International recommendations on the diagnosis and treatment of acquired hemophilia A.

Acquired hemophilia A (AHA), a rare bleeding disorder caused by neutralizing autoantibodies against coagulation factor VIII (FVIII), occurs in both men and women without a previous history of bleeding. Patients typically present with an isolated prolonged activated partial thromboplastin time due to FVIII deficiency. Neutralizing antibodies (inhibitors) are detected using the Nijmegen-modified Bethesda assay. Approximately 10% of patients do not present with bleeding and, therefore, a prolonged activated partial thromboplastin time should never be ignored prior to invasive procedures. Control of acute bleeding and prevention of injuries that may provoke bleeding are top priorities in patients with AHA. We recommend treatment with bypassing agents, including recombinant activated factor VII, activated prothrombin complex concentrate, or recombinant porcine FVIII in bleeding patients. Autoantibody eradication can be achieved with immunosuppressive therapy, including corticosteroids, cyclophosphamide and rituximab, or combinations thereof. The median time to remission is 5 weeks, with considerable interindividual variation. FVIII activity at presentation, inhibitor titer and autoantibody isotype are prognostic markers for remission and survival. Comparative clinical studies to support treatment recommendations for AHA do not exist; therefore, we provide practical consensus guidance based on recent registry findings and the authors' clinical experience in treating patients with AHA.

Clinical evaluation of bleeds and response to haemostatic treatment in patients with acquired haemophilia: A global expert consensus statement.

BACKGROUND: Acquired haemophilia (AH) is a rare bleeding disorder with significant morbidity and mortality. Most patients initially present to physicians without experience of the disease, delaying diagnosis and potentially worsening outcomes. Existing guidance in AH is limited to clinical opinion of few experts and does not address monitoring bleeds in specific anatomical locations. AIM: Derive consensus from a large sample of experts around the world in monitoring bleeding patients with AH. METHODS: Using the Delphi methodology, a structured survey, designed to derive consensus on how to monitor bleeding patients with AH, was developed by a steering committee for completion by a group of haematologists with an interest in AH. Consensus was defined as ≥75% agreement with a given survey statement. After three rounds of survey refinement, a final list of consensus statements was compiled. RESULTS: Thirty-six global specialists in AH participated. The participants spanned 20 countries and had treated a median of 12.0 (range, 1-50) patients with AH within the preceding 5 years. Consensus was achieved in all items after three survey rounds. In addition to statements on general management of bleeding patients, consensus statements in the following areas were presented: urinary tract, gastrointestinal tract, muscles, skin, joints, nose, pharynx, mouth, intracranial and postpartum. CONCLUSIONS: Here, we present consensus statements derived from a broad sample of global specialists to address monitoring of location-specific bleeds and evaluating efficacy of bleeding treatment in patients with AH. These statements could be applied in practice by treating physicians and validated by individual population surveys.

The Future of Hemophilia Treatment: Longer-Acting Factor Concentrates versus Gene Therapy.

Gene therapy is the only novel technology that currently offers the prospect of a lasting cure for hemophilia and freedom from the burden of repeated injections. Recent data from a handful of patients who have undergone gene therapy for hemophilia B are very encouraging with a sustained factor IX (FIX) level of 0.05 IU/mL maintained for over 4 years. While this level is above the current usual target trough levels, it falls well short of the level that patients on prophylaxis with longer-acting products can expect. Prophylaxis is also associated with high peak levels, which permits patients to maintain an active lifestyle. A major barrier to widespread adoption of gene therapy is a high seroprevalence of antibodies to adeno-associated virus (AAV) vectors in the general population. Young children would be the best candidates for gene therapy in view of much lower seroprevalence to AAV in infants. A stable level of FIX early in life would prevent the onset of joint bleeds and the development of arthropathy. The recent experience with apolipoprotein tiparvovec (Glybera; uniQure, Amsterdam, the Netherlands) indicates that gene therapy is unlikely to prove to be a cheap therapeutic option. It is also quite possible that other new technologies that do not require viral vectors (such as stem cell therapy) may overtake gene therapy during development and make it redundant.

The first Team Haemophilia Education meeting, 2015, Amsterdam, The Netherlands.

