein occlusion remains unclear and requires further studies. Therefore, the following article will present the risk factors of RVO associated with coagulation disorders, as well as the acquired and genetic risk factors of thrombophilia. According to Virchow’s triad, all factors mentioned above lead to thrombus formation, which causes pathophysiological changes inside venous vessels in the fundus of the eye, which in turn results in the vessel occlusion. Therefore, a diagnosis of retinal vein occlusion should be based on both eye examination and general examination, including laboratory tests.

Osteonecrosis of the Femoral Head in Patients with Hypercoagulability-From Pathophysiology to Therapeutic Implications

Osteonecrosis of the femoral head (ONFH) is a debilitating disease with major social and economic impacts. It frequently affects relatively young adults and has a predilection for rapid progression to femoral head collapse and end-stage hip arthritis. If not diagnosed and treated properly in the early stages, ONFH has devastating consequences and leads to mandatory total hip arthroplasty. The pathophysiology of non-traumatic ONFH is very complex and not fully understood. While multiple risk factors have been associated with secondary ONFH, there are still many cases in which a clear etiology cannot be established. Recognition of the prothrombotic state as part of the etiopathogeny of primary ONFH provides an opportunity for early medical intervention, with implications for both prophylaxis and therapy aimed at slowing or stopping the progression of the disease. Hereditary thrombophilia and hypofibrinolysis are associated with thrombotic occlusion of bone vessels. Anticoagulant treatment can change the natural course of the disease and improve patients' quality of life. The present work focused on highlighting the association between hereditary thrombophilia/hypofibrinolysis states and ONFH, emphasizing the importance of identifying this condition. We have also provided strong arguments to support the efficiency and safety of anticoagulant treatment in the early stages of the disease, encouraging etiological diagnosis and prompt therapeutic intervention. In the era of direct oral anticoagulants, new therapeutic options have become available, enabling better long-term compliance.

Successful treatment with rivaroxaban of an extended deep vein thrombosis complicated by pulmonary embolism in a patient with familial antithrombin III deficiency: a case report

BACKGROUND

Patients with low levels of antithrombin III (AT III) are at an increased risk of developing arteriovenous thromboembolic disease.

CASE SUMMARY

We report a case of a 28-year-old woman who presented with a 1-week history of spontaneous right calf pain and swelling. A heterozygous AT III deficiency, phenotypically expressed as deep vein thrombosis, was reported in the patient's mother and sister. Blood workup revealed residual AT III activity at 58% with normal protein C and protein S levels. Computed tomographic angiography (CTA) revealed subsegmental bilateral pulmonary embolism (PE) and deep vein thrombosis in the right leg extending into the inferior vena cava up to the confluence of the left renal vein. Placement of an inferior vena cava filter was not considered. Given the patient's haemodynamic stability, anticoagulant therapy with 15 mg of rivaroxaban twice a day was initiated instead. Echocardiography after 10 days of treatment revealed complete resolution of the thrombus located in the inferior vena cava, while CTA revealed complete resolution of the PE.

DISCUSSION

Patients with AT III deficiency are likely to be heparin-resistant and will require higher heparin doses or the administration of AT III replacement therapy for the treatment of thrombosis, both of which are associated with an increased risk for haemorrhagic complications. Direct factor Xa inhibition by rivaroxaban provided an alternative mechanism for anticoagulation, which was found to be particularly useful in this patient with familial AT III deficiency, deep vein thrombosis, and PE.

Hereditary Antithrombin Deficiency Presenting with Deep Venous Thrombosis During the Second Pregnancy

A 37-year-old woman developed deep venous thrombosis (DVT) of the left lower extremity at 8 weeks of gestation during her second pregnancy. There was no personal or family history of thrombosis. She received intravenous heparin, but heparin resistance was noted. The plasma antithrombin activity decreased to 45% in the acute phase, and it remained low postpartum. Her mother also had low plasma antithrombin activity (46%), and genetic testing revealed a heterozygous SERPINC1 mutation. Even without a family history of thrombosis, we should suspect hereditary antithrombin deficiency in patients with initial DVT and perform thorough investigation.

Therapeutic Implications of Inherited Thrombophilia in Pregnancy

BACKGROUND

Inherited (hereditary) thrombophilia is a genetic disorder that affects coagulation, being responsible for more than 60% of idiopathic (spontaneous or unprovoked) thromboembolic events. Association of inherited thrombophilia with pregnancy increases the risk of thromboembolic disease, and it may be related to many complications, such as preeclampsia, recurrent miscarriage intrauterine growth restriction, early detachment of placenta, and prematurity.

AREAS OF UNCERTAINTY

Interpretation of a positive test for thrombophilia in pregnant women is difficult because they have many natural changes in the coagulation system. Genetic diagnosis of thrombophilia, after a thrombotic event or during a pregnancy complication, has a major importance, not only to define its etiology but also to determine the duration of anticoagulant treatment and risk stratification for prophylaxis treatment.

DATA SOURCES

Literature search was performed using electronic database (PubMed) between April 1981 and November 2018. We used different keywords and MeSH terms to generate the most relevant results related to the inherited thrombophilia and its impact on pregnancy.

