Non-catheter associated venous thrombosis in hemophilia A and B. A critical review of all reported cases

Activated protein C resistance in the copresence of emicizumab and activated prothrombin complex concentrates

Background

Venous thromboembolic events have been reported in persons with hemophilia A who received emicizumab and activated prothrombin complex concentrate (APCC) concomitantly, but the relevant mechanism(s) remains unclear. We speculated that activated protein C (APC) and antithrombin (AT) resistance might be associated with these adverse events.

Objectives

To investigate APC and AT resistance in factor (F)VIII-deficient (FVIIIdef) plasma in the presence of emicizumab and APCC.

Methods

In pooled normal plasma or FVIIIdef plasma samples mixed with emicizumab (50 μg/mL) and FVIII-bypassing agents, including recombinant FVIIa (2.2 μg/mL), APCC (1.3 IU/mL), or plasma-derived FVIIa/FX (1.5 μg/mL), the suppression effect of AT (0-2.4 μM) and APC (0-16 nM) was assessed by tissue factor-triggered thrombin generation assay. The APC effects in FVIIIdef plasma with the copresence of emicizumab, FII (1.3 μM), and/or FIXa (280 pM) were also examined.

Results

The AT resistance in emicizumab and each bypassing agent was not observed. Moreover, APC dose-dependent suppression effect was observed in pooled normal plasma or FVIIIdef plasma mixed with emicizumab and recombinant FVIIa or plasma-derived FVIIa/FX. However, APC-catalyzed inactivation had little effect on thrombin generation assay potential in FVIIIdef plasma spiked with emicizumab and APCC. The addition of FIXa to emicizumab in FVIIIdef plasma could lead to partial APC resistance. Furthermore, FVIIIdef plasma spiked with emicizumab, FIXa, and FII was markedly resistant to APC-mediated inactivation.

Conclusion

FII and FIXa in APCCs were key clotting factors for APC resistance in FVIIIdef plasma supplemented with emicizumab and APCCs. The APC resistance in persons with hemophilia A receiving emicizumab and APCC may contribute to venous thromboembolic events.

Nothing short of a revolution: Novel extended half-life factor VIII replacement products and non-replacement agents reshape the treatment landscape in hemophilia A

Hemophilia A, an X-linked genetic disorder, is characterized by a deficiency or dysfunction of clotting Factor VIII. The treatment landscape has substantially changed by introducing novel extended half-life factor VIII (EHL-FVIII) replacement therapies such as efanesoctocog Alfa and non-factor replacement therapy such as emicizumab. These agents signal a shift from treatments requiring multiple weekly infusions to advanced therapies with long half-lives, offering superior protection against bleeding and improving patient adherence and quality of life. While EHL-FVIII treatment might lead to inhibitor development in some patients, non-factor replacement therapy carries thrombotic risks. Therefore, ongoing research and the generation of robust clinical evidence remain vital to guide the selection of optimal and cost-effective first-line therapies for hemophilia A patients.

Hemophilia patients: are they naturally anticoagulated?

Hemophilia is an X-linked bleeding disorder, characterized by low plasma levels of coagulation factor VIII (FVIII) (hemophilia A) or FIX (hemophilia B). Because of this, hemophilia patients (HP) were considered as naturally-anticoagulated and therefore protected from thrombosis. Over the last decades hemophilia care underwent striking changes by the introduction of prophylaxis with repeated injections of standard or modified coagulation factor products that maintain steady-state trough levels of the deficient factor. Meanwhile, new medications, not based on replacement therapy, were developed (i.e., emicizumab and others). However, emicizumab (the only licensed drug) can be used only for prophylaxis; during acute bleeding or surgery, HP require additional therapies, supplementing emicizumab with FVIII/IX concentrates or with bypassing agents (e.g., recombinant activated FVII or activated prothrombin complex concentrate). Owing to the new therapeutic strategies, the hemostatic competency of HP is now much better assured than in the past and therefore their life expectancy is considerably improved. Furthermore, the combined effects of the improved life-expectancy and of the steady-state hemostatic competence achieved by prophylaxis, make HP to be near(normal). They are, therefore, liable to be affected by the circumstantial risk factors of venous thromboembolism (VTE) that are common in the general population. Furthermore, HP undergo frequent surgery/invasive procedures (especially major orthopedic surgery) when they are treated with coagulation factor concentrates or bypassing agents that may increase the risk of post-operative VTE. Therefore, one wonders if HP should be considered for perioperative antithrombotic prophylaxis to prevent postoperative VTE.Clinical data on the value of antithrombotic prophylaxis in this setting are scanty. Indeed, data from an observational multicentre prospective study of 46 HP who underwent orthopedic surgery concluded that the prevalence of postoperative symptomatic VTE was similar to that estimated in the general population. Multicenter prospective trials are warranted to address the value of antithrombotic prophylaxis to avoid post-operative VTE in HP, especially during major surgery when regular prophylaxis is supplemented with additional coagulation factor products or bypassing agents. Until this information is available, HP undergoing major surgery whilst on antihemorrhagic prophylaxis supplemented with coagulation factor concentrates or bypassing agents, should at least receive intermittent pneumatic compression.

