The inherited basis of venous thrombosis

Purification and characterization of thrombin from camel plasma: interaction with camel tick salivary gland thrombin inhibitor

BACKGROUND

Thrombin is the most important enzyme in the hemostatic process by permitting rapid and localized coagulation in case of tissue damage. Camel thrombin is the natural and proper target enzyme for the previously purified camel tick salivary gland thrombin inhibitor.

RESULTS

In this study, the camel thrombin was purified homogenously in a single affinity chromatographic step on the heparin-agarose affinity column with a specific activity of 3242 NIH units/mg proteins. On SDS-PAGE, the purified camel thrombin contained two forms, 37 kDa α-thrombin and 28 kDa β-thrombin, and the camel prothrombin was visualized as 72 kDa. The camel thrombin Km value was found out as 60 µM of N-(p-Tosyl)-Gly-Pro-Arg-p-nitroanilide acetate and displayed its optimum activity at pH 8.3. The PMSF was the most potent inhibitor of camel thrombin. Camel tick salivary gland thrombin inhibitor has two binding sites on camel thrombin and inhibited it competitively with Ki value of 0.45 µM.

CONCLUSIONS

The purified camel thrombin was found to be more susceptible toward the camel tick salivary gland thrombin inhibitor than bovine thrombin.

Does exist a correlation between endometriosis and thrombophilic disorders? A pilot study

OBJECTIVE

At present, there is growing evidence of the existence of a genetic predisposition in both thrombophilic disorders and endometriosis. The aim of our study was to evaluate for the first time the prevalence of some thrombophilic disorders in patients with endometriosis.

MATERIALS AND METHODS

We conducted a retrospective study on 138 patients with endometriosis and 278 healthy control women. All women were subjected to a blood examination testing for thrombophilic screening and the variables examinated were: hyperhomocysteinemia, factor V Leiden and factor II prothrombin G20210A mutations in heterozygosis and homozigosis.

RESULTS

A significant reduced prevalence (p < 0.05) of factor V Leiden mutation in endometriosis patients was found, whereas no significant differences (p = NS) for factor II and hyperhomocysteinemia were observed.

CONCLUSION

Our preliminary data do not show any association between thrombophilic condition and endometriosis. Before assuming hormonal therapies, a thrombophilic plasmatic screening seems to be unnecessary in patients affected by endometriosis.

Deep-vein thrombosis prophylaxis in foot and ankle surgery: what is the current state of practice?

BACKGROUND

When contemplating thromboprophylaxis for patients undergoing elective foot and ankle surgery the potential for complications secondary to venous thromboembolism (VTE) must be balanced against the cost, risk, and effectiveness of prophylactic treatment. The incidence of pulmonary embolism (PE) following foot and ankle surgery is considerably lower than after hip or knee surgery. The purpose of this study was to assess current trends in practice regarding VTE prophylaxis among expert orthopaedic foot and ankle surgeons.

METHODS

An e-mail-based survey of active AOFAS (American Orthopaedic Foot and Ankle Society) committee members was conducted (n = 100). Surgeons were questioned as to their use, type, and duration of thromboprophylaxis following elective ankle fusion surgery. Scenarios included the following: (1) A 50-year-old woman with no risk factors; (2) a 50-year-old woman with a history of PE; and (3) a 35-year-old woman actively using birth control pills (BCPs).

RESULTS

The response rate for the survey was 80% (80/100). Replies regarding the use of thromboprophylaxis were as follows: (1) in the absence of risk factors, 57% of respondents (45/80) answered, "No prophylaxis required"; (2) for the scenario in which the patient had experienced a previous PE, 97.5% of respondents (78/80) answered, "Yes" to prophylaxis use; (3) for the scenario in which the patient was on BCP, 61.3% of respondents (49/80) stated that they would give some type of thromboprophylaxis. The most commonly recommended methods of prophylaxis were aspirin, 49% (24/49), and low-molecular-weight heparin, 47% (23/49). The recommended length of time for thromboprophylaxis varied widely, from 1 day to more than 6 weeks.

CONCLUSION

. There remains wide variation in the practice of deep-vein thrombosis thromboprophylaxis within the foot and ankle community. Because risks for foot and ankle patients differ from those in the well-studied areas of hip and knee, specific guidelines are needed for foot and ankle surgery.

LEVELS OF EVIDENCE

Level V: Expert Opinion.

Deep venous thrombosis following different isolated lower extremity fractures: what is known about prevalences, locations, risk factors and prophylaxis?

