Fondaparinux for Thromboembolic Treatment and Prophylaxis of Heparin-Induced Thrombocytopenia

Steps Toward Recapitulating Endothelium: A Perspective on the Next Generation of Hemocompatible Coatings

Endothelium, the lining in this blood vessel, orchestrates three main critical functions such as protecting blood components, modulating of hemostasis by secreting various inhibitors, and directing clot digestion (fibrinolysis) by activating tissue plasminogen activator. No other surface can perform these tasks; thus, the contact of blood and blood-contacting medical devices inevitably leads to the activation of coagulation, often causing device failure, and thromboembolic complications. This perspective, first, discusses the biological mechanisms of activation of coagulation and highlights the efforts of advanced coatings to recapitulate one characteristic of endothelium, hereafter single functions of endothelium and noting necessity of the synergistic integration of its three main functions. Subsequently, it is emphasized that to overcome the challenges of blood compatibility an endothelium-mimicking system is needed, proposing a synergy of bottom-up synthetic biology, particularly synthetic cells, with passive- and bioactive surface coatings. Such integration holds promise for developing advanced biomaterials capable of recapitulating endothelial functions, thereby enhancing the hemocompatibility and performance of blood-contacting medical devices.

Autoimmune Heparin-Induced Thrombocytopenia

Autoimmune thrombocytopenia (aHIT) is a severe subtype of heparin-induced thrombocytopenia (HIT) with atypical clinical features caused by highly pathological IgG antibodies ("aHIT antibodies") that activate platelets even in the absence of heparin. The clinical features of aHIT include: the onset or worsening of thrombocytopenia despite stopping heparin ("delayed-onset HIT"), thrombocytopenia persistence despite stopping heparin ("persisting" or "refractory HIT"), or triggered by small amounts of heparin (heparin "flush" HIT), most cases of fondaparinux-induced HIT, and patients with unusually severe HIT (e.g., multi-site or microvascular thrombosis, overt disseminated intravascular coagulation [DIC]). Special treatment approaches are required. For example, unlike classic HIT, heparin cessation does not result in de-escalation of antibody-induced hemostasis activation, and thus high-dose intravenous immunoglobulin (IVIG) may be indicated to interrupt aHIT-induced platelet activation; therapeutic plasma exchange may be required if high-dose IVIG is ineffective. Also, aHIT patients are at risk for treatment failure with (activated partial thromboplastin time [APTT]-adjusted) direct thrombin inhibitor (DTI) therapy (argatroban, bivalirudin), either because of APTT confounding (where aHIT-associated DIC and resulting APTT prolongation lead to systematic underdosing/interruption of DTI therapy) or because DTI inhibits thrombin-induced protein C activation. Most HIT laboratories do not test for aHIT antibodies, contributing to aHIT under-recognition.

Heparin-Induced Thrombocytopenia at the Emergency Department Due to Intermittent Heparin Flush in a Patient Undergoing Stem Cell Transplant

Heparin-induced thrombocytopenia (HIT) is an adverse reaction to heparin products, but not warfarin. HIT usually occurs 5‒10 days after exposure to heparin. Here, we report a case of HIT with multiple thrombotic events and severe thrombocytopenia resulting from intermittent intravenous heparin flushes for maintenance of a newly placed subclavian central venous catheter (CVC) for stem cell transplant. The patient is a woman in her forties with multiple myeloma who presented to the emergency department (ED) with dyspnea, pleuritic-type chest pain, hemoptysis, and worsening left-leg swelling. Heparin had been used to flush the CVC. Her platelet count began dropping approximately one week after insertion. The patient was receiving other medications known to cause thrombocytopenia. She had undergone multiple platelet transfusions. In the ED, her lab results showed thrombocytopenia), anemia; renal insufficiency; and elevated troponin, prothrombin time, and D-dimer levels. Because of the hemoptysis and thrombocytopenia, she initially received platelet transfusion and oxygen. She was found to have deep vein thrombosis of the lower extremity and started a referral to interventional radiology for inferior vena cava (IVC) filter placement. However, further review and consultation of the Benign Hematology service, discussion about the timing of decreased platelet count shortly after CVC placement and heparin administration, and the presence of thrombosis, suggested a high pre-test probability of HIT. Anticoagulation with argatroban was initiated, and IVC filter insertion was canceled. Further workup confirmed HIT diagnosis and saddle pulmonary embolism. During the patient's hospitalization, her platelets continued to improve and reached baseline upon discharge. She was transitioned to fondaparinux at the time of discharge. A few weeks later, she had successful stem cell transplantation. Emergency physicians treating patients with thrombocytopenia receiving heparin, even in small amounts, should consider the possibility of HIT and be familiar with its management.

