Fondaparinux: pharmacology and clinical experience in cardiovascular medicine.

Fondaparinux is a synthetic, five-saccharide chain, AT-dependent, anti-FXa agent. Studies showed that fondaparinux acts in prevention and treatment of venous thromboembolism and in ischemic heart disease, without significant bleeding risk. The drug inhibits thrombin generation, has long half-life and can be administered once-daily without laboratory monitoring. It may be used in HIT treatment.

Local inhibition of tissue factor reduces the thrombogenicity of disrupted human atherosclerotic plaques: effects of tissue factor pathway inhibitor on plaque thrombogenicity under flow conditions.

BACKGROUND: Plaque disruption and subsequent thrombus formation lead to acute coronary syndromes and progression of atherosclerotic disease. Tissue factor (TF) appears to mediate plaque thrombogenicity. Tissue factor pathway inhibitor (TFPI) is the major physiological inhibitor of TF. This study analyzes the role of TF on thrombogenicity of disrupted human atherosclerotic plaques and the therapeutic possibilities of its specific inhibition. METHODS AND RESULTS: Human atherosclerotic and normal arterial segments were exposed to heparinized blood at flow conditions modeling medium-grade coronary stenosis in the Badimon perfusion chamber. The antithrombotic effects of the specific inhibition of plaque TF was assessed by reduction in the deposition of radiolabeled platelets and fibrin(ogen) and immunohistochemical analysis of perfused arteries. TF activity was inhibited by both recombinant TFPI and a polyclonal antibody against human TF. Human lipid-rich plaques were more thrombogenic than less advanced atherosclerotic plaques. Specific inhibition of TF activity reduced plaque thrombogenicity, inhibiting both platelet and fibrin(ogen) deposition (580 versus 194 plateletsx10(6)/cm2; P<0.01, and 652 versus 172x10(12) molecules of Fg/cm2; P<0.05, respectively) and thrombosis (immunohistochemistry). CONCLUSIONS: This study documents the key role of TF activity in acute arterial thrombosis after atherosclerotic plaque disruption and provides evidence of the benefit of blocking plaque TF activity. Therefore the inhibition of the TF pathway opens a new therapeutic strategy in the prevention of acute coronary thrombosis after plaque disruption.

Tissue factor in atherosclerosis.

Thrombosis is a key feature of the initiation and progression of atherosclerosis and its clinical sequelae. Acute thrombosis can lead to arterial occlusion and consequently provoke myocardial infarction, unstable angina, stroke and sudden death. Acute thrombosis can also be a complication of arterial bypass surgery, balloon angioplasty, atherectomy, or coronary artery stenting. The thrombotic response is influenced by several factors, among them the thrombogenicity of the vessel wall and of certain blood components as well as their interaction with the lipid pool. Tissue factor (TF) is considered to be the primary cofactor of cellular origin that is involved in activation of the coagulation pathway. The active form of TF has been shown to be present in specimens of human coronary artery in association both with acellular lipid areas and with macrophages and smooth muscle cells, which suggests that TF plays a major role in determining plaque thrombogenicity. We discuss here what is currently known about the role of tissue factor in atherogenesis, and focus attention on pharmacological approaches in this area.

Direct antithrombins: new perspectives in cardiovascular medicine.

Thrombin converts fibrinogen to fibrin and is the most powerful activator of platelets thus playing a crucial role in arterial and venous thrombosis. The limitations of heparin, largely used in the therapy of arterial and venous thromboembolism, has prompted the development of new antithrombotic drugs, able to directly inhibit thrombin. They comprise hirudin, bivalirudin and argatroban, which are antithrombins for parenteral use, and the orally active ximelagatran which, once absorbed, is converted to the active compound melagatran. Hirudin is a polypeptide able to irreversibly block both the active site and the fibrin(ogen) binding site of thrombin; bivalirudin, a synthetic hirudin derivative, has the same binding sites of hirudin to thrombin but has a shorter pharmacological action and is safer for clinical use. Several clinical trials which tested these drugs in acute coronary syndromes, coronary angioplasty and venous thromboembolism. demonstrate that hirudin and bivalirudin are superior to heparin in significantly reducing cardiac major events. The advantage of hirudin and bivalirudin over heparin was also confirmed in adjuncts to thrombolytic therapy as well as in percutaneous angioplasty relating to thrombotic events but not to restenosis. Hirudin was also significantly better than both unfractionated heparin and low molecular weight heparin (LMWH) in the prophylaxis of venous thromboembolism in patients undergoing elective arthroplasty. Major bleeding associated to hirudin was not different from that observed with heparin. Preliminary data also indicate that melagatran/ximelagatran may be used in the prophylaxis of venous thromboembolism and in the prevention of arterial embolism in patients with non-valvular atrial fibrillation.