INTRODUCTION

Deep venous thrombosis (DVT) offers a high risk of morbidity and mortality, especially in case of pulmonary embolism. Precise data as to DVT after isolated lower extremity fractures (ILEFs) are rare. Even organizations like the American Academy of Orthopaedic Surgeons or the American College of Chest Physicians do not state exact recommendations as to optimal DVT prophylaxis (ppx) after ILEFs.

PREVALENCE

The incidence of DVT ranges from 5 to 86 % depending on the fracture whereas femur fractures offer the highest risk for clotting. The incidence seems to decrease in more distal fractures.

LOCATION

The risk to develop proximal clots is likely low, however, especially these are feared by surgeons. DVT can occur in both the injured and uninjured leg with a trend for higher incidences in the injured leg.

RISK FACTORS

Risk factors for DVT after ILEF seem to be similar to risk factors for DVT development after orthopaedic surgery and in general. Risk factors caused by surgeons are the use of a tourniquet, prolonged operative time and a delay from injury to surgery.

PROPHYLAXIS

Low molecular weight heparin is favoured by many authors, however, warfarin and acetylsalicylic acid are also used. Clear recommendations are still missing.

CONCLUSION

The rate of morbidity caused by DVT after ILEF is poorly understood so far. Exact data on prevalences are missing and optimal DVT prophylaxis still has to be defined.

Near real-time immuno-optical sensor for diagnosing single point mutation: a model system: sensor for factor V Leiden diagnosis

Factor V leiden (FVL) is an abnormality of factor V (FV), a blood coagulation factor. It is a hereditary blood coagulation disorder with a high frequency (3-7% of general population). The most common type of FVL is caused by a single amino acid mutation and, therefore, its diagnosis is currently done only by DNA analysis, which takes a long time and is expensive. We have developed a rapid, accurate, and cost-effective, sandwich immuno-optical sensing method. To produce monoclonal antibodies against FV or FVL, having minimal cross-reactivity with the other molecule, a 20 amino acid sequence (20-mer) of FV or FVL at around the mutation site was utilized. The antibodies were screened first with the 20-mers and then the ones showing no cross-affinity were reacted with native FV or FVL molecules and they showed some cross-reactivity. Using two antibodies having strongest affinity to either FV or FVL molecule, a FV and a FVL preferred sensors, were produced. After verifying that the levels of the antibody affinity to the two different molecules remained constant with changes in analyte concentration, a two-sensor system is developed to quantify FV and FVL in plasma samples. The system quantified the levels of FV and FVL at the maximum error of 0.5 microg/ml-plasma, in their physiological concentration range of 0-12 microg/ml-plasma. The levels of both molecules may provide us whether the patient has FVL or not but also the seriousness level of the disease (homozygous and different level of heterozygous).

Factor V Leiden and increased risk for arterial thrombotic disease in young Brazilian patients

The contribution of mutations in the prothrombin (FII G20210A), methylenetetrahydrofolate reductase (C677T) genes and factor V Leiden (FVL) to the pathogenesis of arterial thrombosis remains controversial. In this study, these polymorphisms were investigated by polymerase chain reaction-restriction fragment length polymorphism in a group of 53 patients that presented arterial thrombosis other than myocardial infarction as a first thrombotic event and 275 control subjects living in the state of Minas Gerais, Brazil. Odds ratio (OR) and chi tests were applied for statistical comparisons. Similar frequencies were detected among patients and control subjects for the C677T mutation. The 20210A mutation was present in 3.6% of the control subjects but was not detected among ischemic stroke patients. Significant differences were detected only for factor V Leiden (odds ratio 7.11; 95% confidence interval 1.55-32.73). Our data indicate that, among these genetic factors, factor V Leiden was identified as an important risk factor for arterial thrombosis in this group of patients. In addition, our results indicate regional differences in the incidence of these genetic factors in Brazil, as compared to the incidences reported in other studies.

Fluorophore-mediated, fiber-optic, multi-analyte, immunosensing system for rapid diagnosis and prognosis of cardiovascular diseases

A prototype of a fiber-optic, multi-analyte, immunobiosensing system was developed to simultaneously quantify disease-representing biomarkers in blood plasma. This system was for simultaneous quantification of two different groups of multi-biomarkers related to cardiovascular diseases (CVD): anticoagulants (protein C, protein S, antithrombin III, and plasminogen) for deficiency diagnosis; and cardiac markers (B-type natriuretic peptide, cardiac troponin I, myoglobin, and C-reactive protein) for coronary heart disease diagnosis. As an initial effort towards the development of a disposable and easy-to-use sensing cartridge as a rapid diagnostic tool for CVD related diseases, a prototype of a flow control system was also developed to automatically perform simultaneous four-analyte quantification. Currently, the system is capable of quantifying the multiple anticoagulants in their clinically significant sensing ranges within 5 minutes, at an average signal-to-noise (S/N) ratio of 25. A simultaneous assay of the four cardiac markers can be performed within 10 min, at an average S/N ratio of 20. When this highly portable multi-analyte sensing system is completed and successfully tested for CVD patient's plasma, it can provide rapid (<10 min) and reliable diagnostic and prognostic information at a patient's bedside.

