Hypercoagulability in venous and arterial thrombosis

Thromboelastometry for assessment of hemostasis and disease severity in 42 dogs with naturally-occurring heatstroke

BACKGROUND

Thromboelastometry (TEM) provides a comprehensive overview of the entire coagulation process and has not been evaluated in heatstroke-induced coagulopathies in dogs.

OBJECTIVES

To determine the diagnostic and prognostic utility of TEM in dogs with heatstroke.

ANIMALS

Forty-two client-owned dogs with heatstroke.

METHODS

Prospective observational study. Blood samples for intrinsic and extrinsic TEM (INTEM and EXTEM, respectively) were collected at presentation and every 12 to 24 hours for 48 hours. Coagulation phenotype (hypo-, normo-, or hypercoagulable) was defined based on TEM area under the 1st derivative curve (AUC).

RESULTS

Case fatality rate was 31%. Median TEM variables associated with death (P < .05 for all) included longer INTEM clotting time, lower AUC at presentation and at 12 to 24 hours postpresentation (PP), lower INTEM alpha angle, maximum clot firmness, and maximum lysis (ML) at 12 to 24 hours PP, and lower EXTEM ML at 12 to 24 hours PP. Most dogs were normo-coagulable on presentation (66% and 63% on EXTEM and INTEM, respectively), but hypo-coagulable 12 to 24 PP (63% for both EXTEM and INTEM). A hypo-coagulable INTEM phenotype was more frequent at presentation and 12 to 24 PP among nonsurvivors compared to survivors (55% vs 15% and 100% vs 50%, P = .045 and .026, respectively). AKI was more frequent (P = .015) in dogs with hypo-coagulable INTEM tracings at 12 to 24 hours. Disseminated intravascular coagulation was more frequent (P < .05) in dogs with a hypo-coagulable INTEM phenotype and in nonsurvivors at all timepoints.

CONCLUSIONS AND CLINICAL RELEVANCE

Hypocoagulability, based on INTEM AUC, is predictive of worse prognosis and occurrence of secondary complications.

Acute effects of high intensity interval training versus moderate intensity continuous training on haemostasis in patients with coronary artery disease

Exercise training is associated with an acute net increase in coagulation, which may increase the risk of atherothrombosis in coronary artery disease (CAD) patients. We sought to compare the acute haemostatic effects of a bout of moderate-intensity continuous (MICT) and high-intensity interval training (HIIT) in patients with CAD. Patients after a recent myocardial infarction were randomized into a HIIT or MICT session of exercise training on a stationary bike. Blood was sampled at baseline, after the exercise bout and after a one-hour resting period. We measured overall haemostatic potential (OHP), overall coagulation potential (OCP), fibrinogen, D-dimer and von Willebrand factor (vWF) and calculated overall fibrinolytic potential (OFP). Linear mixed models for repeated measures were constructed to assess the treatment effect. A total of 117 patients were included. OCP, OHP, fibrinogen, D-dimer and vWF significantly increased after exercise and returned to baseline after a one-hour rest, OFP decreased after exercise and returned to baseline levels after a one-hour rest. Linear mixed models showed a significant difference between HIIT and MICT in fibrinogen (p 0.043) and D-dimer (p 0.042). Our study has shown that an exercise bout is associated with a transient procoagulant state in patients with CAD, with similar exercise-induced haemostatic changes for HIIT and MICT.

The effect of rivaroxaban on biomarkers in blood and plasma: a review of preclinical and clinical evidence

Rivaroxaban is a direct, oral factor Xa inhibitor that is used for the prevention and treatment of various thromboembolic disorders. Several preclinical and clinical studies have utilized specific molecules as biomarkers to investigate the potential role of rivaroxaban beyond its anticoagulant activity and across a range of biological processes. The aim of this review is to summarize the existing evidence regarding the use of blood-based biomarkers to characterize the effects of rivaroxaban on coagulation and other pathways, including platelet activation, inflammation and endothelial effects. After a literature search using PubMed, almost 100 preclinical and clinical studies were identified that investigated the effects of rivaroxaban using molecular biomarkers. In agreement with the preclinical data, clinical studies reported a trend for reduction in the blood concentrations of D-dimers, thrombin-antithrombin complex and prothrombin fragment 1 + 2 following treatment with rivaroxaban in both healthy individuals and those with various chronic conditions. Preclinical and also some clinical studies have also reported a potential impact of rivaroxaban on the concentrations of platelet activation biomarkers (von Willebrand factor, P-selectin and thrombomodulin), endothelial activation biomarkers (matrix metalloproteinase-9, intercellular adhesion molecule-1 and vascular cell adhesion molecule-1) and inflammation biomarkers (interleukin-6, tumor necrosis factor-α and monocyte chemoattractant protein-1). Based on the results of biomarker studies, molecular biomarkers can be used in addition to traditional coagulation assays to increase the understanding of the anticoagulation effects of rivaroxaban. Moreover, there is preliminary evidence to suggest that rivaroxaban may have an impact on the biological pathways of platelet activation, endothelial activation and inflammation; however, owing to paucity of clinical data to investigate the trends reported in preclinical studies, further investigation is required to clarify these observations.

What is the best prophylaxis against venous thromboembolism in Asians following total knee arthroplasty? A systematic review and network meta-analysis

PURPOSE

Asians have a low venous thromboembolism (VTE) incidence following total knee arthroplasty (TKA). This systematic review and network meta-analysis was conducted to evaluate the best prophylaxis against VTE in Asians following total knee arthroplasty in current literature.

MATERIALS AND METHODS

A systematic search of PubMed, Embase and CINAHL was conducted in adherence with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Prophylaxis types were separated into low-molecular-weight heparin (LMWH), novel oral anti-coagulants (NOAC), mechanical-only prophylaxis (MOP) and no prophylaxis (NP). The primary outcome was VTE incidence, grouped according to diagnosis modality (ultrasound, venography, clinical). The secondary outcome was bleeding incidence, grouped into minor and major bleeding.

RESULTS

Fourteen eligible articles, totalling 4259 patients, were pooled with the following significant results: NOACs had lower venography-diagnosed VTE incidence than LMWH (12.77%, p = 0.02) and NP (20.64, p < 0.001). MOP had lower venography-diagnosed VTE incidence than LMWH (23.72%, p < 0.001), NOACs (10.95%, p < 0.001) and NP (31.59%, p < 0.001) but, interestingly, a statistically higher ultrasound-diagnosed VTE incidence than LMWH (6.56%, p = 0.024) and NP (4.88%, p = 0.026). No significant differences were observed between prophylaxis types for symptomatic VTE, pulmonary embolism (PE) or death. LMWH and NOACs had a higher minor bleeding incidence than NP (11.71%, p < 0.001 and 6.33%, p < 0.02, respectively). No significant differences were observed between prophylaxis types for major bleeding incidence.

