Showing papers in "Seminars in Thrombosis and Hemostasis in 2011"

Obesity and venous thrombosis: a review.

Abstract: The world is experiencing an obesity pandemic, with rates of obesity rising for more than two decades. Obesity is defined as a body mass index (BMI) of 30 kg/m (2) or greater. Of particular concern are the risks that millions of obese people are likely to develop chronic diseases and at earlier ages than their parents might have. The risk of venous thrombosis increases with obesity, so that the incidence of this pathology is also expected to rise significantly. There is remarkable and consistent evidence from a systematic review, as well as cohort and case-control studies that obesity might predispose to venous thromboembolism (VTE). The risk appears to be at least double that for normal weight subjects (BMI 20 to 24.9 kg/m (2)). Plausible mechanisms exist to explain this relationship, including the physical effects of body fat limiting venous return and a proinflammatory, prothrombotic, and hypofibrinolytic milieu. Loss of body weight has been shown to reduce the concentrations of coagulation factors and plasminogen activator inhibitor-1 toward the normal range. Whether weight loss would prevent secondary occurrence of VTE in the absence of anticoagulant therapy could not be discerned from this literature search.

Thrombosis and sickle cell disease.

Abstract: Sickle cell disease (SCD) is characterized by the presence of sickle hemoglobin, which has the unique property of polymerizing when deoxygenated. The pathophysiology of acute and chronic clinical manifestations of SCD have shown the central role of dense, dehydrated red cells in acute and chronic clinical manifestations of this pathology. Recent studies have indicated that SCD is characterized by a hypercoagulable state that contributes to the vaso-occlusive events in microcirculation, leading to acute and chronic sickle cell-related organ damage. This review discusses, in the context of SCD, (1) abnormalities in the coagulation system, (2) perturbation of platelet activation and aggregation, (3) vascular endothelial dysfunction, (4) the contribution of cell inflammatory responses, and (5) the connection with nitric oxide metabolism. We also review the available studies on the therapeutic approaches in clinical management of hypercoagulability in SCD.

Vitronectin in vascular context: facets of a multitalented matricellular protein.

Abstract: Vitronectin is an abundant adhesive glycoprotein in blood plasma and is found associated with different extracellular matrix sites, the vessel wall, and tumor cells, particularly upon tissue remodeling, injury/repair, or under disease conditions. Plasma vitronectin is a structurally labile molecule that may be converted into a multimeric/multivalent form by interaction with various (hemostatic) factors or through surface binding. Several distinct binding domains along the vitronectin sequence for integrin-type cell adhesion receptors, for urokinase receptor or proteoglycans as well as for growth factors, endow vascular matrix- or fibrin-associated vitronectin with differentiated cell attachment and aggregatory properties. These were found to be relevant for modulation of the cell-matrix interface in angiogenesis, hemostasis and thrombus formation, or wound repair, respectively. Other vitronectin ligands include plasminogen activator inhibitor (PAI)-1 or high molecular weight kininogen that confer strong antiadhesive functions upon integrin- or urokinase receptor-mediated cell interactions with vitronectin. Together, vitronectin acts as a potent matricellular factor, coordinating cell migration with pericellular proteolysis and growth factor signaling at sites of tissue remodeling or in tumors. Structure-function studies of such vitronectin-related ligands and receptors lead to the characterization of their mode of action, also stimulating the search for new antagonists in tumor angiogenesis, platelet aggregation, or atherosclerosis. This review focuses on new developments in vitronectin biology, with particular emphasis on regulatory mechanisms of the protein in the context of cell adhesion/migration/proliferation and cell-dependent proteolysis, relevant for our understanding of hemostasis, thrombosis, tissue repair, and vascular diseases.

The plasma contact system 2.0.

Abstract: The contact system is a protease cascade that is initiated by factor XII activation on cardiovascular cells. The system starts procoagulant and proinflammatory reactions, via the intrinsic pathway of coagulation and the kallikrein-kinin system, respectively. The biochemistry of the contact system in vitro is well understood. However, activators of the system in vivo and their contributions to disease states have remained enigmatic. Recent experimental and clinical data have identified misfolded proteins, collagens, and polyphosphates as the long-sought activators of the contact system in vivo. Here we present an overview about contact system activators and their contributions to health and pathology.

