Factor VIII deficiency does not protect against atherosclerosis

Reducing the risk of atherosclerotic cardiovascular disease in people with hemophilia: the importance of primary prevention

Revolutionary advances in the treatment of hemophilia has led to a significant improvement in life expectancy. Associated with this has been an increase in age-related diseases especially atherosclerotic cardiovascular disease (CVD). While people with hemophilia (PWH) develop atherosclerosis at rates similar to those of the general population, rates of atherothrombosis and mortality related to CVD have been much lower, due to their hypocoagulable state. Changing treatment paradigms, aimed at reducing the risk of bleeding by improving hemostasis to levels approaching normality, has meant that the protection they are thought to have had may be lost. CVD risk factors are just as common in PWH as in the general population, but appear to be undertreated. In particular, primary prevention of CVD is vital in all individuals, but particularly in PWH as treatment of established CVD can be difficult. Active identification and management of CVD risk factors, such as obesity, physical inactivity, hypertension, and hypercholesterolemia, is required. In particular, statins have been shown to significantly reduce cardiovascular and all-cause mortality with few adverse events and no increased risk of bleeding in the general population, and their use needs urgent assessment in PWH. Further longitudinal research into preventing CVD in PWH, including accurate CVD risk assessment, is required to optimize prevention and management.

Coronary artery stenosis in Japanese people living with HIV-1 with or without haemophilia

An extremely high prevalence (12.2%) of moderate-to-severe coronary artery stenosis (CAS) was documented in asymptomatic Japanese haemophiliacs living with HIV-1 (JHLH) in our previous study. The cause of this phenomenon remains unknown. We conducted the CAS screening in people living with HIV-1 without haemophilia (PLWH without haemophilia) to compare the prevalence of CAS in JHLH and PLWH without haemophilia and to identify the risk factors including inflammation markers. Ninety-seven age-matched male PLWH without haemophilia who consulted our outpatient clinic between June and July 2021 were randomly selected, and 69 patients who provided informed consent were screened for CAS using coronary computed tomography angiography (CCTA). The number of JHLH cases was 62 in this study. The prevalence of moderate (> 50%) to severe (> 75%) CAS was significantly higher in JHLH [14/57 (24.6%) vs. 6/69 (8.7%), p = 0.015], and the ratio of CAS requiring urgent interventions was significantly higher [7 (12.3%) vs. 1 (1.4%), p = 0.013] in JHLH than in PLWH without haemophilia. Among the inflammatory markers, serum titres of intercellular adhesion molecule-1 (p < 0.05) and interleukin-6 (p < 0.05) in JHLH were significantly higher than those in PLWH without haemophilia. Although some patient demographics were different in the age-matched study, it might be possible to speculate that intravascular inflammation might promote CAS in JHLH.

Atherosclerosis in Patients with Congenital Hemophilia: A Focus on Peripheral Artery Disease

Advances in the treatment of hemophilia have increased the life expectancy of this population and we are currently facing diseases associated with aging, including cardiovascular ones. Coronary atherosclerosis, with acute myocardial infarction as the most severe form of manifestation, has been recognized as part of the comorbidities of hemophiliacs. However, little is known about peripheral artery disease. Available data show that hemophiliacs have cardiovascular risk factors and atherosclerosis similar to the general population. Impaired thrombus formation and phenotype of atheroma plaque rather than the burden of atherosclerosis explains their lower cardiovascular mortality. Since the effect of traditional cardiovascular risk factors overpowers that of decreased coagulability and promotes the onset and progression of atherosclerotic lesions, screening for traditional cardiovascular risk factors and peripheral artery disease should be integrated into standard hemophilia care. There is evidence that invasive treatments and long-term antithrombotic therapy are generally safe, provided that coagulation factor levels are taken into account and replacement therapy is given when necessary.

Antithrombotic Treatment in Patients With Hemophilia: an EHA-ISTH-EAHAD-ESO Clinical Practice Guidance

Cardiovascular disease is an emerging medical issue in patients with hemophilia (PWH) and its prevalence is increasing up to 15% in PWH in the United States. Atrial fibrillation, acute and chronic coronary syndromes, venous thromboembolism, and cerebral thrombosis are frequent thrombotic or prothrombotic situations, which require a careful approach to fine-tune the delicate balance between thrombosis and hemostasis in PWH when using both procoagulant and anticoagulant treatments. Generally, PWH could be considered as being naturally anticoagulated when clotting factors are <20 IU/dL, but specific recommendations in patients with very low levels according to the different clinical situations are lacking and mainly based on the anecdotal series. For PWH with baseline clotting factor levels >20 IU/dL in need for any form of antithrombotic therapy, usually treatment without additional clotting factor prophylaxis could be used, but careful monitoring for bleeding is recommended. For antiplatelet treatment, this threshold could be lower with single-antiplatelet agent, but again factor level should be at least 20 IU/dL for dual antiplatelet treatment. In this complex growing scenario, the European Hematology Association in collaboration with the International Society on Thrombosis and Haemostasis, the European Association for Hemophilia and Allied Disorders, the European Stroke Organization, and a representative of the European Society of Cardiology Working Group on Thrombosis has produced this current guidance document to provide clinical practice recommendations for health care providers who care for PWH.

Acute coronary syndrome management in hemophiliacs: How to maintain balance?: A review

To analyze existing literature and understand how to balance the minimization of bleeding risk and ensuring adequate anticoagulation during coronary intervention treatment and long-term postoperative anticoagulation in hemophilia patients during the perioperative period, in order to provide guidance for healthcare professionals in developing effective treatment plans. This narrative review will analyze existing studies, case reports, and clinical guidelines to determine the most effective strategies for managing acute coronary syndrome in hemophilia patients. When evaluating the literature, factors such as patient age, medical history, and severity of the condition will be considered. The current management guidelines for acute coronary syndrome in hemophilia patients are not based on systematic evaluation and mainly rely on expert opinions. This article provides a comprehensive analysis of existing literature and recommends coagulation factor replacement therapy before anticoagulation and intervention treatment, as well as personalized anticoagulation treatment during the postoperative period for better management of hemophilia patients with acute coronary syndrome. These recommendations can help healthcare professionals develop more effective treatment plans for hemophilia patients.