CONCLUSION

NOACs are a superior form of chemoprophylaxis, compared with LMWH, in reducing venography-diagnosed VTE incidence with no added bleeding incidence. However, routine chemoprophylaxis may not be required as LMWH and NOACs do not appear to reduce symptomatic VTE incidence compared with MOP and NP with an increased minor bleeding incidence. Mechanical prophylaxis in the form of graduated compression stockings or intermittent pneumatic compression should be routinely considered with significantly lower rates of venography-diagnosed VTE compared with NP. On the basis of current evidence, we recommend an individualised approach to select the most appropriate prophylaxis type.

Thrombosis as the First Manifestation of Granulomatosis with Polyangiitis Disease in an Adolescent

Background

Granulomatosis with polyangiitis disease (GPA) is a rare vasculitis characterized by granulomatous inflammation of respiratory tracts, glomerulonephritis, and vasculitis of other organs. Case Presentation. A 13-year-old girl was referred due to swelling and pain on her left arm. The Doppler and compression ultrasonography showed noncompressible left brachial and axillary vein thrombosis. Sinus computed tomography (CT) demonstrated pansinusitis, and spiral chest CT showed alveolar hemorrhage. Laboratory tests showed hematuria, proteinuria, and highly positive antineutrophil cytoplasmic antibody (cANCA). Laboratory tests of coagulopathy were normal. The patient was recognized as a case of GPA.

Conclusion

Although GPA is not frequently associated with thrombosis especially in children, this is the first report that shows thrombosis may be the first manifestation of GPA in an adolescent.

Incidence of venous thromboembolism in Asian patients undergoing anterior cruciate ligament reconstruction without the use of mechanical or chemical prophylaxis

Background:

Venous thromboembolism (VTE) is a clinically relevant complication of major orthopedic surgeries. The prevalence of VTE and the indications for VTE thromboprophylaxis in Asian patients undergoing arthroscopic anterior cruciate ligament (ACL) reconstruction are not clear. This study aims to evaluate the prevalence of clinically significant venous thromboembolic events (VTE) in Asian patients undergoing arthroscopic ACL reconstruction without mechanical or chemical thromboprophylaxis.

Methods:

All patients who underwent ACL reconstruction by a single surgeon from 2006 to 2018 in a single tertiary institution were reviewed. The inclusion criteria for the study included Asian patients of common ethnic groups in Singapore (Chinese, Malay, Indian) and underwent primary or revision ACL reconstruction, or ACL reconstruction combined with meniscal surgery. The exclusion criteria were patients with incomplete medical records, pre-existing anticoagulant treatment within 1 year prior to the surgery and additional procedures that altered the standard rehabilitation protocol, less than 6 months of follow-up duration. All patients received general anesthesia. The single-bundle ACL technique with autologous hamstring tendon reconstruction was performed. No chemical DVT prophylaxis was given. The patients were screened for clinically for VTE. Symptomatic patients were referred for ultrasonography.

Results:

Of the 581 patients reviewed, 3 patients had a clinical suspicion of deep vein thrombosis, but subsequent ultrasonography showed no thrombosis. Hence, the prevalence of clinically significant VTE was 0%.

Conclusion:

Given the low prevalence of clinically significant VTE, there is no need for routine mechanical or chemical thromboprophylaxis or radiologic screening in Asian patients undergoing arthroscopic ACL reconstruction.

Asymptomatic Deep Venous Thrombosis After Elective Hip Surgery Could Be Allowed to Remain in Place Without Thromboprophylaxis After a Minimum 2-Year Follow-Up

BACKGROUND

It is not clear how to treat asymptomatic deep venous thromboses (DVTs) following elective hip arthroplasty because the natural course of DVTs is unclear. It is therefore valuable to understand the natural course of DVTs and their relation to thromboprophylactic methods.

METHODS

We followed 742 consecutive patients who underwent elective hip arthroplasty followed by mechanical or chemical prophylaxis of a DVT. All patients underwent preoperative and postoperative duplex ultrasonography of both limbs. Patients who developed postoperative DVT in the popliteal or calf vein were followed without thromboprophylaxis. DVT-positive patients were prospectively followed up with duplex ultrasonography at 3, 6, 12, and 24 months postoperatively.

RESULTS

Incidences of preoperative and postoperative DVTs were 3.9% and 33.0%, respectively. Nonfatal pulmonary embolism (PE) occurred in 1 patient after negative echography. All DVTs that developed in the calf vein postoperatively and without anticoagulation remained benign, and 93% of the DVTs ultimately disappeared.

CONCLUSION

These results confirmed that the natural course of asymptomatic distal DVTs is benign, with no risk of leading to PE. Thus, distal DVTs could be allowed to remain untreated without chemical prophylaxis to prevent PE in Asian populations.

The effect of hyperthyroidism on procoagulant, anticoagulant and fibrinolytic factors

Several coagulation and fibrinolytic parameters appear to be affected by thyroid hormone excess;however, the net effect on the haemostatic system remains unclear. We aimed to update our previous review and systematically summarise and meta-analyse the data by assessing the effects of thyrotoxicosis on the coagulation and fibrinolytic system in vivo. Data sources included MEDLINE (2006–2012), EMBASE (2006–2012), and reference lists. The sources were combined with our previous search containing studies from 1980–2006. Eligible studies were all observational or experimental studies. Two investigators independently extracted data and rated study quality. Weighted mean proportion and 95% confidence intervals were calculated and pooled using a fixed and a random-effects model. A total of 29 articles consisting of 51 studies were included, as in several articles more than one study was described. We included four intervention (before and after treatment in hyperthyroid patients), five cross-sectional (hyperthyroid subjects and euthyroid controls), and four experimental (before and after use of thyroid hormone in euthyroid subjects) medium/high quality studies for meta-analysis. We found that thyrotoxicosis shifts the haemostatic balance towards a hypercoagulable and hypofibrinolytic state with a rise in factors VIII and IX, fibrinogen, von Willebrand factor, and plasminogen activator inhibitor-1. This was observed in endogenous and exogenous thyrotoxicosis, and in subclinical as well as overt hyperthyroidism. We conclude that both subclinical and overt hyperthyroidism induce a prothrombotic state, which is therefore likely to be a risk factor for venous thrombosis.

A Mathematical Model of Venous Thrombosis Initiation

We present a mathematical model for the initiation of venous thrombosis (VT) due to slow flow and the consequent activation of the endothelial cells (ECs) lining the vein, in the absence of overt mechanical disruption of the EC layer. It includes all reactions of the tissue factor (TF) pathway of coagulation through fibrin formation, incorporates the accumulation of blood cells on activated ECs, accounts for the flow-mediated delivery and removal of coagulation proteins and blood cells from the locus of the reactions, and accounts for the activity of major inhibitors including heparan-sulfate-accelerated antithrombin and activated protein C. The model reveals that the occurrence of robust thrombin generation (a thrombin burst) depends in a threshold manner on the density of TF on the activated ECs and on the concentration of thrombomodulin and the degree of heparan-sulfate accelerated antithrombin activity on those cells. Small changes in any of these in appropriate narrow ranges switches the response between "no burst" and "burst." The model predicts synergies among the inhibitors, both in terms of each inhibitor's multiple targets, and in terms of interactions between the different inhibitors. The model strongly suggests that the rate and extent of accumulation of activated monocytes, platelets, and MPs that can support the coagulation reactions has a powerful influence on whether a thrombin burst occurs and the thrombin response when it does. The slow rate of accumulation of cells supporting coagulation is one reason that the progress of VT is so much slower than that of arterial thrombosis initiated by subendothelial exposure.