Congenital Amegakaryocytic Thrombocytopenia: Clinical Presentation, Diagnosis, and Treatment

Abstract: Congenital amegakaryocytic thrombocytopenia (CAMT, MIM #604498) is a rare inherited bone marrow failure syndrome presenting as isolated hypomegakaryocytic thrombocytopenia at birth without other characteristic physical anomalies. Most of the patients develop a severe aplastic anemia and trilineage cytopenia during the first years of life and hematopoietic stem cell transplantation is the only curative treatment. In most of the cases the disease is caused by homozygous or compound heterozygous mutations in the gene MPL encoding the receptor for the hematopoietic growth factor thrombopoietin. The present review summarizes clinical and laboratory data for 96 patients with CAMT, reported since 1990.

Von Willebrand disease: local diagnosis and management of a globally distributed bleeding disorder.

Abstract: von Willebrand disease (VWD) is the most common inherited bleeding disorder and arises from deficiencies and/or defects in the plasma protein von Willebrand factor (VWF). The current report overviews the diagnosis and management of VWD as reflected by differential processes applied within centers around the world. The prevalence of VWD, as well as the frequency of different VWD types, is also reported. VWD prevalence data varies according to methodology used, with epidemiological/population screening estimates approximating 1% of the population (or 10,000 cases per million population), several orders of magnitude higher than estimates from bleeding disorders registry data or regional/center analysis (which instead range from 50% of all VWD cases, as does the frequency of specific qualitative VWD types (i.e., 2A, 2B, 2M, and 2N). Although type 2A VWD is considered the most common form of type 2 VWD, in some reports workers consider type 2M VWD to be as, or more, common. Although not considered to be a "true" VWD, given its platelet origin, platelet-type VWD is only rarely identified. Finally, management of VWD also differs according to geographic region. Most developed countries use standard therapy, employing desmopressin (DDAVP) wherever possible, factor concentrate in other situations, and antifibrinolytic therapy as required. In contrast, the relative high cost and unavailability of factor concentrates in developing countries, and sometimes the unavailability of DDAVP, requires different management strategies to be applied.

Obstructive sleep apnea syndrome and cardiovascular diseases.

Abstract: Obstructive sleep apnea syndrome (OSAS) is a chronic disease characterized by recurrent episodes of partial or complete upper airway collapse and obstruction during sleep, associated with intermittent oxygen desaturation, sleep fragmentation, and symptoms of disruptive snoring and daytime sleepiness. Increasing focus is being placed on the relationship between OSAS and all-cause and cardiovascular disease-related mortality, but it still largely unclear whether this association is causative or simply speculative and epidemiological. Basically, reliable clinical evidence supports the hypothesis that OSAS might be associated with essential and resistant hypertension, as well as with an incremental risk of developing stroke, cardiac rhythm perturbations (e.g., atrial fibrillation, bradyarrhythmias, supraventricular and ventricular arrhythmias), coronary artery disease, acute myocardial infarction, and heart failure. Although it is still unclear whether OSAS might represent an independent risk factor for several acute or chronic conditions, or rather might trigger cardiovascular disease in the presence of traditional cardiovascular risk factors (e.g., obesity, diabetes, and dyslipidemia), there is a plausible biological background underlying this association, in that most of the mechanisms implicated in the pathogenesis of OSAS (i.e., hypoxia, hypercapnia, negative intrathoracic pressure, micro-arousal, sympathetic hyperactivity, metabolic and hormonal changes, oxidative stress, phlogosis, endothelial dysfunction, hypercoagulability, and genetic predisposition) might also be involved in the pathogenesis of cardiovascular disorders. In this article we discuss the different aspects of the relationship between OSAS and pathogenically different conditions such as systemic hypertension, coronary artery disease, stroke, metabolic abnormalities, arrhythmias, and heart failure, and we also discuss the kaleidoscope of phenomena implicated in the pathogenesis of this challenging disease.

Thrombocytopenia Absent Radius Syndrome

Abstract: Thrombocytopenia-absent radius (TAR) syndrome is a relatively uncommon condition characterized by absent radii with the presence of thumbs and congenital or early-onset thrombocytopenia that tends to resolve in childhood. The precise cause of this condition is unknown, although recently a microdeletion of chromosome 1q21.1 has been found in all investigated individuals. However, this microdeletion alone is not sufficient to cause TAR syndrome, and another, uncharacterized genetic alteration is thought to be involved in the pathogenesis.

C1-Inhibitor: More Than a Serine Protease Inhibitor

Abstract: C1-inhibitor (C1-inh) is a crucial regulator of the activation of plasmatic cascade systems involved in inflammation contributing to the homeostasis in the generation of proinflammatory mediators. The importance of C1-inh is illustrated by patients with hereditary angioedema where decreased levels of C1-inh lead to an uncontrolled generation of vasoactive peptides resulting in potential life-threatening subcutaneous edema. Recent publications, however, suggest that the anti-inflammatory properties of C1-inh do not strictly depend on its capacity to regulate the complement and contact phase system. This review summarizes the biochemical characteristics of C1-inh and its role in the regulation of plasmatic cascade systems as well as the role of the nonserpin domain.