Building the foundation for a community-generated national research blueprint for inherited bleeding disorders: research priorities to transform the care of people with hemophilia

BACKGROUND

Decades of research have transformed hemophilia from severely limiting children's lives to a manageable disorder compatible with a full, active life, for many in high-income countries. The direction of future research will determine whether exciting developments truly advance health equity for all people with hemophilia (PWH). National Hemophilia Foundation (NHF) and American Thrombosis and Hemostasis Network conducted extensive inclusive all-stakeholder consultations to identify the priorities of people with inherited bleeding disorders and those who care for them.

RESEARCH DESIGN AND METHODS

Working group (WG) 1 of the NHF State of the Science Research Summit distilled the community-identified priorities for hemophilia A and B into concrete research questions and scored their feasibility, impact, and risk.

RESULTS

WG1 defined 63 top priority research questions concerning arthropathy/pain/bone health, inhibitors, diagnostics, gene therapy, the pediatric to adult transition of care, disparities faced by the community, and cardiovascular disease. This research has the potential to empower PWH to thrive despite lifelong comorbidities and achieve new standards of wellbeing, including psychosocial.

CONCLUSIONS

Collaborative research and care delivery will be key to capitalizing on current and horizon treatments and harnessing technical advances to improve diagnostics and testing, to advance health equity for all PWH.

Applicability of the European Society of Cardiology Guidelines on the management of acute coronary syndromes to older people with haemophilia A - A modified Delphi consensus by the ADVANCE Working Group

INTRODUCTION

As people with haemophilia (PWH) receive better treatment and live longer they are more likely to encounter cardiovascular disease (CVD) and other comorbidities. ESC guidelines for the acute management of patients presenting with acute coronary syndrome (ACS) are based on the non-haemophilia population.

AIM

To review the guidelines and propose relevant adaptations for PWHA without inhibitors who are treated with prophylaxis and present with ACS.

METHODS

As part of the ADVANCE Group, 20 European haemophilia experts used a modified Delphi approach to develop and gain consensus on proposed adaptations of the ESC guidelines for PWHA without inhibitors.

RESULTS

Of the 32 Class I recommendations across both guidelines, adaptions were considered necessary and proposed for 15. The adaptions highlight the need to provide sufficient FVIII trough levels at the time of antithrombotic treatment in people with haemophilia A (HA) without inhibitors. Patients receiving emicizumab prophylaxis and requiring oral anticoagulation therapy or combined single antiplatelet plus oral anticoagulation therapy will require additional FVIII replacement therapy.

CONCLUSION

In the absence of high-quality clinical evidence, the combined expert opinion used to develop these adaptions to the current ESC guidelines may help to guide clinicians in their treatment decisions when a PWHA presents with ACS.

Evaluation of cardiovascular disease risk factors, inflammatory markers and subclinical atherosclerosis in patients with hemophilia

Aim: To assess and compare the risk factors of cardiovascular disease (CVD) between patients with hemophilia (PwH) and healthy controls in a single center cohort in Turkey. Material and Methods: Anthropometric parameters including height, weight, and body mass index were recorded. Fasting glucose, HbA1c, high sensitive C-Reactive Protein (hs-CRP), adiponectin, lipid parameters (total cholesterol, HDL-cholesterol, LDL-cholesterol, triglycerides) were assessed. International Physical Activity Questionnaires (IPAQ) and carotid intima media thickness (CIMT) measurements were performed. The data from PwH (n=80) and healthy controls (n=36) were compared. Independent associates of CIMT value were analyzed. Results: Hypertension, diabetes mellitus, metabolic syndrome and smoking frequencies were remarkable in PwH. Family history of CVD was significantly more frequent ( p=0.005) and when considered with IPAQ scores; PwH was much more sedentary than controls (p&lt;0.001). Total cholesterol, LDL-cholesterol were significantly higher in the control group (p =0.003,=0.003) while hs-CRP levels were higher in PwH (p=0.009). Age and IPAQ score were significant independent predictors of CIMT (p=0.004 and 0.003, respectively). Conclusion: As a result of aging; PwH exposure to the same CVD risk factors as the general population. Screening for CVD risk factors in PwH other than hemophilia evaluation will be essential.

Cardiovascular Risk Factors in Patients with Congenital Hemophilia: A Focus on Hypertension

Aging hemophiliacs face cardiovascular disease. Lots of evidence has been gathered that hemophiliacs have a more unfavorable cardiovascular profile than the general population does, especially due to the increased prevalence of hypertension (HTN). Among the existing scattered evidence, our study provides the most comprehensive and systematized analysis of the determinants of HTN in hemophiliacs. We discussed the contribution to the HTN substrate of hemophilia-specific factors, such as type, severity and the presence of inhibitors. The complex mechanism of kidney dysfunction in relation to hematuria and viral infections was meticulously addressed. Furthermore, we highlighted the new pathogenic concepts of endothelial dysfunction and the association between HTN and hemophilic arthropathy. The clustering of cardiovascular risk factors is common in hemophiliacs, and it enhances the negative vascular effect of HTN and aggravates HTN. It usually leads to an increased risk for coronary and cerebrovascular events. Our work provides reliable evidence to guide and improve the management of HTN in hemophiliacs.

Acute coronary syndrome in patients with hemophilia: a delicate balancing act

Therapeutic advances have resulted in increased life expectancy in patients with hemophilia. Consequently, the prevalence of coronary artery disease in this population is increasing. Little is known about the optimal management of acute coronary syndrome in these patients. Current guidelines for the management of this condition are based mainly on expert opinion and generally recommend administration of the clotting factor prior to the anticoagulant, antiplatelet, and interventional therapies. We report a case that illustrates the potential harm that may come from this approach: evolution of non-ST-segment elevation acute coronary syndrome into ST-elevation acute coronary syndrome during the administration of recombinant clotting factor. We review available literature and describe the refined informatics-based guidelines for managing acute coronary syndrome in patients with hemophilia we developed in response to the presented clinical case. We propose adopting this novel informatics-based approach, which aids in the identification and early treatment of these patients, operationalizes timely involvement of hematology experts, and gathers data for further study.

Current Therapeutic Approach to Atrial Fibrillation in Patients with Congenital Hemophilia

Cardiovascular disease in hemophiliacs has an increasing prevalence due to the aging of this population. Hemophiliacs are perceived as having a high bleeding risk due to the coagulation factor VIII/IX deficiency, but it is currently acknowledged that they also have an important ischemic risk. The treatment of atrial fibrillation (AF) is particularly challenging since it usually requires anticoagulant treatment. The CHA2DS2-VASc score is used to estimate the risk of stroke and peripheral embolism, and along with the severity of hemophilia, guide the therapeutic strategy. Our work provides the most complete, structured, and updated analysis of the current therapeutic approach of AF in hemophiliacs, emphasizing that there is a growing interest in therapeutic strategies that allow for short-term anticoagulant therapy. Catheter ablation and left atrial appendage occlusion have proven to be efficient and safe procedures in hemophiliacs, if appropriate replacement therapy can be provided.

