fibrin and Arterial-Occlusive-Diseases

Fibrinogen is cleaved by thrombin to fibrin, which provides the blood clot with its essential structural backbone. As an acute phase protein, the plasma levels of fibrinogen are increased in response to inflammatory conditions. In addition to fibrinogen levels, fibrin clot structure is altered by a number of factors. These include thrombin levels, treatment with common cardiovascular medications, such as aspirin, anticoagulants, statins and fibrates, as well as metabolic disease states such as diabetes mellitus and hyperhomocysteinaemia. In vitro studies of fibrin clot structure can provide information regarding fibre density, clot porosity, the mechanical strength of fibres and fibrinolysis. A change in fibrin clot structure, to a denser clot with smaller pores which is more resistant to lysis, is strongly associated with cardiovascular disease. This pathological change is present in patients with arterial as well as venous diseases, and is also found in a moderate form in relatives of patients with cardiovascular disease. Pharmacological therapies, aimed at both the treatment and prophylaxis of cardiovascular disease, appear to result in positive changes to the fibrin clot structure. As such, therapies aimed at 'normalising' fibrin clot structure may be of benefit in the prevention and treatment of cardiovascular disease.

Topics: Arterial Occlusive Diseases; Blood Coagulation; Cardiovascular Agents; Cardiovascular Diseases; Fibrin; Fibrinogen; Fibrinolysin; Fibrinolysis; Humans; Porosity; Venous Thrombosis

Although current thrombolytic agents have proven their clinical benefit, the failure to rapidly reperfuse some patients and the persistent bleeding risk represent areas for improvement in therapy. In the past two years, the field has been advanced by the regulatory approval of agents with greater ease of administration, continued development of new agents and exploration of the use of more advanced antiplatelet therapies in combination with thrombolytic agents. Finally, a new class of directly acting fibrinolytic agents is available.

Topics: Animals; Arterial Occlusive Diseases; Catheterization, Central Venous; Contraindications; Fibrin; Fibrinolytic Agents; Graft Occlusion, Vascular; Humans; Metalloendopeptidases; Plasminogen Activators; Platelet Glycoprotein GPIIb-IIIa Complex; Recombinant Proteins; Stroke; Tenecteplase; Thrombolytic Therapy; Tissue Plasminogen Activator; Urokinase-Type Plasminogen Activator

The existence of a system in the human body capable of inducing the dissolution of endogenous pathologically formed thrombi was appreciated in ancient times. Considered in detail in this article are the data that have elucidated the physiologic regulation of which plasmin formation is dependent on, the plasma concentration of plasminogen, availability of activators of plasminogen in the plasma and surrounding tissue environment, the concentration of naturally present inhibitors, and the existence of fibrin in the circulation. Important in this rapidly progressive scientific discipline is consideration of the factors which control the synthesis of the components of this proteolytic enzyme system. Recently abundant information has indicated that this plasminogen-plasmin proteolytic enzyme system can be utilized therapeutically. Knowledge of the mechanisms of this system has permitted identification of agents that can be exogenously administered to releave thrombotic obstruction to blood flow in the venous (pulmonary emboli, deep vein thrombosis) and arterial (peripheral and central vessels) circulatory systems. Particularly important is the demonstration that thrombolytic agents can directly attack and alleviate the immediate cause of acute myocardial infarction. As a result of the innovations in the present decade, it is evident that the plasminogen system can be advantageously employed to reverse the pathologic effects of all thrombotic diseases.

Topics: alpha 1-Antitrypsin; alpha-2-Antiplasmin; alpha-Macroglobulins; Antifibrinolytic Agents; Antithrombin III; Arterial Occlusive Diseases; Arteriosclerosis; Complement C1 Inactivator Proteins; Disseminated Intravascular Coagulation; Fibrin; Fibrinogen; Fibrinolysin; Fibrinolysis; Fibrinolytic Agents; Humans; Kidney Diseases; Liver Diseases; Myocardial Infarction; Neoplasms; Plasminogen; Pulmonary Embolism; Thrombophlebitis