RESULTS

Screening for inherited thrombophilia in young women is recommended in case of personal history of venous thromboembolism, first-degree relatives with a history of high-risk thrombophilia, or personal history of second-trimester miscarriage. Decision to recommend thromboprophylaxis with anticoagulant treatment in pregnant women with inherited thrombophilia is determined by history of venous thromboembolism, type and associated risk of inherited thrombophilia, and presence of additional risk factors. Low-molecular-weight heparins are the preferred agents for prophylaxis in pregnancy, while the doses vary depending on thrombophilia type, personal history, and associated risk factors.

CONCLUSIONS

Association between 2 procoagulant conditions, inherited thrombophilia and pregnancy, has an important impact for the mother and fetus. This review will summarize the impact of each inherited prothrombotic factor on cardiovascular and pregnancy outcomes and will discuss the role of anticoagulation treatment for women diagnosed with inherited thrombophilia.

Potential different impact of inhibition of thrombin function and thrombin generation rate for the growth of thrombi formed at site of endothelial injury under blood flow condition

INTRODUCTION

Thrombin inhibitor and anti-Xa are now widely used in clinical practice. However, the difference between thrombin inhibitor and anti-Xa in prevention of thrombosis is still to be elucidated.

MATERIALS AND METHODS

Computer simulator implementing the function of platelet, coagulation, fibrinolysis and blood flow was developed. The function of thrombin is defined as to activated platelet at the rate of 0.01 s^-1 and to produce fibrin at the rate of 0.1 s^-1 in control. The effect of thrombin inhibitor was settled to reduce the rate of platelet activation and fibrin generation changed from 10 to 100% as compared to the control. The local thrombin generation rate on activated platelet was settled as 1.0 s^-1 as a control. The effect of anti-Xa was settled to reduce to thrombin generation rate on activated platelet from 10% to 100% as compared to the control. The sizes of thrombi formed at site of endothelial injury in the presence and absence of thrombin inhibitor and anti-Xa were compared.

RESULTS AND CONCLUSIONS

The size of thrombi formed by 30-s perfusion of blood at site of endothelial injury reduced both in the presence of thrombin inhibitor and anti-Xa. There was significant positive relationship between thrombin inhibitor effect and the size of formed thrombi with R value of 0.96. (p < 0.0001) However, the sizes of thrombi were not influence by anti-Xa until it decreased 30% or less as compared to control. There was no significant relationship between anti-Xa effect and the size of formed thrombi. (R = 0.39, p = 0.09) Our results suggest the different dose-dependent effects of thrombin inhibitor and anti-Xa on thrombus formation at least in specific conditions. Computer simulation may help to predict quantitative antithrombotic effects of various antithrombotic agents.

Efficacy of Oral Factor Xa Inhibitor for Venous Thromboembolism in a Patient with Antithrombin Deficiency

A 19-year-old man was referred due to sudden onset of right foot pain and chest discomfort. Contrast-enhanced computed tomography revealed massive thrombi in the right pulmonary artery and femoral vein. The patient's father had experienced multiple recurrences of venous thromboembolism (VTE) and was diagnosed with inherited antithrombin deficiency by a genetic examination. The patient was administered the oral factor Xa inhibitor rivaroxaban (30 mg). After seven days, the thrombus disappeared. Rivaroxaban (15 mg) was continued for 6 months with no recurrence, indicating the efficacy of this factor Xa inhibitor for the treatment and prevention of VTE in patients with antithrombin deficiency.

The influence of thrombophilia on the long-term survival of patients with a history of venous thromboembolism

Data on the long-term survival following venous thromboembolism (VTE) are rare,and the influence of thrombophilia has not been evaluated thus far. Our aim was to assess thrombophilia-parameters as predictors for long-term survival of patients with VTE. Overall, 1,905 outpatients (99 with antithrombin-, protein C or protein S deficiency, 517 with factor V Leiden, 381 with elevated factor VIII and 160 with elevated homocysteine levels, of these 202 had a combination and 961 had none of these risk factors) were included in the study between September 1, 1994 and December 31, 2007. Retrospective survival analysis showed that a total of 78 patients (4.1%) had died during the analysis period, among those four of definite or possible pulmonary embolism and four of bleeding. In multivariable analysis including age and sex an association with increased mortality was found for hyperhomocysteinemia (hazard ratio 2.0 [1.1.-3.5]) whereas this was not the case for all other investigated parameters. We conclude that the classical hereditary thrombophilia risk factors did not have an impact on the long-term survival of patients with a history of VTE. Thus our study supports the current concept that thrombophilia should not be a determinant for decision on long term anticoagulation. However, hyperhomocysteinaemia, known as a risk factor for recurrent VTE and arterial disease, might impact survival.