Hemostasis in Hypothyroidism and Autoimmune Thyroid Disorders

CONTEXT

There are contradictory results on the effect of hypothyroidism on the changes in hemostasis. Inadequate population-based studies limited their clinical implications, mainly on the risk of venous thromboembolism (VTE). This paper reviews the studies on laboratory and population-based findings regarding hemostatic changes and risk of VTE in hypothyroidism and autoimmune thyroid disorders.

EVIDENCE ACQUISITION

A comprehensive literature search was conducted employing MEDLINE database. The following words were used for the search: Hypothyroidism; thyroiditis, autoimmune; blood coagulation factors; blood coagulation tests; hemostasis, blood coagulation disorders; thyroid hormones; myxedema; venous thromboembolism; fibrinolysis, receptors thyroid hormone. The papers that were related to hypothyroidism and autoimmune thyroid disorder and hemostasis are used in this review.

RESULTS

Overt hypothyroidism is more associated with a hypocoagulable state. Decreased platelet count, aggregation and agglutination, von Willebrand factor antigen and activity, several coagulation factors such as factor VIII, IX, XI, VII, and plasminogen activator-1 are detected in overt hypothyrodism. Increased fibrinogen has been detected in subclinical hypothyroidism and autoimmune thyroid disease rendering a tendency towards a hypercoagulability state. Increased factor VII and its activity, and plasminogen activator inhibitor-1 are among several findings contributing to a prothrombotic state in subclinical hypothyroidism.

CONCLUSIONS

Overt hypothyroidism is associated with a hypocoagulable state and subclinical hypothyroidism and autoimmune thyroid disorders may induce a prothrombotic state. However, there are contradictory findings for the abovementioned thyroid disorders. Prospective studies on the risk of VTE in various levels of hypofunctioning of the thyroid and autoimmune thyroid disorders are warranted.

Prevalence of Venous Thromboembolic Events Is Low in Asians After Total Knee Arthroplasty Without Chemoprophylaxis

BACKGROUND

This retrospective cohort study was designed to establish the prevalence of clinically significant venous thromboembolic events (VTE) in our patients undergoing total knee arthroplasty (TKA) without chemoprophylaxis.

METHODS

A single-surgeon cohort of patients who underwent TKA from 2006 to 2014 were included. All patients had a pneumatic tourniquet applied and a drain inserted postoperatively. Tranexamic acid was not used perioperatively. All patients were under a standardized postoperative protocol with routine mechanical prophylaxis against VTE. None of the patients received prophylactic anticoagulation. All patients ambulated on the second postoperative day. Only symptomatic patients were referred for radiological examination to exclude VTE. We evaluated the patient demographics and calculated the prevalence of VTE in our cohort.

RESULTS

A total of 966 patients were reviewed. Mean age was 66.1 ± 7.8 years. Mean body mass index was 28.2 ± 4.7 kg/m². Mean tourniquet time was 53 ± 23 minutes. Patients stayed in hospital for a mean of 5.4 ± 3.1 days. There was 100% compliance to mechanical prophylaxis. And 11.1% of our patients were on concomitant antiplatelet or anticoagulant use. There were 8 patients with clinically significant VTE. This translates to a prevalence of 0.82%. Seven patients developed deep vein thrombosis and 1 patient died from massive pulmonary embolism.

CONCLUSION

The prevalence of clinically significant VTE in our patients who underwent TKA without routine chemoprophylaxis is 0.82%. With proper patient selection, risk stratification, and stringent perioperative protocols, routine chemoprophylaxis may not be necessary in Asians undergoing TKA.

Prevalence of Deep Vein Thrombosis and Pulmonary Embolism Treated with Mechanical Compression Device After Total Knee Arthroplasty in Asian Patients

The purpose of this study was: (1) to determine the prevalence of deep vein thrombosis (DVT) after the use of a mechanical compression device only, without pharmacological thromboprophylaxis; (2) to investigate the factors associated with DVT; and (3) to investigate the natural course of DVT and PE. We reviewed consecutive series of 874 patients (1434 knees) who received treatment with a mechanical compression device only for prevention of DVT after primary TKA. The prevalence of DVT was 6.6% (94 of 1434 knees). Proximal thrombi were found in 6 of 1434 knees (0.4%). No patient had PE on perfusion lung scans. Further sonograms and venograms for the patients with thrombi at 6 months after the operation revealed that all thrombi were resolved.

Prevalence of deep vein thrombosis and pulmonary embolism treated with mechanical compression device after total hip arthroplasty

Several reports have suggested that there is a strikingly low prevalence of deep vein thrombosis (DVT) and pulmonary embolism (PE) after total hip arthroplasty (THA) in Asian patients. We determined the prevalence of DVT and PE after the use of a mechanical compression device only without pharmacological thromboprophylaxis in 459 patients (516 hips). The overall prevalence of DVT was 4.8% (27 of 561 hips). Nine of 27 hips had proximal thrombi. Three patients (0.7%) had asymptomatic PE. In our patients, combinations of absent thrombophilic polymorphisms with low clinical prothrombotic risk factors led to a low prevalence of DVT and virtually no symptomatic PE. Therefore, mechanical compression device only suffices to prevent DVT and PE in Asian patients.

The use of pneumatic tourniquets is safe in Asians undergoing total knee arthroplasty without anticoagulation

BACKGROUND

There has always been controversy surrounding the use of pneumatic tourniquets in total knee arthroplasty (TKA) as they have been implicated in venous thromboembolic events (VTE). We aimed to evaluate the incidence of clinically significant VTE in Asians who underwent conventional TKA under tourniquet throughout the duration of surgery, without post-operative chemical VTE prophylaxis, but using post-operative pneumatic compression devices.

METHODS

Five hundred and thirty-one patients of a single surgeon who underwent elective total knee arthroplasty were retrospectively reviewed. All patients had a tourniquet applied to the operated limb. None of the patients received chemoprophylaxis against VTE. Post-operatively, only symptomatic patients were referred for ultrasonography. The patients were then stratified according to the tourniquet time: <60, 61 to 90, 91 to 120, and >120 min. The overall incidence as well as the incidence of venous thromboembolic events for each group was then calculated.

RESULTS

Of the 531 patients reviewed, 3 patients suffered from deep venous thrombosis (DVT) while 1 patient developed a fatal pulmonary embolism (PE). Hence, the overall incidence of clinically significant VTE was 0.75%. The 3 patients with DVT had tourniquet time of 61 to 90 min while the patient with PE had a tourniquet time of more than 120 min.

CONCLUSION

With a low overall incidence of VTE, the use of tourniquet in Asians during conventional total knee arthroplasty appears safe when post-operative pneumatic compression devices are used instead of chemical VTE prophylaxis. However, the risk of VTE seems to increase with a tourniquet time of more than 60 min.