Cardiovascular disease in hereditary haemophilia: The challenges of longevity

The development of effective and safe treatments has significantly increased the life expectancy of persons with haemophilia (PWH). This has been accompanied by an increase in the comorbidities of ageing including cardiovascular disease, which poses particular challenges due to the opposing risks of bleeding from haemophilia and antithrombotic treatments versus thrombosis. Although mortality secondary to coronary artery disease in PWH is less than in the general population, the rate of atherosclerosis appears similar. The prevalence of atrial fibrillation in PWH and risk of secondary thromboembolic stroke are not well established. PWH can be safely supported through acute coronary interventions but data on the safety and efficacy of long‐term antithrombotics are scarce. Increased awareness and research on cardiovascular disease in PWH will be crucial to improve primary prevention, acute management, secondary prevention and to best support ageing PWH.

Reduced cardiovascular morbidity in patients with hemophilia: results of a 5-year multinational prospective study

In this prospective study, PWH have a lower-than-predicted incidence of CVD.

The QRISK-2011 risk predictor is not valid for PWH.

Hemophilia is a congenital bleeding disorder caused by low levels of clotting factor VIII or IX. The life expectancy of people with hemophilia (PWH) has increased with the availability of clotting factor concentrates. At the same time, the incidence of cardiovascular disease (CVD) has increased; in retrospective studies, there are conflicting data regarding if, despite this increase, the incidence is still lower than in the general population. We prospectively compared the incidence of CVD in PWH vs the predicted incidence. This prospective, multicenter, observational study included adult PWH (aged >30 years) from The Netherlands and United Kingdom. They were followed up for a 5-year period, and CVD incidence was compared with a predicted event rate based on the QRISK2-2011 CVD risk model. The primary end point was the observed fatal and nonfatal CVD incidence after 5 years compared with the estimated events and in relation to severity of hemophilia. The study included 709 patients, of whom 687 (96.9%) completed 5 years’ follow-up or reached an end point. For 108 patients, the QRISK score could not be calculated at inclusion. For the remaining 579, fewer CVD events were observed than predicted: 9 vs 24 (relative risk, 0.38; 95% confidence interval, 0.18-0.80; P = .01), corresponding with an absolute risk reduction of 2.4%. Severe hemophilia treated on demand had the highest risk reduction. There was no statistically significant relation between severity of hemophilia and incidence of CVD. In hemophilia, a lower-than-predicted CVD incidence was found, supporting the theory that hemophilia protects against CVD. The study is registered at www.clinicaltrials.gov as #NCT01303900.

Clinical burden of hemophilia in older adults: Beyond bleeding risk

The prospect of hemophilia patients has dramatically improved in the last few decades with the introduction of various interventions that can effectively treat or prevent their bleeding risk. The life expectancy of patients can now reach that of the healthy population, but this has paved the way for several previously unrecognized morbidities to manifest in older adults with hemophilia. Such clinical complications are attributed to suboptimal management or poor access to effective therapy during childhood as well as chronicity and prolonged exposure to the underlying pathophysiology of the disease and its treatment. Complications common in the aging population are also becoming increasingly relevant in this vulnerable patient subgroup. In this review, we highlight peculiarities of such morbidities including chronic viral infections and liver disease, debilitating joint impairment and bone disease, cardiovascular and chronic kidney disease, and cancers. We also reflect on topics of special interest in adulthood such as sexuality.

Current Therapeutic Approach to Acute Myocardial Infarction in Patients with Congenital Hemophilia

Advances in the treatment of hemophilia have made the life expectancy of hemophiliacs similar to that of the general population. Physicians have begun to face age-related diseases not previously encountered in individuals with hemophilia. Treatment of acute myocardial infarction (AMI) is particularly challenging because the therapeutic strategies influence both the patient's thrombotic and hemorrhagic risk. As progress has been made in the treatment of AMI over the last decade, we performed an in-depth analysis of the available literature, highlighting the latest advances in the therapy of AMI in hemophiliacs. It is generally accepted that after the optimal substitution therapy has been provided, patients with hemophilia should be treated in the same way as those in the general population. New-generation stents that allow short dual antiplatelet therapy and potent P2Y12 receptor inhibitors have begun to be successfully used. At a time when specific recommendations and relevant data are scarce, our study provides up-to-date information to physicians involved in the treatment of AMI in hemophiliacs.

Cardiac surgery in patients with Hemophilia:is it safe?

Background

The life expectancy of hemophiliacs is similar to that of the general population. As a result, the prevalence of age-related cardiovascular diseases has increased. We present our experience with hemophilia patients who underwent cardiac surgery in our Medical Center between 2004 and 2019.

Methods

All hemophilia patients who underwent cardiac surgery were identified, and their peri-operative data evaluated retrospectively.

Results

Ten patients were identified: six with hemophilia-A, one with hemophilia-B, and three with hemophilia-C (factor XI deficiency). Cardiac procedures included ten coronary artery bypass grafts and one aortic valve replacement. Hemophilia-A and B patients were treated with factor substitution, whereas patients with factor XI deficiency were treated with fresh frozen plasma. One patient died, and one patient suffered from non-active gastrointestinal bleeding.

Conclusions

While major cardiac surgery can be performed safely on patients with hemophilia, a multidisciplinary team approach and strict postoperative monitoring are essential in order to achieve optimal results.

