Anna Maria Cerbone

Functionally thrombasthenic state in normal platelets following the administration of ticlopidine.

To elucidate the bleeding tendency that follows the administration of ticlopidine, we investigated the skin bleeding time and some ex vivo functions of platelets obtained from eight healthy volunteers before and 1 wk after daily administration of 500 mg of ticlopidine. We found the following: ticlopidine significantly (P less than 0.001) prolonged the skin bleeding time and impaired the binding of radiolabeled fibrinogen and von Willebrand Factor, the clot retraction and the aggregation of platelets in response to ADP, epinephrine, thrombin, ionophore A23187, collagen, or arachidonic acid. In contrast, the administration of this drug did not affect intraplatelet levels of cAMP, agglutination and binding of von Willebrand Factor in response to ristocetin, shape change in response to ADP, collagen, thrombin, or arachidonic acid, or binding of prostaglandin E1 to resting platelets. Secretion of ATP in response to ADP or epinephrine was completely inhibited, whereas secretion as well as thromboxane synthesis in response to high concentrations of collagen, arachidonic acid, calcium ionophore A23187, or thrombin was unaffected. Studies with monoclonal antibodies showed that the glycoprotein IIb-IIIa complex (the putative receptor for fibrinogen and von Willebrand Factor on the surface of platelets exposed to naturally occurring aggregating agents) was quantitatively unaffected by ticlopidine. This observation was further confirmed by densitometric scannings of Periodic Acid-Schiff-stained gels of platelet suspensions. The onset, as well as the cessation of the inhibitory effect of ticlopidine on platelets was very slow, and reached a maximum after a 3-5-d administration. In addition, ticlopidine appeared to be a much more potent inhibitor when administered to subjects than when added in vitro to platelets. Finally, abnormalities comparable to those found in volunteers taking ticlopidine were observed when platelets from untreated subjects were incubated in the plasma of ticlopidine-treated subjects. We conclude that ticlopidine induces a thrombasthenic state in normal platelets without affecting the glycoprotein IIb-IIIa complex quantitatively. Furthermore, our data suggest that one or more active metabolites rather than the native drug mediate the abnormalities of platelet function observed in ticlopidine-treated subjects.

Inherited Thrombophilia: Implications for Prevention and Treatment of Venous Thromboembolism

Inherited thrombophilia, defined as a genetically determined tendency to develop venous thromboembolism (VTE), contributes to the pathogenesis of approximately 40% of VTE episodes. About 50% of carriers of inherited thrombophilic traits develop VTE, but the impact of the different abnormalities is variable in terms of clinical penetrance. Some rare abnormalities (natural anticoagulant deficiencies, homozygous factor V Leiden, and combined defects) result in more severe thrombophilic phenotypes, characterized by early-onset events, more frequent recurrence, and positive family history, whereas the common polymorphisms (heterozygous factor V Leiden and prothrombin G20210A) are associated with lower VTE risk, often in association with triggering risk factors. Therefore, clinical implications of inherited thrombophilia should be assessed in the framework of coexisting and/or circumstantial risk factors involved in the multifactorial pathogenesis of VTE. These considerations should be taken into account when assessing the need and modalities of primary and secondary thromboprophylaxis in patients carrying inherited thrombophilic traits.

Treatment of hemophilia: a review of current advances and ongoing issues.