Relationship between venous and arterial thrombosis: a review of the literature from a causal perspective.

Abstract: Venous thrombosis and arterial thrombosis are traditionally regarded as two different diseases with respect to pathophysiology, epidemiology, and treatment strategies. Research findings of the past few years suggest that this categorical distinction may be too strict. However, whether the described relationship between venous and arterial thrombosis is real or a result of other factors such as confounding, chance, or bias is still unclear. In this review, we discuss the current literature while using causal diagrams to better understand possible causal relations between cardiovascular risk factors, atherosclerosis, arterial thrombosis, and venous thrombosis. Furthermore, we propose study designs to investigate the causal link between venous and arterial thrombosis. In addition, we comment on the effect of statin use on the occurrence of both arterial and venous thrombosis. The possible clinical implications of these findings are discussed.

Multiple myeloma, venous thromboembolism, and treatment-related risk of thrombosis.

Abstract: Venous thromboembolism (VTE) is a disease with a high prevalence in elderly people, affecting > 5% of the population > 65 years of age. Cancer patients have a 4.3-fold higher incidence of thrombotic complications, due to multiple risk factors that are not always related to the disease. Among hematologic malignancies, multiple myeloma (MM) confers a high risk of developing such complications, with a VTE rate of nearly 10%. Multiple factors are involved in MM-related VTE, such as increased blood viscosity, high levels of immunoglobulin, procoagulant activity of monoclonal protein, and inflammatory cytokines. Since the introduction of the immunomodulatory derivatives (IMiDs) thalidomide and lenalidomide in the therapeutic armamentarium of MM, VTE has emerged as one of the leading complications, in particular in patients with newly diagnosed MM. In this setting, IMiDs-based treatments are associated with rates of VTE reaching values up to 14 to 26%, particularly when dexamethasone or chemotherapy are added. The optimal prophylaxis for patients receiving these antiangiogenetic agents is still a matter of debate. Due to the lack of prospective randomized clinical trials, different studies have used various anticoagulant prophylaxes, including fixed low-dose warfarin (1 mg or 1.25 mg), therapeutic doses of warfarin (international normalized ratio between 2.0 and 3.0), low molecular weight heparin, or low-dose aspirin. As yet, no study has clearly demonstrated a significant superiority of one prophylactic regimen in comparison with the others. Further investigation and more randomized clinical trials are needed to define the best thromboprophylaxis.

The Coagulation System in Children: Developmental and Pathophysiological Considerations

Abstract: The coagulation system in children is complex and ever changing, a fact encapsulated in the term developmental hemostasis. Studies confirm that there are quantitative and almost certainly qualitative differences in the coagulation system with age, and the control of these changes comes from something external to the liver. What remains uncertain is the magnitude of the qualitative changes and the implications of the changes for the growing child. At the very least, developmental hemostasis probably provides a protective mechanism for neonates and children and hence contributes to the decreased risk of thromboembolic and/or hemorrhagic events in these age groups. In addition, developmental hemostasis could also reflect the role that hemostatic proteins play in physiological development and hence the demand of other processes, such as angiogenesis. Finally, without doubt, developmental hemostasis affects the interactions of anticoagulant drugs with the coagulation system. This article will initially discuss the most recent evidence with respect to qualitative age-related changes in the coagulation system. Subsequently the article will discuss the coagulation system during childhood in light of the three aforementioned areas of clinical impact and suggest possible strategies to further understand this complex and exciting field of study.

Hemorrhagic Acquired Factor XIII (13) Deficiency and Acquired Hemorrhaphilia 13 Revisited

Abstract: Coagulation factor XIII (F13) circulates in blood as a heterotetramer composed of an A subunit dimer and a B subunit dimer. It is activated by thrombin and crosslinks fibrin monomers. Congenital F13 deficiency demonstrates a lifelong bleeding tendency, abnormal wound healing, and recurrent miscarriages, and it first manifests as umbilical bleeding after birth. In contrast, secondary F13 deficiencies due to its overconsumption and/or hypobiosynthesis by disseminated intravascular coagulation, major surgery, liver diseases, and other disorders are rather common but rarely complicated with bleeding symptoms. Recently, consultations with physicians who have patients with hemorrhagic-acquired F13 deficiency with anti-F13 inhibitors (acquired hemorrhaphilia 13) have indicated an increase in this disease in Japan. We performed a nationwide survey, supported by the Japanese Ministry of Health, Welfare and Labor and confirmed 21 Japanese cases of this disease with anti-F13 inhibitors. Because neither prolonged clotting times nor reduced platelet counts are observed in patients with this disease, many more cases may have been overlooked. Physicians must be mindful of acquired hemorrhaphilia 13 when seeing such patients and should measure F13 activity. Products containing F13 are effective for hemostasis generally, and immunosuppressive therapy must be started immediately to eradicate anti-F13 antibodies.