Absence of Effect of Emicizumab on D-Dimer Concentrations in Adult Patients with Severe Hemophilia A

BACKGROUND

The D-dimer (DD) assay is an essential biological test for the diagnosis and monitoring of thrombotic conditions. DD testing is usually not performed as part of the routine laboratory management of patients with hemophilia (PWH). There is an increasing concern about the risk of thrombotic complications in PWH, which is likely related to age, cardiovascular risk factors, invasive thrombogenic procedures, over-correction of Factor VIII (FVIII) or FIX, or administration of new therapeutic agents mimicking FVIII or rebalancing coagulation.

OBJECTIVE

This retrospective study sought to assess the basal DD levels in PWH treated prophylactically with FVIII, and to evaluate potential changes after switching to emicizumab.

METHOD

Patients over 18 years of age treated with emicizumab within a single center over the period 2017-2022 were included in the study.

RESULT

DD levels were measured in 40 adult PWH (37 severe/ three moderate / two with FVIII inhibitor) with a median age of 46 years (range: 19-82; Q1-Q3: 30,25-56,5), before and at least 3 months after emicizumab initiation. No significant changes were revealed, with DD median values of 257 ng/mL (range: 250-2876; Q1-Q3: 250-493,5) before and 250 ng/mL (range: 50-6205; Q1-Q3: 250-380,25) after the switch (p  =  0.9).

CONCLUSION

Most adult PWH on prophylaxis using FVIII display DD levels within the normal range, which remain unchanged after switching to emicizumab. In view of these reassuring results, monitoring of DDs at the start of emicizumab treatment does not appear necessary but could be considered when combined with other bypassing agents or high dose FVIII.

Challenging clinical scenarios for therapeutic anticoagulation: A practical approach

Therapeutic anticoagulation remains a fundamental backbone in the treatment and prevention of venous thromboembolism. However, while modern therapies are increasingly safe, anticoagulation is not without risks, particularly in those at high risk for or with recent bleeding. When weighing concurrent risks and benefits in each challenging clinical scenario, an individualized assessment of the risk and acuity of bleeding should be balanced by the indication for anticoagulation. Addressing modifiable risk factors and routine re-evaluation of any changes in this balance is critical. This review outlines available data and current guidelines for the management of anticoagulation in high-risk populations, including those with thrombocytopenia, elderly and high-fall risk, inherited bleeding disorders, and in acute coronary syndrome. We also examine management after clinically significant bleeding episodes, including intracranial hemorrhage, gastrointestinal bleeding, hemoptysis, retroperitoneal bleeding, hematuria, and abnormal uterine bleeding. The aim is to provide a comprehensive review of available literature to guide clinicians in providing optimal, safe, and individualized care for patients in these challenging scenarios.

Therapeutic and technological advancements in haemophilia care: Quantum leaps forward

INTRODUCTION

Recent technological innovations in haemophilia have advanced at an astounding pace, including gene therapy programmes and bioengineered molecules for prophylaxis, products that reduce treatment burden through half-life extension, unique mechanisms of action, and subcutaneous administration. Additional technological advancements have emerged that are anticipated to further transform haemophilia care.

AIM

Review new and emerging haemophilia therapies, including replacement and bypassing products, digital applications, utilisation of big data, and personalised medicine.

METHODS

Data were obtained from peer-reviewed presentations/publications, and ongoing studies in haemophilia, ultrasonography, and artificial intelligence (AI).

RESULTS

Available treatments include new recombinant factors VIII (FVIII) and IX (FIX), extended half-life FVIII/IX products, a new FVIIa product for inhibitor patients, and a FVIIIa-mimetic. Several novel therapeutics are in clinical trials, including FVIIIa mimetics and inhibitors of naturally-occurring anticoagulants. Ongoing gene therapy trials suggest that a single vector infusion using an optimised construct can produce factor activity that reduces bleeding to near zero for years. Today, persons with haemophilia (PwH) approach a lifespan comparable to that of the general population, presenting treatment challenges for age-related co-morbidities. Technological innovations have broadened beyond therapeutics to include large database analyses utilising remote data collection with handheld devices, and to tailor AI applications. Current development efforts include patient-performed ultrasonography, algorithms for scan interpretation, and point-of-care haemostatic testing devices.

CONCLUSIONS

We have entered a golden age for haemophilia treatment and care with wide-ranging advancements targeting improved quality of life (QoL). Future-focused efforts by clinical and patient communities may provide equitable access and care for people impacted by haemophilia worldwide.

Bleeder With a Clot: Thrombosis Following Treatment of Bleeding in a Child With Severe Hemophilia B

A 16-year-old boy with severe hemophilia B and minimal bleeding manifestations in his early childhood presented with gastrointestinal bleeding at 11 years of age. Following administration of prothrombin complex concentrate, he developed peripheral venous thrombosis and cerebral sinovenous thrombosis, posing a management dilemma. His cerebral sinovenous thrombosis resolved spontaneously, proving watchful waiting to be a useful strategy. He developed spontaneous intracranial bleed at 14 years of age for which he was treated with factor IX concentrate and commenced on prophylaxis. We discuss the factors contributing to genotype-phenotype dissonance in severe hemophilia and considerations before commencing prophylaxis in such cases.