Replacement of the congenitally deficient factor VIII or IX through plasma-derived or recombinant concentrates is the mainstay of treatment for hemophilia. Concentrate infusions when hemorrhages occur typically in joint and muscles (on-demand treatment) is able to resolve bleeding, but does not prevent the progressive joint deterioration leading to crippling hemophilic arthropathy. Therefore, primary prophylaxis, ie, regular infusion of concentrates started after the first joint bleed and/or before the age of two years, is now recognized as first-line treatment in children with severe hemophilia. Secondary prophylaxis, whenever started, aims to avoid (or delay) the progression of arthropathy and improve patient quality of life. Interestingly, recent data suggest a role for early prophylaxis also in preventing development of inhibitors, the most serious complication of treatment in hemophilia, in which multiple genetic and environmental factors may be involved. Treatment of bleeds in patients with inhibitors requires bypassing agents (activated prothrombin complex concentrates, recombinant factor VIIa). However, eradication of inhibitors by induction of immune tolerance should be the first choice for patients with recent onset inhibitors. The wide availability of safe factor concentrates and programs for comprehensive care has now resulted in highly satisfactory treatment of hemophilia patients in developed countries. Unfortunately, this is not true for more than two-thirds of persons with hemophilia, who live in developing countries.

Cost of care of haemophilia with inhibitors

Summary.  In Western countries, the treatment of patients with inhibitors is presently the most challenging and serious issue in haemophilia management, direct costs of clotting factor concentrates accounting for >98% of the highest economic burden absorbed for the healthcare of patients in this setting. Being designed to address questions of resource allocation and effectiveness, decision models are the golden standard to reliably assess the overall economic implications of haemophilia with inhibitors in terms of mortality, bleeding‐related morbidity, and severity of arthropathy. However, presently, most data analyses stem from retrospective short‐term evaluations, that only allow for the analysis of direct health costs. In the setting of chronic diseases, the cost‐utility analysis, that takes into account the beneficial effects of a given treatment/healthcare intervention in terms of health‐related quality of life, is likely to be the most appropriate approach. To calculate net benefits, the quality adjusted life year, that significantly reflects such health gain, has to be compared with specific economic impacts. Differences in data sources, in medical practice and/or in healthcare systems and costs, imply that most current pharmacoeconomic analyses are confined to a narrow healthcare payer perspective. Long‐term/lifetime prospective or observational studies, devoted to a careful definition of when to start a treatment; of regimens (dose and type of product) to employ, and of inhibitor population (children/adults, low‐responding/high responding inhibitors) to study, are thus urgently needed to allow for newer insights, based on reliable data sources into resource allocation, effectiveness and cost‐utility analysis in the treatment of haemophiliacs with inhibitors.

Acquired inhibitors of coagulation factors: part I-acquired hemophilia A.

Acquired hemophilia A (AHA) is a rare, but often severe, bleeding disorder caused by autoantibodies against clotting factor VIII (FVIII). AHA occurs more frequently in the elderly and in association with several conditions, such as malignancies, autoimmune diseases, postpartum, or drug exposure; however, about half of the cases remain idiopathic. At variance with congenital hemophilia, where hemarthroses are the most common bleeding symptoms, hemorrhages in AHA involving soft tissues (muscle, skin) are more frequently reported. AHA is diagnosed in patients: with negative personal or family bleeding history; in which prolonged activated partial thromboplastin time is not corrected after mixing and incubating equal volumes of patient and normal plasma for ~2 hours at 37°C; FVIII levels are reduced; and a specific FVIII-inhibiting activity is detected. Prompt recognition and treatment of AHA are mandatory, as inadequate management and complications of the disease are associated with high mortality rates. Therapeutic approaches should aim to control acute bleeds, eradicate FVIII-autoantibody production, treat associated diseases, and when possible, eliminate them. Present knowledge about this often overlooked and challenging condition has significantly increased following establishment of recent national and international studies, as will also be reviewed in this article.