LEVEL OF EVIDENCE

Therapeutic studies, level III.

Does venous thromboembolism affect rehabilitation after hip fracture surgery?

PURPOSE

Venous thromboembolism (VTE), including deep vein thrombosis and pulmonary embolism, is a serious and life-threatening complication in elderly (older than 65 years) patients undergoing hip fracture surgery (HFS). However, few have reported on the influences of VTE on postoperative rehabilitation in these patients. This study was performed to determine whether VTE affects clinical outcomes in patients who underwent HFS.

MATERIALS AND METHODS

We retrospectively evaluated 330 HFSs in 325 consecutive patients, which were performed from January 2009 to June 2010. From chart review, we identified 15 patients with symptomatic VTE. We compared Geriatric depression scale, Modified Barthel index and Berg balance scale scores as well as 10 meter gait speed at discharge and hospital stay between a symptomatic VTE group and a non-VTE group.

RESULTS

No significant difference in clinical outcomes at discharge between the two groups was found, although hospital stay was longer in patients with symptomatic VTE (p=0.012).

CONCLUSION

East Asian patients have a low incidence of symptomatic VTE after HFS, and the clinical outcomes of patients with symptomatic VTE were similar to patients without VTE, although there was a longer rehabilitation period.

Alterations of specific biomarkers of metabolic pathways in vascular tree from patients with Type 2 diabetes

The aims of this study were to check whether different biomarkers of inflammatory, apoptotic, immunological or lipid pathways had altered their expression in the occluded popliteal artery (OPA) compared with the internal mammary artery (IMA) and femoral vein (FV) and to examine whether glycemic control influenced the expression of these genes. The study included 20 patients with advanced atherosclerosis and type 2 diabetes mellitus, 15 of whom had peripheral arterial occlusive disease (PAOD), from whom samples of OPA and FV were collected. PAOD patients were classified based on their HbA1c as well (HbA1c ≤ 6.5) or poorly (HbA1c > 6.5) controlled patients. Controls for arteries without atherosclerosis comprised 5 IMA from patients with ischemic cardiomyopathy (ICM). mRNA, protein expression and histological studies were analyzed in IMA, OPA and FV. After analyzing 46 genes, OPA showed higher expression levels than IMA or FV for genes involved in thrombosis (F3), apoptosis (MMP2, MMP9, TIMP1 and TIM3), lipid metabolism (LRP1 and NDUFA), immune response (TLR2) and monocytes adhesion (CD83). Remarkably, MMP-9 expression was lower in OPA from well-controlled patients. In FV from diabetic patients with HbA1c ≤6.5, gene expression levels of BCL2, CDKN1A, COX2, NDUFA and SREBP2 were higher than in FV from those with HbA1c >6.5.

The atherosclerotic process in OPA from diabetic patients was associated with high expression levels of inflammatory, lipid metabolism and apoptotic biomarkers. The degree of glycemic control was associated with gene expression markers of apoptosis, lipid metabolism and antioxidants in FV. However, the effect of glycemic control on pro-atherosclerotic gene expression was very low in arteries with established atherosclerosis.

Incidence of clinically significant venous thromboembolic events in Asian patients undergoing total knee arthroplasty without anticoagulation

This study aimed to evaluate the incidence of clinically significant venous thromboembolic events (VTE) in Asian patients undergoing total knee arthroplasty (TKA) without anticoagulation. All patients who underwent TKA by a single surgeon from 2006 to 2010 in Singapore General Hospital were reviewed. Only symptomatic patients were referred for ultrasonography. Of the 531 patients reviewed, 3 patients developed symptoms of deep vein thrombosis with subsequent ultrasonographic confirmation, whereas 1 patient developed fatal pulmonary embolism without any clinical or radiologic evidence of deep vein thrombosis. Hence, the incidence of clinically significant VTE was 0.75%. Given the low incidence of clinically significant VTE, there is a need to review the current practice of routine chemoprophylaxis in Asian patients undergoing TKA.

Deep venous thrombosis and pulmonary embolism are uncommon in East Asian patients after total hip arthroplasty

BACKGROUND

In Western countries, deep vein thrombosis (DVT) and pulmonary embolism (PE), are relatively common after THA and many surgeons recommend routine pharmacologic thromboprophylaxis. There is some suggestion in the literature that the incidences of DVT and PE may be lower in East Asian patients. Therefore, it would be important to establish the incidences in a large number of East Asian patients who did not receive pharmacologic thromboprophylaxis.

PURPOSE

We therefore determined the incidence of DVT and PE and evaluated the associated risk factors in a series of East Asian patients who underwent primary THA without pharmacologic prophylaxis.

METHODS

We retrospectively evaluated all 861 patients who underwent 992 elective primary THAs from May 2003 to December 2009. We identified patients with symptomatic DVT, symptomatic PE, and fatal PE. For potential risk factors we considered age, gender, body mass index (BMI), administration of aspirin, type of anesthesia, operation time, approach, simultaneous bilateral THAs, and duration of immobilization between symptomatic and asymptomatic patients.

RESULTS

We identified eight patients with symptomatic DVT, one of whom also had a symptomatic PE; there were no cases of fatal PE. The incidences of fatal PE, symptomatic PE, and symptomatic DVT were 0 %, 0.1 %, and 0.8 %, respectively. Longer duration of immobilization predicted symptomatic DVT or PE.

CONCLUSIONS

East Asian patients have a low incidence of symptomatic DVT and PE and virtually no fatal PEs after primary THA. The incidences and risk factors should be taken into consideration when deciding whether to prophylactically treat these patients with pharmacologic agents.

LEVEL OF EVIDENCE

Level IV, prognostic study. See the Guidelines for Authors for a complete description of levels of evidence.

[Diagnosis and management of acute mesenteric ischemia]

The prevalence of significant splanchnic arterial stenoses is increasing, but remains mostly asymptomatic due to abundant collateral circulation. Acute insufficiency of mesenteric arterial blood flow accounts for 60 to 70% of cases of mesenteric ischemia and results mostly from a superior mesenteric embolus. Despite major advances have been achieved in understanding the pathogenic mechanisms of bowel ischemia, its prognosis remains dismal with mortality rates about 60%. The diagnosis of acute mesenteric ischemia depends upon a high clinical suspicion, especially in patients with known risk factors. Rapid diagnosis is essential to prevent intestinal infarction. However, early signs and symptoms of mesenteric ischemia are non specific, and definitive diagnosis often requires radiologic examinations. Early and liberal implementation of angiography has been the major advance over the past 30 years which allowed increasing diagnostic accuracy of acute mesenteric ischemia. CT and MR-based angiographic techniques have emerged as alternatives less invasive and more accurate to analyse splanchnic vessels and evaluate bowel infarction. The goal of treatment of patients with acute mesenteric ischemia is to restore intestinal oxygenation as quickly as possible after initial management that includes rapid hemodynamic monitoring and support. Surgery should not be delayed in patients suspected of having intestinal necrosis.

Is routine chemical thromboprophylaxis after total hip replacement really necessary in a Japanese population?