How I treat heterozygous hereditary antithrombin deficiency in pregnancy

Untreated hereditary antithrombin deficiency in pregnancy is associated with maternal venous thromboembolism (VTE) and possibly with fetal loss. Thromboprophylaxis during pregnancy is recommended, but dosages remain controversial. Our objective was to perform a retrospective assessment of thrombotic events and pregnancy outcomes in women with hereditary antithrombin deficiency managed according to a standard protocol. Pregnancies in individuals with hereditary antithrombin deficiency were identified from a hospital database. Women with no prior VTE received enoxaparin 40 mg daily until 16 weeks gestation and thereafter 40 mg twice daily. Women with prior VTE received intermediate dose enoxaparin (1 mg/kg) once daily, increased to twice daily at 16 weeks and anti-Xa monitored dosing. Thromboprophylaxis was stopped at initiation of labour or 12 hours prior to caesarean and 50 IU/kg antithrombin concentrate given. Thromboprophylaxis was restarted after delivery. Eighteen pregnancies in 11 women with antithrombin deficiency were identified. Seventeen pregnancies (94%) were successful. Median gestation was 39 weeks (range 30–41) and median birth-weight was 2,995 g (910–4,120 g),but 6/17 infants (35%) were small for gestational age (p=0.01). Estimated blood loss at delivery was median 375 ml (200–600 ml). Four pregnancies were complicated by VTE; one newly presented with a thrombotic event, two patients were not taking thromboprophylaxis and one occurred despite thromboprophylaxis. Two novel mutations(p.Leu317Ser and p.His33GInfsX32) are described. In conclusion, in antithrombin deficiency the use of low-molecular-weight heparin in pregnancy and puerperium with antithrombin concentrate predelivery was associated with successful pregnancy outcome; rates of VTE appear to be lower than previously reported, but remain elevated

Clinical and biochemical characterization of the prothrombin Belgrade mutation in a large Serbian pedigree: new insights into the antithrombin resistance mechanism

Essentials Prothrombin Belgrade mutation leads to antithrombin resistance. Clinical and biochemical phenotypes in a large family with this mutation were investigated. In carriers, we detected decreased factor II activity and increased endogenous thrombin potential. Prothrombin Belgrade mutation represents a strong prothrombotic risk factor.

SUMMARY

Background The recently reported c.1787G>A mutation in the prothrombin gene leads to Arg596Gln replacement in the protein molecule (prothrombin Belgrade). This substitution impairs binding of antithrombin to thrombin and results in inherited thrombophilia, known as antithrombin resistance. Objectives We aimed to elucidate the clinical and biochemical characteristics of thrombophilia associated with antithrombin resistance in a large Serbian family with the prothrombin Belgrade mutation. Patients and methods Nineteen family members were investigated, among whom 10 were carriers of the c.1787G>A mutation. In all subjects the clinical phenotype was determined and laboratory investigations of hemostatic parameters were performed. Results Six out of the 10 mutation carriers developed thromboembolic events, mainly deep venous and mesenteric vein thrombosis. The median age of the first thrombotic event was 26.5 (12-41) years, whereas the incidence rate of first thrombosis was 2.2% per year. In all mutation carriers prothrombin activity was significantly decreased in comparison with non-carriers, clearly distinguishing each group. However, the presence of the mutation did not affect the prothrombin antigen level in plasma. The endogenous thrombin potential was significantly increased in all carriers in comparison with non-carriers, indicating the presence of blood hypercoagulability. Interestingly, levels of D-dimer and the F1+2 fragment were similar in both groups. Conclusions Although rare, the prothrombin Belgrade mutation represents strong thrombophilia with early onset of thrombosis in the investigated family. According to our results, decreased prothrombin activity may be a simple screening test for detection of this mutation in thrombotic patients.

Hypercoagulable States

The hypercoagulable states consist of a group of prothrombotic clinical disorders associated with an increased risk for thromboembolic events. The abnormalities lead to inappropriate thrombus formation. After a review of the coagulation process, inherited disorders (including antithrombin-III deficiency, protein CS system deficiencies, disorders of plasmin generation, dysfibrinogenemias, and homocysteinuria) and acquired disorders (including responses to surgery, cancer, drugs, and the antiphospholipid syndrome) are described. Screening and management methods are discussed. Copyright © 1997 by W. B. Saunders Company.

Issues in the Diagnosis and Management of Hereditary Antithrombin Deficiency

Objective: To review insights gained in the past several years about hereditary antithrombin (AT) deficiency and to outline approaches to the management of patients with AT deficiency in the acute and chronic settings. Data Sources: An extensive literature search of Scopus (January 2008-April 2016) was performed for the terms congenital antithrombin deficiency, inherited antithrombin deficiency, or hereditary antithrombin deficiency. Additional references were identified by reviewing literature citations. Study Selection: All relevant English-language case reports, reviews, clinical studies, meeting abstracts, and book chapters assessing hereditary AT deficiency were included. Data Synthesis: AT deficiency significantly increases the risk of venous thromboembolism (VTE). The risk of VTE is particularly high during pregnancy, the postpartum period, and following major surgery. Effective clinical management includes determination of the appropriate type and duration of antithrombotic therapy (ie, AT replacement for acute situations) while minimizing the risk of bleeding. For persons newly diagnosed with AT deficiency, age, lifestyle, concurrent medical conditions, family history, and personal treatment preferences can be used to individualize patient management. Patients should be informed of the risks associated with hormonal therapy, pregnancy, surgical procedures, and immobility, which further increase the risk of VTE in patients with AT deficiency. Conclusion: AT deficiency poses the highest risk for VTE among the hereditary thrombophilias, often requiring long-term anticoagulation. Undertaking an evaluation for hereditary thrombophilia is controversial; however, a diagnosis of VTE in association with AT deficiency can have management implications. An important treatment option for patients with this disorder in high-risk situations is AT concentrate.