Haemophilia remains a complex disorder to diagnose and manage, requiring close cooperation between multidisciplinary healthcare professionals. There are still many unmet challenges in haemophilia care. The first Team Haemophilia Education (THE) meeting, held on 7-8 May 2015 in Amsterdam, The Netherlands, aimed to promote the optimal care of haemophilia patients through education of the multidisciplinary treatment team. This was achieved by reviewing the latest developments in haemophilia management, considering how these can be implemented in the clinic to improve patient care and providing a platform for networking and debate for all haemophilia treatment team members. Haemophilia treatment centres from several countries were asked to complete a premeeting online questionnaire to establish the biggest challenges that they face when managing patients. The concerns expressed were used to develop the agenda, which comprised a combination of formal presentations, case studies and informal workshops covering such topics as pharmacokinetics, laboratory assays and tailoring of treatment to individual patients. This report is a summary of the key developments in haemophilia care presented by various investigators and healthcare professionals at THE meeting 2015.

A genome-wide association study of resistance to HIV infection in highly exposed uninfected individuals with hemophilia A.

Human genetic variation contributes to differences in susceptibility to HIV-1 infection. To search for novel host resistance factors, we performed a genome-wide association study (GWAS) in hemophilia patients highly exposed to potentially contaminated factor VIII infusions. Individuals with hemophilia A and a documented history of factor VIII infusions before the introduction of viral inactivation procedures (1979-1984) were recruited from 36 hemophilia treatment centers (HTCs), and their genome-wide genetic variants were compared with those from matched HIV-infected individuals. Homozygous carriers of known CCR5 resistance mutations were excluded. Single nucleotide polymorphisms (SNPs) and inferred copy number variants (CNVs) were tested using logistic regression. In addition, we performed a pathway enrichment analysis, a heritability analysis, and a search for epistatic interactions with CCR5 Δ32 heterozygosity. A total of 560 HIV-uninfected cases were recruited: 36 (6.4%) were homozygous for CCR5 Δ32 or m303. After quality control and SNP imputation, we tested 1 081 435 SNPs and 3686 CNVs for association with HIV-1 serostatus in 431 cases and 765 HIV-infected controls. No SNP or CNV reached genome-wide significance. The additional analyses did not reveal any strong genetic effect. Highly exposed, yet uninfected hemophiliacs form an ideal study group to investigate host resistance factors. Using a genome-wide approach, we did not detect any significant associations between SNPs and HIV-1 susceptibility, indicating that common genetic variants of major effect are unlikely to explain the observed resistance phenotype in this population.

Enhanced pharmacokinetic properties of a glycoPEGylated recombinant factor IX: a first human dose trial in patients with hemophilia B.

Replacement therapy with factor IX (FIX) concentrates is the recommended treatment for patients with hemophilia B, an X-linked bleeding disorder occurring in 1:25,000 male births. N9-GP is a recombinant FIX molecule with a prolonged half-life which is obtained by site-directed glycoPEGylation where a 40-kDa polyethylene glycol molecule is attached to the activation peptide of FIX. This first human dose trial in patients with hemophilia B investigated the safety and pharmacokinetic properties of a single IV dose of N9-GP. Sixteen previously treated patients received one dose of their previous FIX product followed by one dose of N9-GP at the same dose level (25, 50, or 100 U/kg). None of the patients developed inhibitors. One patient developed transient hypersensitivity symptoms during administration of N9-GP and was excluded from pharmacokinetic analyses. In the remaining 15 patients, N9-GP was well-tolerated. The half-life was 93 hours, which was 5 times higher than the patient's previous product. The incremental recovery of N9-GP was 94% and 20% higher compared with recombinant and plasma-derived products, respectively. These results indicate that N9-GP has the potential to reduce dosing frequency while providing effective treatment of bleeding episodes with a single dose. The trial was registered at www.clinicaltrials.gov as NCT00956345.

Difficult clinical challenges in haemophilia: international experiential perspectives.

Haemostasis management in people with haemophilia can present a range of challenges to physicians. Specific challenges that may be encountered relate to regimens for immune tolerance induction, use of central venous access devices, optimizing care of paediatric patients with inhibitors and improving outcomes in acquired haemophilia. There are also challenges related to performing surgery, and the establishment of specialist centres is valuable with regard to this. These challenges are considered in the light of available data, and with perspectives gained from the experience of experts treating patients around the world. Sharing this knowledge may help to improve patient management.