Antithrombotic Therapy: Prevention and Treatment of Atherosclerosis and Atherothrombosis

Atherosclerosis is a multifactorial vascular disease that develops in the course of a lifetime. Numerous risk factors for atherosclerosis have been identified, mostly inflicting pro-inflammatory effects. Vessel injury, such as occurring during erosion or rupture of atherosclerotic lesions triggers blood coagulation, in attempt to maintain hemostasis (protect against bleeding). However, thrombo-inflammatory mechanisms may drive blood coagulation such that thrombosis develops, the key process underlying myocardial infarction and ischemic stroke (not due to embolization from the heart). In the blood coagulation system, platelets and coagulation proteins are both essential elements. Hyperreactivity of blood coagulation aggravates atherosclerosis in preclinical models. Pharmacologic inhibition of blood coagulation, either with platelet inhibitors, or better documented with anticoagulants, or both, limits the risk of thrombosis and may potentially reverse atherosclerosis burden, although the latter evidence is still based on animal experimentation.Patients at risk of atherothrombotic complications should receive a single antiplatelet agent (acetylsalicylic acid, ASA, or clopidogrel); those who survived an atherothrombotic event will be prescribed temporary dual antiplatelet therapy (ASA plus a P2Y12 inhibitor) in case of myocardial infarction (6-12 months), or stroke (<6 weeks), followed by a single antiplatelet agent indefinitely. High risk for thrombosis patients (such as those with peripheral artery disease) benefit from a combination of an anticoagulant and ASA. The price of gained efficacy is always increased risk of (major) bleeding; while tailoring therapy to individual needs may limit the risks to some extent, new generations of agents that target less critical elements of hemostasis and coagulation mechanisms are needed to maintain efficacy while reducing bleeding risks.

Evaluation of Unfavorable Cardiovascular and Metabolic Risk Factors in Children and Young Adults with Haemophilia

OBJECTIVE

Increased risk of unfavorable cardiovascular risk factors has been recognised in ageing patients with haemophilia (PwH), but needs further studies in younger patients. The purpose of this study was to assess obesity, hypertension (HT), metabolic variables, insulin resistance and metabolic syndrome in young PwH.

METHODS

Forty-eight haemophilia A and B patients and 35 age and sex matched healthy controls were included in the study. Anthropometric measurements, blood pressure (BP), fasting glucose and insulin levels, serum lipids and diet were evaluated. The metabolic syndrome was defined according to the criteria of the International Diabetes Federation for pediatric and adult age groups.

RESULTS

The mean age of PwH was 21±9 years (range, 6-40 years). Of those ≥18 years, 46% were were obese/overweight while there were no obese/overweight cases in the <18 year-old patients. Obesity was more prevalent in PwH with arthropathy (p=0.017). Seven percent of the PwH between 10 and 18 years-old and 25% of those ≥18 years had metabolic syndrome. There was no difference in metabolic syndrome frequency between PwH and controls >10 years-old (19.5% vs 10% respectively, p=0.34). Fifty percent of the PwH ≥18 years-old had elevated BP or HT. Fasting blood glucose levels of PwH were significantly higher compared to controls (p=0.02).

CONCLUSION

Our study showed that obesity, HT and metabolic syndrome are frequent problems, especially in PwH with arthropathy. Early prevention and management of overweight, obesity and their sequelae must be addressed in clinical practice in order to maximize the overall health of the haemophilia population.

The continuums of impairment in vascular reactivity across the spectrum of cardiometabolic health: A systematic review and network meta-analysis

This study aimed to assess, for the first time, the change in vascular reactivity across the full spectrum of cardiometabolic health. Systematic searches were conducted in MEDLINE and EMBASE databases from their inception to March 13, 2017, including studies that assessed basal vascular reactivity in two or more of the following health groups (aged ≥18 years old): healthy, overweight, obesity, impaired glucose tolerance, metabolic syndrome, or type 2 diabetes with or without complications. Direct and indirect comparisons of vascular reactivity were combined using a network meta-analysis. Comparing data from 193 articles (7226 healthy subjects and 19344 patients), the network meta-analyses revealed a progressive impairment in vascular reactivity (flow-mediated dilation data) from the clinical onset of an overweight status (-0.41%, 95% CI, -0.98 to 0.15) through to the development of vascular complications in those with type 2 diabetes (-4.26%, 95% CI, -4.97 to -3.54). Meta-regressions revealed that for every 1 mmol/l increase in fasting blood glucose concentration, flow-mediated dilation decreased by 0.52%. Acknowledging that the time course of disease may vary between patients, this study demonstrates multiple continuums of vascular dysfunction where the severity of impairment in vascular reactivity progressively increases throughout the pathogenesis of obesity and/or insulin resistance, providing information that is important to enhancing the timing and effectiveness of strategies that aim to improve cardiovascular outcomes.

A cross-sectional analysis of cardiovascular disease in the hemophilia population

Men with hemophilia were initially thought to be protected from cardiovascular disease (CVD), but it is now clear that atherothrombotic events occur. The primary objective of the CVD in Hemophilia study was to determine the prevalence of CVD and CVD risk factors in US older men with moderate and severe hemophilia and to compare findings with those reported in age-comparable men in the Atherosclerosis Risk in Communities (ARIC) cohort. We hypothesized if lower factor levels are protective from CVD, we would see a difference in CVD rates between more severely affected and unaffected men. Beginning in October 2012, 200 patients with moderate or severe hemophilia A or B (factor VIII or IX level ≤ 5%), aged 54 to 73 years, were enrolled at 19 US hemophilia treatment centers. Data were collected from patient interview and medical records. A fasting blood sample and electrocardiogram (ECG) were obtained and assayed and read centrally. CVD was defined as any angina, any myocardial infarction by ECG or physician diagnosis, any self-reported nonhemorrhagic stroke or transient ischemic attack verified by physicians, or any history of coronary bypass graft surgery or coronary artery angioplasty. CVD risk factors were common in the population. Compared with men of similar age in the ARIC cohort, patients with hemophilia had significantly less CVD (15% vs 25.8%; P < .001). However, on an individual patient level, CVD events occur and efforts to prevent cardiovascular events are warranted. Few men were receiving secondary prophylaxis with low-dose aspirin, despite published opinion that it can be used safely in this patient population.

Haemophilia and ageing

Advances in the development of effective and safe treatments for haemophilia over the last 50 years have resulted in a significant increase in the life expectancy of persons with haemophilia (PWH). The management of this new cohort of middle-aged and elderly PWH is challenging because of the opposing risks of haemophilia and age-related cardiovascular disease and malignancy. Furthermore, this cohort of ageing PWH has the additional comorbidities of human immunodeficiency virus/hepatitis C and chronic haemophilic arthropathy. This article reviews the prevalence, underlying mechanisms and treatment strategies for managing these comorbidities. International collaboration is essential for registry data and further prospective trials to inform optimal evidence-based management for this rare disorder in the future.