Topics: Anticoagulants; Antifibrinolytic Agents; Arterial Occlusive Diseases; Blood Coagulation; Blood Coagulation Disorders; Blood Platelets; Coagulants; Contraceptives, Oral; Estrogens; Female; Fibrin; Humans; Pregnancy; Pregnancy Complications, Hematologic; Thrombin; Thromboembolism; Thrombophlebitis; Thrombosis

Topics: Aminocaproates; Anabolic Agents; Androgens; Antifibrinolytic Agents; Arterial Occlusive Diseases; Blood Platelets; Clofibrate; Drug Combinations; Ethylestrenol; Fibrin; Fibrinolysin; Fibrinolysis; Humans; Inflammation; Insulin; Methods; Phenformin; Plasminogen; Sulfonylurea Compounds

Thrombin plays a major role in thrombus formation through activation of platelets and conversion of fibrinogen to fibrin.. To investigate the antithrombotic effects of the oral direct thrombin inhibitor (DTI) ximelagatran and the parenteral DTI r-hirudin in humans.. Healthy male volunteers randomized into four parallel groups each with 15 subjects received either ximelagatran (20, 40 or 80 mg orally) or r-hirudin (0.4 mg kg-1 intravenous bolus + infusion of 0.15 mg kg-1 h-1 for 2 h and 0.075 mg kg-1 h-1 for 3 h). Antithrombotic effects were assessed as changes in total thrombus area (TTA) and total fibrin area (TFA) from baseline, using the Badimon perfusion chamber model at baseline and 2 h and 5 h after drug administration.. Two hours postdosing, ximelagatran showed antithrombotic effects at both high and low shear rates (TTA% of mean baseline value +/- SEM was 76 +/- 13% and 71 +/- 17% [both P < 0.05] for the 20-mg dose, 85 +/- 11% [P > 0.05] and 62 +/- 15% [P < 0.05] for the 40-mg dose and 60 +/- 11% and 26 +/- 7% [both P < 0.05] for the 80-mg dose, respectively). r-Hirudin also showed a significant antithrombotic effect at high and low shear rates (76 +/- 11% [P = 0.05] and 57 +/- 17% [P < 0.05] of baseline values, 2 h postdosing, respectively). The inhibitory effects on TFA were similar to those on TTA.. The oral DTI ximelagatran shows antithrombotic effects under both high and low shear conditions. The antithrombotic effect of 40-80 mg ximelagatran appeared comparable to that of parenterally administered r-hirudin, which has been previously demonstrated to be clinically effective in acute coronary syndromes.

Topics: Adult; Arterial Occlusive Diseases; Azetidines; Benzylamines; Blood Coagulation Tests; Fibrin; Fibrinolytic Agents; Hirudins; Humans; Male; Perfusion; Pharmacokinetics; Stress, Mechanical; Thrombin; Thrombosis; Veins

To minimize intraoperative blood loss a watertight knitted Dacron aortoiliac prosthesis has been developed by impregnation with bovine collagen. A potential disadvantage is that collagen may be associated with an increase in thrombus formation. We conducted a prospective randomized trial to study the systemic effects of collagen-impregnated prostheses and of aortoiliac operation as such on the coagulation mechanism during the first 10 days after operation. Forty-one patients randomly received either a collagen-impregnated (n = 20) or a nonimpregnated prosthesis (n = 21). Twelve patients who underwent cholecystectomies served as controls. Three markers of the coagulation mechanism were monitored: beta-thromboglobulin, fibrinopeptide A, and fibrin/fibrinogen degradation products. We found no significant differences in median beta-thromboglobulin, fibrinopeptide A, and fibrin/fibrinogen degradation product levels between patients in the collagen-impregnated prosthesis group and patients in the nonimpregnated prosthesis group. This indicates that collagen does not stimulate the coagulation cascade any more than conventional Dacron protheses do. In a comparison of patients who underwent aortoiliac reconstruction and patients who underwent cholecystectomies, the results indicated a significant increased platelet activation and fibrin metabolism in aortoiliac reconstruction group compared with the control group. Finally, we observed a significantly higher preoperative fibrin metabolism in patients with vascular disease than in control subjects. This difference is attributable to the high preoperative fibrin/fibrinogen degradation product values in patients with aortic aneurysms.