Von Willebrand Factor Multimeric Assay in Acquired von Willebrand Disease Diagnosis: A Report of Experience from North Estonia Medical Centre.

Objectives Acquired von Willebrand syndrome (AVWS) is a rare and frequently underdiagnosed bleeding disorder with an unknown prevalence. The diagnosis of AVWS is made based on laboratory investigations and the presence of clinical symptoms. Evaluation and management of affected patients are complex due to the need for multiple laboratory assays. Materials and Methods Here, we describe the clinical and laboratory data of seven patients with a diagnosis of AVWS. All patients met the criteria for AVWS based on laboratory findings, bleeding symptoms, and the absence of any previous history of a bleeding disorder. Results In all cases, the laboratory findings, lack of bleeding anamnesis, and family history suggested the presence of AVWS. Von Willebrand factor multimeric analysis showed decreased high-molecular weight (HMW) multimers in six cases. Patients with lower HMW multimers experienced more severe bleeding complications. Conclusions The diagnosis of AVWS is complex and requires extensive laboratory evaluation. Interdisciplinary collaboration and complex laboratory evaluations are of paramount importance for the early recognition of AVWS and optimal AVWS diagnosis as well as successful clinical management.

Long-term safety and efficacy of N8-GP in previously treated adults and adolescents with hemophilia A: Final results from pathfinder2.

BACKGROUND: N8-GP (turoctocog alfa pegol; Esperoct® , Novo Nordisk A/S, Bagsvaerd, Denmark) is a glycoPEGylated human recombinant factor VIII with a half-life of ~1.6-fold of standard FVIII products. pathfinder2 (NCT01480180) was a multi-national, open-label trial of N8-GP in previously treated adolescent and adult patients with severe hemophilia A. OBJECTIVE: We report end-of-trial efficacy and safety of N8-GP from pathfinder2. METHODS: pathfinder2 main phase and extension phase part 1 results have been previously reported. During extension phase part 2, patients could switch from N8-GP prophylaxis 50 IU/kg every fourth day (Q4D) or 75 IU/kg once weekly (Q7D), depending on bleeding status. Extension phase part 2 collected long-term safety and efficacy data for all regimens until trial end (first patient in main phase, 30 January 2012; trial end, 10 December 2018). RESULTS: Overall, 186 patients were exposed to N8-GP for up to 6.6 years (median 5.4 years). The estimated annualized bleeding rate (ABR) was 2.14 (median 0.84) for the Q4D prophylaxis arm and 1.31 (median 1.67) for the Q7D prophylaxis arm. Nearly 30% of patients experienced zero bleeds throughout the entire duration of the trial, the hemostatic response was 83.2% across all treatment arms, and patient-reported outcomes were maintained or slightly improved. No safety concerns were detected. CONCLUSION: Data from the completed pathfinder2 trial, one of the largest and longest-running clinical trials to investigate treatment of severe hemophilia A, demonstrate the efficacy and safety of N8-GP in previously treated adolescent and adult patients.

Clinical evaluation of glycoPEGylated recombinant FVIII: Efficacy and safety in severe haemophilia A.

Turoctocog alfa pegol (N8-GP) is a novel glycoPEGylated extended half-life recombinant factor VIII (FVIII) product developed for prophylaxis and treatment of bleeds in patients with haemophilia A, to enable higher activity levels with less frequent injections compared with standard FVIII products. This phase III (NCT01480180), multinational, open-label, non-randomised trial evaluated the safety and clinical efficacy of N8-GP when administered for treatment of bleeds and for prophylaxis, in previously treated patients aged ≥12 years with severe haemophilia A. Patients were allocated to receive N8-GP for prophylaxis or on-demand treatment for up to 1.8 years. Patients on prophylaxis were administered one dose of 50 IU/kg of N8-GP every fourth day. Bleeds were treated with doses of 20-75 IU/kg. Total exposure to N8-GP in the trial was 14,114 exposure days (159 patient-years). For the prophylaxis arm (n=175), the median annualised bleeding rate (ABR) was 1.33 (interquartile range, 0.00-4.61), the mean ABR was 3.70 (95 % confidence interval 2.94-4.66) and 70 (40 %) patients had no bleeds during the trial. Across treatment arms, 83.6 % of bleeds resolved with one injection and 95.5 % with up to two injections. N8-GP had a favourable safety profile and was well tolerated. The frequency and types of adverse events reported were as expected in this population. One patient developed inhibitory antibodies against FVIII (≥0.6 Bethesda units [BU]) after 93 N8-GP exposure days. No clinically significant safety concerns were identified and N8-GP was effective for prophylaxis and treatment of bleeds in previously treated patients.