Abnormally high prevalence of major components of the metabolic syndrome in subjects with early-onset idiopathic venous thromboembolism

BACKGROUND Although patients with idiopathic VTE are at higher than normal risk of asymptomatic atherosclerosis and of cardiovascular events, the impact of cardiovascular risk factors on VTE is poorly understood. OBJECTIVE To assess the prevalence of the metabolic syndrome and of its components in patients with early-onset idiopathic VTE. METHODS As many as 323 patients referred to our Thrombosis Ward for a recent (<6-months) early-onset idiopathic venous thromboembolism (VTE), were compared with 868 gender- and age-matched subjects, in whom a history of venous thrombosis had been excluded, referred during the same period time to our Ward. All had undergone a clinical assessment for smoking habits and for the presence of the components of the metabolic syndrome. RESULTS The metabolic syndrome was detected in 76/323 cases (23.5%) and in 81/868 controls (9.3%) (p<0.001; OR:2.990; 95%C.I.:2.119-4.217). Smoking was more common in patients with idiopathic VTE than in controls. In addition to the metabolic syndrome as a whole, its major individual determinants (arterial hypertension, impaired fasting glucose plasma levels, abdominal obesity, hypertriglyceridemia, low HDL-cholesterol) significantly correlated with idiopathic VTE (p always <0.05). The prevalence of thrombotic events was lower in females than in males (p=0.000; OR:2.217), the latter being most often hypertensives, smokers, hypertriglyceridemics, carriers of a metabolic syndrome and of impaired fasting glucose than females. In a multivariate analysis, arterial hypertension, impaired fasting glucose, abdominal obesity, and hypercholesterolemia independently predicted idiopathic venous events. CONCLUSIONS Both metabolic syndrome as a whole and its major components individually considered, independently predict early-onset idiopathic VTE.

Homozygous C677T Mutation of the 5,10 Methylenetetrahydrofolate Reductase Gene and Hyperhomocysteinemia in Italian Patients With a History of Early-Onset Ischemic Stroke

To the Editor: Case-control1 2 and prospective3 4 studies have suggested an association between moderate hyperhomocysteinemia and risk of ischemic stroke. Homozygosity for the C-to-T substitution at nucleotide 677 of the gene of 5,10-methylenetetrahydrofolate reductase (MTHFR) is associated with a 50% reduction of the activity of this enzyme5 and is the most common inherited cause of moderate hyperhomocysteinemia. In 1996 Klujitmans et al6 reported a threefold increase in the risk of early-onset cardiovascular disease in homozygotes for the C677T MTHFR mutation. However, the association of this genetic marker with arterial vascular events has been disputed by a nested case-control study.7 Markus et al8 recently failed to show an association between cerebrovascular disease and the MTHFR genotype, a comparable prevalence of homozygosity for the C677T MTHFR mutation being detectable in a population of 345 patients with ischemic stroke or transient ischemic attacks (TIA) and in 161 control subjects (10.7% versus 13.7%, respectively). Nor were nonfasting log homocysteine plasma levels able to identify subjects with a stroke history in that setting, as judged by the analysis of a subgroup of patients (n=160) and control subjects (n=75) in whom this amino acid was measured. However, as expected, the authors found a significant relationship between MTHFR genotype and homocysteine levels, the latter being also independently related to log serum folate. In the frame of a larger study on juvenile thrombotic events, we have evaluated a population of 60 consecutive patients with a history of early-onset ischemic stroke (29 females and 31 males, aged 5 to 64 years [mean age, 38; mean age at time of diagnosis, 34; range 4 to 49 years]) documented within 72 to 96 hours from the event by CT and/or MRI scans. Subjects who had suffered from TIA or who exhibited abnormalities of carotid …