Clinical significance of cross-linked fibrin degradation products in essential mixed cryoglobulinemia.

Cross-linked fibrin degradation products (XDP) were measured with a highly sensitive and specific ELISA in 21 patients with essential mixed cryoglobulinemia (EMC) and in 16 controls. Patients had significantly increased levels of XDP, together with abnormalities in routine coagulation tests. Moreover, XDP were higher in patients with more severe disease. These results support the hypothesis that EMC patients have a chronic disseminated intravascular coagulation (DIC), and underline the significance of XDP measurement in the evaluation of these patients.

Lipoprotein (a) and fibrinolytic system in liver cirrhosis. Coagulation Abnormalities in Liver Cirrhosis (CALC) Study Group.

Several observations have suggested that lipoprotein (a) (Lp(a)) is a risk factor for coronary artery disease because of potential interference with fibrinolysis secondary to its activation of plasminogen. However, there are few data on the possible role of Lp(a) in liver cirrhosis. The present study was carried out, to better elucidate its relationship to the fibrinolytic system in liver cirrhosis. We studied the plasma levels of Lp(a) and the fibrinolytic parameters of 95 patients with liver cirrhosis (57 men, 38 women, aged 26-81). Patients in Child-Pugh class C (n = 32) had significantly lower levels of Lp(a) than those in class B (n = 45), and the class B had lower Lp(a) values than class A (n = 18) (1.4 (0.0-3.7) vs 2.9 (0.0-6.1) vs 3.4 (1.8-5.5); the data are log-transformed). Alpha-2-antiplasmin and plasminogen, had patterns similar to those of Lp(a), tissue plasminogen activator (t-PA) was significantly increased only in class C (class A: 7.5 +/- 5.8 ng/ml; class B: 10.8 +/- 7.7 ng/ml; class C: 19.1 +/- 11.3 ng/ml). Patients with systemic hyperfibrinolysis (cross-linked fibrin degradation products, XDP > 200 ng/ml) also had lower levels of Lp(a) than those without 1.6 (0.0-4.4) vs (0.0-6.1); p = 0.0002. There was a significant correlation between Lp(a) and plasminogen (r = 0.43; p = 0.001). Lipoprotein (a) progressively decreases as liver cirrhosis worsens but it appears unlikely to be involved in causing the hyperfibrinolytic state often observed in advanced liver cirrhosis, in which there are marked abnormalities of several other fibrinolytic parameters, also including increased t-PA and decreased inhibitors.

Fibrinolytic response in subjects with hypertriglyceridemia and low HDL cholesterol.