Venous Thrombosis in Acquired Hemophilia: The Complex Management of Competing Pathologies

Introduction  Venous thrombosis is rare in the setting of factor VIII (FVIII) deficiency. Cases of deep vein thrombosis (DVT) have been described in hemophiliacs after recent major surgery, or in association with the administration of FVIII concentrate and activated prothrombin complex concentrates, but occurrence of spontaneous DVT is even more uncommon. Aim  We describe the challenging management of extensive DVT in a patient with acquired hemophilia A with concurrent hemorrhagic manifestations and review similar published cases. Methods  We summarize a series of 10 cases with the following demographics: 6 males and 4 females; median age at presentation of 65 (21-80); mean inhibitor titer of 68.5 Bethesda Units (BU 1.9 to BU 350). Results  Four cases were idiopathic and six had associated conditions (cancer [two cases], recent pregnancy [two cases], and recent surgery [two cases]). Three cases had an inferior vena cava filter inserted for acute lower limb DVT/pulmonary embolism. Inhibitor eradication was achieved with high-dose steroids with or without cyclophosphamide, and adjunct Rituximab administration was used in three cases. One patient received concurrent therapeutic plasma exchange (TPE). Inhibitor eradication was fastest with concurrent TPE at 6 days (range: 6-733 days). The 30-day survival was 90%. Conclusions  There was adequate response of inhibitors to immunosuppression with steroids and cyclophosphamide therapy. For more refractory disease, Rituximab is emerging as a beneficial and cost-effective adjunct with better rates of complete remission, and the threshold for its use may be lowered in this complex cohort with dual competing pathologies.

High levels of coagulation factors and venous thrombosis risk: strongest association for factor VIII and von Willebrand factor

Essentials Elevated procoagulant levels are associated with an increased risk of venous thrombosis (VT). The dependency on concurrent increased factor levels and VT was analyzed in a large study. Factor VIII (FVIII) and von Willebrand factor (VWF) were associated with the highest VT risk. The risks for other procoagulant factor levels were largely explained by FVIII and VWF. SUMMARY: Background Coagulation factors are essential for robust clot formation. However, elevated levels of procoagulant factors are associated with an increased risk of venous thrombosis (VT). The precise contribution of these factors to the development of VT is not yet understood. Objectives We determined the thrombosis risk for the highest levels of eight selected coagulation factors. Furthermore, we analyzed which of these coagulation factors had the strongest impact on the supposed association. Methods We used data of 2377 patients with a first VT and 2940 control subjects in whom fibrinogen, von Willebrand factor (VWF), factor II, FVII, FVIII, FIX, FX and FXI levels were measured. Results The odds ratios (ORs) for the various coagulation factor levels (> 99th percentile versus ≤ 25th percentile) varied between 1.8 and 4, except for FVIII (OR 23.0; 95% confidence interval [CI] 14.7-36.0) and VWF (OR 24.0; 95% CI 15.3-37.3). Adjustment for FVIII and VWF in a mediation analysis reduced the risks of the other factors to unity, with the exception of FIX and FXI (remaining ORs between 1.7 and 1.9). Conversely, the ORs for FVIII and VWF levels remained high after adjustment for all other procoagulant factors (FVIII: 16.0; 95% CI 9.7-26.3; VWF: 17.6; 95% CI 10.7-28.8). Conclusions Our results imply that the observed relationship between VT and coagulation factor levels can be largely explained by FVIII and VWF. FVIII and VWF levels were also associated with the highest VT risk.

Total Hip Arthroplasty in Hemophilia Patients: A Mid-term to Long-term Follow-up

OBJECTIVE

To report the results of mid-term to long-term follow-up after primary total hip arthroplasty (THA) in hemophiliacs and to hypothesize that THA can provide satisfactory outcomes in these patients.

METHODS

Twenty-four primary THA performed in 21 hemophilia patients between 2002 and 2012 were reviewed retrospectively, including 20 cases of hemophilia A and 1 case of hemophilia B. The standard lateral approach was used for all implantations. Substitution therapy for factor VIII and activated prothrombin complex concentrates were administered to patients with hemophilia A and B, respectively. Total and hidden blood loss were calculated. Outcomes were assessed using the Harris hip score before surgery and at the final follow-up visit. Complications were recorded by clinical and radiographic assessment and then compared to those in previous reports.

RESULTS

The mean follow-up period was 113 months (range, 5-15 years). The average total blood loss was 3559 mL (range, 1494-7506 mL). The mean amount of red blood cell (RBC) transfusion was 4.4 U (range, 0-14 U). The mean amount of clotting factor used in the perioperative period for management of hemophilia was 14 031.3 U (range, 8100-25 200 U). Harris hip scores improved from 37 points (range, 15-81) before surgery to 90 points (range, 70-96) at the last follow-up. No signs of loosening, infection or other complications of the implant components occurred after discharge. The overall survivorship of the implants was 100% for all patients, and no revision surgery was performed.