The international society on thrombosis and haematosis von Willebrand disease database: an update.

Abstract: The online locus-specific database for von Willebrand disease (VWFdb) acts as a repository for sequence variant data and associated resources for those with an interest in the disorder. It currently holds details of 561 mutations and 217 polymorphisms in the von Willebrand factor (VWF) gene. Lists can be queried and displayed by VWF region or disease type. A total of 42% of the mutations are located in the large exon 28, the most heavily studied VWF region, and mutations have been reported in all but 4 of the 51 protein-coding exons. Polymorphisms are reported in the 5' and 3' untranslated regions and in 33 exons and 35 introns. Additional resources include references linked to sequence variation entries, descriptors of each VWD type, genomic and cDNA sequences, nomenclature for VWF and its attributes, Human Genome Variation Society sequence variant nomenclature recommendations, multimer images, and related densitometry traces for type 2 VWD. Analysis of recessively inherited VWD indicates that whereas the majority (69%) of type 3 VWD patients are homozygous for their mutations, the majority (62%) of 2N patients are compound heterozygous. Comparison of missense substitutions reported as mutations with those reported as polymorphisms suggests that loss or gain of cysteine, tryptophan, methionine, or glutamate residues are more likely to result in a pathogenic effect than loss/gain of other VWF residues.

Diet and thrombosis risk: nutrients for prevention of thrombotic disease.

Abstract: An increased prothrombotic state is a major risk factor for the development of heart attacks, strokes, and venous thromboembolism. Platelet activation and aggregation play an important role in determining a prothrombotic state. Although pharmaceutical agents such as aspirin, heparin, and warfarin are able to reduce prothrombotic tendency, long-term drug treatment may produce a variety of side effects, including bleeding. Diet is generally recognized to be significantly involved in modifying the individual risk for the development of thrombotic diseases, although its influence during the treatment of these disorders is probably less important. Dietary intervention has proven effective in lowering serum lipid levels, which are otherwise essential elements in the pathogenesis of cardiovascular disease. Likewise, certain dietary components have also been proven effective in decreasing platelet activation through various mechanisms and therefore may contribute to attenuating the future risk of thrombosis. This article provides an up-to-date review of the role of nutrient and nonnutrient supplements on platelet aggregation and risk of thrombosis.

Bleeding and thrombosis in multiple myeloma and related plasma cell disorders.

Abstract: A variety of disease- and treatment-related factors affect the coagulation system and the risk of bleeding and thrombotic complications in patients with multiple myeloma (MM) and related plasma cell disorders (PCD). As commonly observed in other cancer settings, the malignant clone induces a cytokine environment responsible for a hypercoagulable state. The increase of blood viscosity and impairment of platelet and coagulation function due to circulating monoclonal proteins are considered key mechanisms in the hemostatic abnormalities frequently detected in patients with PCD. However, clinically significant bleeding is relatively rare and poorly correlated with these abnormalities. Management is often challenging because of the multifactorial pathogenesis and underestimation or misdiagnosis of acquired bleeding disorders, particularly acquired von Willebrand syndrome. In recent years, growing interest in thromboembolic risk has emerged after the introduction of novel and more effective antimyeloma agents (thalidomide and lenalidomide), which was associated with increased risk of venous thromboembolism, particularly when associated with dexamethasone and multiagent chemotherapy in newly diagnosed patients. The clinical impact of bleeding and thrombotic complications in patients with PCD, with emphasis on MM, will be discussed in this review, reporting the current knowledge about pathophysiologic mechanisms and implications for management.

Pediatric Hemophilia: A Review

Abstract: The hemophilias are the most common X-linked inherited bleeding disorders, which if not properly managed can lead to chronic disease and lifelong disabilities. The challenges and issues in newborns are different from that in older children and adults. Bleeding events still predominate as the diagnostic trigger in children, however, the sites of bleeding vary with age. While delivery-associated intracranial hemorrhage (ICH), circumcision, and venipuncture bleeding are common in the newborn period, joint disease and head trauma occur in the older child and adolescent. Awareness of clinical manifestations and treatment complications are crucial in instituting appropriate management and implementing preventive strategies. Currently, inhibitors and ICH are the most challenging complications and prophylaxis is emerging as the optimal preventive care strategy.