Risk factors for cardiovascular disease in children and young adults with haemophilia

INTRODUCTION

The origins of cardiovascular disease (CVD) begin in childhood. The primary objective of this cross-sectional cohort study was to determine the prevalence of cardiovascular risk factors in patients with congenital haemophilia A or B followed at Rady Children's Hospital San Diego Hemophilia and Thrombosis Treatment Center (HTC). We hypothesized that cardiovascular risk factors could be identified as part of a comprehensive clinic visit.

MATERIALS AND METHODS

Standardized measurement of weight, height, waist circumference and blood pressure plus non-fasting glucose and lipid panel were performed. Participants and/or caregivers completed questionnaires about family history, medical history and lifestyle. Clinical data were abstracted from the medical record. Descriptive statistics, Student's t test, correlation, Mann-Whitney U test and chi-square test were performed to analyse the data.

RESULTS

Forty-three males (mean 12 years, range 5-20 years) enrolled. High rates of overweight and obesity, (pre)hypertension and abnormal lipids were identified. Subjects with normal weight had more days of >60 minutes of physical activity compared with those with overweight or obesity (5.2 ± 2.4 vs. 3.8 ± 2.5 day; P = 0.07). Higher weight was correlated with higher factor consumption (cor = 0.88; P < 0.001). There was no difference in target joints based on weight category (30% in normal weight vs. 25% in overweight or obese, χ2 = 0.11, P = 0.74), which may be attributed to high rates of prophylaxis.

CONCLUSIONS

Modifiable risk factors for CVD were identified as part of the study during comprehensive clinic visits. The HTC team may develop behavioural interventions to target cardiovascular risk reduction as part of the comprehensive care model.

The coagulation system in atherothrombosis: Implications for new therapeutic strategies

Clinical manifestations of atherosclerotic disease include coronary artery disease (CAD), peripheral artery disease (PAD), and stroke. Although the role of platelets is well established, evidence is now accumulating on the contribution of coagulation proteins to the processes of atherosclerosis and atherothrombosis. Coagulation proteins not only play a role in fibrin formation and platelet activation, but also mediate various biological and pathophysiologic processes through activation of protease-activated-receptors (PARs). Thus far, secondary prevention in patients with CAD/PAD has been the domain of antiplatelet therapy, however, residual atherothrombotic risks remain substantial. Therefore, combining antiplatelet and anticoagulant therapy has gained more attention. Recently, net clinical benefit of combining aspirin with low-dose rivaroxaban in patients with stable atherosclerotic disease has been demonstrated. In this review, based on the State of the Art lecture "Clotting factors and atherothrombosis" presented at the ISTH Congress 2017, we highlight the role of coagulation proteins in the pathophysiology of atherothrombosis, and specifically focus on therapeutic strategies to decrease atherothrombotic events by optimization of vascular protection.

Prevalence of Hypertension (HTN) and Cardiovascular Risk Factors in a Hospitalized Pediatric Hemophilia Population

Improved life expectancy in hemophilia has led to a greater interest in age-related disorders. Hypertension (HTN) as well as cardiovascular disease have been increasingly reported in hemophilic adults but there is currently very limited data in the pediatric population. We conducted a cross-sectional study using data from the 2012 National Health Cost and Utilization Project database to determine the prevalence of HTN and associated cardiovascular risk factors in a hospitalized pediatric hemophilia population, between the ages of 0 to 21 years, in comparison with the general pediatric population. The prevalence of HTN was significantly higher in children with hemophilia (CWH) in comparison with the general pediatric population (1.71% vs. 1.02%, P-value=0.005). When adjusting the analysis for sex, the prevalence of HTN in the hemophilia cohort remained higher, although not statistically significant (1.52% vs. 1.22%, P-value=0.2568). When examining the concomitant presence of ≥1 cardiovascular risk factors in the hypertensive subgroups, CWH had a higher prevalence of obesity (2.64% vs. 1.32%, P-value <0.0001). Interestingly, diabetes mellitus was more prevalent in nonhemophilic children (1.47% vs. 0.56%, P-value=0.0015). These data suggest that cardiovascular risk factors need to be closely monitored in CWH, and a better preventive strategy is likely needed to identify those hemophilic patients at higher risk of developing cardiovascular disease in adulthood.

Factor X Friuli Coagulation Disorder: Almost 50 Years Later

The story of factor X (FX) Friuli. Factor X Friuli was discovered in 1969 to 1970. However, the story of that disease was an international event since patients with this defect were studied in France and in Italy, and different diagnoses were reached-FVII; FX; combined prothrombin complex; and combined FII, FVII, and FX deficiencies. The diagnostic difficulties were due to the peculiar clotting pattern presented by these patients, namely, prolonged partial thromboplastin time, prolonged prothrombin time but normal Russell viper venom clotting time. Only suitable anti-FX antisera clarified the pattern. Altogether 12 homozygotes and 102 heterozygotes have been followed during 4 decades. Six homozygotes died, 2 of them due to HIV infection and 1 due to hepatitis B liver cirrhosis. The other 3 died of nontransfusion-related morbidity. Bleeding tendency has been moderate in agreement with the extrinsic or intrinsic system assay results-FX level of 4% to 5% is considered normal. Heterozygotes may present occasional bleeding manifestations usually during surgery or delivery. Molecular analysis have shown that the mutation responsible for the defect is a Pro343Ser substitution in exon 8. Chimeric FX Friuli mice have been useful in studying the effect of FX levels on embryonic or natal mortality of these animals. No new homozygote but several heterozygotes have been recently seen. The study of FX Friuli has revolutionized the diagnostic approach to FX deficiencies. The FX should be assayed by all assay systems. The FX Friuli has never been described in any other country, and all patients studied come from the Friuli Meduna River Valley.

A case report of acute inferior myocardial infarction in a patient with severe hemophilia A after recombinant factor VIII infusion

RATIONALE

The extent of protective effects of hemophilia against thrombotic events such as myocardial infarction (MI) and other acute coronary syndromes remains to be determined, as major risk factors for cardiovascular disease exist despite factor VIII (FVIII) deficiency. We present a case report of a 41-year-old male with severe hemophilia A and several cardiovascular risk factors.

PATIENT CONCERNS

This morbidly obese patient developed chest pressure, followed by chest pain and difficulty in breathing shortly after receiving on-demand treatment with intravenous recombinant FVIII (rFVIII) (turoctocog alfa) dosed per body weight.

DIAGNOSES

An electrocardiogram revealed a diagnosis of inferior ST-segment elevation MI.