CONCLUSIONS

With modern techniques and hematological management, THA in patients with hemophilia leads to significant improvement in joint function with a relatively low incidence of complications. Increased blood loss and substitution therapy have no obvious negative influences on the mid-term to long-term results of THA.

Thromboembolic event rate in patients exposed to anti-inhibitor coagulant complex: a meta-analysis of 40-year published data

Anti-inhibitor coagulant complex (AICC), an activated prothrombin complex concentrate, has been available for the treatment of patients with inhibitors since 1977, and thromboembolic events (TEEs) have been reported after infusion of AICC in patients with congenital or acquired hemophilia. With the aim of estimating the TEE incidence rate (IR) related to AICC exposure in these patients, a systematic review of the literature was carried out in Medline, according to PRISMA guidelines, from inception date to March 2017. The IR of TEEs was estimated through a meta-analytic approach by using a generalized linear mixed model based on a Poisson distribution. Thirty-nine studies were included (1980-2016). Overall, 46 TEEs were reported; of these, 13 were reported as disseminated intravascular coagulations, 11 as myocardial infarctions, and 3 as thrombotic cerebrovascular accidents. The pooled TEE IR was 2.87 (95% confidence interval [CI], 0.32-25.40) per 100 000 AICC infusions (5.42 in retrospective studies [95% CI, 0.92-31.82]; 1.09 in prospective studies [95% CI, 0.01-238.77]). The TEE rate was 5.09 (95% CI, 0.01-1795.60) per 100 000 AICC infusions administered on demand, whereas no TEEs were reported with prophylaxis. Interestingly, the estimated IR in patients with congenital hemophilia was <0.01 per 100 000 infusions. These findings provide robust evidence of safety of AICC over almost 40 years of published studies.

Anticoagulation beyond direct thrombin and factor Xa inhibitors: indications for targeting the intrinsic pathway?

Antithrombotic drugs like vitamin K antagonists and heparin have been the gold standard for the treatment and prevention of thromboembolic disease for many years. Unfortunately, there are several disadvantages of these antithrombotic drugs: they are accompanied by serious bleeding problems, it is necessary to monitor the therapeutic window, and there are various interactions with food and other drugs. This has led to the development of new oral anticoagulants, specifically inhibiting either thrombin or factor Xa. In terms of effectiveness, these drugs are comparable to the currently available anticoagulants; however, they are still associated with issues such as bleeding, reversal of the drug and complicated laboratory monitoring. Vitamin K antagonists, heparin, direct thrombin and factor Xa inhibitors have in common that they target key proteins of the haemostatic system. In an attempt to overcome these difficulties we investigated whether the intrinsic coagulation factors (VIII, IX, XI, XII, prekallikrein and high-molecular-weight kininogen) are superior targets for anticoagulation. We analysed epidemiological data concerning thrombosis and bleeding in patients deficient in one of the intrinsic pathway proteins. Furthermore, we discuss several thrombotic models in intrinsic coagulation factor-deficient animals. The combined results suggest that intrinsic coagulation factors could be suitable targets for anticoagulant drugs.

[Thrombotic events in patients with hemophilia]

The paper describes 4 clinical cases of thrombotic events (pulmonary embolism, deep vein thrombophlebitis, acute myocardial infarction, ischemic stroke) that have occurred in patients with hemophilia. It discusses the possible causes of their development and methods for their prevention and treatment. Controlled natural hypocoagulation, in which the dose of an administered deficient factor decreases to such an extent that in order to maintain the safe level of hypocoagulation (plasma factor activity is 15-20%; activated partial thromboplastin time is 1.5-2 times normal values), is proposed as one of the treatment options.

Incidence and outcome of retained Port-A-Cath fragments during removal

PURPOSE

Port-A-Cath devices are frequently used for long-term venous access. We postulate that long-term use predisposes them to getting stuck and retained in a central vein at the time of removal. We aim to report the incidence and outcome of this complication.

METHODS

Between January 2006 and July 2016, a retrospective review of all Port-A-Cath removals that were performed at our centre was conducted. At the time of removal, catheters that could not be removed from the vein were considered retained.

RESULTS

During the study period, 107 children had 174 episodes of silicone Sitimplant (Vygon, Ecouen, France) Port-A-Cath insertions. These children required 135 removal episodes and there were 3 (2.2%) instances whereby the catheter fragment was retained. These episodes of retained catheters only occurred in children with factor VIII deficiency (4.1% incidence in this cohort). For each episode of catheter insertion and removal, the catheters had been left in situ for a mean duration of 43 months in children with factor deficiency and no retained fragments, and the mean duration was 91 months in children with factor deficiency and retained catheter fragments (p = 0.0011).

CONCLUSIONS

Port-A-Caths that are retained after attempted removal is a complication encountered predominantly in catheters that have been in use for a prolonged duration. Furthermore, factor replacement therapy in haemophiliacs may be a risk factor for this complication.