Decidual hemostasis, inflammation, and angiogenesis in pre-eclampsia.

Abstract: Invasion of the decidua by extravillous trophoblasts (EVTs) is accompanied by thrombin generation from decidual cell (DC)-expressed tissue factor (TF). This TF protects against hemorrhage as EVTs breach capillaries and subsequently invade and remodel spiral arteries and arterioles. Pre-eclampsia (P-EC) is the world's leading cause of fetal and maternal morbidity and mortality. It is associated with decidual hemorrhage and maternal thrombophilias, which form excess thrombin from DCs, and with maternal infections and other inflammatory conditions that are associated with excess expression of the proinflammatory cytokines interleukin (IL)-1 β and tumor necrosis factor (TNF) α. In human first-trimester leukocyte-free DCs, (1) thrombin enhances expression of soluble fms-like tyrosine kinase-1 (sFlt-1), a potent inhibitor of angiogenesis; (2) thrombin, IL-1β and TNF-α increase monocyte-recruiting chemokine expression leading to a macrophage excess in the pre-eclamptic decidua. The pathogenesis of P-EC likely stems from shallow EVT invasion leading to impaired decidual vascular remodeling. The resulting reduced uteroplacental blood flow is associated with a hypoxic placenta, which appears to secrete excess sFlt-1 into the maternal plasma. A regulatory role for DCs in vascular remodeling is indicated because impaired decidual vascular remodeling could stem from an aberrant local antiangiogenic milieu elicited by excess sFlt-1 and/or macrophage-inhibited EVT decidual invasion.

Heparin-induced thrombocytopenia: real-world issues.

Abstract: Heparin-induced thrombocytopenia (HIT) is a prothrombotic drug reaction caused by platelet-activating antibodies. HIT sera often activate platelets without needing heparin-such heparin-"independent" platelet activation can be associated with HIT beginning or worsening despite stopping heparin ("delayed-onset HIT"). We address important issues in HIT diagnosis and therapy, using a recent cohort of HIT patients to illustrate influences of heparin type; triggers for HIT investigation; serological features of heparin-independent platelet activation; and treatment. In our cohort of recent HIT cases ( N = 13), low-molecular-weight heparin (dalteparin) was a common causative agent ( N = 8, 62%); most patients were diagnosed after HIT-thrombosis had occurred; and danaparoid was the most frequently selected treatment. Heparin-independent platelet activation was common (7/13 [54%]) and predicted slower platelet count recovery (>1 week) among evaluable patients (5/5 vs 1/6; P = 0.015). In our experience with argatroban-treated patients, HIT-associated consumptive coagulopathy confounds anticoagulant monitoring. Our observations provide guidance on practical aspects of HIT diagnosis and management.

Management of inherited von Willebrand disease in Italy: results from the retrospective study on 1234 patients.

Abstract: Von Willebrand disease (VWD) is the most common inherited bleeding disorder and is due to quantitative and/or qualitative defects of von Willebrand factor (VWF). Despite the improved knowledge of the disease, detailed data on VWD types requiring specific treatments have not been reported thus far. To determine the number and types of VWD requiring therapy with desmopressin (DDAVP) and/or VWF/FVIII concentrates in Italy, a national registry on VWD (RENAWI) was organized. Only 16 of 48 centers included VWD in the RENAWI with diagnoses performed locally. Patients with uncertain results were retested by two expert laboratories using multimeric analysis and mutations of the VWF gene. A total of 1234 of 1529 (81%) cases satisfied the inclusion criteria and could be classified as VWD1 (63%), VWD2A (7%), VWD2B (6%), VWD2M (18%), VWD2N (1%), and VWD3 (5%). VWD types were also confirmed by DNA analyses and occur in young adults (83%), mainly in women (58%). Mucosal bleedings (32 to 57%) are more frequent than hematomas (13%) or hemarthrosis (6%). Most patients were exposed to an infusion trial with desmopressin (DDAVP) and found responsive with the following rates: VWD1 (69%), VWD2A (26%), VWD2M (29%), and VWD2N (71%). However, DDAVP was not always used to manage bleeding in all responsive patients and VWF/FVIII concentrates were given instead of or together with DDAVP in VWD1 (30%), VWD2A (84%), VWD2B (62%), VWD2M (63%), VWD2N (30%), and VWD3 (91%). Data of the RENAWI showed that correct VWD identification and classification might be difficult in many Italian centers. Therefore, evidence-based studies should be organized only in well-characterized patients tested by laboratories that are expert in the clinical, laboratory, and molecular markers of VWD.