Outcome Analysis for Treatment in 100 Patients with Deep Vein Thrombosis

The treatment of acute deep vein thrombosis has been the subject of much research aimed at delineat ing the safest and most effective approach to diagnosis and treatment. Studies regarding long-term treatment have been limited by the narrow scope of laboratory and clinical analyses of many patients. In this study of 100 patients with a history of deep vein thrombosis, treated on an outpatient basis by a diverse group of clinicians, follow-up data were retrieved in order to determine the outcomes of various approaches to acute and long-term care. Among individuals followed for > 1 year, in only two patients (2%) was death attributable to a thrombotic event related to the etiology of the first episode of deep vein thrombosis. Most deceased patients succumbed to unrelated causes (11%). Among the 77 survivors, most (52%) received long-term antiplatelet therapy. All individ uals with a plasma coagulation defect, whether inherited or acquired, received anticoagulation with either heparin or warfarin. Since the long-term clinical outcome of most patients with deep vein thrombosis is dependent upon the underlying factor predisposing to thrombosis, the most important treatment decision is to select the therapy most likely to provide benefit without causing hemorrhage. An tiplatelet therapy, heparin, or warfarin may be chosen as appropriate for the individual patient.

Syndromes of Thrombosis and Hypercoagulability: Congenital and Acquired Thrombophilias

This article stresses the common hereditary and acquired blood protein defects associated with thrombosis. The most common of the hereditary defects apear to be APC-R, SPS, antithrombin, protein C, and protein S deficiency, and the most common acquired defects are anticardiolipin antibodies and the lupus anticoagulant (antiphospholipid antibodies). Therefore, these are the defects that should first be looked for in an individual with unexplained thrombosis. If these more common defects are not found, then the rarer defects including HC II, plasminogen or TPA deficiency, dysfibrinogenemia, el evated PAI-1 and hyperhomocysteinemia should be sought. The importance of finding these defects has significant impli cations for therapy of the individual patient and for institutions of family studies to identify, inform, and possibly treat others at risk. It is expected that as knowledge of hemostasis expands, more hereditary and acquired defects, such as elevated lipopro tein (a) or defects of extrinsic (tissue factor) pathway inhibitor (EPI, TFPI), may be associated with enhanced risks of throm bosis. Finally, it must be recalled that a diagnosis of thrombo sis, like that of anemia, is only a generic and partial diagnosis; just as in the anemic patient, the etiology must be clearly de fined. Only in this manner can cost-effective and appropriate therapy for both primary treatment and secondary prevention be designed. In addition, the demonstration of a hereditary defect will allow primary prevention in afflicted family mem bers by allowing the choice of appropriate therapy.

Inherited Thrombophilia

Thrombophilia alters normal hemostasis, shifting the balance in favor of thrombus formation. Inherited conditions include factor V Leiden (FVL), prothrombin G20210A mutation, deficiencies in natural anticoagulants (antithrombin [AT], protein C, and protein S), hyperhomocysteinemia, and elevations in clotting factors (factors VIII and XI). Although FVL and prothrombin mutation are common disorders, deficiencies in the natural anticoagulants are rare. The risk of initial thrombosis conferred by inherited thrombophilia varies with the highest risk in those homozygous for either FVL or prothrombin mutation, or with AT deficiency. In the nonpregnant patient, the presence of a thrombophilia does not affect treatment of an acute event. Although vitamin B supplementation has been shown to decrease the levels of homocysteine, the treatment has failed to show a benefit in thrombus prevention and is therefore not recommended.

Clinical profile, common thrombophilia markers and risk factors in 85 young Indian patients with arterial thrombosis

CONTEXT AND OBJECTIVE

Arterial thrombosis may occur consequent to hereditary thrombophilia and increased lipoprotein(a) [Lp(a)] and fibrinogen. Our aim was to study the prevalence of common thrombophilia markers in 85 consecutive cases of arterial thrombosis.

DESIGN AND SETTING

A retrospective study was conducted from 85 consecutive young patients treated as outpatients or admitted due to stroke or myocardial infarction at a tertiary care hospital.

METHODS

Eighty-five Indian patients (age < 45 years) presenting ischemic stroke (n = 48) or myocardial infarction (n = 37) and 50 controls were studied for seven thrombophilia markers including antithrombin (AT), factor V, protein C, protein S, activated protein C resistance (APC-R), fibrinogen and Lp(a). Functional assays for protein C, protein S, factor V and APC-R were performed using clotting-based methods. Semi-quantitative estimation of fibrinogen was done using Clauss's method and Lp(a) using immunoturbidimetry. Statistical analysis was done using the Epi Info 6 software.