INTERVENTIONS

The patient underwent an urgent coronary angiography using a radial artery approach. During the next 12 months, he received dual antiplatelet treatment, acetylsalicylic acid 100 mg, and clopidogrel 75 mg daily. His treatment for severe hemophilia A was changed to plasma-derived FVIII replacement therapy.

OUTCOMES

During this 12-month period, he experienced several small bleeds in his elbows.

CONCLUSIONS

The temporal relationship between rFVIII infusion and onset of the MI suggests a possible association; however, apart from obesity, the patient also had other major risk factors for arterial thrombosis, such as hypertension and smoking. Furthermore, atherosclerotic disease and underlying atherosclerotic changes could not be excluded with certainty. This case highlights the importance of studies assessing the impact of excess body weight on rFVIII dosing.

Management of Hemophilia in Older Patients

In recent decades, several improvements in hemophilia care have resulted in increased quality of life and life expectancy for those affected by this inherited hemorrhagic condition. Nowadays, individuals with hemophilia enjoy a life expectancy at birth close to that of males in the general population. As a consequence of the increasing age of the hemophilia population, a growing number of these patients develop age-related co-morbidities, such as cardiovascular disease and cancer, the management of which represents a new challenge for caregivers at hemophilia treatment centers. This narrative review focuses on the clinical problems arising in older people with hemophilia, with particular attention to the optimal therapeutic strategies.

Two global haemostatic assays as additional tools to monitor treatment in cases of haemophilia A

Haemophilia A patients with similar levels of factor VIII (FVIII) may have different bleeding phenotypes and responses to treatment with FVIII concentrate. Therefore, a test which determines overall haemostasis may be appropriate for treatment monitoring in some patients. We studied two global haemostatic methods: endogenous thrombin potential (ETP) and overall haemostatic potential (OHP) before and after injection of FVIII concentrate in patients with haemophilia A treated prophylactically and on-demand. A significant correlation between FVIII and both ETP and OHP was observed, while ETP and OHP differed between patients with severe and mild clinical phenotypes. Both ETP and OHP differed significantly between severe, moderate and mild haemophilia A and controls. ETP and OHP increased after intravenous injection of FVIII concentrate in both groups of patients, but in spite of higher pre-treatment values of both ETP and OHP in patients treated prophylactically, and much higher post-treatment FVIII levels in comparison with the values in patients treated on-demand, no difference after treatment was observed for either ETP or OHP. ETP and OHP may be additional alternatives for monitoring (and even for individual tailoring) treatment in patients with haemophilia A.

Comparing thrombin generation in patients with hemophilia A and patients on vitamin K antagonists

Essentials It is unknown if hemophilia patients with atrial fibrillation need anticoagulation. Endogenous thrombin potentials (ETP) in hemophilia patients and patients on coumarins were compared. Severe hemophilia patients had comparable ETP to therapeutic international normalized ratio (INR). In non-severe hemophilia, 33% had higher ETP than therapeutic INR and may need anticoagulation. Click to hear Dr Negrier's perspective on global assays for assessing coagulation SUMMARY: Background It is unknown whether patients with hemophilia A with atrial fibrillation require treatment with vitamin K antagonists (VKAs) to the same extent as the normal population. Objective To compare hemostatic potential in hemophilia patients and patients on VKAs using thrombin generation (TG). Methods In this cross-sectional study, TG, initiated with 1pM tissue factor, was measured in 133 patients with severe (FVIII < 1%, n = 15) and non-severe (FVIII 1-50%, n = 118) hemophilia A, 97 patients on a VKA with an international normalized ratio (INR) ≥ 1.5 and healthy controls. Endogenous thrombin potential (ETP) (nm*min) was compared according to FVIII level (< 1%, 1-19% and 20-50%) with healthy controls and patients with sub-therapeutic INR (1.5-1.9) and therapeutic INR (≥ 2.0). Medians and interquartile ranges (IQRs) were calculated. Results Compared with healthy controls (898 [IQR 803-1004]), both hemophilia patients and patients on VKAs had lower median ETPs at 304 (196-449) and 176 (100-250), respectively. ETP was quite similar in severe hemophilia patients (185 [116-307]) and patients with a therapeutic INR (156 [90-225]). Compared with patients with therapeutic INR, ETP in patients with FVIII 1-19% and patients with FVIII 20-50% was higher at 296 (203-430) and 397 (219-632), respectively. All patients with therapeutic INR had an ETP < 400. Considering this threshold, 93% of severe hemophilia patients, 70% of patients with FVIII 1-19% and 52% of patients with FVIII 20-50% had an ETP < 400. Conclusion In severe hemophilia patients, TG was comparable to that in patients with a therapeutic INR. In one-third of non-severe hemophilia patients, TG was higher. These results suggest that anticoagulation therapy should be considered in a substantial proportion of non-severe hemophilia patients.

Management of cardiovascular disease in aging persons with haemophilia

With the aging of the haemophilia population, age related comorbidities become more and more a medical issue. Managing haemophilia patients with cardiovascular disease is a difficult task for many haemophilia-treating physicians. Over the years, insights on prevalence, risk factors and management of cardiovascular disease in haemophilia have improved substantially. It is now recognised that many risk factors, such as hypertension and overweight, occur quite frequently in patients with haemophilia. Several new insights in anticoagulation management of atrial fibrillation and coronary ischaemia in haemophilia have been suggested. This review provides an general overview of the current knowledge of these topics in literature.

Comorbidities of cardiovascular disease and cancer in hemophilia patients

As life expectancy greatly increases in persons with hemophilia (PWH), more age-related diseases such as cancer and cardiovascular disease (CVD) emerge among this patient group. The aim of this study was to review the available evidence on the epidemiology of CVD events, and incidence and survival of cancer in PWH. The prevalence of CVD events among PWH seems to be similar to that of the general population. Some known risk factors for the event, including aging, hypertension, and hyperlipidemia, are also associated with its occurrence in PWH. There is no evidence showing occurrence of the event directly to clotting factor concentrate administration. On the other hand, the incidence of non-virus related cancer seems to be higher in PWH than the general population. In addition, PWH with cancer were younger at the time of diagnosis. In regards to hemophilia effect on cancer prognosis, further basic and large-scale prospective studies are urgently needed.