Cost-effectiveness analysis of alternative anticoagulation in suspected heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is a life-threatening complication associated with high medical costs. Factor Xa inhibitors have gradually replace approved treatment with intravenous direct thrombin inhibitors despite their off-label indication, because of easier management and favorable economic profile.Whether they are cost-effective remains unclear. We evaluated the cost-effectiveness of approved and off-label anticoagulants in patients with suspected HIT, based on census data from the largest Swiss hospital between 2015 and 2018. We constructed a decision tree model that reflects important clinical events associated with HIT. Relevant cost data were obtained from the finance department or estimated based on the Swiss-wide cost tariff. We estimated averted adverse events (AE) and incremental cost-effectiveness ratio as primary outcome parameters. We performed deterministic and probabilistic sensitivity analyses with 2000 simulations to assess the robustness of our results. In the base-case analysis, the total cost of averting one AE was 49,565 CHF for argatroban; 30,380 CHF for fondaparinux, and 30,610 CHF for rivaroxaban; after adjusting for 4Ts score: 41,152 CHF (argatroban); 27,710 CHF (fondaparinux) and 37,699 CHF (rivaroxaban). Fondaparinux and rivaroxaban were more clinically-effective than argatroban with AE averted of 0.820; 0.834 and 0.917 for argatroban, fondaparinux and rivaroxaban, respectively. Treatment with fondaparinux resulted in less cost and more AE averted, hence dominating argatroban. Results were most sensitive to AE rates and prolongation of stay. Monte Carlo simulations affirmed our base-case analysis. This is the first cost-effectiveness analysis comparing argatroban with fondaparinux and rivaroxaban using primary data. Fondaparinux and rivaroxaban resulted in more averted AE but fondaparinux had greater cost savings. Fondaparinux could be a viable alternative to argatroban.

COVID-19 and coagulopathy

The SARS-CoV-2 is a new coronavirus responsible for the COVID-19 disease and has caused the pandemic worldwide. A large number of cases have overwhelmed the healthcare system worldwide. The COVID-19 infection has been associated with a heightened risk of thromboembolic complications. Various mechanisms are leading to the high thrombotic risk in COVID-19 patients such as inflammation, endotheliitis, hyperviscosity, and hypercoagulability. We searched PubMed, EMBASE, and CINAHL from January 2020 to December 2020. We used the following search terms: COVID-19, coagulopathy, and thrombosis. We reviewed the epidemiology, clinical features, mechanisms, and treatment of COVID-19-associated coagulopathy.

The Effect of Various Types of Anticoagulant Therapy on the Reduction of Mortality in COVID-19

Coronavirus disease 2019 (COVID-19) is a viral infection that, in severe course, leads to the development of a cytokine storm, systemic inflammatory response and coagulopathy. Unlike other sepsis-associated disseminated intravascular coagulopathy, COVID-19 induced coagulopathy is realized mainly in thrombosis. Researchers around the world are currently developing adequate diagnostic, monitoring and anticoagulant therapy approaches to safely and effectively manage patients with severe COVID-19. The need to develop laboratory monitoring is due to the fact that 20% of patients have changes in hemostasis indicators, while in patients with a severe form of the disease, they are present in 100% of cases. In case of deaths from COVID-19, there is an increase in the concentration of D-dimer and fibrinogen degradation products. Thus, the severity of hemostasis disorders has an important prognostic value. Anticoagulant therapy is included in the list of all recommendations as an effective means of reducing mortality from COVID-19. The questions of the recommended groups and doses of anticoagulant drugs are still open. The approach to the choice of an anticoagulant should be based not only on risk factors, characteristics of the course of the disease, anamnesis, but also on the wishes of the patient during long-term therapy at the post-hospital stage.

Practical considerations in prevention and treatment of venous thromboembolism in hospitalized patients with COVID-19

PURPOSE

There are increasing reports in the literature of high rates of coagulopathy and venous thromboembolism (VTE) among hospitalized patients with coronavirus disease 2019 (COVID-19). Understanding of these abnormalities is continually evolving, but these conditions may pose a risk to patients with COVID-19 beyond the risk typically seen in critically ill patients.