Quebec platelet disorder: update on pathogenesis, diagnosis, and treatment.

Abstract: Quebec platelet disorder (QPD) is an autosomal dominant bleeding disorder associated with reduced platelet counts and a unique gain-of-function defect in fibrinolysis due to increased expression and storage of urokinase plasminogen activator (uPA) by megakaryocytes. QPD increases risks for bleeding and its key clinical feature is delayed-onset bleeding, following surgery, dental procedures or trauma, which responds only to treatment with fibrinolytic inhibitors. The genetic cause of the disorder is a tandem duplication mutation of the uPA gene, PLAU, which upregulates uPA expression in megakaryocytes by an unknown mechanism. The increased platelet stores of uPA trigger plasmin-mediated degradation of QPD α-granule proteins. The gain-of-function defect in fibrinolysis is thought to be central to the pathogenesis of QPD bleeding as the activation of QPD platelets leads to release of uPA from α-granules and accelerated clot lysis. The purpose of this review is to summarize current knowledge on QPD pathogenesis and the recommended approaches to QPD diagnosis and treatment.

Inherited thrombocytopenia due to GATA-1 mutations

Abstract: The GATA family of transcription factors, including the founding member, GATA-1, have an important role in gene regulation. GATA-1 is integral to successful hematopoiesis. A wide variety of mutations in GATA-1 affect its function, as well as its interaction with its cofactors (especially Friend of GATA) and the genes upon which GATA-1 acts. Here we review the known mutations, focusing on the specific alterations within the amino acid sequence, the resulting effect on hematopoietic development, and the clinical manifestations that result. Attention is also paid to the relationship between Trisomy 21, also known as Down syndrome, and the phenomenon of a truncated GATA-1, named GATA-1s. The evidence for specific interaction between GATA-1 and chromosome 21, which may explain the correlation between these two mutations, is briefly reviewed.

The functions of microparticles in pre-eclampsia.

Abstract: Pre-eclampsia (P-EC), a heterogenic multisystem disorder characterized by hypertension and proteinuria, usually develops in the second half of pregnancy. The incidence is 2 to 5%, and P-EC is therefore a major cause of maternal and perinatal morbidity and mortality. Although the exact etiology is unknown, placental factors released into the maternal circulation lead to systemic maternal inflammation and endothelial dysfunction. Growing evidence indicates that placenta-derived microparticles, best known as syncytiotrophoblast microparticles (STBM), are important among these factors. This review provides an overview of the presence and function(s) of STBM and other cell-derived microparticles and exosomes.

Thromboembolism in inflammatory bowel disease: an insidious association requiring a high degree of vigilance

Abstract: Venous and arterial thromboembolism are both serious extraintestinal manifestations of inflammatory bowel disease (IBD). Acquired risk factors seem to play a more prominent role than congenital in promoting thrombotic events. Prevention of thromboembolism is thus mainly aimed at minimizing the acquired/reversible risk factors (e.g., inflammation, immobility, hospitalization, steroid therapy, central intravenous catheters, smoking, oral contraceptives, and deficiency of B vitamins and folate). The diagnosis of venous and arterial thromboembolism is extremely challenging and requires a high degree of vigilance. Deep vein thrombosis and pulmonary embolism may be clinically silent or manifest with only few specific symptoms. Thrombosis of the portal vein system may occur with nonspecific symptoms such as abdominal pain, nausea/vomiting, abdominal tenderness, ascites, and fever. The diagnosis of arterial thromboembolism may also be challenging, particularly when the splanchnic region is involved. Indeed, arterial thrombosis of the splanchnic region tends to be overlooked and misinterpreted as a clinical exacerbation of IBD. Early diagnosis plays a central role in optimizing the therapeutic intervention and reducing the risk of short-term and long-term thrombosis-associated complications. The decision regarding the duration of systemic anticoagulation must take into account the individual risk of intestinal bleeding.

Prevention of venous thromboembolism: focus on mechanical prophylaxis.