Topics: Adult; Aged; Aged, 80 and over; Aorta; Aortic Aneurysm; Arterial Occlusive Diseases; beta-Thromboglobulin; Blood Vessel Prosthesis; Collagen; Female; Femoral Artery; Fibrin; Fibrin Fibrinogen Degradation Products; Fibrinopeptide A; Graft Occlusion, Vascular; Humans; Iliac Artery; Male; Middle Aged; Platelet Activation; Polyethylene Terephthalates

Topics: Adult; Age Factors; Aged; Arterial Occlusive Diseases; Dicumarol; Female; Femoral Fractures; Fibrin; Fibrinogen; Half-Life; Heparin; Humans; Iodine Radioisotopes; Male; Middle Aged; Postoperative Care; Tibial Fractures; Time Factors

Thrombi in cerebral large vessel occlusion associated with active cancer are often fibrin and platelet-rich white thrombi. However, evaluating the thrombus composition in a short time before thrombectomy is often ineffective. We sought to determine factors related to white thrombi in acute ischemic stroke due to large vessel occlusion in cancer patients.. Consecutive cancer patients undergoing thrombectomy for acute ischemic stroke due to large vessel occlusion between January 2018 and May 2022 were retrospectively reviewed. The patients were classified into white thrombus and red thrombus groups on the basis of the pathological findings of retrieved thrombi. Patient characteristics and laboratory findings were compared between the two groups.. In acute ischemic stroke in cancer patients, active cancer, no internal carotid artery occlusion, and higher D-dimer levels (≥3.5 μg/mL) may be associated with occlusion with fibrin and platelet-rich white thrombi.

Topics: Arterial Occlusive Diseases; Brain Ischemia; Fibrin; Humans; Ischemic Stroke; Neoplasms; Retrospective Studies; Stroke; Thrombectomy; Thrombosis

This study's purpose was to improve understanding of the forces driving the complex mechanical interaction between embolic material and current stroke thrombectomy devices by analyzing the histological composition and strength of emboli retrieved from patients and by evaluating the mechanical forces necessary for retrieval of such emboli in a middle cerebral artery (MCA) bifurcation model.. Embolus analogs (EAs) were generated and embolized under physiological pressure and flow conditions in a glass tube model of the MCA. The forces involved in EA removal using conventional endovascular techniques were described, analyzed, and categorized. Then, 16 embolic specimens were retrieved from 11 stroke patients with large-vessel occlusions, and the tensile strength and response to stress were measured with a quasi-static uniaxial tensile test using a custom-made platform. Embolus compositions were analyzed and quantified by histology.. Uniaxial tension on the EAs led to deformation, elongation, thinning, fracture, and embolization. Uniaxial tensile testing of patients' emboli revealed similar soft-material behavior, including elongation under tension and differential fracture patterns. At the final fracture of the embolus (or dissociation), the amount of elongation, quantified as strain, ranged from 1.05 to 4.89 (2.41 ± 1.04 [mean ± SD]) and the embolus-generated force, quantified as stress, ranged from 63 to 2396 kPa (569 ± 695 kPa). The ultimate tensile strain of the emboli increased with a higher platelet percentage, and the ultimate tensile stress increased with a higher fibrin percentage and decreased with a higher red blood cell percentage.. Current thrombectomy devices remove emboli mostly by applying linear tensile forces, under which emboli elongate until dissociation. Embolus resistance to dissociation is determined by embolus strength, which significantly correlates with composition and varies within and among patients and within the same thrombus. The dynamic intravascular weakening of emboli during removal may lead to iatrogenic embolization.