Acquired factor VIII deficiency: two case reports and a review of literature

Background

Acquired factor VIII (FVIII) deficiency, or acquired hemophilia A (AHA), is a rare autoimmune disorder involving antibody-mediated depletion of coagulation FVIII, leading to severe, life-threatening bleeding. The condition is often associated with other autoimmune disorders, and its treatment involves replacement of FVIII and various modes of immunosuppression. Recently, a few noteworthy therapeutic advances have been made. We present two cases of severe AHA in Chinese women. One of these women developed this disorder in the setting of possible parvovirus B19 infection, which has not yet been reported in association with AHA. Other notable features of her case included paradoxical venous thrombosis and possible association with Sjogren’s syndrome and myositis. The other woman failed to respond to usual first-line therapies despite exhibiting a less severe clinical course, illustrating the varied but potentially stubborn behavior of this disorder.

Case 1

An 87-year-old woman presented with diffuse ecchymoses, melena, vaginal bleeding. Labs showed hemoglobin (Hgb) nadir of 5.7 mg/dL, elevated partial thromboplastin time (PTT), FVIII level <1%, mixing study consistent with an inhibitor, elevated anti-Sjogren’s-Syndrome-related antigen A antibody, elevated creatinine kinase, and elevated parvovirus IgM and IgG. Imaging of her arm showed diffuse myositis and deep venous thrombosis. After intravenous and oral steroids, her FVIII levels normalized, and her symptoms subsided.

Case 2

A 59-year-old woman presented with recurrent ecchymoses and hematomas in her extremities. Labs showed Hgb of 11.7 mg/dL, elevated PTT, FVIII level of 3%, and mixing study consistent with an inhibitor. Despite receiving a long course of steroids, several courses of IVIG, and a few courses of Rituximab, her FVIII level remained critically low.

Conclusion

The rarity of AHA limits our understanding of this disease and the ability to perform trials to discover optimal therapies. We hope that these case reports and discussion will shed further light on the varied clinical manifestations and natural histories of this disorder to guide better recognition and treatment of AHA.

Venous Thromboembolism in Children with Cancer and Blood Disorders

Venous thromboembolism (VTE) in children is multifactorial and most often related to a combination of inherited and acquired thrombophilias. Children with cancer and blood disorders are often at risk for VTE due to disease-related factors such as inflammation and abnormal blood flow and treatment-related factors such as central venous catheters and surgery. We will review risk factors for VTE in children with leukemia, lymphoma, and solid tumors. We will also review risk factors for VTE in children with blood disorders with specific focus on sickle cell anemia and hemophilia. We will present the available evidence and clinical guidelines for prevention and treatment of VTE in these populations.

Upper Limb Deep Vein Thrombosis in Patient with Hemophilia A and Heterozygosity for Prothrombin G20210A: A Case Report and Review of the Literature

Deep vein thrombosis (DVT) is a rare disease in patients with hemophilia A. We report a case of 22-year-old male with severe hemophilia A who presented to the emergency room with 5-day history of right arm pain that was attributed initially to bleeding event. In the absence of external signs of bleeding or hematoma and normal hemoglobin level, we suspected an underlying DVT. Doppler ultrasonography of the right upper limb revealed thrombosis of the subclavian vein and this was confirmed by CT venography. The d-dimer level was normal and investigations for prothrombotic state revealed heterozygosity for prothrombin G20210A mutation. Treatment with factor VIII and low molecular weight heparin led to successful resolution and marked improvement of his clinical condition.

The current state of adverse event reporting in hemophilia

INTRODUCTION

Replacement of the missing clotting factor is the mainstay of hemophilia treatment. Whilst historically many hemophilia patients were infected with blood-borne viruses transmitted via plasma-derived products, nowadays the formation of alloantibodies against the missing clotting factor is the main adverse event of treatment. Areas covered: This paper provides an overview of the current national and international adverse event reporting systems, what these surveillance schemes taught us about side effects of the products presently in use, and elaborates on how to adapt these systems to the challenges we face with the changing treatment landscape. Expert commentary: Treatment of inherited bleeding disorders was accompanied by severe complications in the past, resulting in major morbidity and mortality. Current products are much safer, but still require monitoring via efficient safety surveillance systems. Adverse events are reported in national and international systems. With many new products entering the market, as well as non-factor replacement therapies, new safety issues may arise. It is important to identify potential adverse events early by making surveillance systems suitable to pick up unknown or unexpected effects, and to recognize and communicate patterns of adverse events rapidly.

Lemierre Syndrome: A Retrospective Study of the Role of Anticoagulation and Thrombosis Outcomes

Lemierre syndrome (LS) is a multisystemic infection beginning in the oropharynx and leading to thrombosis of the internal jugular vein (IJV) with septic emboli and potential thrombotic extension to the central nervous system. Although patient outcomes have improved with early initiation of antimicrobial therapies, there is no consensus regarding the role of anticoagulation in LS. To better define the role of anticoagulation therapy in LS and determine whether anticoagulation improves thrombosis outcomes, we conducted a retrospective chart review of pediatric and adult patients diagnosed with LS and managed at our institution from January 1998 to December 2014. Eighteen patients (9 females and 9 males) were included in this analysis, 6 of whom received ≥4 weeks of anticoagulation therapy (median 23.1 weeks, range 6.9-32.9 weeks). Six patients were in the pediatric age group (<18 years). All patients received broad-spectrum antibiotics. All patients had improvement in their thrombi by 3 months (nonanticoagulated patient group: complete response [CR], n = 9; partial response [PR], n = 3; anticoagulated patient group: CR, n = 2; PR, n = 4). No patient developed recurrent thrombosis or progression during the follow-up period, regardless of anticoagulation status. Our study suggests that anticoagulation in LS may not affect thrombosis outcomes.