Cost effectiveness of haemophilia treatment: a cross-national assessment.

The aim of this study was to assess the incremental cost effectiveness of on-demand versus prophylactic haemophilia therapy in Germany, Sweden, the United Kingdom and The Netherlands from the third-party payers' perspective. Using a decision tree model, the cost effectiveness of on-demand versus prophylactic therapy was analysed by extrapolating data from the European Haemophilia Economic Study to a 1-year analytic time horizon. Five hundred and six patients with severe haemophilia A and B, without inhibitors and at least 14 years of age, were enrolled in this study. Patients treated prophylactically had fewer bleeds than patients treated on-demand. With prophylactic treatment, the incremental cost per avoided bleeding ranged from 6,650 Euro dollars for patients 30 years of age or younger in Germany to 14,140 Euro dollars for patients over 30 years old in Sweden. If quality of life was taken into account, patients receiving prophylactic treatment had higher mean utilities than patients on on-demand therapy. The incremental effectiveness ratios in Germany were 1.2 million Euro dollars per quality-adjusted life year gained for patients 30 years or younger and HIV-positive and 2.2 million Euro dollars for patients 30 years or younger and HIV-negative. In the group aged over 30 years and HIV-positive the on-demand treatment strategy was dominant, whereas in the over 30 years/HIV-negative group the incremental cost-utility ratio was 4.7 million Euro dollars per quality-adjusted life year. Based on our decision analysis, the use of prophylactic treatment was overall more effective than on-demand therapy in young haemophiliacs, but at extremely high cost.

Recombinant activated factor VII in the treatment of bleeds and for the prevention of surgery-related bleeding in congenital haemophilia with inhibitors.

The availability of recombinant activated factor VII (rFVIIa, eptacog alfa activated) has greatly advanced the care of patients with haemophilia A or B who have developed inhibitors against the infused replacement factor. Recombinant FVIIa is licensed for the on-demand treatment of bleeding episodes and the prevention of bleeding in surgery or invasive procedures in patients with congenital haemophilia with inhibitors. This article attempts to review in detail the extensive evidence of rFVIIa in congenital haemophilia patients with inhibitors. Patients with acute bleeding episodes are best treated on demand at home, to achieve the short- and long-term benefits of rapid bleed control. Key prospective studies have shown that rFVIIa achieves consistently high efficacy rates in the management of acute (including joint) bleeds in inhibitor patients in the home treatment setting. Substantial post-approval data from key registries also support the on-demand efficacy profile of rFVIIa established by the prospective clinical trials. The availability of rFVIIa has allowed major surgery to become a reality for inhibitor patients. Studies in key surgery, including orthopaedic procedures, have found that rFVIIa provides consistently high efficacy rates. Importantly, the wealth of data does not raise any unexpected safety concerns surrounding rFVIIa use; this is likely because rFVIIa is a recombinant product with a localised mechanism of action at the site of vascular injury. In summary, rFVIIa is established as an effective and well-tolerated first-line treatment for on-demand bleeding control and bleed prevention during minor and major (including elective orthopaedic) surgery in inhibitor patients. Use of rFVIIa has been a major step towards narrowing the gap in outcomes between inhibitor patients and non-inhibitor patients.

The incidence of lymphoma in the UK haemophilia population between 1978 and 1999.

OBJECTIVE: To determine the incidence of non-Hodgkin's lymphoma (NHL) and Hodgkin's disease (HD) in the UK haemophilia population during the 22 year period 1978-1999. DESIGN AND METHODS: An analysis of patient data included on the UK Haemophilia Centre Doctors' Organisation lymphoma register. The number of cases of NHL and HD occurring in HIV-positive and negative patients in each 3-year period were compared with the expected incidence in the general male population. RESULTS: Eighty-nine cases of lymphoma were identified. Seventy-two cases (81%) occurred in HIV-positive patients (67 NHL, five HD), and 17 cases (19%) in HIV-negative patients (nine NHL, eight HD). The incidence of NHL in the HIV-positive cohort was significantly increased, with a ratio of observed to expected cases of 83.92 (P < 0.001) in the period 1985-1996. The ratio reduced to 42.15 during the period 1997-1999, presumably as a consequence of the introduction of highly active antiretroviral therapy (HAART). There was a significant excess of HD in HIV-positive patients, with an observed to expected ratio of 10.50 between 1985 and 1999 (based on five cases, P < 0.001). During the whole observation period, there was a significant excess of HD in HIV-negative patients, with an observed to expected ratio of 2.66 (based on eight cases, P < 0.05). CONCLUSION: The incidence of lymphoma is significantly higher in HIV-positive UK haemophilia patients compared with HIV-negative individuals. Since the introduction of HAART, the incidence of lymphoma has tended to fall in the HIV-positive group.