Topics: Arterial Occlusive Diseases; Carotid Arteries; Erythrocyte Count; Fibrin; Hemodynamics; Humans; Intracranial Embolism; Ischemic Stroke; Mechanical Phenomena; Middle Cerebral Artery; Models, Biological; Platelet Count; Pressure; Tensile Strength; Thrombectomy

It is widely known that myocardial damage is not immediately terminated after the elimination of epicardial occlusion in cases of myocardial infarction. In situ thrombosis during epicardial occlusion might contribute to poor myocardial perfusion after reperfusion of an occluded epicardial artery. In the current study, we sought to determine the effects of ischemia and reperfusion on microvascular thrombotic occlusion.. Thirty male Wistar rats were included in the study. After the rats had been anesthetized and thoracotomized, the left coronary artery was occluded for 30 minutes in the first group, and it was occluded for 30 minutes and reperfused for an additional 20 minutes in the second group. Ten rats were used as a sham-operated control group. After completion of the study protocol, excised heart preparations were analyzed by immunohistochemistry and electron microscopy.. A significant difference was found between the infarction plus reperfusion group and the other 2 groups, with respect to microvascular fibrin and thrombocyte deposition in immunohistochemistry analysis. These results were confirmed by morphological examination with electron microscopy.. In situ fibrin formation accompanies microvascular obstruction in acute myocardial infarction. Our results indicate that additional therapeutic approaches are needed in order to achieve better tissue perfusion in contemporary treatment of acute myocardial infarction after successful reopening of the infarct-related artery.

Topics: Animals; Arterial Occlusive Diseases; Coronary Vessels; Fibrin; Male; Myocardial Infarction; Rats; Rats, Wistar; Thrombosis

Thrombosis is a leading cause of morbidity and mortality worldwide. Current diagnostic strategies rely on imaging modalities that are specific for distinct vascular territories, but a thrombus-specific whole-body imaging approach is still missing. Moreover, imaging techniques to assess thrombus composition are underdeveloped, although therapeutic strategies may benefit from such technology. Therefore, our goal was to test whether positron emission tomography (PET) with the fibrin-binding probe (64)Cu-FBP8 allows multisite thrombus detection and fibrin content estimation.. Thrombosis was induced in Sprague-Dawley rats (n=32) by ferric chloride application on both carotid artery and femoral vein. (64)Cu-FBP8-PET/CT imaging was performed 1, 3, or 7 days after thrombosis to detect thrombus location and to evaluate age-dependent changes in target uptake. Ex vivo biodistribution, autoradiography, and histopathology were performed to validate imaging results. Arterial and venous thrombi were localized on fused PET/CT images with high accuracy (97.6%; 95% confidence interval, 92-100). A single whole-body PET/MR imaging session was sufficient to reveal the location of both arterial and venous thrombi after (64)Cu-FBP8 administration. PET imaging showed that probe uptake was greater in younger clots than in older ones for both arterial and venous thrombosis (P<0.0001). Quantitative histopathology revealed an age-dependent reduction of thrombus fibrin content (P<0.001), consistent with PET results. Biodistribution and autoradiography further confirmed the imaging findings.. We demonstrated that (64)Cu-FBP8-PET is a feasible approach for whole-body thrombus detection and that molecular imaging of fibrin can provide, noninvasively, insight into clot composition.

Topics: Animals; Arterial Occlusive Diseases; Biopsy, Needle; Copper Radioisotopes; Disease Models, Animal; Fibrin; Image Processing, Computer-Assisted; Immunohistochemistry; Male; Positron-Emission Tomography; Random Allocation; Rats; Rats, Sprague-Dawley; Sensitivity and Specificity; Venous Thrombosis; Whole Body Imaging

Collagen is a powerful thrombotic stimulus that functions by direct and indirect binding to various platelet receptors. A variety of collagen types are known and several (e.g., collagen Types I, III, IV) are found in vascular tissues and are exposed upon disruption of the endothelium or more extensive vessel wall rupture. Some murine models of thrombosis purport to expose collagen to initiate thrombosis, however, the nature and extent of this exposure is not clear. This study was undertaken to place a known collagen-dominated surface into the in vivo arterial or venous circulation as a method for direct study of collagen-induced thrombosis in mice. The epigastric artery was removed from donor mice and a microsuture with attached needle was knotted into one cut end. Anesthetized mice had this needle/suture/small-artery inserted into and out of a 0.5-mm length of the larger carotid artery or femoral vein, leaving the collagen-rich adventitial surface of the epigastric artery intralumenally in the larger vessel. Extensive platelet and fibrin deposition on this surface were in evidence and were quantitated with fluorescence imaging; administration of clopidogrel reduced thrombus development in both arteries and veins. A method was developed to evert the epigastric artery and disrupt the exteriorized endothelium; with the same needle/suture vessel-insertion technique, this surface stimulated significantly less thrombotic response in both arteries and veins, suggesting differential thrombogenesis based on the molecular composition of the induction factor. This new model of thrombosis offers a method for directly assessing the role of collagen-mediated thrombosis in murine arteries and veins.