Prophylaxis against venous thromboembolism after elective total hip replacement is routinely recommended. Our preference has been to use mechanical prophylaxis without anticoagulant drugs. A randomised controlled trial was performed to evaluate whether the incidence of post-operative venous thromboembolism was reduced by using pharmacological anticoagulation with either fondaparinux or enoxaparin in addition to our prophylactic mechanical regimen. A total of 255 Japanese patients who underwent primary unilateral cementless total hip replacement were randomly assigned to one of three postoperative regimens, namely injection of placebo (saline), fondaparinux or enoxaparin. There were 85 patients in each group. All also received the same mechanical prophylaxis during and after the operation, regardless of their assigned group. The primary measurement of efficacy was the presence of a venous thromboembolic event by day 11, defined as deep-vein thrombosis detected by ultrasonography, documented symptomatic deep-vein thrombosis or documented symptomatic pulmonary embolism. The duration of follow-up was 12 weeks.

The rate of venous thromboembolism was 7.2% with the placebo, 7.1% with fondaparinux and 6.0% with enoxaparin (p = 0.95 for the comparison of all three groups). Our study confirmed the effectiveness and safety of mechanical thromboprophylaxis without the use of anticoagulant drugs after total hip replacement in Japanese patients.

Retrograde superior mesenteric artery stenting for acute mesenteric arterial thrombosis

Retrograde superior mesenteric artery stenting (ROMS) represents a significant development in the treatment of acute mesenteric ischemia. Compared to traditional surgical mesenteric bypass, ROMS is a less invasive technique that avoids many complications associated with emergent mesenteric bypass. This case report illustrates that retrograde superior mesenteric artery (SMA) stenting is an option for the treatment of acute mesenteric ischemia for patients in extremis.

The etiology and pathogenesis of vascular disorders of the intestine

Intestinal ischemia includes all the conditions in which the blood supply to the gastrointestinal tract is not adequate to its metabolic demand. Several ischemic intestinal disorders differ in clinical presentation (acute versus chronic), etiology (occlusive versus nonocclusive), pathophysiology (arterial or venous), severity (mucosal versus transmural necrosis), and location (small bowel versus large bowel). Atherosclerosis, thromboembolic disease, hypoperfusion states, and hypercoagulable disorders are the most common causes. Reperfusion, oxygen-derived free radicals, and eicosanoids contribute to the pathogenesis of bowel injury and the systemic response that occur after ischemia. The diagnosis and treatment of intestinal ischemia are still challenging despite the advances of radiology, intensive care, and surgery. This article reviews the latest data about etiology and pathophysiology of bowel ischemia to explain the bases of diagnosis and treatment of this condition.

Fibrinogen-elongated gamma chain inhibits thrombin-induced platelet response, hindering the interaction with different receptors

The expression of the elongated fibrinogen gamma chain, termed gamma', derives from alternative splicing of mRNA and causes an insertion sequence of 20 amino acids. This insertion domain interacts with the anion-binding exosite (ABE)-II of thrombin. This study investigated whether and how gamma' chain binding to ABE-II affects thrombin interaction with its platelet receptors, i.e. glycoprotein Ibalpha (GpIbalpha), protease-activated receptor (PAR) 1, and PAR4. Both synthetic gamma' peptide and fibrinogen fragment D*, containing the elongated gamma' chain, inhibited thrombin-induced platelet aggregation up to 70%, with IC(50) values of 42+/-3.5 and 0.47+/-0.03 microm, respectively. Solid-phase binding and spectrofluorimetric assays showed that both fragment D* and the synthetic gamma' peptide specifically bind to thrombin ABE-II and competitively inhibit the thrombin binding to GpIbalpha with a mean K(i) approximately 0.5 and approximately 35 microm, respectively. Both these gamma' chain-containing ligands allosterically inhibited thrombin cleavage of a synthetic PAR1 peptide, of native PAR1 molecules on intact platelets, and of the synthetic chromogenic peptide D-Phe-pipecolyl-Arg-p-nitroanilide. PAR4 cleavage was unaffected. In summary, fibrinogen gamma' chain binds with high affinity to thrombin and inhibits with combined mechanisms the platelet response to thrombin. Thus, its variations in vivo may affect the hemostatic balance in arterial circulation.

Relationship between Progression to AIDS and Thrombophilic Abnormalities in HIV Infection

Background: HIV-infected patients are at increased risk of venous and arterial thrombosis. We hypothesized that acquired thrombophilic abnormalities that could predispose to thrombosis are most pronounced in patients in advanced stages of HIV infection.

Methods: We included 109 consecutive HIV-infected patients in the study and tested them twice for currently known thrombophilic abnormalities at an interval of at least 3 months (median, 3 months; range, 3–12 months). Detailed information was collected about the date of diagnosis of HIV infection, HIV treatment, and previous episodes of venous and arterial thrombosis.

Results: After HIV infection was diagnosed, 16% of the patients experienced symptomatic thrombosis (venous, 10%; arterial, 6%). Repeated measurements established protein C deficiency in 9% of the patients, increased factor VIII concentrations in 41%, high fibrinogen concentrations in 22%, and free protein S deficiency in 60%. Median factor VIII concentrations were higher in patients with AIDS (CD4 cell counts &lt;2 × 108/L) than in patients with a non–AIDS-defining illness (2260 IU/L vs 1 490 IU/L; P &lt; 0.001), whereas median free protein S concentrations were lower (450 IU/L vs 580 IU/L; P &lt; 0.001). Developing AIDS was associated with increasing factor VIII concentrations and decreasing free protein S concentrations. Increasing factor VIII concentrations were correlated with increasing fibrinogen concentrations and decreasing free protein S concentrations.

Conclusions: Multiple acquired and persistent thrombophilic abnormalities are more frequently observed in HIV-infected patients than in the healthy population. The frequencies of these thrombophilic abnormalities increase with the progression to AIDS. These findings may contribute to the high prevalence of venous and arterial thrombosis in HIV-infected patients.

The 2007 John Charnley Award. Factors leading to low prevalence of DVT and pulmonary embolism after THA: analysis of genetic and prothrombotic factors

We evaluated 136 hips (104 patients) to determine the prevalence of and contributing factors in deep vein thrombosis (DVT) and pulmonary embolism (PE) in those who were not given thromboprophylaxis when undergoing primary cementless total hip arthroplasty (THA). We performed coagulation assays, a full blood count, blood typing, and serum chemical profile tests for all patients on three separate occasions. Molecular genetic testing was performed preoperatively to detect the genetic traits involving DVT. DVT was diagnosed by roentgenographic venography, and PE was diagnosed by perfusion lung scanning. Our patients had a low prevalence of DVT and no patient had PE. Patients with bilateral THA had similar rates (p = 0.158; CI, -0.134-0.125) of venographic DVT as patients with unilateral THA (16 of 65 or 25% versus 12 of 72 or 17% respectively). We observed a relationship between DVT and factor V Leiden mutation, antithrombin-III level, and prothrombin promoter G20210A mutation. We saw no relationship between DVT and coagulation or thrombophilic data. We conclude combinations of absent thrombophilic polymorphisms with low clinical prothrombotic risk factors led to low prevalence of DVT and virtually absent PE after THA in the current series of patients, who had not received any form of prophylactic or therapeutic treatment for DVT.