The combination of hypertriglyceridemia and low high-density lipoprotein cholesterol (HDL-C) appears to be an excessively high risk factor for coronary artery disease (CAD). In the Helsinki study, both coronary events and mortality were decreased by gemfibrozil, especially in subjects with low HDL-C and high triglycerides (TG). On the other hand, it is known that high levels of TG can be associated with high levels of circulating plasminogen activator inhibitor (PAI), which is also a possible risk factor for CAD. The aim of the present study was to see: 1) whether the combination of low HDL-C and high TG is associated with a more impaired fibrinolytic response than in either isolated condition, and 2) whether gemfibrozil administration can improve fibrinolysis in patients with both high TG and low HDL-C. Twelve non-obese, non-diabetic subjects (eight men, four women; mean age 55 +/- 13 yrs) with low HDL-C (< 35 mg/dL men; < 45 mg/dL women) and high TG (mean 253.6 +/- 42.6 mg/dL) entered the study (Group A). Additionally fourteen comparable subjects with normal HDL-C were also investigated (Group B), plus 12 comparable subjects with isolated low HDL-C (Group C). Ten healthy people served as the control group. The following plasma fibrinolytic parameters were measured: tissue plasminogen activator antigen, PAI antigen and activity, euglobulin fibrinolytic activity (EFA) on fibrin plates, plasminogen and alpha-2-antiplasmin activities. All except the latter two values were also measured after venous occlusion (vo). In baseline conditions, patients in Groups A and B had higher EFA values before vo and higher PAI-1 antigen and alpha-2-antiplasmin levels after vo than those of controls or the subjects in Group C. The relationship between PAI antigen and PAI activity and TG was not confirmed in our population (n = 48). We also saw no interference due to HDL-C, while there was a significant relationship between EFA before vo and both TG and cholesterol. After gemfibrozil treatment (600 mg bid for 12 weeks), the lipid profiles of subjects with high TG and low HDL-C were significantly improved. There was also a slight reduction of PAI activity after vo, while the PAI-1 antigen had decreased significantly from baseline after vo (56.3 +/- 13 ng/mL before vo; 48.4 +/- 21 ng/mL after vo; P = 0.04). The higher risk of CAD in patients with low HDL-C and high TG might be in part related to impairment of fibrinolysis, which occurs in patients with isolated high TG. The close relationship existing between both TG and cholesterol levels and fibrinolytic activity confirm the key role of this latter process in the development of CAD.

The hyperfibrinolytic state of liver cirrhosis: possible pathogenetic role of ascites.

We evaluated coagulation and fibrinolytic parameters in both plasma and ascitic fluid of 39 patients with ascites secondary to liver cirrhosis and in 14 cirrhotic patients without ascites, in order to verify if the peritoneal compartment could be involved in the pathogenesis of the hyperfibrinolytic state of the disease. An activation of fibrinolysis, as suggested by increased levels of FDP, D-dimer and tissue plasminogen activator (t-PA) was demonstrated in both ascitic fluid and to a lesser extent in plasma. A positive correlation was also observed between plasma and ascitic fluid plasminogen, anti-plasmin and fibrinogen, while a negative correlation was found between plasma and ascitic fluid plasminogen activator inhibitor-1 (PAI-1). Moreover, plasma PAI-1 was significantly lower in patients with ascites than in those without ascites and among ascitic patients in those who had bleeding into soft tissues when compared to those who did not present haemorrhagic events. Finally, a significant association was also shown between positivity for plasma D-dimer (> 200 ng/ml) and the presence of ascites. Taken together, our data suggest an exchange of some coagulation and fibrinolytic proteins between plasma and ascitic fluid and point out the key role of PAI-1 in regulating plasma fibrinolytic potential and in bleeding complications in cirrhotic patients.

Plasma levels of tumor necrosis factor and endothelial response in patients with chronic arterial obstructive disease or Raynaud's phenomenon.

Tumor necrosis factor alpha (TNF-alpha) is a cytokine that affects endothelial cells' function by changing their antithrombotic potential to a net procoagulant effect. Only a few data have so far been reported for the pathophysiologic role of TNF in vascular diseases in the involvement of microvessels and/or macrovessels and a prothrombotic state. In the present study the authors evaluated plasma TNF (and interleukin-1) levels in 20 patients with chronic arterial obstructive disease (CAOD) with intermittent claudication and 10 CAOD patients with more severe disease (pain at rest/skin ulcers). In addition, they studied 10 patients with Raynaud's phenomenon (RP), suspected to be secondary to a collagen disease. The control group consisted of 20 subjects matched for sex and age with the three groups of patients. TNF levels were assayed by enzyme-linked immunosorbent assay. The antigen levels of von Willebrand factor (vWF), tissue plasminogen activator (t-PA), and its inhibitor (PAI) were also determined as markers of release from the endothelium, while the fragment 1 + 2 of prothrombin (F1 + 2) and thrombin-antithrombin III (TAT) complexes were assessed as indexes of systemic thrombin generation. TNF levels were significantly higher in both groups of CAOD patients than in controls or RP patients, and the same was true for vWF. t-PA was significantly higher only in the CAOD subjects with more severe disease. No differences among groups were seen in PAI antigen/activity or thrombin generation. When data were corrected for age, TNF no longer differentiated CAOD patients from controls and RP subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Incoherent optical two-dimensional Fourier transform using the chirp-z algorithm.