SUMMARY

There are currently no widely accepted evidence-based guidelines regarding specifics related to treatment and prevention of COVID-19-related coagulopathies. Areas of management requiring clinical equipoise include agent selection and dosing, continuation vs interruption of home oral anticoagulant therapy during hospital admission, and postdischarge VTE prophylaxis. Clinicians may wish to consider use of a stratified, 3-tiered approach of low-intensity anticoagulation, intermediate-intensity anticoagulation, and therapeutic-dose anticoagulation. Patients can be categorized by tier depending on their risk factors for VTE, acuity of illness, and laboratory values such as D-dimer level.

CONCLUSION

Practical guidance on anticoagulation considerations and dosing suggestions are provided to assist clinicians faced with challenging anticoagulation-related situations in caring for hospitalized patients with COVID-19 until formal evidence-based guidelines become available.

Fondaparinux in a critically Ill patient with heparin-induced thrombocytopenia: A case report

RATIONALE

Fondaparinux, as a factor Xa-inhibitor, is used off label to manage heparin-induced thrombocytopenia (HIT), but little experience with HIT patients has been reported in the literature. Moreover, the use of fondaparinux for full anticoagulation in critically ill patients with HIT and renal insufficiency is limited.

PATIENT CONCERNS

A trauma patient, who had received low molecular weight heparin (LMWH) and heparin to treat venous thromboembolism, developed thrombocytopenia and multiple organ dysfunction in the intensive care unit (ICU). Also, her deep venous thromboembolism (DVT) continued to progress.

DIAGNOSIS

The final diagnosis was HIT.

INTERVENTIONS

Fondaparinux was temporarily used for anticoagulation treatment of DVT for 7 days when another anticoagulant (argatroban) was unavailable. Although the patient had kidney dysfunction, a full therapeutic dose of 7.5 mg fondaparinux was administered every morning through subcutaneous injection for consecutive 7 days.

OUTCOMES

The patient's thrombocytopenia and thrombosis were successfully treated without bleeding complications during therapeutic fondaparinux administration.

LESSONS

This is the first case reporting the successful use of fondaparinux for full anticoagulation for DVT in a critically ill patient with HIT and renal insufficiency. Our experience suggests that fondaparinux might be an alternative for anticoagulation treatment in patients with HIT and kidney dysfunction if another anticoagulant (argatroban) is unavailable.

Frequent off-label use of fondaparinux in patients with suspected acute heparin-induced thrombocytopenia (HIT)--findings from the GerHIT multi-centre registry study

INTRODUCTION

In life-threatening immune heparin-induced thrombocytopenia (HIT), treatment with an approved non-heparin anticoagulant is essential. However, off-label use with fondaparinux has been reported in the literature. The study aim was to collect data on "real-life" management of patients with suspected acute HIT regarding diagnostic and therapeutic strategies.

PATIENTS AND METHODS

In a national multi-centre registry study, patients with a 4T's HIT-probability score of ≥ 4 points and treatment with at least one dose of (A)rgatroban, (L)epirudin, (D)anaparoid, or (F)ondaparinux were retrospectively evaluated.

RESULTS

Of 195 patients, the 4T's scores were 4/5/6/7/8 points in 46 (23.6%)/50 (25.6%)/74 (38.0%)/13 (6.7%)/7 (3.6%) patients, respectively. During heparin therapy, 47 (24.1%) thromboembolic events, 5 (2.6%) skin lesions, 1 (0.5%) amputation, 24 (12.3%) Hb-relevant bleedings, and 2 (1.0%) fatalities occurred. A functional heparin-induced platelet activation assay was performed in 96.9%, a platelet factor 4/heparin-dependent enzyme immunoassay in 89.2%, a particle gel immunoassay in 12.3%, and a serotonin-release assay in none of the patients. Argatroban was used in 16.4%, lepirudin in 2.1%, danaparoid in 23.6%, fondaparinux in 40.0% of the patients; the sequential therapy strata were: AF (5.6%), DA (5.6%), DF (2.6%), DL (2.1%), ADF (1.5%), and DFL (0.5%).

CONCLUSIONS

The current diagnostic laboratory strategy for suspected HIT is mostly (>96%) based on the recommended 2-step strategy (immunoassay plus functional assay). However, there is a wide fondaparinux off-label use (up to 50.3%) for suspected HIT, even in those patients with a high clinical pretest probability. Efficacy and safety of fondaparinux for HIT-treatment require further evaluation.