Factors leading to decreased rates of deep vein thrombosis and pulmonary embolism after total knee arthroplasty

We evaluated a total of 473 knees (264 patients) to determine the prevalence of deep vein thrombosis and pulmonary embolism (PE) in those who were not given thromboprophylaxis after total knee arthroplasty (TKA). Deep vein thrombosis was diagnosed by roentgenographic venography, and PE was diagnosed by perfusion lung scanning. In patients with bilateral TKA, 47 (11%) of 418 venograms showed positive findings for thrombi, whereas in patients with unilateral TKA, 11 (20%) of 55 venograms showed positive findings for thrombi (P = .758). No patient had symptoms of PE, and findings for the perfusion lung scans were negative in all patients. We neither treat our patients for deep vein thrombosis and PE prophylactically nor therapeutically unless patient has a symptomatic PE.

Risk Factors and Presentation of Deep Venous Thrombosis among Asian Patients: A Hospital-Based Case-Control Study in Singapore

Deep venous thrombosis (DVT) is perceived to occur less frequently among Asians than Caucasians, although the reason for this has not been fully understood. Hence, there may be differences in risk factors and presentations among Asian patients compared to their Caucasian counterparts. This study examined the association of classical risk factors and presentations among Asian patients with DVT. We retrospectively reviewed 862 symptomatic patients referred to the vascular diagnostic laboratory in a hospital for suspected DVT over a 30-month period. Two hundred and seventy-seven patients (32.1%) tested positive for DVT on duplex ultrasound. After adjusting for age and gender, ethnicity was not a statistically significant demographic factor associated with DVT. Two hundred and seventy-one patients diagnosed as having DVT on ultrasound were matched for age, gender, and ethnicity to negative controls to study the significance of risk factors and presenting symptoms or signs. In multivariate analysis, independent risk factors for DVT included immobility (odds ratio [OR] = 2.61, 95% confidence interval [95% CI] 1.63-4.15], malignancy (OR = 1.77, 95% CI 1.01-3.10), and a history of thrombophilia (OR = 9.95, 95% CI 1.26-78.87). The significant forms of DVT presentation were limb swelling (OR = 2.53, 95% CI 1.41-4.54) and pulmonary embolism (OR = 11.45, 95% CI 3.23-40.59). Fever of more than 37.5 degrees C was a negative predictive factor (OR = 0.42, 95% CI 0.23-0.76). This study shows that the common risk factors of DVT such as surgery and fractures do not affect Asians as much as Caucasians. Instead, thrombophilia and underlying malignancy are prominent risk factors among Asians. Diagnosis of DVT in Asians based on clinical grounds can also be problematic as few presentations are specific.

Fatal thrombosis of antithrombin-deficient mice is rescued differently in the heart and liver by intercrossing with low tissue factor mice

BACKGROUND

We previously reported that the targeted disruption of murine antithrombin (AT) gene resulted in embryonic lethality before 16.5 gestational days (gd) because of severe cardiac and hepatic thrombosis.

OBJECTIVE AND METHODS

To investigate the influences of lowered tissue factor (TF) activity upon hypercoagulation of AT-/- embryos, we crossed AT+/- with low TF (mTF-/- hTF+) mice to yield homozygous AT-deficient mice with the extremely low TF activity, that is expressed from the inserted human TF mini gene.

RESULTS

AT-/- embryos either with 50% TF (AT-/- mTF+/- hTF+) or with low (approximately 1% TF, AT-/- mTF-/- hTF+) were not born, although the survival was prolonged until 18.5 gd. In both genotypes, histological examination showed disseminated thrombosis in hepatic sinusoidal space or in the portal veins, suggesting that the thrombogenesis caused loss of hepatic blood flow. As in original AT-/-, AT-/- mTF+/- hTF+ showed subcutaneous (s.c.) bleeding and also suffered from the myocardial degeneration apparently because of coronary thrombus formation. However, AT-/- mTF-/- hTF+ had no skin hemorrhage and the thrombosis and degeneration were completely abolished in the heart. Myocardium of adult low TF mice had exhibited fibrosis secondary to hemorrhage; however, it was significantly decreased in low TF mice with AT+/-.

CONCLUSIONS

Our current model suggests that, in the heart, TF plays an important role in the thrombogenesis and it counterbalances AT-dependent anticoagulation. AT may be a potent anticoagulant during mice development and the activation and subsequent regulation of TF-procoagulant activity take place differently between the liver and the heart. These differences appear to point to local regulatory mechanisms in murine hemostasis.

Do some inhibitors of COX-2 increase the risk of thromboembolic events?: Linking pharmacology with pharmacoepidemiology

Inhibitors of the cyclo-oxygenase (COX)-2 isoenzyme were developed with the expectation that their use would be accompanied by a reduction in adverse reactions thought to be mediated through COX-1 compared with conventional nonselective NSAIDs. However, the results of some clinical studies and other evidence have led to the hypothesis that use of COX-2 inhibitors may contribute to an increased risk of adverse thromboembolic (TE) events. In this review, we have evaluated the evidence from small-scale in vitro and in vivo pharmacological studies, clinical trials and large-scale pharmacoepidemiological studies and commented on the relationship between the pharmacological characteristics related to thromboembolic events and the clinical effects in large-scale clinical trials and pharmacoepidemiological studies. Overall, the pharmacological evidence suggests that a prothrombotic effect of COX-2 selective inhibitors is plausible. To date, despite the results from the Vioxx Gastrointestinal Outcome Research (VIGOR) study from which the clinical concern regarding cardiovascular TE risk arose, the published data from other randomised controlled trials (RCTs), retrospective observational studies and spontaneous reporting schemes provide a conflicting body of evidence on the TE risk with COX-2 inhibitors. Concerns that COX-2 inhibitors may be associated with prothrombotic effects remain and these need to be addressed in large scale, RCTs designed specifically to investigate the possibility of an excess of adverse cardiovascular outcomes in users of some or all selective COX-2 inhibitors, both with and without concomitant low-dose aspirin (acetylsalicylic acid). Consideration must also be given to other pathophysiological mechanisms for potential cardiovascular risk linked with inhibition of COX-2. In view of the evidence reviewed, it is recommended that selective COX-2 inhibitors should be prescribed with caution, only in patients with conditions for which these drugs have proven efficacy and with careful monitoring of outcomes and adverse events. This is particularly important in the elderly, in patients with cardiovascular/renal disease and in patients with other risk factors that might predispose them to adverse events.

Regulation of Hemostasis by the Sympathetic Nervous System: Any Contribution to Coronary Artery Disease?