Topics: Animals; Arterial Occlusive Diseases; Blood Coagulation; Blood Platelets; Carotid Arteries; Clopidogrel; Collagen; Disease Models, Animal; Epigastric Arteries; Femoral Vein; Fibrin; Mice; Mice, Inbred C57BL; Platelet Aggregation Inhibitors; Thrombosis; Ticlopidine; Time Factors; Venous Thrombosis

We compared the antithrombotic effects in vivo of 2 chemically different carbon monoxide-releasing molecules (CORM-A1 and CORM-3) on arterial and venous thrombus formation and on hemostatic parameters such as platelet activation, coagulation, and fibrinolysis. The hypotensive response to CORMs and their effects on whole blood gas analysis and blood cell count were also examined.. CORM-A1 (10-30 µmol/kg, i.v.), in a dose-dependent fashion, significantly decreased weight of electrically induced thrombus in rats, whereas CORM-3 inhibited thrombosis only at the highest dose used (30 µmol/kg). CORM-A1 showed a direct and stronger inhibition of platelet aggregation than CORM-3 in healthy rats, both in vitro and in vivo. The antiaggregatory effect of CORM-A1, but not CORM-3, correlated positively with weight of the thrombus. Concentration of active plasminogen activator inhibitor-1 in plasma also decreased in response to CORM-A1, but not to CORM-3. Neither CORM-A1 nor CORM-3 had an effect on plasma concentration of active tissue plasminogen activator. CORM-3, but not CORM-A1, decreased the concentration of fibrinogen, fibrin generation, and prolonged prothrombin time. Similarly, laser-induced venous thrombosis observed intravitally via confocal system in green fluorescent protein mice was significantly decreased by CORMs. Although both CORM-A1 and CORM-3 (30 µmol/kg) decreased platelets accumulation in thrombus, only CORM-A1 (3-30 µmol/kg) inhibited platelet activation to phosphatidylserine on their surface.. CORM-3 and CORM-A1 inhibited thrombosis in vivo, however CORM-A1, which slowly releases carbon monoxide, and displayed a relatively weak hypotensive effect had a more pronounced antithrombotic effect associated with a stronger inhibition of platelet aggregation associated with a decrease in active plasminogen activator inhibitor-1 concentration. In contrast, the fast CO releaser CORM-3 that displayed a more pronounced hypotensive effect inhibited thrombosis primarily through a decrease in fibrin generation, but had no direct influence on platelet aggregation and fibrynolysis.

Topics: Animals; Arterial Occlusive Diseases; Blood Coagulation; Blood Gas Analysis; Blood Platelets; Blood Pressure; Boranes; Carbon Monoxide; Carbonates; Disease Models, Animal; Dose-Response Relationship, Drug; Fibrin; Fibrinogen; Fibrinolysis; Fibrinolytic Agents; Green Fluorescent Proteins; Injections, Intravenous; Male; Mice; Mice, Inbred C57BL; Mice, Transgenic; Microscopy, Confocal; Organometallic Compounds; Plasminogen Activator Inhibitor 1; Platelet Aggregation; Prothrombin Time; Rats; Rats, Wistar; Solubility; Thrombosis; Time Factors; Venous Thrombosis; Water