A review of venous thromboembolism prophylaxis for hospitalized medical patients

In the last decade, greater focus has been directed toward venous thromboembolism (VTE) prophylaxis in hospitalized, non-surgical patients. Both deep venous thrombosis and pulmonary embolism are potentially preventable causes of patient morbidity and mortality related to hospitalization. Despite the availability of high-quality, evidence-based guidelines for VTE prevention, there is compelling evidence that many hospitalized patients do not receive appropriate VTE prevention measures. Hospitalists play an important role in the implementation of appropriate VTE prophylaxis measures for this patient population; thus, knowledge of updated recommendations is vital to their practice, as well as patient safety. We provide a comprehensive evidence-based clinical review of VTE prophylaxis for nonsurgical hospitalized patients, including risk factors and risk assessment, indications for prophylaxis, recommended therapeutic options, and updates from recently released practice guidelines by the American College of Physicians and the American College of Chest Physicians, published in 2011 and 2012, respectively.

Chronic fondaparinux use in a hemodialysis patient with heparin-induced thrombocytopenia type II and extracorporeal circuit thrombosis-a case report and review of the literature

Heparin-induced thrombocytopenia (HIT) is a potentially life-threatening condition that can develop after exposure to unfractionated or low-molecular-weight heparins. Treatment options appear to be limited in patients on concurrent intermittent hemodialysis. We report the case of an 88-year-old man newly initiated on high-flux hemodialysis who developed HIT and extracorporeal circuit thrombosis after 3 weeks of exposure to unfractionated heparin. Our patient was successfully treated with fondaparinux 2.5 mg subcutaneously three times per week and citrate during dialysis sessions. Antifactor Xa levels were measured on several occasions while receiving fondaparinux.

Role of factor xa inhibitors in cancer-associated thrombosis: any new data?

The association between cancer and venous thromboembolism (VTE) has been well documented in the literature. Prevention and treatment of VTE in cancer patients is imperative. Typically, the mainstay regimen for VTE prevention and treatment has been anticoagulation therapy, unless contraindicated. This therapy consists of unfractionated heparin (UFH), low-molecular-weight heparin (LMWH), factor Xa inhibitor, or vitamin K antagonist (VKA). Current guidelines recommend LMWH over VKA for the treatment of VTE in cancer patients. Factor-specific anticoagulants have been proven safe and effective, and recently factor Xa inhibitors have emerged as a treatment alternative to heparins and VKA. Currently, three factor Xa inhibitors have been identified: fondaparinux (the only one approved so far by the US Food and Drug Administration), idraparinux (in clinical trials), and idrabiotaparinux (in clinical trials). This paper will examine the role of these agents, focusing on fondaparinux, for the prevention and treatment of VTE in cancer patients.

Fondaparinux cross-reacts with heparin antibodies in vitro in a patient with fondaparinux-related thrombocytopenia

Heparin-induced thrombocytopenia (HIT) related to fondaparinux has been rarely reported, although the ability of fondaparinux to cross-react with heparin antibodies has been often a subject of debate. A patient previously exposed to unfractionated heparin and low-molecular-weight heparin (LMWH) was diagnosed with HIT. During treatment with fondaparinux for 5 consecutive days, his thrombocytopenia significantly deteriorated. A functional platelet activation test in vitro showed clear platelet activation after serum exposure with fondaparinux. After discontinuation of fondaparinux, the platelet count was rapidly reestablished. Fondaparinux cross-reacted with heparin antibodies in this case of HIT, resulting in a deterioration of thrombocytopenia. The implication of this drug in HIT was observed clinically and demonstrated in vitro using a platelet activation test.

[Heparin-induced thrombocytopenia]

Heparin-induced thrombocytopenia (HIT) is an adverse drug reaction that carries an increased risk of thromboembolic complications. HIT is caused by platelet-activating antibodies directed against a complex of platelet factor 4 (PF4) and heparin. HIT typically manifests in the second week after initiation of heparin therapy with a platelet count reduction of more than 50% of the highest level after the start of heparin administration as well as thromboembolic events. The clinical probability can be calculated by the 4 T's score. The laboratory diagnosis of HIT is based on confirmation of PF4/heparin antibodies or on functional tests that provide evidence of heparin-dependent platelet-activating antibodies. A low 4 T's score and negative HIT test virtually rule out the presence of HIT. Patients with acute HIT require anticoagulation with a compatible anticoagulant in a therapeutic dose. The drugs currently available for this include the direct thrombin inhibitors argatroban, lepirudin, bivalirudin, and desirudin and the indirect factor Xa inhibitors danaparoid and fondaparinux.