An incoherent optical method for computing two-dimensional complex-valued Fourier transforms is described. It is based on implementing the two-dimensional chirp-z algorithm with incoherent optical convolutions and indirect representation of complex-valued functions.

Plasma fibronectin and microvascular damage in essential mixed cryoglobulinaemia.

Plasma fibronectin (FN) was measured in 17 patients with essential mixed cryoglobulinaemia (EMC) and in 17 normal subjects by single radial immunodiffusion (RID) and enzyme-linked immunosorbent assay (ELISA). In 9 patients the presence of FN in the cryoprecipitates was also assessed by immunoblotting. In the EMC group, plasma FN levels were significantly lower than in control subjects, using both methods, and FN was constantly demonstrated in EMC cryoprecipitates. Capillaroscopic observation of the capillary bed in skin and bulbar conjunctiva, performed in all cases, showed severe alterations of microcirculation in EMC patients. A negative correlation between plasma FN and capillaroscopic abnormalities of skin capillaries was observed. These data support the hypothesis that plasma fibronectin plays a role in the pathogenesis of systemic vasculitis in EMC.

Clinical significance of endothelial damage markers in essential mixed cryoglobulinemia.

Essential mixed cryoglobulinemia (EMC) is a rheumatic disorder characterized by widespread vasculitis. To better define the nature of the vasculitic process and to possibly outline assessment methods reliable for using in a clinical context, we studied plasma levels of three endothelial related peptides: fibronectin (FN), von Willebrand factor (vWF) and tissue plasminogen activator (t-PA), and those of thrombin-antithrombin III complexes (TAT) as markers of activation of the coagulation in 21 patients and in 16 controls. In EMC we found a picture consisting of reduced FN and increased vWF, t-PA, and TAT levels, suggesting a condition of endothelial cell damage with thrombin formation in vivo. Since we previously demonstrated the presence of chronic disseminated intravascular coagulation in these patients, we may assume that endothelial cells stressed by cryoprecipitation or stimulated by soluble mediators may be actively involved in the vasculitic process and possibly express procoagulant properties. This is a good example of the complex interplay existing between autoimmunity and coagulation mechanisms. We also suggest that FN, vWF, t-PA and TAT should be considered as additional clinical parameters when evaluating patients with EMC.

Structural and functional characterization of plasma fibronectin in patients with essential mixed cryoglobulinaemia.

Experimental studies suggest that plasma fibronectin may be involved in the cryoprecipitation of cryoglobulins in essential mixed cryoglobulinaemia; reduced plasma concentrations of the glycoprotein have been shown in the disease. The present work was undertaken in order to verify this latter finding and to detect a possible structural alteration of plasma fibronectin as result of enzymatic digestion of the molecule in vivo. This could, in turn, induce a decreased reactivity of the protein in immunometric assays and a reduced opsonic activity, which is normally due to the affinity of fibronectin to the C1q component of complement. Moreover, since a polymorphic variant of fibronectin has been described in plasma during experimental vascular injury and in patients with autoimmune vascular diseases, the aim of this study was also to verify the presence of a polymorphism of the glycoprotein in cryoglobulinaemic vasculitis. Twenty seven patients with essential mixed cryoglobulinaemia and 26 normal subjects were included in the study. Significantly reduced concentrations of plasma fibronectin, as assessed by ELISA, were found in patients when compared with controls (231.7 +/- 15.3 vs 316.1 +/- 16.6 mg/l, P less than 0.0002). In contrast, when affinity-purified plasma fibronectin from 10 patients with essential mixed cryoglobulinaemia and 8 healthy subjects were analysed by western blotting, employing a panel of five monoclonal antibodies to different regions of the molecule, no differences were observed between patients and controls, suggesting integrity of the glycoprotein in the disease.(ABSTRACT TRUNCATED AT 250 WORDS)

High prevalence of antiphosphatidylinositol antibodies in young patients with cerebral ischemia of undetermined cause.