Abstract: Venous thromboembolism (VTE), including deep vein thrombosis and pulmonary embolism, is a leading health-care problem whose pathogenesis is usually related to the so-called Virchow's triad and involves a variety of factors classified as inherited or acquired, predisposing, or triggers. The main goal of thromboprophylaxis is to reduce mortality and morbidity associated with VTE risk factors. Although striking evidence now indicates that the various pharmacological anticoagulant therapies can substantially lower the risk, this benefit might be offset by a small but definite risk of hemorrhage in some circumstances. Mechanical prophylaxis methods have been suggested because they counteract most of the components of the Virchow's triad and are not associated with any bleeding risk. Although early and frequent ambulation has been historically advised for preventing VTE, this measure is inadequate per se and frequently not feasible as the sole means of mechanical thromboprophylaxis. Accordingly, additional measures are being used in clinical practice, including graded compression stockings, intermittent pneumatic compression devices, and venous foot pumps. Although the efficiency of these measures has been extensively assessed in several clinical studies, there remain unanswered questions, including their suboptimal use and the lack of unequivocal clinical evidence supporting real benefits for preventing VTE. Overall, mechanical compression methods can reduce the risk of VTE by nearly two thirds when used as the only form of thromboprophylaxis and by about half when combined with a pharmacological approach. The main mechanism of action appears to be related to a milking (wavelike) effect to evacuate leg veins and reduce venous stasis because an effect on the enhancement of fibrinolysis remains unproven. Although the biological and clinical evidence suggests that graduate compression stockings are an effective, relatively cheap, and more comfortable thromboprophylactic measure, they appear less effective overall than intermittent pneumatic compression. In conclusion, although the preventive benefits of mechanical prophylaxis on VTE might be circumscribed to select medical and surgical settings, there appears to exist no clinical reason to discourage adoption of these measures when indicated.

Safety and efficacy of low molecular weight heparins in children: a systematic review of the literature and meta-analysis of single-arm studies.

Abstract: Within the last two decades low molecular weight heparins (LMWH) have gained increasing widespread use as anticoagulants in children. The use of LMWH has been implemented into clinical care even though there is a lack of firm evidence on the efficacy and safety of LMWH in this population due to the absence of sufficiently powered randomized controlled trials. In the absence of clinical trials, we performed a meta-analysis of available single-arm studies using LMWH in children. A systematic search of electronic databases (Medline, EMBASE, OVID, Web of Science, The Cochrane Library) for studies published from 1980 to 2010 was conducted using keywords in combination both as MeSH terms and text words. Two authors independently screened citations and those meeting a priori defined inclusion criteria were retained. Data on year of publication, study design, country of origin, number of patients, ethnicity, venous thromboembolic events type, and frequency of recurrence and major bleedings were abstracted. Pooled incidence rates (IR) including 95% confidence intervals (95% CIs) on efficacy and safety data of LMWH administration on primary prophylaxis, as well as on secondary prophylaxis in children following symptomatic thromboembolism (TE) were shown. We included 2251 pediatric patients derived from 35 single-arm studies from 12 study countries who were eligible for analysis in the present systematic review. Pooled incidence rates (95% CI) to develop first TE on primary prophylaxis, further TE event on LMWH secondary prophylaxis, or a major bleeding event on LMWH were 0.047 (0.023 to 0.091), 0.052 (0.037 to 0.073) for efficacy, and 0.054 (0.039 to 0.074) for safety (treatment data only), respectively. Efficacy and safety data are comparable with adult data. The present systematic review suggests that use of LMWH in children as primary prophylaxis and in treatment of symptomatic thrombosis is effective and safe. However, properly designed randomized controlled trials are needed.

Dental infection and vascular disease.

Abstract: Periodontitis is a chronic inflammatory response to bacterial plaque in which the anchoring bone and soft tissues supporting teeth are destroyed, resulting in tooth mobility and loss. Dental caries involves the spread of infection from the dentine to the vascular dental pulp and periapical bony tissues, before involvement of adjacent soft tissues and spreading sepsis. Several case-controlled, cross-sectional, and cohort studies report correlation between periodontitis and increased cardiovascular, cerebrovascular, and peripheral artery disease, as determined by clinical disease, angiography, ultrasonography, and reduced flow-mediated dilation. Some studies report a similar relationship of atherosclerosis with periapical infection and potentially also with coronal caries, and this review identifies the need to investigate these associations further. Smoking and cadmium exposure are epidemiologically confounding environmental risk factors shared by atherosclerosis and periodontitis. Further complicating epidemiological studies are the risk factors for both atherosclerosis and periodontitis, with which periodontitis appears to have separate positive feedback relationships. These include diabetes, increased plasma lipid levels, hypertension, and white blood cell count. Animal and human intervention studies provide some direct support of a causal role for periodontitis in atherosclerosis, and possible mechanisms include bacterial invasion of arteries, specific atherogenic properties of oral bacteria, the acute phase response, and cytokine polymorphisms.

Glanzmann thrombasthenia-like syndromes associated with Macrothrombocytopenias and mutations in the genes encoding the αIIbβ3 integrin.