The impact of HIV on mortality rates in the complete UK haemophilia population.

OBJECTIVE: To estimate the effect of HIV-1 infection on subsequent mortality in a complete population. DESIGN: Prospective cohort study. SUBJECTS: A total of 7250 haemophilic males were registered in the UK Haemophilia Centre Doctors' Organisation database, 1977-1998. Most were infected with hepatitis C virus. In the early 1980s, 1246 were infected with HIV-1 from contaminated clotting factor concentrate. The main outcome measure was the date of death. RESULTS: During 1977-1984 annual mortality in severely haemophilic males was 0.9%. For those with HIV, annual mortality increased progressively from 1985 reaching over 10% during 1993-1996 before falling to 5% in 1997-1999, whereas without HIV it remained approximately 0.9% throughout 1985-1999. For moderately/mildly haemophilic males the annual mortality was 0.4% during 1977-1984. Without HIV it remained approximately 0.4% throughout 1985-1999, but with HIV it was similar to that in severe haemophilia with HIV. Survival was strongly related to age at HIV infection. The large temporal changes in mortality with HIV were largely accounted for by HIV-related conditions. Without HIV annual liver disease mortality remained below 0.2% throughout 1985-1999, but with HIV it was 0.2% during 1985-1990, 0.8% during 1991-1996, and 0.8% during 1997-1999. CONCLUSION: These data provide a direct estimate of the effect of HIV-1 infection on subsequent mortality in a population with a high prevalence of hepatitis C. From approximately 3 years after HIV infection, large, progressive increases in mortality were seen. From 1997, after the introduction of effective treatment, substantial reductions occurred, although mortality from liver disease remained high.

Adverse outcome of human islet-allogeneic blood interaction.

BACKGROUND: A report of inflammatory damage when islets come into contact with allogeneic blood prompted us to confirm the finding. METHODS: Fresh handpicked human islets were incubated in blood group matched, nonsensitized allogeneic blood. Destruction was quantified by assaying the supernatants for proinsulin release and by blood clot histology. The effect on global hemostasis was assessed by thromboelastography (TEG), and heparin-bonded tubing was used to assess the effect on blood cellular counts. In separate experiments, islets were incubated in allogeneic blood with heparin or Reopro (monoclonal anti-GpIIbIIIa). Islets were also incubated in serum, and cryosections were stained for C1q, C4, C3, C5b-9, immunoglobulin (Ig)M, and IgG binding using immunohistochemistry. RESULTS: Histologic assessment showed severe destruction in 37% of islets in contact with allogeneic blood versus none in controls and a sevenfold increase in proinsulin release from controls (n = 6)(P < 0.005). TEG (n = 11) showed accelerated coagulation in the presence of islets (P < 0.001). Analysis of blood cellular counts (n = 3) showed consumption of platelets, neutrophils, and monocytes in the presence of islets (P < 0.001). Inhibition of coagulation with heparin (n = 3) or inhibition of platelet aggregation with Reopro (n = 3), separately or together (n = 3), did not make a substantial improvement in the destruction in terms of histology or proinsulin release. Immunohistochemical staining (n = 4) revealed C1q, C4, C3, and C5b-9 deposition along with IgG binding. IgM binding was weak if anything. CONCLUSION: This study confirms and extends the finding that human islet-allogeneic blood interaction results in significant destruction of islet tissue with activation of the coagulation cascade and platelet, neutrophil, and monocyte consumption. There was evidence for activation of complement by the classical pathway along with IgG binding.

Blood products for hemophilia: past, present and future.