Evaluation of the modifying effects of unfavourable genotypes on classical clinical risk factors for ischaemic stroke

OBJECTIVES

Ischaemic stroke is a frequent heterogeneous multifactorial disease that is affected by a number of genetic mutations and environmental factors. We hypothesised the clinical importance of the interactions between common, unfavourable genetic mutations and clinical risk factors in the development of ischaemic stroke.

METHODS

The Factor V Leiden G1691A (Leiden V), the prothrombin G20210A, the methylenetetrahydrofolate reductase C677T (MTHFR C677T) mutations, the angiotensin converting enzyme I/D (ACE I/D), and apolipoprotein allele e4 (APO e4) genotypes were examined by the polymerase chain reaction (PCR) technique in 867 ischaemic stroke patients and 743 healthy controls. Logistic regression models were used to estimate the roles of the co-occurrences of the clinical risk factors and common genetic mutations in ischaemic stroke.

RESULTS

The Leiden V mutation in combination with hypertension or diabetes mellitus increased the risk of ischaemic stroke. We found synergistic effects between the ACE D/D and MTHFR 677TT genotypes and drinking or smoking. The presence of the APO e4 greatly facilitated the unfavourable effects of hypertension, diabetes mellitus, smoking, or drinking on the incidence of ischaemic stroke.

CONCLUSION

In certain combinations, pairing of common unfavourable genetic factors, which alone confer only minor or non-significant risk, with clinical risk factors can greatly increase the susceptibility to ischaemic stroke.

Infestin, a thrombin inhibitor presents in Triatoma infestans midgut, a Chagas' disease vector: gene cloning, expression and characterization of the inhibitor

This work describes the purification, gene cloning and expression of infestin, a thrombin inhibitor from midguts of Triatoma infestans. Infestin is located in the midgut and its purification was performed by anion-exchange and affinity chromatographies. The N-terminal sequence and the sequence of tryptic peptides were determined. Using RT-PCR, total RNA and infestin cDNA information, a DNA fragment was cloned which encodes a multi non-classical Kazal-type serine protease inhibitor. Isolated native infestin has two non-classical Kazal-type domains and shows an apparent molecular mass of 13 kDa, while its gene codes for a protein with four non-classical Kazal-type domains corresponding to an apparent molecular mass of 22 kDa. Two recombinant infestins, r-infestin 1-2 and r-infestin 1-4, were constructed using the vector pVT102U/alpha and expressed in S. cerevisiae. Native and r-infestin 1-2 showed very similar inhibitory activities towards thrombin and trypsin with dissociation constants of 43.5 and 25 pM for thrombin and 2.0 and 3.1 nM for trypsin, respectively. No other serine protease of the blood coagulation cascade was inhibited by the r-infestin 1-2. Surprisingly, r-infestin 1-4 inhibited not only thrombin and trypsin (K(i) of 0.8 and 5.2 nM, respectively), but also factor XIIa, factor Xa and plasmin (K(i) of 78 pM, 59.2 and 1.1 nM, respectively).

Pulmonary embolism following operative treatment of ankle fractures: a report of three cases and review of the literature

The risks of thromboembolism following operative treatment of ankle fractures are deep vein thrombosis (DVT) and pulmonary embolism (PE). These are potentially life-threatening complications. Many orthopedic surgeons fail to appreciate the potential complications of thromboembolic events because of their rare and delayed occurrence in foot and ankle operations. The purpose of this report is to describe the potential for DVT and PE following ankle operations. We present three cases in which patients who underwent operative treatment of ankle fractures subsequently developed PE. We also review the literature on the prevalence of thrombosis, risk factors, methods of prophylaxis, and use of prophylaxis in surgical procedures of the lower extremity.

Genetic thrombophilia in patients with retinal vascular occlusion

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Contraception in women at high risk or with established cardiovascular disease

Oral contraceptives are one of the most effective and widely used reversible contraceptive methods. Over 90 million women worldwide, including over 44 million in developing countries, are now using oral contraceptives. Despite their advantages, there is concern about the links between combined oral contraceptives and the risk of cardiovascular disease. The risk attributable to oral contraceptive use in women < 35 years of age is small, even if they smoke, but there are substantially increased risks in older women who both smoke and use oral contraceptives. Differences between oral contraceptive types in the relative risk of venous thromboembolism contribute little to the total cardiovascular mortality associated with oral contraceptive use, even though the total number of cardiovascular events is increased. It is important to consider the user's age and smoking status when determining oral contraceptive-attributable risks. Hormonal oral contraceptives have changed and now contain lower doses of estrogen and progestagen.