Abstract: Glanzmann thrombasthenia (GT) is the most widely studied inherited disorder of platelets; it is caused by the absence of platelet aggregation due to quantitative and/or qualitative deficiencies of the αIIbβ3 integrin coded by the ITGA2B and ITGB3 genes located at 17q21-23. Although platelet count and platelet volume (and morphology) are normal in classic GT, some reports have inferred a role for αIIbβ3 in megakaryocytopoiesis and some novel but rare point mutations in either of the ITGA2B and ITGB3 genes have been associated with an altered platelet production and selective deficiencies in platelet function. This was brought to light by the discovery of mutations at Arg995 in αIIb and Asp723 in β3 that lead to platelet anisotropy (increased size variation) and thrombocytopenia. Significantly, Arg995 and Asp723 form a salt linkage binding the cytoplasmic tails of αIIbβ3 together keeping the integrin in a bent resting state. Mutations weakening this link (if not abolishing it) increase the activation state of αIIbβ3 and interfere with megakaryocytopoiesis. Other mutations affecting platelet production involve extracellular but membrane proximal domains of β3. Our purpose is to review the mutations in the ITGA2B and ITGB3 genes that lead to anisotropy and to discuss mechanisms by which this can be brought about.

Impact of Persistent Antiphospholipid Antibodies on Risk of Incident Symptomatic Thromboembolism in Children: A Systematic Review and Meta-Analysis

Abstract: The aim of this study was to estimate the impact of antiphospholipid (aPL) antibodies on the risk of incident thromboembolism (TE; arterial and venous) in children via meta-analysis of published observational studies. A systematic search of electronic databases (Medline, EMBASE, OVID, Web of Science, The Cochrane Library) for studies published from 1966 to 2010 was conducted using keywords in combination both as MeSH terms and text words. Two authors independently screened citations and those meeting the a priori defined inclusion criteria were retained. Data on year of publication, study design, country of origin, number of patients/controls, ethnicity, TE type, and frequency of recurrence were abstracted. Heterogeneity across studies was evaluated, and summary odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using either fixed-effects or random-effects models. Of 504, 16 pediatric studies met the inclusion criteria. In total 1403 patients and 1667 population-based controls ≤18 years were enrolled. No significant heterogeneity was discerned across studies, and no publication bias was detected. Thus, data from arterial and venous TE were analyzed together. In addition, meta-regression analysis did not reveal statistically significant differences between site of TE, age at first TE, country, or publication year. A statistically significant association with a first TE was demonstrated for persistent aPL antibodies, with an overall summary ORs/CI of 5.9/3.6-9.7 (arterial 6.6/3.5-12.4; deep vein thrombosis 4.9/2.2-10.9). The present meta-analysis indicates that detection of persistent aPL is clinically meaningful in children with, or at risk for, TE and underscores the importance of pediatric thrombophilia screening programs.

Prevention of venous thromboembolism in medical patients with thrombocytopenia or with platelet dysfunction: a review of the literature.

Abstract: Current guidelines for venous thromboembolism (VTE) primary prophylaxis are based on randomized clinical trials that exclude subjects at a potentially high bleeding risk. Thus no specific recommendation/algorithm for pharmacological prophylaxis in patients with thrombocytopenia and/or platelet dysfunction is available. Because at least 25% of subjects admitted to medical departments exhibit these conditions, information on this subject is provided here to optimize their VTE prophylaxis. Low platelet number/function and clotting abnormalities are common in patients with liver cirrhosis. However, these patients have a high incidence of portal and idiopathic venous thromboses, implying that cirrhotic coagulopathy does not protect against thrombosis. At variance with severe thrombocytopenia ( 50,000/μL) should not interfere with VTE prevention decisions. In severe thrombocytopenia, prophylaxis should be considered on an individual basis, however. In patients with antiphospholipid antibodies and thrombocytopenia, a thrombotic tendency is usually associated rather than a bleeding risk. VTE prophylaxis in high-risk conditions is thus suggested in these patients. Except in cases with contraindications to anticoagulation, antithrombotic prophylaxis should be always considered in hospitalized cancer patients with thrombocytopenia, especially in those with hematologic malignancies and multiple VTE risk factors. Aspirin treatment is not as effective as heparins in lowering the risk of VTE. Studies in stroke suggest that thromboprophylaxis with heparins is safe in patients with ischemic stroke undergoing aspirin treatment. The need for VTE prophylaxis in patients on chronic treatment with aspirin and/or clopidogrel should be evaluated after assessing the individual risk-benefit ratio.