RESULTS

Thirty-three samples (38.8%) tested positive for one or more thrombophilia markers. The three commonest abnormalities were elevated Lp(a) (20%), fibrinogen (17.6%) and low APC-R (14.2%). Low levels of protein C, protein S and AT were present in 4.7, 9.4 and 7% of the patients, respectively. Overall, the risk factor profile was: smoking (33%), positive family history (15.3%), hyperlipidemia (7%), hypertension, diabetes mellitus and obesity (2.3% each).

CONCLUSIONS

An association was found between low levels of protein C, protein S and AT and arterial thrombosis, but only elevated fibrinogen levels, smoking, positive family history and hyperlipidemia showed statistical significance.

Amelioration of the severity of heparin-binding antithrombin mutations by posttranslational mosaicism

The balance between actions of procoagulant and anticoagulant factors protects organisms from bleeding and thrombosis. Thus, antithrombin deficiency increases the risk of thrombosis, and complete quantitative deficiency results in intrauterine lethality. However, patients homozygous for L99F or R47C antithrombin mutations are viable. These mutations do not modify the folding or secretion of the protein, but abolish the glycosaminoglycan-induced activation of antithrombin by affecting the heparin-binding domain. We speculated that the natural β-glycoform of antithrombin might compensate for the effect of heparin-binding mutations. We purified α- and β-antithrombin glycoforms from plasma of 2 homozygous L99F patients. Heparin affinity chromatography and intrinsic fluorescence kinetic analyses demonstrated that the reduced heparin affinity of the α-L99F glycoform (K(D), 107.9 ± 3nM) was restored in the β-L99F glycoform (K(D), 53.9 ± 5nM) to values close to the activity of α-wild type (K(D), 43.9 ± 0.4nM). Accordingly, the β-L99F glycoform was fully activated by heparin. Similar results were observed for recombinant R47C and P41L, other heparin-binding antithrombin mutants. In conclusion, we identified a new type of mosaicism associated with mutations causing heparin-binding defects in antithrombin. The presence of a fully functional β-glycoform together with the activity retained by these variants helps to explain the viability of homozygous and the milder thrombotic risk of heterozygous patients with these specific antithrombin mutations.

Antithrombin Cambridge II(A384S) mutation frequency and antithrombin activity levels in 120 of deep venous thrombosis and 150 of cerebral infarction patients in a single center in Southern China

Antithrombin Cambridge II(A384S) mutation shows a relatively high frequency in western population. Some studies suggest that the mutation is an independent genetic risk factor both for deep vein thrombosis (DVT) and for arterial thrombosis, but whether the mutation has racial difference or has a general significance for thrombophilia remains unclear. In this study we performed an analysis of the prevalence of the mutation in Chinese southern population; Also, the antithrombin activity levels were evaluated in each investigated individual. The studies included 120 patients with DVT, 150 patients with cerebral infarction, and 110 controls. The mutation was detected using polymerase chain reaction/PvuII restrictive fragment length polymorphism procedures. Antithrombin activity assay was done using chromogenic substrate method. The results showed that no antithrombin Cambridge II mutation was detected in all three groups (DVT, cerebral infarction and controls), the incidence was 0/380. Plasma antithrombin activity was 91.37% +/- 16.15% in the DVT patients and 102.68% +/- 13.10% in the controls; the antithrombin activity was significantly reduced in the DVT group (P < 0.0001). In DVT patients, eight cases were identified as primary antithrombin deficiency, accounting for an incidence of 6.7%. No significant difference was found for antithrombin activity between cerebral infarction group and controls. These results suggest that antithrombin Cambridge II mutation has a racial difference, and may not be a valuable risk factor of thrombophilia in Asian population, and antithrombin deficiency remains a major genetic risk factor for DVT patients in China.

Hypercoagulable state in a patient with a retinal vein occlusion

PURPOSE

The purpose of this study was to report unusual findings from a hypercoagu-lability workup of a patient with a retinal vein occlusion and to suggest the importance of investigating hypercoagulability in patients with similar presentations.

METHODS

This is a retrospective case report of a patient seen in the clinic during a several-month period.

RESULTS

The laboratory evaluation of the patient showed decreased antithrombin III activity and a prothrombin mutation, and platelet evaluation was consistent with sticky platelet syndrome.

CONCLUSION

It is important to take a detailed history and pursue the possibility of hypercoagulability as an etiology for retinal vein occlusion in patients outside the classic, younger age group. This can lead to prompt intervention and possible prevention of future thrombotic events.

Prevalence of common thrombophilia markers and risk factors in Indian patients with primary venous thrombosis

CONTEXT AND OBJECTIVE

venous thrombosis occurs as a result of interaction of genetic and acquired factors including activated protein C resistance (APC-R), fibrinogen levels, antithrombin, protein C, protein S, lupus anticoagulants and anticardiolipin antibodies. This study was aimed at determining the prevalence of these common thrombophilia markers in Asian Indians with primary venous thrombosis.