Prevalence of methylenetetrahydrofolate reductase mutations in patients with venous thrombosis

BACKGROUND

The objectives of this study are to examine the prevalence of combined methylenetetrahydrofolate reductase (MTHFR) 677C-->T and 1298A-->C mutations in patients with venous thrombosis (VT) and healthy volunteers and to determine if these mutations are in Hardy-Weinberg equilibrium.

METHODS AND RESULTS

Sixty-five patients with VT and 64 healthy volunteers were assessed for MTHFR 677T and 1298C alleles using polymerase chain reaction and restriction fragment length polymorphism. Observed MTHFR genotype frequencies were compared with expected genotype combinations, and their odds ratios were determined. MTHFR allele frequency did not differ between VT and control groups; however, differences were observed for MTHFR genotype distribution. MTHFR 677T and 1298C alleles occurred in cis in our population, and therefore mutation crossover has occurred. There was deviation from the Hardy-Weinberg equilibrium for combined MTHFR genotypes, although this may at least partly be attributable to linkage disequilibrium. MTHFR 677CT/1298CC and 677TT/1298CC genotypes (P<.05) were not observed in either group.

CONCLUSIONS

The absence of MTHFR 677CT/1298CC and 677TT/1298CC genotypes in both groups suggests that certain MTHFR genotypes may carry a selective advantage. Our discovery of a substantial number of MTHFR mutations in cis configuration suggests that any MTHFR allele linkage disequilibrium present is incomplete.

Retinal vascular occlusion and deficiencies in the protein C pathway

PURPOSE

To report abnormalities in the protein C pathway and other vascular occlusion risk factors in patients with retinal vascular occlusion.

METHODS

In a study, we investigated 76 consecutive patients who had in-patient evaluation of venous or arterial retinal vascular occlusion. All patients underwent comprehensive tests for coagulation disorders including determinations of protein C, protein S, lupus anticoagulants, and resistance to activated protein C and were screened for vascular disease risk factors. Resistance to activated protein C was confirmed by a polymerase chain reaction method to detect the specific factor V R506Q mutation. For comparative purposes, we also screened 209 consecutive inpatients with deep vein thrombosis from the same geographic region for resistance to activated protein C as well as protein C and protein S deficiencies.

RESULTS

Ten (29%) of 35 patients with central retinal vein occlusion (CRVO) had factor V R506Q mutation. The factor V R506Q mutation was detected in four (19%) of 21 patients with branch retinal vein occlusion. The higher frequency in factor V R506Q mutation compared with the expected 9% mutation prevalence in a white population was highly significant for the central retinal vein occlusion group but not for the branch retinal vein occlusion group. In all patients with resistance to activated protein C, the factor V R506Q mutation was detected; 16 were heterozygous, one homozygous. No cases of lupus anticoagulants, protein C, or protein S deficiencies were detected. Forty (19%) of 209 patients with deep vein thrombosis were carriers of the factor V R506Q mutation.

CONCLUSIONS

The prevalence of the factor V R506Q mutation is similar in patients with central retinal vein occlusion and patients with deep vein thrombosis and represents a relevant risk factor. Screening for this mutation is therefore recommended in all patients with central retinal vein occlusion.

Genetic determinants of heritable venous thrombosis: genotyping methods for factor V(Leiden)A1691G, methylenetetrahydrofolate reductase C677T, prothrombin G20210A mutation, and algorithms for venous thrombosis investigations

OBJECTIVES

To implement cost effective and clinically relevant thrombophilic genotyping and homocysteine analysis in our coagulation laboratory.

METHODS

We describe genotyping assays for three of the genetic defects associated with hereditary thrombosis: factor V(Leiden) A1691G, methylenetetrahydrofolate reductase C677T, and prothrombin gene G20210A. A second confirmatory assay for factor V(Leiden) using allele specific oligonucleotide polymerase chain reaction is also presented. We suggest an algorithm for the rational integration of the traditional assays routinely used to investigate venous thrombosis with genotyping and plasma homocysteine measurements.

RESULTS

These polymerase chain reaction based assays were designed to be performed under identical reaction conditions, permitting simultaneous setup, amplification, digestion, and analysis.

CONCLUSIONS

The three genotyping assays presented are robust and relatively easy to perform. Use of an algorithm will ensure efficient resource utilization and minimize unnecessary testing.