[A new deal with new anticoagulants?]

The anticoagulant market has been very active recently with the development of new compounds including injectable anti-Xa such as fondaparinux, already available, and idraparinux, already replaced by its new biotynilateed form, and new oral drugs which can be divided into anti-IIa with dabigatran already available, and anti-Xa, such as the recently marketed rivaroxaban and apixaban still in the development stage. Others are coming forward. The competition is strong and the place for each drug remains to be determined. This review discusses these new anticoagulants in terms of efficacy and tolerance based on data in the literature. These recent reports mainly concern prophylaxis for orthopedic surgery but also consider treatment of deep venous thrombosis. The results of studies in heart patients have raised much curiosity since they will be determinant in the future use of innovating compounds, which could replace current oral anticoagulants. This will be upcoming but not yet for tomorrow.

Heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is an immune-mediated hypercoagulable disorder caused by antibodies to platelet factor 4 (PF4) and heparin. HIT develops in temporal association with heparin therapy and manifests either as an unexplained thrombocytopenia or thrombocytopenia complicated by thrombosis. The propensity for thrombosis distinguishes HIT from other common drug-induced thrombocytopenias. Diagnosing HIT in hospitalized patients is often challenging because of the frequency of heparin use, occurrence of thrombocytopenia from other causes, and development of asymptomatic PF4/heparin antibodies in patients treated with heparin. This review summarizes our current understanding of the pathogenesis, clinical features, diagnostic criteria, and management approaches in HIT.

Fondaparinux and the management of heparin-induced thrombocytopenia: the journey continues

OBJECTIVE

To review the available literature addressing the role of fondaparinux in the management of heparin-induced thrombocytopenia (HIT).

DATA SOURCES

Primary articles were identified by a MEDLINE search (2004-June 2009) of English-language literature using the MeSH headings fondaparinux, heparin, low-molecular-weight heparin, and thrombocytopenia. Relevant consensus guidelines (2006-June 2009) were also identified.

STUDY SELECTION AND DATA EXTRACTION

All published studies and case reports, as well as relevant consensus guidelines, evaluating the use of fondaparinux for the management of HIT were included.

DATA SYNTHESIS

The role of fondaparinux in the management of HIT is a therapeutic controversy challenging clinicians today. An open-label, prospective pilot study of 7 patients with acute HIT supports fondaparinux as an alternative anticoagulant. Additionally, a total of 12 patients with HIT from a larger case study and retrospective cohort were successfully treated with fondaparinux. Much of the supporting data exists in the form of case reports, each demonstrating normalization of platelet counts without any evidence of new thrombosis. The differences in clinical scenarios as well as the role and dose of fondaparinux make interpretation of these reports difficult. Three case reports have been published raising concerns regarding fondaparinux causing or failing to manage HIT appropriately. However, common weaknesses such as small sample sizes and nonuniform definitions of HIT limit the usefulness of these findings. The updated American College of Chest Physicians consensus guidelines now recognize fondaparinux as an option in the management of HIT; however, the level of evidence supporting this is of low quality. The use of fondaparinux as a bridging agent between direct thrombin inhibitor and warfarin therapy has been proposed. A recently published case report gives support to this approach.

CONCLUSIONS

Controlled clinical trials evaluating the use of fondaparinux in the management of HIT need to be completed before this therapy can be routinely recommended.

Anticoagulation in a Neurosurgical Patient with Heparin-Induced Thrombocytopenia Type II with Argatroban and Fondaparinux after Clipping of an Intracranial Aneurysm

BACKGROUND: Therapeutic anticoagulation in patients after a major neurosurgical procedure remains critical because of the risk of a major intracranial bleed. Novel drugs could play a beneficial role in this setting. CASE REPORT: We describe a patient with heparin-induced thrombocytopenia type II and pulmonary embolism who was anticoagulated with argatroban and, later, with fondaparinux. No intracranial bleeding was detected when anticoagulation was performed with argatroban and, later, fondaparinux. CONCLUSION: Both substances could have therapeutic potential in this context.