Carotid plaque is a new risk factor for peripheral vestibular disorder: a retrospective cohort study

Many chronic diseases are associated with dizziness or vertigo, as is peripheral vestibular disorder (PVD). Although carotid plaque development is linked to atherosclerosis, it is unclear whether such plaques can lead to the development of PVD. We therefore conducted this study to investigate the presence of an association between carotid plaque and new PVD events.In this retrospective study, we consecutively enrolled 393 patients ≥20 years old who had been treated for chronic diseases such as hypertension, dyslipidemia, and diabetes mellitus for ≥6 months at a primary care clinic (Oki Clinic, Japan) between November 2011 and March 2013. Carotid plaque presence was measured with high-resolution ultrasonography for all patients. During a 1-year follow-up period, an otorhinolaryngologist diagnosed and reported any new PVD events (the main end point). Hazard ratios (HRs) and 95% confidence intervals (CIs) for new PVD occurrence were estimated using the Cox proportional hazard regression model.The mean age of the participants was 65.5 years; 33.8% were men, and 12.7%, 82.4%, and 93.1% had diabetes mellitus, hypertension, and dyslipidemia, respectively. There were 76 new PVD events; patients with carotid plaque had a greater risk of such events (crude HR: 3.25; 95% CI: 1.62-6.52) compared to those without carotid plaque. This risk was even higher after adjusting for traditional risk factors for atherosclerosis (adjusted HR: 4.41; 95% CI: 1.75-11.14).Carotid plaques are associated with an increased risk of new PVD events.

Prevalence and Risk Factors Associated With Hypertension in Hemophilia: Cross-Sectional Analysis of a National Discharge Register

Introduction:

Improved life expectancy of persons with hemophilia (PWHs) has led to a greater interest in the role of age-related chronic diseases, such as hypertension, in this cohort. Several observational studies have reported an increased prevalence of hypertension in PWHs; however, this has not been assessed using a large, national database in the United States.

Aims:

We hypothesized the prevalence of hypertension is increased in PWHs and compared the prevalence of hypertension and associated risk factors among patients with and without hemophilia.

Methods:

A cross-sectional analysis was performed using discharge data among adult males from the National Inpatient Sample over the 3-year period, 2009 to 2011. Hypertension was compared across groups using Rao-Scott χ2 test. Multivariable logistic regression was used to estimate the odds of hypertension in patients with hemophilia after adjustment for hypertension-associated risk factors.

Results:

The prevalence of hypertension in patients with hemophilia was less than the prevalence of hypertension in patients without hemophilia (39.5% vs 56.3%, P < .001). Hemophilia was associated with a decreased odds of hypertension after adjusting for associated risk factors (odds ratio: 0.87; 95% confidence interval: 0.81-0.94).

Conclusion:

In contrast to the findings of several other recent studies, we report a decreased prevalence of hypertension in PWHs. The discrepancy among the reported prevalence of hypertension in our study and several others highlights the potential biases inherent to retrospective and cross-sectional studies and underscores the need for well-designed prospective studies to determine the true incidence of hypertension in PWHs, which may lie somewhere in between our findings and the findings of others.

Is the cardiovascular toxicity of NSAIDS and COX-2 selective inhibitors underestimated in patients with haemophilia?

Joint pain secondary to chronic arthropathy represents one of the most common and debilitating complications of haemophilia, often requiring analgesic care. When compared with nonselective non-steroidal anti-inflammatory drugs (ns-NSAIDs), selective COX-2 inhibitors (coxibs) offer the major advantage of not increasing the bleeding risk, thus being a better choice of analgesics for haemophilia patients. However, several studies have highlighted the cardiovascular risks posed by coxibs and NSAIDs. Given the assumed protection against thrombosis conferred by the deficiency in coagulation factors VIII or IX, these precautions regarding the use of coxibs and NSAIDs have never really been taken into account in haemophilia management. However, contrary to what has long been suspected, haemophilia patients are indeed affected by the same cardiovascular risk factors as nonhaemophiliac patients. Further studies should be conducted to evaluate the impact of NSAIDs on cardiovascular risks and the prevalence of hypertension in haemophilia patients.

Managing older patients with hemophilia

With access to safe factor products, the life expectancy of persons with hemophilia (PWHs) has increased almost 10-fold over the past 7 decades. Unfortunately, hand in hand with this success comes the burden of aging. As PWHs age, they are subject to develop many of the same risk factors as the general population, including increasing rates of hypertension, obesity, and diabetes. Such comorbidities predispose them to chronic diseases, such as cardiovascular disease and chronic kidney disease, although how their coagulopathy affects the expression of these conditions remains unclear. The older hemophilia population faces additional challenges, such as chronic joint arthropathy, which provokes falls and fractures, and complications related to HIV and hepatitis C infections, which greatly affect the incidence of cancer and liver disease. In light of the paucity of evidence-based guidelines to direct therapy, a new challenge has arisen for hematologists to optimally manage these complex age-related issues. In general, elderly PWHs should be treated similarly to their peers without hemophilia, with the addition of factor replacement therapy as appropriate. Primary prevention of risk factors should be emphasized, and close coordination between specialties is essential. This review will focus on common complications affecting the older hemophilia population, including cardiovascular disease, malignancy, liver disease, renal insufficiency, and joint disease.

Consensus review of the treatment of cardiovascular disease in people with hemophilia A and B

With advances in care, increasing numbers of people with hemophilia (PWH) achieve near-normal life expectancies and present with typical age-related cardiovascular conditions. Evidence-based guidelines for medical or surgical management of cardiovascular conditions in individuals with hemophilia are limited. Published recommendations exist for the management of some common cardiovascular conditions (eg, ischemic heart disease, atrial fibrillation), but identifying optimal strategies for anticoagulant or antithrombotic therapy constitutes the primary challenge of managing nonoperative cardiovascular disease (CVD) in PWH. In general, as long as factor concentrates or other hemostatic therapies maintain adequate hemostasis, the recommended medical and surgical management of CVD in PWH parallels that in individuals without hemophilia. The presence of factor inhibitors complicates hemophilia management. Published outcomes of CVD treatment in PWH are similar to those in the general population. Specific knowledge about factor replacement, factor inhibitors, and disease-specific treatment distinguishes the cardiovascular care of PWH from similar care of individuals without this rare bleeding disorder. Furthermore, a multidisciplinary approach incorporating a hematologist with an onsite coagulation laboratory, ideally associated with a hemophilia treatment center, is integral to the management of CVD in PWH.