Thrombus propagation on disrupted plaque is a major cause of acute coronary events and serious complication after coronary intervention. 5-Hydroxytryptamine (5-HT) is a potent vasoactive and platelet-aggregating substance that is predominantly mediated by 5-HT2A receptor. However, the roles of 5-HT2A receptor in occlusive thrombus formation on disrupted plaque remain obscure.. We investigated the role of 5-HT2A receptor in thrombus formation using a rabbit model of repeated balloon-injury.. Three weeks after a first balloon-injury of the femoral arteries, luminal diameter, neointimal growth, and vasoconstriction by 5-HT in vitro were examined. Thrombus propagation and the role of 5-HT2A receptor after a second balloon-injury were evaluated using sarpogrelate, a selective 5-HT2A receptor antagonist.. Three weeks after the first balloon-injury, luminal stenosis was evident in the femoral arteries, where the neointima expressed tissue factor and 5-HT2A receptor. The hypercontractile response of the stenotic arteries to 5-HT was significantly reduced by sarpogrelate. Balloon-injury of the neointima with substantially reduced blood flow promoted the formation of occlusive thrombus that was immunoreactive against glycoprotein IIb-IIIa, 5-HT2A receptor and fibrin. Intravenous injection of sarpogrelate significantly inhibited ex vivo platelet aggregation induced by adenosine 5'-diphosphate, thrombin and collagen alone as well as with 5-HT, and significantly prevented occlusive thrombus formation in vivo.. The 5-HT2A receptor appears to play a crucial role in occlusive thrombus formation in diseased arteries via platelet aggregation and vasoconstriction. Inhibition of 5-HT2A receptor might help reduce the onset of acute coronary events and of acute coronary occlusion after the intervention.

Topics: Animals; Arterial Occlusive Diseases; Catheterization; Disease Models, Animal; Femoral Artery; Fibrin; Platelet Aggregation; Platelet Glycoprotein GPIIb-IIIa Complex; Rabbits; Receptor, Serotonin, 5-HT2A; Serotonin; Serotonin Antagonists; Succinates; Thrombosis; Tunica Intima; Vasoconstriction

Topics: Animals; Aorta; Arterial Occlusive Diseases; Arteries; Blood Cells; Carotid Artery Injuries; Catheterization; Constriction, Pathologic; Fibrin; Immunohistochemistry; Rabbits; Rats; Rats, Wistar; Time Factors

Intraluminal beta-irradiation has been shown to decrease neointimal proliferation after angioplasty in experimental models. The purpose of this study was to test the technical feasibility and biological effects of (186)Re-labeled stents.. Thirty-four New Zealand White rabbits were fed a 0.5% cholesterol diet before balloon angioplasty and insertion of Palmaz stents in the infrarenal aorta. The animals were killed 7 weeks after stent implantation. Two of 34 animals died prematurely (aortic leak, pneumonia). Control stents (n=7) were compared with (186)Re stents (2.6 MBq [n=6], 8.1 MBq [n=5], 16.0 MBq [n=6], and 25.3 MBq [n=8]). Stent application was successful in all cases. No thrombus occlusion was observed. After 7 weeks, neointima formation was 2.2+/-0.2 mm(2) in the control group. In the treatment groups, a dose-dependent neointima reduction was detectable (0.5+/-0.5 mm(2) [2.6 MBq], 0.4+/-0.4 mm(2) [8.1 MBq], and 0 mm(2) [16.0 MBq, 25.3 MBq]). No induction of neointimal formation was observed at the edges of the stents. Radiation resulted in delayed reendothelialization.. (186)Re stents were capable of reducing neointima formation in a dose-dependent fashion. (186)Re stents did not cause late thrombosis or neointimal induction at the stent margins in the observation period of 7 weeks.

Topics: Animals; Aorta, Abdominal; Arterial Occlusive Diseases; Brachytherapy; Disease Models, Animal; Dose-Response Relationship, Radiation; Endothelium, Vascular; Fibrin; Half-Life; Male; Rabbits; Radioisotopes; Rhenium; Stents; Time Factors; Tunica Intima; Tunica Media