How I treat patients with inherited bleeding disorders who need anticoagulant therapy

Situations that ordinarily necessitate consideration of anticoagulation, such as arterial and venous thrombotic events and prevention of stroke in atrial fibrillation, become challenging in patients with inherited bleeding disorders such as hemophilia A, hemophilia B, and von Willebrand disease. There are no evidence-based guidelines to direct therapy in these patients, and management strategies that incorporate anticoagulation must weigh a treatment that carries a risk of hemorrhage in a patient who is already at heightened risk against the potential consequences of not treating the thrombotic event. In this paper, we review atherothrombotic disease, venous thrombotic disease, and atrial fibrillation in patients with inherited bleeding disorders, and discuss strategies for using anticoagulants in this population using cases to illustrate these considerations.

Recombinant factor VIIa enhances platelet deposition from flowing haemophilic blood but requires the contact pathway to promote fibrin deposition

In prior microfluidic studies with haemophilic blood perfused over collagen, we found that a severe deficiency (<1% factor level) reduced platelet and fibrin deposition, while a moderate deficiency (1-5%) only reduced fibrin deposition. We investigated: (i) the differential effect of rFVIIa (0.04-20 nm) on platelet and fibrin deposition, and (ii) the contribution of the contact pathway to rFVIIa-induced haemophilic blood clotting. Haemophilic or healthy blood with low and high corn trypsin inhibitor (CTI, 4 or 40 μg mL(-1) ) was perfused over collagen at an initial venous wall shear rate of 100 s(-1) . At 100 s(-1) wall shear rate, where FXIIa leads to thrombin production without added tissue factor, FXI-deficient blood (3%) or severely FVIII-deficient blood (<1%) produced no fibrin at either CTI level. Whereas rFVIIa potently enhanced platelet deposition, fibrin generation was not rescued. Distinct from the high CTI condition, engagement of the contact pathway (low CTI) in moderately FVIII-deficient (3%) or moderately FIX-deficient blood (5%) resulted in enhanced platelet and fibrin deposition following 4 nm rFVIIa supplementation. In mildly FVIII-deficient blood (15%) at <24 h since haemostatic therapy, rFVIIa enhanced both platelet and fibrin generation in either CTI condition although fibrin was produced more quickly and abundantly in low CTI. For tissue factor-free conditions of severe haemophilic blood clotting, we conclude that rFVIIa reliably generates low levels of 'signaling' thrombin sufficient to enhance platelet deposition on collagen, but is insufficient to drive fibrin polymerization unless potentiated by the contact pathway.

Thromboprophylaxis and Incidence of Venous Thromboembolism in Patients With Hemophilia A or B Who Underwent High-Risk Orthopedic Surgeries

Total hip replacement (THR) and total knee arthroplasty (TKA) carry a high risk of postoperative venous thromboembolism (VTE); therefore, anticoagulation prophylaxis is recommended in these patients. Unfortunately, there are no guidelines about VTE prophylaxis in patients with hemophilia who underwent these high-risk surgeries. To determine whether these patients have high risk of VTE, we conducted a retrospective study on patients with hemophilia who underwent elective THR/TKA at our institute from 2004 to 2012. Postoperatively, we collected information on duration and method of factor VIII/IX infusion, VTE-prophylaxis, and complications. There were 23 patients with hemophilia, 18 (78%) with hemophilia A and 5 (22%) with hemophilia B, who underwent high-risk surgeries (39% THR and 61% TKA). The VTE prophylaxis included sequential compression device, 12 (52%), and prophylactic enoxaparin, 1 (4%). Ten (43%) patients did not receive VTE prophylaxis. At 1-year follow-up, we did not find any evidence of clinical VTE in our patients. Better risk stratification is needed to identify patients who would benefit from pharmacological prophylaxis.

Challenges in treating elderly patients with haemophilia: a focus on cardiology

Seventy years ago, the average life expectancy for patients with severe haemophilia A was less than 17 years. Today, due to the availability of safe and effective clotting factor concentrates, life expectancy is nearly normal, at least in patients without viral infections. More individuals are living into their 70s and 80s, acquiring a range of diseases that are common in elderly persons. One of the most important challenges includes the treatment of comorbidities, especially cardiovascular diseases. Although most evidence suggests that haemophilia, at least the severe manifestation, partially protects against myocardial infarction, stroke and venous thromboembolism, typical cardiovascular risk factors can still be present despite the clotting defect. Patients with haemophilia are equally or even more prone to obesity, hypertension, diabetes, and dyslipidaemia, and this is especially true for HIV-infected individuals using highly active antiretroviral therapy. The management of elderly haemophilia patients with cardiovascular comorbidities is hampered by a lack of evidence-based guidelines. Nevertheless, experience in treating cardiovascular disease is growing amongst the haemophilia community, and several authors have published their own recommendations for managing a variety of commonly encountered cardiovascular scenarios in haemophilia patients. Basic recommendations exist for risk-factor management, the adaptation of factor replacement therapy in the at-risk elderly, management of coronary revascularization, the management of acute coronary syndrome and atrial fibrillation. This review outlines our current knowledge about cardiovascular risk in elderly haemophilia patients, recommendations for clinical decision making, and our own experiences of managing individuals with coronary heart disease and atrial fibrillation.