DESIGN AND SETTING

this was a cross-sectional study carried out in Mumbai.

METHODS

samples from 78 patients with a confirmed diagnosis of venous thrombosis and 50 controls were tested. Semi-quantitative estimation (functional assays) of protein C, protein S and antithrombin was performed. Quantitative estimation of fibrinogen was done using the Clauss method. Lupus anticoagulants were screened using lupus-sensitive activated partial thromboplastin time and β2-glycoprotein-I dependent anticardiolipin antibodies were estimated by ELISA. APC-R was measured using a clotting-based method with factor V deficient plasma and Crotalus viridis venom. Statistical analysis was performed using Epi-info (version 6).

RESULTS

the popliteal vein was the most commonly involved site. Forty-four samples (56%) gave abnormal results. The commonest were elevated fibrinogen and APC-R (17.9% each), followed by low protein S (16.6%).

CONCLUSIONS

this study confirms the literature findings that fibrinogen level estimation and screening for APC-R are important for the work-up on venous thrombosis patients since these, singly or in combination, may lead to a primary thrombotic episode. The frequency of the other thrombophilia markers was higher among the patients than among the controls, but without statistically significant difference.

Haemorrhagic transformation of cerebral infarction in an AIDS patient--thrombophilia screen essential!

Patients with advanced HIV disease with low CD4 count are more prone to thrombo-embolism and various predisposing factors have been identified. These include the presence of anticardiolipin antibodies and the lupus anticoagulant, deficiencies of proteins C and S, heparin co-factor II and antithrombin. Increased levels of Von Willebrand factor and d-dimers have also been linked with thrombo-embolism, as has the presence of concurrent infections and malignancies. We report a case of an AIDS patient who presented with acute hemiparesis. He was severely immunosuppressed. Computed tomography of the head confirmed cerebral infarction with haemorrhagic transformation. He had no known risk factors apart from being severely immunocompromised and had high anticardiolipin antibodies and low free protein S.

Use of subcutaneous lepirudin in an obese surgical intensive care unit patient with heparin resistance

OBJECTIVE

To report the use of subcutaneous lepirudin in an obese patient with heparin resistance.

CASE SUMMARY

A 34-year-old morbidly obese male (weight 145 kg) presented with hypoxia on postoperative day 1 following a sigmoid colectomy. A continuous unfractionated heparin infusion was started for a suspected pulmonary embolism. Doses were escalated without therapeutic activated partial thromboplastin time (aPTT) response and an antithrombin (AT) level was obtained. The AT level was reported as 78% (reference range 85-120%). Computed tomography angiography ruled out pulmonary embolism and lepirudin 50 mg administered subcutaneously twice daily was started (serum creatinine 1.3 mg/dL) for prevention of venous thromboembolism. The resulting aPTT values were therapeutic (63 and 60 sec, reference range 24-34, therapeutic heparin range 55-85). The dose was adjusted to 25 mg twice daily. aPTT values were 35 and 48 seconds. His serum creatinine increased to 1.6 mg/dL and minor bleeding was noted. The dose was decreased to 25 mg once daily, with resulting aPTT values of 31, 39, and 41 seconds. The patient was discharged to home without development of venous thromboembolism, as confirmed by duplex ultrasonography.

DISCUSSION

Commonly administered anticoagulants, such as unfractionated heparin, low-molecular-weight heparins, and fondaparinux, exert their effect by complexing with AT and thrombin (Factor IIa), activating AT and preventing thrombin from exerting coagulation effect. Without AT present, these drugs have little effect on inhibiting the coagulation cascade. Lepirudin is a synthetic irreversible direct thrombin inhibitor and does not rely on AT to exert its anticoagulation action. It can be given subcutaneously and is eliminated primarily by the kidneys. Dosage adjustments for both renal function and obesity need to be considered and aPTT should be monitored.

CONCLUSIONS

In obese patients or those with heparin resistance, subcutaneous lepirudin can be monitored and the regimen adjusted based on aPTT values. Further studies are warranted to maximize efficacy and define dosing.

Pulmonary embolism from persistent dilatation of the bladder secondary to anticholinergic side effects

OBJECTIVE

To discuss the risk that bladder distention resulting from anticholinergic side effects of antipsychotics can cause iliac vein compression syndrome (IVCS) and subsequent pulmonary embolism (PE).

METHOD

Case report, review of the literature and discussion.

RESULTS

We report the case of a 65-year-old man with depression who experienced PE associated with IVCS due to a distended urinary bladder resulting from anticholinergic side effects. PE disappeared after conservative therapy with heparin followed by warfarin.

CONCLUSION

When drugs with anticholinergic effects are given to immobilized patients such as those with severe depression, close observation including monitoring of urine volume is needed to prevent IVCS caused by drug-induced urinary retention, and subsequent PE.