Within the last two decades, hemostasis factors have emerged as 'new' risk factors for coronary artery disease. Historical studies on the physiology of the sympathetic nervous system (SNS) attributed accelerated blood clotting to the components of the fight-flight response. Although this has not been demonstrated, exaggerated clotting related to SNS hyperactivity might confer an increased arterial thrombotic risk. This review outlines the effects of sympathetic activation as mimicked by adrenergic infusions and as elicited by mental stress and physical exercise, and the molecular mechanisms involved. A selective review of the pertinent literature was undertaken. Sympathetic activation provokes a simultaneous increase in molecules of both the coagulation and fibrinolysis pathways within minutes, resulting in net hypercoagulability as a part of normal human physiology. Catecholamines and adrenergic receptors interact to mediate hemostatic changes. Exaggerated procoagulant changes in individuals with a preexistent atherosclerotic disease, in those experiencing ongoing stressful life circumstances and in the physically untrained might confer a thrombotic threat with sympathetic activation. Initial evidence suggests that nonselective β-adrenergic blockade may attenuate clotting acceleration upon SNS activation. Prospective studies are needed to demonstrate whether exaggerated clotting as elicited by the SNS is associated with an increased risk of cardiovascular morbidity and mortality. If confirmed, intervention studies targeted at reducing this risk, for example with drugs, psychotherapy (including stress management) and regular physical exercise, would be warranted.

Role of the gamma-carboxyglutamic acid domain of activated factor X in the presence of calcium during inhibition by antithrombin-heparin

BACKGROUND

Factor (F)Xa has 11 gamma-carboxylated glutamic acid (Gla) residues that are involved in calcium-dependent membrane binding. The serpin antithrombin (AT) is an important physiological regulator of FXa activity in an inhibition reaction that is enhanced by heparin. Recently, Rezaie showed that calcium further enhanced the heparin-catalyzed AT inhibition of FXa by promoting 'ternary complex' formation, and these results showed a role for the gamma-carboxyl-glutamate (Gla)-domain of FXa.

OBJECTIVES

In this study, we used recombinant FXa mutants to assess the role of individual Gla residues in augmenting or antagonizing the AT-heparin inhibition reaction in the presence of calcium.

RESULTS AND CONCLUSIONS

In the absence of heparin, AT inhibition of plasma and the recombinant FXas were essentially equivalent. Similar to plasma-derived FXa, calcium increased about 3-fold the inhibition rate of wild-type recombinant FXa by AT-heparin over that in the presence of EDTA. Interestingly, three different effects were found with the recombinant FXa Gla-mutants for AT-heparin inhibition: (i) Gla-->Asp 14 and 29 were enhanced without calcium; (ii) Gla-->Asp 16 and 26 were not enhanced by calcium; and (iii) Gla-->Asp 19 was essentially the same as wild-type recombinant FXa. These results support a theory that mutating individual Gla residues in FXa alters the calcium-induced conformational changes in the Gla region and affects the antithrombin-heparin inhibition reaction.

Cost-effectiveness of testing for hypercoagulability and effects on treatment strategies in patients with deep vein thrombosis

PURPOSE

Among patients with deep vein thrombosis, hypercoagulable conditions impart a substantial risk of recurrent thrombosis. We sought to determine the cost-effectiveness of testing for these disorders, as well as which tests should be selected and how results should be used.

METHODS

Using a Markov state-transition model, strategies of testing or not testing for a hypercoagulable state followed by anticoagulation for 6 to 36 months were compared in a hypothetical cohort of patients with apparently idiopathic deep vein thrombosis who were followed for life. Strategies were compared based on lifetime costs, quality-adjusted life-years (QALYs), and marginal cost-effectiveness.

RESULTS

In the base case, testing followed by 24 months of anticoagulation in patients with a hypercoagulable condition was more cost-effective ($54,820; 23.76 QALYs) than usual care, which comprised 6 months of anticoagulation without testing ($55,260; 23.72 QALYs). All hypercoagulable conditions tested were common enough and associated with a sufficient risk of recurrence to justify inclusion in a test panel. Twenty-four months of initial anticoagulation was preferred (<$50,000/QALY) for most conditions, whereas lifetime anticoagulation was preferred for patients with antiphospholipid antibody syndrome ($2928/QALY) or homozygous factor V Leiden mutation ($3804/QALY). Models using newer evidence on recurrence suggested 18 to 36 months of anticoagulation without testing as the preferred approach.

CONCLUSION

Testing for hypercoagulable disorders in patients with idiopathic deep vein thrombosis followed by 2 years of anticoagulation in affected patients is cost-effective. A simpler approach of treating all patients with prolonged anticoagulation without testing is justified if data confirm the persistent risk of recurrent thrombosis.

Venous and arterial thrombosis in rat models

Fucosylated chondroitin sulfate is a glycosaminoglycan from sea cucumber, made up of alternating beta-D-glucuronic acid and N-acetyl-beta-D-galactosamine units, like mammalian chondroitin sulfate. But the beta-D-glucuronic acid residues have branches of sulfated fucose, which confer high anticoagulant and antithrombotic properties on this compound. We have now compared the anticoagulant, bleeding and antithrombotic effects of this fucosylated chondroitin sulfate and its carboxyl-reduced derivative. Both compounds have similar anticoagulant action, mostly due to acceleration of thrombin inhibition in the presence of heparin cofactor II. The native glycosaminoglycan shows a correlation among anticoagulant, bleeding and antithrombotic effects. Inhibition of thrombosis in an arterio-venous shunt occurs at low doses, which are almost ineffective in modifying the anticoagulant activity of plasma. In a venous experimental model, on the contrary, antithrombotic activity requires high doses and occurs concomitantly with an increase in the anticoagulant activity of plasma. The action of fucosylated chondroitin sulfate on thrombosis is apparently unrelated to its effect on platelet aggregation. The carboxyl-reduced derivative of fucosylated chondroitin sulfate prevented thrombosis in the arterio-venous shunt, but not in the venous experimental model. This derivative did not increase bleeding, in spite of its potent anticoagulant activity. Therefore, our results reveal a dissociation of the anticoagulant, bleeding and antithrombotic effects of the glycosaminoglycan. Furthermore, we demonstrate that a polysaccharide may be a potent inhibitor of one type of thrombotic episode, but inactive on another. We propose that the different effects of fucosylated chondroitin sulfate and its carboxyl-reduced derivative on venous thrombosis may be related to adherence of the glycosaminoglycan to the vessel wall.

[Factor V Leiden and myocardial infarction: a case, review of the literature with a meta-analysis]

Mutation in blood coagulation factor V Leiden is the most frequently genetic polymorphism implied in venous thrombosis. A 57 year old man was hospitalised for acute myocardial infarction (MI). An emergency coronary angiography was performed, and no significant stenosis was observed. The haematologic check-up showed an heterozygous Leiden mutation of factor V. We report all publications about the relation between factor V Leiden and coronary thrombosis, and we performed a meta-analysis. We analysed the relation in general population and in subgroups, such as, younger and older, and patient with or without coronary stenosis. In global population, the meta-analysis did not found significant association between Factor V Leiden and myocardial infarction (OR = 1.25; IC = 0.97-1.58). In contrast, in patients less than < 55 years old after MI, Factor V Leiden prevalence was significantly higher than in control group (OR = 1.48; IC = 1.05-2.08). In addition, after MI without significant coronary stenosis Factor V Leiden prevalence was significantly higher than in normal patients (OR = 2.84; IC = 1.46-5.51). After MI, in patients without significant coronary stenosis, Factor V Leiden prevalence was significantly higher than in patients with significant coronary stenosis (OR = 3.26; IC = 1.67-6.36). Our study suggests that Factor V Leiden could be search after MI in young subjects and/or without significant stenosis.

