Thrombogenic effect

Hydrophobic polymer materials that slowly release N O can be used on the surface of medical devices. Many medical devices suffer from the surface adhesion of blood platelets. To minimize this thrombogenic effect, blood thinners such as heparin, coumarin, and aspirin are often used. However, systemic administration of antiplatelet agents could increase the risk of uncontrolled bleeding elsewhere in the body. In contrast, biocompatible polymer films would solve this problem [153]. It is possible to create polymeric surfaces that mimic the inner surface of a blood vessel by... 

RF catheter ablation is complicated by thromboembolism in about 0.6% of patients (23). The risk of stroke from RF ablation may be higher in paroxysmal AF patients with prior TIA (24). As reflected by elevated plasma D-dimer levels, RF ablation has a thrombogenic effect that persists through the first 48 hours after the procedure (25). Activation of the coagulation cascade in RF ablation procedures is not related to the delivery of RF energy, but is related to the placement of intravascular catheters and to the duration of the ablation procedure (26,27). Furthermore, RF lesions themselves have been shown to be thrombogenic (28). The risk of a thromboembolic complication is higher for left-sided ablations... 

A study in 11 insulin-dependent diabetics, free of vascular complications, taking low-dose oral contraceptives (ethinylestradiol/gestodene 30/75 micrograms) found that although the plasma levels of most haemostatic variables were comparable to those of non-diabetics using the same oral contraceptive preparation, the rate of fibrin formation was increased and the fibrinolytic response attenuated. This implies that women with diabetes can have a higher sensitivity to the thrombogenic effects of oral contraceptives. ... 

Factor IX Replacement Hemophilia B therapy may include recombinant (produced via transfection of mammalian cells with the human factor IX gene) or plasma-derived (concentrate from pooled plasma) factor IX (see Table 64-2). Guidelines for choosing the factor-concentrate formulation for hemophilia B are similar to the guidelines for hemophilia A. However, older-generation factor IX concentrates containing other vitamin K-dependent proteins (e.g., factors II, VII, and IX), called prothrombin complex concentrates (PCCs), have been associated with thrombogenic side effects. Consequently, these products are not first-line treatment for hemophilia B.11... 

Clotting cascade A series of enzymatic reactions by clotting factors leading to the formation of a blood clot. The clotting cascade is initiated by several thrombogenic substances. Each reaction in the cascade is triggered by the preceding one, and the effect is amplified by positive feedback loops. 

Antipyretic activity. Ethanol (50%) extract of the plant, administered intraperito-neally to guinea pigs, was inactive " . Anti-thrombotic effect. Olive oil extract of the fmit, administered intragastrically to male rabbits at a dose of 150 g/kg, was active. Lipid profile was improved with decreased platelet hyperactivity and subendot-helial thrombogenicity and less severe morphological lesion of the endothelium and vascular wall . 

Mechanism of Action An anticoagulant that inhibits thrombogenic action of thrombin (independent of anf ithrombin II and nof inhibif ed by platelet factor 4). One molecule of lepirudin binds to one molecule of fhrombin. Therapeutic Effect Produces dose-dependent increases in aPTT. 

The more profound and extensive effect of immobilized heparin on the blood clotting system observed in the presence of immobilized trypsin is due to the tryptic lysis of the protein constituents of the complexes of immobilized heparin with the most thrombogenic plasma proteins (thrombin and fibrinogen) (Fig. 11). 

Anabolic steroids have been reported to be thrombogenic (50-52). Stanozolol, fluomesterone, metandienone, methyltestosterone, oxymesterone, and oxymetholone all reduce the synthesis or increase the degradation of clotting factors as a rule this effect is not clinically significant, but it can result in an interaction with anticoagulants. 

TFPI, when administered to rabbits, has been shown to have an antithrombotic effect when thromboplastin was used as a thrombogenic challenge (I 10). TFPI was also shown to be an effective inhibitor when thrombosis was induced in rabbit jugular veins by endothelial destruction and restricted blood flow. The antithrombotic and antiprotease actions of TFPI have been tested in several other animal models. Warn-Cramer et al. investigated the effect of immunodepletion of TFPI in factor Vila and Xa induced coagulation in rabbits (III). These rabbits were observed to be sensitized to the procoagulant effects of factor Vila, but not factor Xa in the absence of factor Vila. Two studies have indicated that TFPI administration reduces the lethal effects of . coli administration in a septic shock model in baboons (I 12). These studies also indicated that TFPI may have an anti-inflammatory effect, as an attenuation of the IL-6 response was also observed. Administration of TFPI has been observed to prevent... 

De Scheerder I, Szilard M, Huang Y et al, Evaluation of the effect of oversizing on vascular injury, thrombogenicity and neointimal hyperplasia using the Magic Wallstent in a porcine coronary model [abstr], JACC 2000 35(2) 70A. 

These results taken together show that abciximab is an effective agent in preventing acute coronary syndromes based on its inhibition of platelet GP Ilb/IIIa and probably also of 0 3 and Mac-1, which thereby induces interference with several thrombogenic and inflammatory pathways. 

On the basis of different effective longevities, anti-thrombogenic coatings are designed to adapt to variable blood-contacting durations. 

These studies provide a base for further development of collagen materials for specific biomaterial applications. Further studies are being directed to the effect of collagen film on blood in terms of platelet and white cell adhesion, protein absorption, and thrombogenicity. 

It is desirable to find a simple surface property that will induce an equally simple and hence predictable behavior of plasma and its proteins and then of blood and its platelets. Are simple guidelines for building non-thrombogenic materials available or even possible Wettability (96), flow (97, 98y 99,100), and the effects of air/liquid interfaces (101) all seem to be relatively simple, physical factors with a clear effect on platelet adhesion. Physical, hydrophobic bonding, e.g., a force imposed... 

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