Inherited Thrombophilia

Inherited thrombophilia can be defined as a genetically determined predisposition to the development of thromboembolic complications. Since the discovery of activated protein C resistance in 1993, several additional disorders have been described and, at present, it is possible to identify an inherited predisposition in about 60 to 70% of patients with such complications. These inherited prothrombotic risk factors include qualitative or quantitative defects of coagulation factor inhibitors, increased levels or function of coagulation factors, defects of the fibrinolytic system, altered platelet function, and hyperhomocysteinemia. In this review, the main inherited prothrombotic risk factors are analyzed from epidemiological, laboratory, clinical, and therapeutic points of view. Finally, we discuss the synergism between genetic and acquired prothrombotic risk factors in particular conditions such as childhood and pregnancy.

[Resistance to curative treatment by unfractionned heparin]

Unfractionated heparin has been used as antithrombotic therapy for many years. Its main effect is attributed to the activation of antithrombin (AT), the heparin/AT complex inactivating both factor IIa (thrombin) and factor Xa. Resistance to unfractionated heparin with clinical or biological expression is uncommon. The occurrence of venous or arterial thrombosis or the extension of thrombosis in a patient receiving unfractionated heparin, should always raise suspicion of either AT deficiency or type 2 heparin-induced thrombocytopenia (HIT type 2). HIT type 2 is not a true heparin resistance but an immune complication that requires heparin discontinuation and the use of alternative anticoagulants. Biological heparin resistance is suspected in the presence of a normal or not prolonged activated partial thromboplastin time despite the administration of increasing dose of heparin. Measurement of anti-Xa activity is useful to adjust heparin treatment. Isolated biological heparin resistance is encountered in several physiological and pathological situations including inflammatory and infectious disorders, pregnancy and thrombocytosis. It also occurs in acquired antithrombin deficiency of nephrotic syndrome, l-asparaginase treatment or cardiopulmonary bypass. Biological heparin resistance is relatively common, but clinically significant resistance to heparin is rare and should always raise suspicion of either AT deficiency or type 2 heparin-induced thrombocytopenia.

Oestrogen treatment of constitutional tall stature in girls: is there a risk of thrombosis or bleeding?

AIM

To evaluate haemostatic effects and clinical outcome of oestrogen treatment of constitutionally tall stature in girls.

METHODS

We conducted a single-centre cohort study, 63 girls referred over a period of 15 years were investigated. The girls were given oestrogen treatment for constitutional tall stature at a median initial dose of 300 ug ethinyl estradiol/day and were consecutively examined for changes in coagulation. Medical records were retrospectively reviewed, additional data were collected at follow-up by blood sampling and interviews.

RESULTS

After 1 year of treatment, levels of antithrombin and von Willebrand factor (VWF) were significantly decreased (p<0.001 and p=0.015, respectively), whereas there was no significant change in levels of plasminogen inhibitor type 1. No venous thromboembolism (VTE) or major side effects were observed. Genetic risk factors for thrombosis were present, as was expected. The mean height reduction was 5.5 cm. The height-reducing effect was inversely correlated with chronological age (r=-0.44, p<0.01) and bone age (r=-0.61, p<0.01).

CONCLUSIONS

Changes in coagulation parameters occurred both towards pro- and anticoagulation. Treatment with high-dose ethinyl estradiol can successfully limit final height, and it is most effective when started at a younger bone age.

Antithrombotic therapy and pregnancy: consensus report and recommendations for prevention and treatment of venous thromboembolism and adverse pregnancy outcomes

Venous thromboembolism and adverse pregnancy outcomes are potential complications of pregnancy. Numerous studies have evaluated both the risk factors for and the prevention and management of these outcomes in pregnant patients. This consensus group was convened to provide concise recommendations, based on the currently available literature, regarding the use of antithrombotic therapy in pregnant patients at risk for venous thromboembolic events and adverse pregnancy outcomes.

Superior mesenteric and portal vein thrombosis caused by congenital antithrombin III deficiency: report of a case

A 50-year-old man presented with a 24-h history of gradually worsening abdominal pain. Enhanced computed tomography showed segmental dilation of the small intestine, wall thickening, and ascites, as well as thrombosis of the superior mesenteric vein (SMV) and portal vein. Thus, an emergency laparotomy was performed, which revealed segmental intestinal infarction caused by the thrombosis in the SMV and portal vein. We resected the necrosed intestine and performed anastomosis. The patient was given intravenous heparin and nafamostat mesilate as anticoagulation therapy. The abdominal pain again recurred 4 days after this operation, necessitating a second laparotomy. Segmental congestion of the intestine was found and another resection was done, after which he recovered rapidly. Blood chemistry subsequently revealed an antithrombin III deficiency, which was confirmed to be inherent, after screening his family. Thus, laboratory testing for these proteins may help define the cause of mesenteric venous thrombosis.

Antithrombin Nagasaki (Ser 116 to Pro): a rare antithrombin variant with abnormal heparin binding presenting during pregnancy

Quantitative antithrombin deficiency constitutes an important risk factor for venous thromboembolism, stillbirth, and other complications of pregnancy. Studies suggest, however, that individuals heterozygous for missense mutations involving the heparin-binding site of antithrombin do not have a significantly increased thrombotic risk. Owing to the rarity of such mutations, it remains unclear whether any specific heparin-binding site defects might be associated with thrombotic potential. We report here the case of a pregnant woman with an exceptionally rare Type II heparin-binding site antithrombin variant. This case highlights the difficult issues that are associated with the management of Type II antithrombin deficiency during pregnancy.