Medical co-morbidities and practice

All-oral treatments of hepatitis C (HCV) have been trialled in patients with hereditary bleeding disorders and found to be effective. Further refinements of dosing and duration are being established. Importantly for patient acceptability these regimens are interferon-free. Cohort studies in older patients with haemophilia direct the need for attention to weight control, exercice, assessment of cardiovascular risk, especially hypertension and detection of osteoporosis. Where patients live a long way from a comprehensive care centre, telemedicine connections can engage centre experts with the patient and his/her local practitioners in devising and monitoring care plans.

Cardiovascular risk in patients with hemophilia

Patients with hemophilia, who have a lifelong hypocoagulability, seem to have a lower cardiovascular mortality than the general population. Nevertheless, the prevalence of cardiovascular risk factors in patients with hemophilia is as prevalent as in the general population, and hypertension is even more common. Furthermore, hemophiliacs have the same degree of atherosclerosis as the general population. The reduced cardiovascular mortality may be explained by reduced thrombus formation resulting from hypocoagulability. On the other hand, hemophilia, which is associated with reduced thrombin generation, may also increase atherosclerotic plaque stability, as has been shown in mice. Because treatment of these events is extremely challenging in patients with increased bleeding tendency, detection and aggressive treatment of risk factors is mandatory.

Inflammation and coagulation in atherosclerosis

Cardiovascular diseases remain to be the leading cause of death in Western societies. Despite major findings in vascular biology that lead to a better understanding of the pathomechanisms involved in atherosclerosis, treatment of the disease has only changed slightly within the last years. A big body of evidence suggests that atherosclerosis is a chronic inflammatory disease of the vessel wall. Accumulation and peroxidation of LDL-particles within the vessel wall trigger a strong inflammatory response, causing macrophage and T-cell accumulation within the vessel wall. Additionally, B-cells and specific antibodies against LDL-particles, as well as the complement system are implicated in atherogenesis. Besides data from clinical trials and autopsy studies it was the implementation of mouse models of atherosclerosis and the emerging field of direct gen-modification that lead to a thorough description of the pathophysiological mechanisms involved in the disease and created overwhelming evidence for a participation of the immune system. Recently, the cross-talk between coagulation and inflammation in atherogenesis has gained attention. Serious limitations and disparities in the pathophysiology of atherosclerosis in mice and men complicated the translation of experimental data into clinical practice. Despite these limitations, new anti-inflammatory medical therapies in cardiovascular disease are currently being tested in clinical trials.

Clinical management of older persons with haemophilia

Life expectancy for people with haemophilia (PWH) has improved and is now approaching that of the general population. The growing population of elderly PWH will therefore increasingly face the age-related morbidities such as cardiovascular diseases, malignant disease, liver disease, and bone and joint related diseases, as well as the lifestyle and psychosocial factors that accompany many of these conditions. For many PWH, frequent contact with haemophilia specialists within the comprehensive care centres supplants the relationship that individuals in the general population have with their general practitioners. As a result, there is a risk that elderly PWH may miss the chronic disease screening opportunities offered to the general population. This review focuses on the screening tests and examinations recommended for age-related comorbidities in the general population that may be applicable to the growing population of older people with haemophilia.

Applicability of the European Society of Cardiology guidelines on management of acute coronary syndromes to people with haemophilia - an assessment by the ADVANCE Working Group

There are no evidence-based guidelines for antithrombotic management in people with haemophilia (PWH) presenting with acute coronary syndrome (ACS). The aim of the study was to review the current European Society of Cardiology guidelines, and to consider how best they should be adapted for PWH. Structured communication techniques based on a Delphi-like methodology were used to achieve expert consensus on key aspects of clinical management. The main final statements are as follows: (i) ACS and myocardial revascularization should be managed promptly by a multidisciplinary team that includes a haemophilia expert, (ii) each comprehensive care centre for adult PWH should have a formal clinical referral pathway with a cardiology centre with an emergency unit and 24 h availability of percutaneous coronary intervention (PCI), (iii) PCI should be performed as soon as possible under adequate clotting factor protection, (iv) bare metal stents are preferred to drug-eluting stents, (v) anticoagulants should only be used in PWH after replacement therapy, (vi) minimum trough levels should not fall below 5-15% in PWH on dual antiplatelet therapy, (vii) the duration of dual antiplatelet therapy after ACS and PCI should be limited to a minimum, (viii) the use of GPIIb-IIIa inhibitors is not recommended in PWH other than in exceptional circumstances, (ix) the use of fibrinolysis may be justified in PWH when primary PCI (within 90 min) is not available ideally under adequate clotting factor management. It is hoped that the results of this initiative will help to guide optimal management of ACS in PWH.

Obesity in haemophilia patients: effect on bleeding frequency, clotting factor concentrate usage, and haemostatic and fibrinolytic parameters

The prevalence of obesity in patients with haemophilia (PWH) is increasing. We investigated the effect of obesity on bleeding frequency and clotting factor concentrate (CFC) usage in PWH and assessed whether prothrombotic changes observed in obesity differ between controls and PWH. Number of bleeds and CFC usage were compared between obese (N = 51) and non-obese (N = 46) haemophilia A patients. Markers of haemostasis and fibrinolysis were compared between PWH, and gender-, age- and body mass index (BMI)-matched non-haemophilic controls (N = 91). Median number of bleeds/patient-month was comparable between obese and non-obese patients with severe haemophilia (P = 0.791). Obese patients with severe haemophilia used 1.4 times more CFC/patient-month than non-obese patients (P = 0.036). When adjusting for weight this difference disappeared (P = 0.451). von Willebrand factor plasma concentration (VWF:Ag), factor VIII activity and endogenous thrombin potential were higher in obese than in non-obese controls. Obesity did not influence these markers in PWH. Plasminogen activator inhibitor type 1 levels were higher in obese vs. non-obese PWH (P < 0.001), whereas levels were comparable between PWH and controls (P = 0.912). Plasmin-α2-antiplasmin complex (PAP) levels appeared to be lower in obese vs. non-obese subjects, both within controls (P = 0.011) and PWH (P = 0.008). However, in PWH, PAP levels were higher than in controls (P < 0.001). Obesity is associated with an increase in net CFC usage in PWH, but has no effect on bleeding frequency. In addition, obesity attenuates hyperfibrinolysis in PWH. Future research investigating whether obese PWH need CFC treatment dosed on weight or whether a lower dosage would suffice to prevent and treat bleedings is needed.