Successful use of argatroban during the third trimester of pregnancy: case report and review of the literature

Direct thrombin inhibitors are commonly used anticoagulants in patients with known or suspected heparin-induced thrombocytopenia (HIT). All three direct thrombin inhibitors available in the United States-argatroban, bivalirudin, and lepirudin-are pregnancy category B drugs based on animal studies, but little data are available on the safety of these agents during human pregnancy. Whereas several case reports support the safe use of lepirudin, only one case report has been published with argatroban and none with bivalirudin. We describe a 26-year-old pregnant woman with portal vein thrombosis and thrombocytopenia treated with argatroban for possible HIT during her last trimester. An argatroban infusion was started at 2 microg/kg/minute during her 33rd week of pregnancy, with the dosage titrated based on the activated partial thromboplastin time; infusion rates ranged from 2-8 microg/kg/minute. Treatment continued until her 39th week of pregnancy, when labor was induced. Argatroban therapy was discontinued 7 hours before epidural anesthesia. The patient successfully delivered a healthy male newborn, devoid of any known adverse effects from argatroban. The infant was found to have a small ventricular septal defect and patent foramen ovale at birth, but it is unlikely that these were caused by argatroban since organogenesis occurs in the first trimester. Even though the cause of this patient's thrombocytopenia was later determined to be idiopathic thrombocytopenic purpura, this is an important case that adds to the literature on use of argatroban during pregnancy.

A comparison of direct thrombin inhibitors in the treatment of Heparin-Induced Thrombocytopenia: a single institution experience

BACKGROUND AND OBJECTIVE

Heparin-Induced Thrombocytopenia (HIT), if left untreated, can lead to thrombocytopenia, thromboembolic complications and even death. Two thrombin inhibitors, lepirudin and argatroban, have been shown to improve clinical outcomes compared to historical controls in the management of HIT. The purpose of this retrospective study was to compare the effects of lepirudin and argatroban in the management of HIT.

METHODS

Adult subjects with a positive anti-heparin platelet factor 4 (PF4) antibody test and >50% decrease in platelet count during the first 30 days of admission over a period of 2 years were included in the study. Patient demographics, platelet counts, choice of antithrombin therapy, occurrence of thrombosis, length of hospital stay, and date and cause of death, if applicable, were collected for each patient.

RESULTS

Eighty-two patients met inclusion criteria: 41 patients did not receive any thrombin inhibitors after the diagnosis of HIT, 24 patients received lepirudin and 17 patients received argatroban. Subjects treated with a thrombin inhibitor were more likely to experience platelet count recovery (87.5% for the lepirudin group and 82.4% for the argatroban group) compared to those who did not receive antithrombin therapy (51.2%) after the diagnosis of HIT was made (P < 0.001). The thrombosis rate for subjects who did not receive antithrombin therapy after the diagnosis of HIT was 26.8%, compared to 8.3% for the lepirudin group and 5.9% for the argatroban group (P < 0.01). The incidence of death was also higher in the group of subjects that did not receive antithrombin therapy (48.8%) compared with the lepirudin group (16.7%) or the argatroban group (23.5%), P < 0.01.

CONCLUSION

Our findings suggest that thrombin inhibitors can improve the outcomes of patients with HIT by decreasing the incidence of morbidity and mortality relating to HIT. No significant difference could be determined in outcomes between argatroban and lepirudin therapy.

Treatment and prevention of heparin-induced thrombocytopenia: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition)

This chapter about the recognition, treatment, and prevention of heparin-induced thrombocytopenia (HIT) is part of the Antithrombotic and Thrombolytic Therapy: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition). Grade 1 recommendations are strong and indicate that the benefits do, or do not, outweigh risks, burden, and costs. Grade 2 suggests that individual patient values may lead to different choices. Among the key recommendations in this chapter are the following: For patients receiving heparin in whom the clinician considers the risk of HIT to be > 1.0%, we recommend platelet count monitoring over no platelet count monitoring (Grade 1C). For patients who are receiving heparin or have received heparin within the previous 2 weeks, we recommend investigating for a diagnosis of HIT if the platelet count falls by >/= 50%, and/or a thrombotic event occurs, between days 5 and 14 (inclusive) following initiation of heparin, even if the patient is no longer receiving heparin therapy when thrombosis or thrombocytopenia has occurred (Grade 1C). For patients with strongly suspected (or confirmed) HIT, whether or not complicated by thrombosis, we recommend use of an alternative, nonheparin anticoagulant (danaparoid [Grade 1B], lepirudin [Grade 1C], argatroban [Grade 1C], fondaparinux [Grade 2C], or bivalirudin [Grade 2C]) over the further use of unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH) therapy or initiation/continuation of vitamin K antagonists (VKAs) [Grade 1B]. The guidelines include specific recommendations for nonheparin anticoagulant dosing that differ from the package inserts. For patients with strongly suspected or confirmed HIT, we recommend against the use of vitamin K antagonist (VKA) [coumarin] therapy until after the platelet count has substantially recovered (usually, to at least 150 x 10(9)/L) over starting VKA therapy at a lower platelet count (Grade 1B); that VKA therapy be started only with low maintenance doses (maximum, 5 mg of warfarin or 6 mg of phenprocoumon) over higher initial doses (Grade 1B); and that the nonheparin anticoagulant (eg, lepirudin, argatroban, danaparoid) be continued until the platelet count has reached a stable plateau, the international normalized ratio (INR) has reached the intended target range, and after a minimum overlap of at least 5 days between nonheparin anticoagulation and VKA therapy rather than a shorter overlap (Grade 1B). For patients receiving VKAs at the time of diagnosis of HIT, we recommend use of vitamin K (10 mg po or 5 to 10 mg IV) [Grade 1C].