Diabetes, vascular complications and antiplatelet therapy: open problems

Diabetes mellitus is commonly associated with both microvascular and macrovascular complications (coronary artery disease, cerebrovascular events, severe peripheral vascular disease, nephropathy and retinopathy). There is wide evidence demonstrating that platelet degranulation and synthesis of TxA2 are increased in diabetic patients. For this reason, many studies on anti-platelet therapy have been made to reduce thrombotic complication of diabetes mellitus. Some diabetic patients, although treated with ASA, have a high prevalence of recurrent thrombotic events, which may presumably be due to an “ASA resistance”. Nevertheless, this drug remains the one with the greatest benefit. To optimize its function, we should try to understand the causes of “aspirin resistance”, try to find the most suitable dosage, recommending patients to comply constantly with the prescription given and to avoid interactions with other drugs. “Clopidogrel resistance” is a term not clearly defined. The clinical implications of “clopidogrel resistance” are unknown. An important consideration affecting the use of aspirin in diabetic patients is its interaction with ACE-inhibitors. Another question is antiplatelet therapy in nephropathic diabetic patients. Although these patients are at high thrombotic and haemorrhagic risk, they should nevertheless be considered eligible to undergo antithrombotic therapy, taking into account the individual’s haemorrhagic risk.

Platelet Fibrinogen Binding in Diabetes Mellitus: Differences Between Binding to Platelets from Nonretinopathic and Retinopathic Diabetic Patients

While it is known that platelets from diabetic patients bind more fibrinogen than do platelets from normal subjects, there has been no study comparing this phenomenon in platelets from nonretinopathic and retinopathic patients. We have made such a comparison and have found the following. In agreement with previous reports, platelets from nonretinopathic diabetic patients bind abnormally high amounts of fibrinogen. No differences in the amount of fibrinogen bound to platelets (stimulated by collagen or thrombin) were found when data from nonretinopathic and retinopathic patients were compared. However, while aspirin (an inhibitor of thromboxane synthesis) reduced the abnormally high fibrinogen binding of platelets from nonretinopathic patients to normal control levels, it did not normalize the high fibrinogen binding of platelets from retinopathic diabetic patients. The combination of aspirin plus apy-rase (an ADP scavenger) almost suppressed fibrinogen binding and aggregation of platelets from normal or nonretinopathic diabetic subjects, whereas it had a somewhat lesser effect on binding and aggregation of platelets from retinopathic subjects. By using a monoclonal antibody (B59.2) to the platelet receptor for fibrinogen, we determined that this receptor was the same in platelets from normal as well as nonretinopathic diabetic subjects and that this antibody could suppress the binding of fibrinogen and the aggregation of platelets from both types of patients just as it did in platelets from normal subjects. Thus, our data indicate that, while platelets from both retinopathic and nonretinopathic patients are hyperaggregable and show abnormally high binding of fibrinogen, they differ in that these abnormalities can be normalized in platelets from nonretinopathic patients by suppressing prostaglandin/ thromboxane formation and scavenging AOP, but not in those from retinopathic patients.

Preventing Postsurgical Venous Thromboembolism: Pharmacological Approaches

The use of antithrombotic drugs for the prevention of venous thromboembolism (VTE) in patients undergoing surgery is presently based on solid principles and high-level scientific evidence. This article reviews current strategies of pharmacological thromboprophylaxis. The level of VTE risk following surgery depends on a variety of factors that the surgeon should take into account, including the type of surgery and the presence of additional risk factors, such as elderly age and cancer. In patients undergoing minor general surgery, early mobilization is sufficient as prophylaxis, whereas in those undergoing major general surgery, thromboprophylaxis with low molecular weight heparin (LMWH), low-dose unfractionated heparin, or the pentasaccharide fondaparinux is recommended. Patients undergoing major orthopedic surgery have a particularly high risk of VTE, and routine thromboprophylaxis with LMWH, fondaparinux, or a vitamin K antagonist (international normalized ratio target: 2.0 to 3.0) is the standard of care in this group of patients. Recently, two new oral anticoagulants, rivaroxaban (a factor Xa inhibitor) and dabigatran etexilate (a direct thrombin inhibitor) have been licensed to be used for thromboprophylaxis after orthopedic surgery in Europe. Mechanical methods of thromboprophylaxis (compression stockings, intermittent pneumatic compression, vena cava filters), not discussed in detail in this review, should always be considered in patients at high thrombotic risk, in association with the pharmacological strategies, or in cases of contraindications to anticoagulants, as in patients or procedures at high risk of bleeding.