The effect of factor VIII deficiencies and replacement and bypass therapies on thrombus formation under venous flow conditions in microfluidic and computational models

Clinical evidence suggests that individuals with factor VIII (FVIII) deficiency (hemophilia A) are protected against venous thrombosis, but treatment with recombinant proteins can increase their risk for thrombosis. In this study we examined the dynamics of thrombus formation in individuals with hemophilia A and their response to replacement and bypass therapies under venous flow conditions. Fibrin and platelet accumulation were measured in microfluidic flow assays on a TF-rich surface at a shear rate of 100 s⁻¹. Thrombin generation was calculated with a computational spatial-temporal model of thrombus formation. Mild FVIII deficiencies (5–30% normal levels) could support fibrin fiber formation, while severe (<1%) and moderate (1–5%) deficiencies could not. Based on these experimental observations, computational calculations estimate an average thrombin concentration of ∼10 nM is necessary to support fibrin formation under flow. There was no difference in fibrin formation between severe and moderate deficiencies, but platelet aggregate size was significantly larger for moderate deficiencies. Computational calculations estimate that the local thrombin concentration in moderate deficiencies is high enough to induce platelet activation (>1 nM), but too low to support fibrin formation (<10 nM). In the absence of platelets, fibrin formation was not supported even at normal FVIII levels, suggesting platelet adhesion is necessary for fibrin formation. Individuals treated by replacement therapy, recombinant FVIII, showed normalized fibrin formation. Individuals treated with bypass therapy, recombinant FVIIa, had a reduced lag time in fibrin formation, as well as elevated fibrin accumulation compared to healthy controls. Treatment of rFVIIa, but not rFVIII, resulted in significant changes in fibrin dynamics that could lead to a prothrombotic state.

Arterial and venous thromboses in patients with idiopathic (immunological) thrombocytopenia: a possible contributing role of cortisone-induced hypercoagulable state

Immunological thrombocytopenias, as other forms of thrombocytopenia, are associated with bleeding. Occasionally, these patients manifest thrombotic events. A total of at least 29 patients were reported to have had either arterial (20 cases) or venous (9 cases) thrombosis while platelet count was less than 50 × 10(3)/μL. The most frequent clinical manifestation was a myocardial infarction. Thrombosis occurred in the large majority of patients during prednisone therapy. Patients receiving cortisone or patients with Cushing syndrome show a hypercoagulable state characterized by elevated factor VIII levels, decreased fibrinolysis, and abnormal von Willebrand factor multimers composition. The same is probably true for prednisone-treated patients with thrombocytopenia. However, the 2 conditions are not identical since prednisone is a mainly glycoactive compound, whereas cortisol produced in excess in Cushing syndrome is mainly mineraloactive. The presence of large, young, hyperactive platelets may also play a role. Prednisone-treated patients with thrombocytopenia have to be considered as potentially thrombophilic.

Antidote strategies to reverse anticoagulation with TB-402, a long-acting partial inhibitor of factor VIII

BACKGROUND

TB-402 is a partially inhibiting antibody of factor VIII that is under development as a long-acting anticoagulant.

PATIENTS AND METHODS

The reversibility of FVIII inhibition by TB-402 was evaluated in vitro after spiking with recombinant human FVIII (rhFVIII), human plasma-derived FVIII (hpdFVIII), recombinant activated human FVII (rhFVIIa), FVIII inhibitor bypassing activity (FEIBA), and prothrombin complex concentrate (PCC). Twelve subjects were randomized to placebo or 35 or 70 IU kg(-1) rhFVIII 48 h after a single dose of 620 μg kg(-1) TB-402. TB-402 concentrations, FVIII activity (FVIII:C), activated partial thromboplastin time (APTT) and thrombin generation were measured over a period of 8 weeks.

RESULTS

In spiked samples, TB-402 inhibited FVIII:C by 30%, prolonged APTT by 4.5 s, and reduced the peak height in the thrombin generation assay to 56% ± 13% of the control value. In the presence of 10 μg mL(-1) TB-402, rhFVIII restored FVIII:C and APTT to the values obtained in the absence of TB-402. The inhibitory effect of TB-402 on thrombin generation was entirely reversed by rhFVIII, hpdFVIII, rhFVIIa, FEIBA, and PCC. In men, the mean half-life (t(1/2) ) of TB-402 was 14.2 days. TB-402 lowered the endogenous thrombin potential by 23% for ~ 35 days. Infusion of 35 IU kg(-1) rhFVIII had a marginal effect, whereas 70 IU kg(-1) rhFVIII restored FVIII:C, reduced APTT back to baseline for 9 h, and restored thrombin generation for ~ 3 h.