New anticoagulant strategies in ST elevation myocardial infarction: trials and clinical implications

New data have re-established the importance of anticoagulation of patients with ST segment elevation myocardial infarction (STEMI), both as an adjuvant to reperfusion therapy or in patients ineligible for reperfusion. Recent randomized trials have found newer agents to be superior to conventional unfractionated heparin. This article summarizes current understanding of the underlying pathophysiology of STEMI and provides a comprehensive review of emerging trial data for low molecular weight heparins, anti-factor Xa agents and direct thrombin inhibitors in this setting.

Successful management of acute thromboembolic disease complicated with heparin induced thrombocytopenia type II (HIT II): a case series

Heparin-induced thrombocytopenia type II (HIT II) is a rare immune-mediated complication of heparin. The diagnosis of HIT is considered in patients exposed to heparin, presenting with thrombocytopenia and thrombosis.

We present two cases with massive pulmonary embolism and HIT, successfully treated with the administration of fondaparinux, an alternative anticoagulant, combined with the insertion of an inferior vena cava filter for the prevention of new thromboembolic events. The two cases supplement the available data of the use of fondaparinux in patients with HIT and pulmonary embolism, before further large studies establish its efficacy and safety in this group of patients. Moreover, the management of these patients reveals the need for future evaluation of the combined therapy of alternative anticoagulant agents with the placement of vena cava filters.

The use of fondaparinux for the treatment of venous thromboembolism in a patient with heparin-induced thombocytopenia and thrombosis caused by heparin flushes

Heparin-induced thrombocytopenia (HIT) is an immunologic drug reaction characterized by paradoxical association with venous and arterial thrombosis. The syndrome is caused by IgG antibodies that are reactive against complexes of platelet factor 4 and heparin. Fondparinux does not bind to platelet factor 4, is structurally too short to induce an antibody response, and could in theory be a useful agent to treat HIT. A 69-year-old white female presented with a lower extremity extensive iliofemoral deep vein thrombosis after a right total knee arthroplasty and was subsequently found to have a pulmonary embolism. The patient was noted to have heparin flushes during her operation. Her platelet drop decreased >50% from baseline during initiation of antithrombotic therapy. She was started on subcutaneous fondaparinux 7.5 mg once daily injection. Her serotonin release assay and enzyme-linked immunosorbent assay for heparin antibodies were positive for HIT. Her platelet count nadir was 60 x 0(3)/mm(3) on day 5 and the platelet count rebounded after 8 days of fondaparinux therapy. No recurrent thrombotic or bleeding events were noted throughout her therapy. Anecdotal reports have shown that fondaparinux can be a useful agent to treat HIT with or without thrombosis.

Fondaparinux: use in thromboprophylaxis of acute medical patients

Fondaparinux is a synthetic pentasaccharide that inhibits thrombin formation and thrombus development via selective antithrombin mediated inhibition of factor Xa. The complete bioavailability (100%) and elimination half-life of approximately 17 hours allows once-daily administration of fondaparinux. In a well designed trial (ARTEMIS) in acute medical patients aged > or = 60 years, fondaparinux was significantly more effective than placebo in terms of reducing the incidence of venous thromboembolism (VTE) up to day 15. The beneficial effect of fondaparinux therapy was observed in all subgroups of patients irrespective of underlying illness (e.g. acute heart failure or acute respiratory disease) in a predefined subgroup analysis of the ARTEMIS trial. Similarly, in a retrospective analysis of the trial, age and renal function did not appear to affect the incidence of VTE in fondaparinux and placebo recipients. Fondaparinux was generally well tolerated in this clinical trial. In patients receiving fondaparinux, the incidence of major bleeding was similar to that in patients receiving placebo and the incidence of minor bleeding was <3%.