Normal levels of anticoagulant heparan sulfate are not essential for normal hemostasis

Endothelial cell production of anticoagulant heparan sulfate (HS(act)) is controlled by the Hs3st1 gene, which encodes the rate-limiting enzyme heparan sulfate 3-O-sulfotransferase-1 (3-OST-1). In vitro, HS(act) dramatically enhances the neutralization of coagulation proteases by antithrombin. The in vivo role of HS(act) was evaluated by generating Hs3st1(-/-) knockout mice. Hs3st1(-/-) animals were devoid of 3-OST-1 enzyme activity in plasma and tissue extracts. Nulls showed dramatic reductions in tissue levels of HS(act) but maintained wild-type levels of tissue fibrin accumulation under both normoxic and hypoxic conditions. Given that vascular HS(act) predominantly occurs in the subendothelial matrix, mice were subjected to a carotid artery injury assay in which ferric chloride administration induces de-endothelialization and occlusive thrombosis. Hs3st1(-/-) and Hs3st1(+/+) mice yielded indistinguishable occlusion times and comparable levels of thrombin.antithrombin complexes. Thus, Hs3st1(-/-) mice did not show an obvious procoagulant phenotype. Instead, Hs3st1(-/-) mice exhibited genetic background-specific lethality and intrauterine growth retardation, without evidence of a gross coagulopathy. Our results demonstrate that the 3-OST-1 enzyme produces the majority of tissue HS(act). Surprisingly, this bulk of HS(act) is not essential for normal hemostasis in mice. Instead, 3-OST-1-deficient mice exhibited unanticipated phenotypes suggesting that HS(act) or additional 3-OST-1-derived structures may serve alternate biologic roles.

The coagulation system

Congenital and acquired hypercoagulable states arise from an imbalance between procoagulant and anticoagulant activity. Although these imbalances are present throughout the entire vascular tree, thrombotic lesions are usually localized in discrete segments of the veins or arteries and in certain organ systems. Thus, hypercoagulable states are likely to be associated with focal defects in the vascular wall to produce thrombosis. Many recently described factors are associated with hypercoagulability. Because thrombosis is a disease in which genetic and acquired risk factors interact dynamically, a thorough history, family history, and physical examination should be performed before ordering an extensive and costly coagulation panel.

Pre-thrombotic state and impaired fibrinolytic potential in coronary heart disease patients with left ventricular dysfunction

Patients with coronary heart disease (CHD) are at considerable risk for recurrent ischaemic events. A pre-thrombotic state and/or impaired fibrinolysis might play an important role in causing recurrent ischaemic events. Two hundred and fifty-seven CHD patients underwent the dobutamine stress echocardiography test (DSE) to investigate the possible presence of inducible ischaemia; 89 patients showed evidence of stunned and/or necrotic myocardium (resting wall motion abnormalities). Factor VIII activity and fibrinogen levels were significantly higher in patients with stunned/necrotic myocardium than in CHD patients with normal resting wall motions (factor VIII activity, P = 0.004; fibrinogen, P = 0.04). Of interest, after stimulating the fibrinolytic system with the DSE test, plasminogen activator inhibitor-1 activity was significantly higher in patients with necrotic/stunned myocardium than in patients with resting normal wall motion (P = 0.03), whereas tissue-type plasminogen activator activity after the DSE test was significantly lower in patients with stunned/necrotic myocardium than in patients with normal wall motion (P = 0.001). Overall, 30 CHD patients developed induced ischaemia (new wall motion abnormalities) during the DSE test. CHD patients with stunned and/or necrotic myocardium presented decreased fibrinolytic potential and the presence of a hypercoagulable state due to increased factor VIII activity, and fibrinogen levels. Therefore, these CHD patients must be considered at high risk of re-developing coronary thrombosis and might benefit from a more aggressive anticoagulant therapy.

Relation of serum sialic acid to blood coagulation activity in type 2 diabetes

The level of serum sialic acid, which is known to reflect atherosclerotic progress and to be related to the incidence of cardiovascular diseases, is increased in patients with diabetes. To elucidate the mechanism of the relation of serum sialic acid to fibrinogen, the relationship between serum sialic acid and markers of blood coagulation activity was investigated in type 2 diabetic patients. The concentration of serum sialic acid showed significant positive correlations with blood platelet count and with plasma concentrations of fibrinogen, D-dimer, thrombin-antithrombin III complex and plasmin-alpha2 plasmin inhibitor complex. These relationships were still significant after adjustment for age, sex, smoking history, body mass index, hemoglobin A, mean arterial pressure and low-density lipoprotein cholesterol. The correlation coefficient of blood fibrinogen with serum sialic acid was still significant after adjustment for D-dimer, thrombin-antithrombin III complex or plasmin-alpha2 plasmin inhibitor complex. On the contrary, blood fibrinogen showed no significant correlation with D-dimer, thrombin-antithrombin III complex or plasmin-alpha2 plasmin inhibitor complex, although an increase in blood fibrinogen is known to be an atherosclerotic risk factor. These results suggest that the serum sialic acid level reflects blood coagulation activity in type 2 diabetic patients and is related to blood fibrinogen level independently of blood coagulation activity.

Congenital thrombophilia associated to obstetric complications

During pregnancy there are hemostatic changes that result in a hypercoagulable state and can have thrombotic consequences. This condition can be aggravated in women who are carriers of congenital thrombophilic factors. This thrombotic tendency can manifest as thrombotic lesions in the placenta with compromise of utero-placental circulation, which are common characteristics present in obstetric complications, such as preeclampsia/eclampsia, miscarriage, fetal loss, intrauterine growth retardation, and abruptio placentae. In this paper we review data concerning about the association of congenital thrombophilia in pregnancy with obstetric complications, mainly preeclampsia and fetal loss, focusing in factor V Leiden and its related activated protein C resistance, prothrombin mutation G20210A and hyperhomocysteinemia related with C677T mutation of methylenetetrahydrofolate reductase. Although factor V Leiden has been the thrombophilic factor most studied, all three thrombophilic mutations have been related with obstetric complications; however, contradictory results about the specific association of each mutation with each type of obstetric complication are described. These discrepancies could obey to the ethnic difference of the studied groups, or to the fact that some studies were performed in closed populations with few migratory movement, where the genetic pool is relatively homogeneous, as well as the different inclusion and exclusion criteria. Even though this variability is present, the significance of recognizing true associations between these thrombophilic mutations and obstetric complications is essential in order to determine the likelihood of routinely screening for these conditions in pregnant women with risk factors for thrombosis and for carrying out specific prophylactic measures.