CONCLUSIONS

TB-402 resulted in a stable long-term anticoagulant effect. rhFVIII and other procoagulants counteracted the effect of TB-402 temporarily, and may be effective antidotes for future clinical practice.

The aging patient with hemophilia

The prospects for many boys born with hemophilia today include a normal life expectancy and minimal to no joint disease. However, despite the availability of safe replacement clotting factor concentrates and effective antiviral treatment, the aging patient with hemophilia today faces many challenges. These include management of their hemophilia as well as the same age-related health issues as experienced in the general population. While increasing, data on the prevalence of comorbidities and their management in the hemophilia population remain limited. This review will focus on issues related to management of hemophilia and complications of cardiovascular, musculoskeletal, hepatic, and renal disease. Available research is summarized and potential approaches to management are discussed.

Congenital prekallikrein deficiency

The congenital deficiency of prekallikrein (PK) is a rare condition in which there is a peculiar discrepancy between a severe in vitro defect and absence of bleeding. The gene controlling PK synthesis is located on chromosome 4 and consists of 14 exons and 15 introns. Only approximately 80 cases of PK deficiency have been described in the literature. Owing to the lack of bleeding, most cases go undetected or, if detected, go unreported. Occasional bleeding or thrombosis have been reported in a few patients but this was only due to the presence of associated risk factors. It is certain that the defect does not protect from thrombosis. Diagnosis is based on the presence of a great prolongation of partial thromboplastin time and normal prothrombin time and thrombin time. The long partial thromboplastin time is fully corrected by the addition of normal plasma or normal serum and presents the unusual feature of shortening on long incubation times. Platelet and vascular tests are normal. Immunological studies allow differentiation into two types, namely cases of true deficiency, which are approximately 70% of the total, and cases with abnormal forms. PK is a glycoprotein synthesized in the liver as a single-chain peptide of 88000 Da. It mostly circulates (∼75%) as a complex with high-molecular-weight kininogen. It is cleaved by FXIIa into a heavy chain and a light chain (catalytic domain), held together by disulfide bonds. Molecular biology techniques have so far only been applied to eleven families, and these studies do not yet allow definite phenotype/genotype conclusions. The exons involved are 5, 8, 11, 14 and 15. The noncoagulative effects of PK, mainly based on the effect of kallikrein, have been studied less, since they appear to be the result of the involvement of other components of the contact phase. Kallikrein can mainly affect the formation of bradykinin from high-molecular-weight kininogen and the activation of pro-urokinase to urokinase. Bradykinin causes inflammation, vasodilatation and an increase in vessel permeability. The activation of pro-urokinase results in enhanced fibrinolysis. However, fibrinolysis has been reported to be normal or defective in these patients.

Prevention of VTE Following total hip and knee arthroplasty in Hemophilia patients

The often debilitating condition of hemophilic arthropathy is treated with elective total joint arthroplasty. Little has been published addressing the role of thromboembolic prophylaxis in the hemophilic patient population following total hip arthroplasty (THA) and total knee arthroplasty (TKA). Although the American College of Chest Physicians and the American Academy of Orthopaedic Surgeons have set guidelines for thromboembolic prophylaxis in the general population, no such standard of care is in place for hemophilic patients. While the risk of thrombosis in hemophilic patients following THA and TKA is thought to be lower, cases have been reported of pulmonary embolism and deep vein thrombosis (DVT) in hemophilic patients.

Complex assemblies of factors IX and X regulate the initiation, maintenance, and shutdown of blood coagulation

Blood hemostasis is accomplished by a complex network of (anti-)coagulatory and fibrinolytic processes. These physiological processes are implemented by the assembly of multiprotein complexes involving both humoral and cellular components. Coagulation factor X, and particularly, factor IX, exemplify the dramatic enhancement that is obtained by the synergistic interaction of cell surface, inorganic and protein cofactors, protease, and substrate. With a focus on structure-function relationship, we review the current knowledge of activity modulation principles in the coagulation proteases factors IX and X and indicate future challenges for hemostasis research. This chapter is organized by describing the principles of hierarchical activation of blood coagulation proteases, including endogenous and exogenous protease activators, cofactor binding, substrate specificities, and protein inhibitors. We conclude by outlining pharmaceutical opportunities for unmet needs in hemophilia and thrombosis.

The clinical significance of the lack of arterial or venous thrombosis in patients with congenital prothrombin or FX deficiency

Several reports have dealt with the occurrence of both arterial and venous thrombosis in patients with haemophilia A, haemophilia B, and von Willebrand disease. Similar thrombotic events have been occasionally reported also in rare congenital coagulation disorders, particularly in fibrinogen or FVII deficiencies. On the contrary no sure venous or arterial thrombotic event has ever been reported in congenital prothrombin or Factor X deficiency. The significance of this observation is discussed. This discrepancy cannot be explained on the basis of the rarity of the two conditions, since in similarly rare congenital bleeding disorders such as FV or FXIII deficiency a few patients with thrombosis have been described. It appears that only these two defects are able to allow a sure protection from thrombosis. These observations may indirectly support the rationale for the use of direct thrombin or Factor X inhibitors in the prophylaxis and/or therapy of thrombotic manifestations.