[Fondaparinux: the present and the future]

The development of new antithrombotic molecules which induced an inhibition of activated factor X (fondaparinux, Arixtra) shows effectiveness and safety in prevention of thromboembolic disease in surgery, but also in the treatment of the pulmonary embolism and major venous thromboses and acute myocardial infarction. Recent clinical trials show that new anti-Xa inhibitors also have interesting properties in antithrombotic therapy. Fondaparinux could offer new therapeutic possibilities that could simplify the management of patients under anticoagulant treatment.

The pharmacoeconomics of deep vein thrombosis treatment

Venous thromboembolism (VTE), encompassing both deep vein thrombosis (DVT) and pulmonary embolism, remains a common and costly condition that is associated with significant morbidity and mortality. Treatment options for initial management of DVT include unfractionated heparin (UFH), low-molecular-weight heparins (LMWHs), and fondaparinux, which is the first of a new class of pentasaccharide antithrombotic agents with anti-factor Xa activity. LMWHs are an important tool in DVT management, offering advantages over UFH such as ease of dosing, lack of need for coagulation monitoring, and reduced risk for heparin-induced thrombocytopenia (HIT). Fondaparinux is also characterized by a simple dosing regimen, no need for coagulation monitoring, and potentially a lower risk of HIT compared with LMWH. In a recent clinical trial of DVT management, efficacy and bleeding rates with fondaparinux appeared similar to those observed with LMWH. In contrast to LMWH, fondaparinux is generally given as a fixed dose across a range of patient weights rather than calculated per individual patient weight. Given the increasing economic burden of VTE, particularly due to its increased rate among the elderly, pharmacoeconomic analyses have become a particularly useful tool to aid in selecting among similarly effective and safe agents for VTE treatment. A recent cost-effective analysis demonstrated that fondaparinux use offers an attractive economic alternative to other agents for initial DVT therapy that could yield cost savings without compromising clinical outcomes or patient safety.

Reducing thrombotic complications in the perioperative setting: an update on heparin-induced thrombocytopenia

Heparins are widely used in the perioperative setting. Immune heparin-induced thrombocytopenia (HIT) is a serious, antibody-mediated complication of heparin therapy that occurs in approximately 0.5%-5% of patients treated with heparin for at least 5 days. An extremely prothrombotic disorder, HIT confers significant risks of thrombosis and devastating consequences on affected patients: approximately 38%-76% develop thrombosis, approximately 10% with thrombosis require limb amputation, and approximately 20%-30% die within a month. HIT antibodies are transient and typically disappear within 3 mo. In patients with lingering antibodies, however, re-exposure to heparin can be catastrophic. In the perioperative setting, heightened awareness is important for the prompt recognition, diagnosis, and treatment of HIT. HIT should be considered if the platelet count decreases 50% and/or thrombosis occurs 5-14 days after starting heparin, with other diagnoses excluded. On strong clinical suspicion of HIT, heparin should be discontinued and a parenteral alternative anticoagulant initiated, even before laboratory confirmation of HIT is obtained. Subsequent laboratory test results may help with the decision to continue with nonheparin therapy or switch back to heparin. Heparin avoidance in patients with current or previous HIT is feasible in most clinical situations, except perhaps in cardiovascular surgery. If the surgery cannot be delayed until HIT antibodies have disappeared, intraoperative alternative anticoagulation is recommended.

Percutaneous coronary interventions in patients with heparin-induced thrombocytopenia

Accomplishing a successful percutaneous coronary intervention in a patient with a suspected or diagnosed heparin-induced thrombocytopenia (HIT) requires the selection of an appropriate alternative anticoagulant and a thorough assessment of bleeding and thrombotic risks. In this review, we suggest an evidence-based management algorithm that takes into account the clinical phase of HIT (acute, recent, and remote HIT) and the associated risk when patients present with acute coronary syndrome. The algorithm also integrates preventive measures directed at decreasing the bleeding risk associated with the antithrombotic and invasive therapies used for HIT and percutaneous coronary intervention.