Hemophilia is an inherited bleeding disorder, which in its severe form is characterized by recurrent hemarthrosis and internal bleeding. In the absence of effective treatment the prognosis is poor, but the development of blood products in the last few decades has transformed the outlook, and patients can now live essentially normal lives. Treatment options vary around the world, with cryoprecipitate still the mainstay of therapy in many developing countries. Many patients were infected with hepatitis and/or HIV through the use of coagulation factor concentrates before the introduction of physical methods of viral inactivation in the mid-1980s. In more affluent countries, the debate in recent years has focused on the relative merits of plasma versus recombinant products. Coagulation factor concentrates are expensive, and cost-benefit and quality-of-life studies will assume an increasing importance in guiding the selection of products. Looking to the future, genetic engineering offers the potential to create coagulation factors with enhanced properties, such as reduced immunogenicity and prolonged half-life. Transgenic animals are a potential source of therapeutic materials. Several trials of gene therapy for hemophilia are already underway.

The airline passenger: current medical issues.

It is widely accepted that travel by air is unlikely to be a hazard to the vast majority of passengers. However, there are potentially adverse effects of cabin air of poor quality and of the reduced oxygen tension of the cabin environment. There is also the possibility of thrombosis related, at least in part, to the relative inactivity of a long journey. It may well be that the toxicity of the oil additives that are used in aircraft engines should be revisited, and that research should be carried out on the relative importance and potential interactions of the many risk factors for thrombosis that could be enhanced during a long flight. Formal guidelines need to be developed for passengers.

The methodology for defining the European standards for the certification of Haemophilia Centres in Europe.

INTRODUCTION: Work Package 4 Development of the standardisation criteria of the European Haemophilia Network project has the main objective of implementing a common and shared European strategy for a certification system for two levels of Haemophilia Centres: European Haemophilia Treatment Centres and European Haemophilia Comprehensive Care Centres in the Member States of the European Union. MATERIALS AND METHODS: An inclusive and participatory process for developing shared standards and criteria for the management of patients with inherited bleeding disorders has been carried out. The process has been implemented through four different consultation events involving the entire European community of stakeholders that significantly contributed in the drafting of the European Guidelines for the certification of Haemophilia Centres. RESULTS: The Guidelines set the standards for the designation of centres that provide specialised and multidisciplinary care (Haemophilia Comprehensive Care Centres) as well as local routine care (Haemophilia Treatment Centres). Standards cover several issues such as: general requirements; patient care; advisory services; laboratory; networking of clinical and specialised services. CONCLUSIONS: The drafting of the European Guidelines for the certification of Haemophilia Centres was performed adopting a rigorous methodological approach. In order to build the widest possible consensus to the quality standards, the main institutional and scientific stakeholders have been involved. The resulting document will significantly contribute in promoting standardisation in the quality of diagnosis and treatment in European Haemophilia Centres.

The European standards of Haemophilia Centres.

INTRODUCTION: The European haemophilia community of professionals and patients has agreed on the principles of haemophilia care to address comprehensive optimal delivery of care which is nowadays scattered throughout Europe. Many of the health facilities call themselves Haemophilia Centres despite their variation in size, expertise and services provided. Only a small number of countries have Haemophilia Centre accreditation systems in place. METHODS: In the framework of the European Haemophilia Network project, following an inclusive process of stakeholder involvement, the European Guidelines for the certification of haemophilia centres have been developed in order to set quality standards for European Haemophilia Centres and criteria for their certification. RESULTS: The Guidelines define the standards and criteria for the designation of two levels of care delivery: European Haemophilia Treatment Centres, providing local routine care, and European Haemophilia Comprehensive Care Centres, providing specialised and multi-disciplinary care and functioning as tertiary referral centres. Additionally, they define standards about general requirements, patient care, provision of an advisory service and establishment of network of clinical and specialised services. CONCLUSIONS: The implementation of the European Guidelines for the certification of Haemophilia Centres will contribute to the reduction of health inequalities through the standardisation of quality of care in European Union Member States and could represent a model to be taken into consideration for other rare disease groups.

Pancreas allograft thrombosis.

Thrombosis of the transplanted pancreas is a common and often catastrophic event. Predisposing factors include the hypercoagulable state of many patients with diabetic renal failure, preservation-related graft endothelial injury, and low-velocity venous flow. Clinical management includes optimization of modifiable risk factors, controlled anticoagulation, graft monitoring, and early therapeutic intervention.