Factor V Leiden mutation in cerebrovascular disease

Several studies indicate a high prevalence of factor V Leiden mutation as the most frequent coagulation defect found in patients with venous thrombosis. The relationship between this mutation and cerebrovascular disease has not been established in adults. In this investigation, we studied 29 patients with ischemic stroke and 20 with intracerebral hemorrhage, all of whom were compared with 20 controls. A region of the factor V gene containing the Leiden mutation site was amplified with polymerase chain reaction and the presence of mutation was determined with restriction enzyme digestion. We found no evidence of an association between factor V Leiden mutation and ischemic stroke or intracerebral hemorrhage. There was no evidence of association in subgroup the analysis by age, smoking status, myocardial infarction, hypertension, diabetes mellitus, or coronary disease. Factor V Leiden mutation doesn't seem to be associated with a risk of cerebrovascular disease.

Prothrombotic abnormalities in childhood ischaemic stroke

Childhood ischaemic stroke, incorporating arterial ischaemic stroke and cerebral sinus venous thrombosis, is associated with significant morbidity and mortality in children. The majority of cases in children present with well-recognised risk factors. The appreciation of the role prothrombotic abnormalities have in disease states is developing rapidly. Prothrombotic abnormalities are abnormalities of the coagulation system, fibrinolytic system, endothelial cells or platelets that lead to a reduced threshold for pathological thrombus formation. Our understanding of the role of prothrombotic abnormalities in childhood ischaemic stroke is increasing and has a direct bearing on the development of effective management and prevention strategies. We provide a brief background of prothrombotic abnormalities and review the available literature on prothrombotic markers in childhood ischaemic stroke. Overall, prothrombotic abnormalities have been identified in 20-50% of children presenting with AIS and 33-99% of children with cerebral sinus venous thrombosis. There appear to be a number of associations emerging including an increased frequency of factor V Leiden mutation, elevated lipoprotein (a), protein C deficiency and antiphospholipid antibodies in children presenting with arterial ischaemic stroke. The pathogenic role of prothrombotic abnormalities as predisposing to initial and recurrent childhood ischaemic stroke is becoming increasingly evident. The impact on treatment, however, will only be clarified with carefully designed, multi-institutional prospective studies.

Deep vein thrombosis

Deep vein thrombosis and its sequelae pulmonary embolism and post-thrombotic syndrome are some of the most common disorders. A thrombus either arises spontaneously or is caused by clinical conditions including surgery, trauma, or prolonged bed rest. In these instances, prophylaxis with low-dose anticoagulation is effective. Diagnosis of deep vein thrombosis relies on imaging techniques such as ultrasonography or venography. Only about 25% of symptomatic patients have a thrombus. Thus, clinical risk assessment and D-dimer measurement are used to rule out deep vein thrombosis. Thrombus progression and embolisation can be prevented by low-molecular-weight heparin followed by vitamin K antagonists. Use of these antagonists for 3-6 months is sufficient for many patients. Those with antithrombin deficiency, the lupus anticoagulant, homozygous or combined defects, or with previous deep vein thrombosis can benefit from indefinite anticoagulation. In cancer patients, low-molecular-weight heparin is more effective than and is at least as safe as vitamin K antagonists. Women seem to have a lower thrombosis risk than men, but pregnancy or use of oral contraceptives or hormone replacement therapy represent important risk factors.

Risk of a first venous thrombotic event in carriers of a familial thrombophilic defect. The European Prospective Cohort on Thrombophilia (EPCOT)

BACKGROUND

Reliable risk estimates for venous thrombosis in families with inherited thrombophilia are scarce but necessary for determining optimal screening and treatment policies.

OBJECTIVES

In the present analysis, we determined the risk of a first venous thrombotic event in carriers of a thrombophilic defect (i.e. antithrombin-, protein C- or protein S deficiency, or factor V Leiden).

PATIENTS AND METHODS

The asymptomatic carriers had been tested prior to this study in nine European thrombosis centers because of a symptomatic carrier in the family, and were followed prospectively for 5.7 years on average between March 1994 and January 2001. Annually, data were recorded on the occurrence of risk situations for venous thrombosis and events (e.g. venous thrombosis, death).

RESULTS

Twenty-six of the 575 asymptomatic carriers (4.5%) and seven of the 1118 controls (0.6%) experienced a first deep venous thrombosis or pulmonary embolism during follow-up. Of these events, 58% occurred spontaneously in the carriers compared with 43% in the controls. The incidence of first events was 0.8% per year (95% CI 0.5-1.2) in the carriers compared with 0.1% per year (95% CI 0.0-0.2) in the controls. The highest incidence was associated with antithrombin deficiency or combined defects, and the lowest incidence with factor V Leiden.

CONCLUSIONS

The incidence of venous events in asymptomatic individuals from thrombophilic families does not exceed the risk of bleeding associated with long-term anticoagulant treatment in the literature (1-3%).