BACKGROUND AND PURPOSE: Anticardiolipin antibodies (aCL) are associated with thrombotic phenomena including cerebral ischemia in young adults. Although aCL are directed to a neoepitope formed by phospholipid and beta2-glycoprotein I (beta2-GPI), immunoassays based on cardiolipin as target antigen are widely used. We previously demonstrated that 47% of aCL-negative systemic lupus erythematosus (SLE) patients had antiphospholipid antibodies (aPL) to epitopes other than cardiolipin, and we found an association between aPL to noncardiolipin antigens and thrombosis. We now assess the prevalence and clinical significance of noncardiolipin aPL in young adults with cerebrovascular disease of undetermined etiology. METHODS: Seventy-seven non-SLE patients, aged <51 years, with cerebral ischemia were studied. Specificity of aPL were characterized by ELISAs using 7 different phospholipids: cardiolipin (CL), phosphatidylserine (PS), phosphatidylinositol (PI), phosphatidylglycerol (PG), phosphatidic acid (PA), phosphatidylcholine, and phosphatidylethanolamine. RESULTS: Thirty-four patients (44.1%), had aPL to 1 or more of the following antigens: 23.4% to CL, 18.2% to PS, 15.6% to PG, 14.3% to PA, and 28.6% to PI. Fifty-nine patients (76.6%) were aCL negative. Of these subjects 23.4% showed aPL to noncardiolipin epitopes. PI was the specificity with highest prevalence in all subgroups, and in 6 patients anti-PI antibodies were the only detectable aPL. The binding of aPL to the different antigens was beta2-GPI dependent. CONCLUSIONS: Our data demonstrate a high prevalence of aPL in young adults with cerebral ischemia of undetermined cause. PI was the specificity with highest prevalence, suggesting that anti-PI antibodies may be an immunological marker in young patients with cerebrovascular disease.

TAT, F1 + 2, and D-dimer levels in patients after coronary angiography with nonionic or ionic contrast media or after cardiac catheterization.

The prothrombotic effects of nonionic contrast media (NICM) have been evaluated in both biological and clinical studies. The question of whether there is a higher risk of thromboembolism during angiography with NICM than with ionic contrast media (ICM) has not yet been answered, nor has the precise role of the angiographic procedure per se in such complications been determined. The present study was performed to compare in vivo the potential prothrombotic effects during cardiac angiography of an NICM with those of an ICM, to estimate the effects of the procedure per se, and to assess how long these effects might be maintained. We measured blood levels of three markers of activation of blood coagulation: thrombin-antithrombin III (TAT) complexes, prothrombin fragment 1 + 2 (F1 + 2), and the split product of fibrin, D-dimer, before and after coronary angiography in three groups of patients. In group 1, 14 patients underwent coronary angiography with the NICM iopamidol 370. In group 2, 10 patients underwent coronary angiography with the ICM ioxaglate. In group 3, 10 patients were evaluated immediately after cardiac catheterization, before the injection of contrast material, as controls. No statistically significant differences between the three groups were found in TAT, F1 + 2, or D-dimer levels at different times before and after coronary angiography. There was a trend toward a transient increase in TAT levels after coronary angiography with iopamidol, which at first suggested a possible brief activation of hemostasis with this NICM, but a similar trend was also seen in the control group. We hypothesize that not only the type of contrast material, but also the angiographic procedure per se and patient-related factors all play roles in determining a prothrombotic state during coronary angiography.

Plasma and urine cyclic nucleotide levels in patients with hyperthyroidism and hypothyroidism.

Plasma levels and 24-h urinary excretion of cyclic AMP and cyclic GMP were measured in 18 patients with hyperthyroidism, 7 patients with hypothyroidism and 25 normal subjects. Mean plasma and urinary levels of both cyclic AMP and cyclic GMP were significantly positive correlations between the serum thyroid hormone levels and plasma and urinary cyclic nucleotide concentrations were also found, suggesting that the elevated extracellular cyclic nucleotide levels in hyperthyroidism are probably a consequence of increased secretion of thyroid hormones. In the hypothyroid patients the extracellular cyclic nucleotide concentrations did not differ significantly from those of the normal subjects.