Tissue factor (TF), the initiator of coagulation, has been implicated as a critical mediator of arterial thrombosis. Previous studies have demonstrated that TF is rapidly induced in the normal rodent arterial wall by balloon injury, but is not associated with fibrin deposition. A second injury, however, performed 10-14 days after the first, is followed by small platelet-fibrin microthrombi. This study was undertaken to better localize active TF in balloon-injured rat arteries and to explore possible mechanisms underlying the apparent discrepancy between injury-induced TF expression and the lack of large platelet-fibrin thrombi. By immunohistochemistry, TF antigen was first detected in the media 24 h after injury to rat aortas, and subsequently accumulated in the neointima. Using an ex vivo flow chamber, no TF activity (Factor Xa generation) was found on the luminal surface of normal or injured aortas. Wiping the luminal surface with a cotton swab exposed TF activity in all vessels; levels were increased approximately 3-fold in arteries containing a neointima. The exposed TF activity was rapidly washed into the perfusate, rendering the luminal surface inactive. The loss of luminal TF into the circulation may attenuate thrombosis at sites of arterial injury.

Topics: Angioplasty, Balloon, Coronary; Animals; Aorta, Abdominal; Aorta, Thoracic; Arterial Occlusive Diseases; Fibrin; Male; Microscopy, Electron, Scanning; Rats; Rats, Sprague-Dawley; Recurrence; Thromboplastin; Thrombosis; Tunica Intima

There is evidence that the coagulation system is activated in patients with peripheral arterial occlusive disease (PAOD). The beneficial effects of the vasoactive drug prostaglandin E1 (PGE1) may rely in part on the modulation of the coagulation system. The study was designed to evaluate the effects of PGE1 on hemostatic and fibrinolytic variables in patients with intermittent claudication. Therefore molecular markers of thrombin (prothrombin fragment 1+2, PTF 1+2; thrombin-antithrombin III complexes, TAT) and fibrin formation (fibrinopeptide A, FPA) and markers of the fibrinolytic activity (fibrin degradation products, D-dimers) were determined before and immediately after the first PGE1 dose (60 microg in 100 ml NaCl over 2 h i.v.) as well as after 4 weeks of daily infusion therapy in 12 PAOD patients and in eight control patients before and after a single placebo infusion. Plasma levels of PTF1+2, TAT, FPA and D-dimers tended to decrease after the initial dose of PGE1. Infusion therapy with PGE1 for 4 weeks led to a decrease of all hemostatic and fibrinolytic parameters with most pronounced changes for PFT1+2, D-dimers and plasminogen activator inhibitor-1 decreasing by 11% (P<0.05), 20% (P<0.05), and 7% (P<0.05), respectively. These variables remained unchanged in controls with placebo infusion. In summary, infusion therapy with PGE1 in patients with PAOD reduces thrombin formation and results in a decrease of fibrin degradation. PGE1 may thus reduce fibrin deposition involved in the pathogenesis of atherosclerosis.

Topics: Aged; Alprostadil; Antithrombin III; Arterial Occlusive Diseases; Case-Control Studies; Dimerization; Fibrin; Fibrinolysis; Fibrinopeptide A; Hemostasis; Humans; Intermittent Claudication; Male; Middle Aged; Peptide Hydrolases; Placebos; Plasminogen Activator Inhibitor 1; Prothrombin; Thrombin; Time Factors

High-intensity focused ultrasound (HIFU) has been shown to be effective in controlling hemorrhage from punctures in blood vessels. The objective of the current study was to investigate the capability of HIFU to stop bleeding after a more severe type of vascular injury, namely longitudinal incisions of arteries and veins.. The superficial femoral arteries, common femoral arteries, carotid arteries, and jugular veins of four anesthetized pigs were exposed surgically. A longitudinal incision, 2 to 8 mm in length, was produced in the vessel. HIFU treatment was applied within 5 seconds of the onset of the bleeding. The HIFU probe consisted of a high-power, 3.5-MHz, piezoelectric transducer with an ellipsoidal focal spot that was 1 mm in cross section and 9 mm in axial dimension. The entire incision area was scanned with the HIFU beam at a rate of 15 to 25 times/second and a linear displacement of 5 to 10 mm. A total of 76 incisions and HIFU treatments were performed.. Control of bleeding (major hemosatsis) was achieved in all 76 treatments, with complete hemostasis achieved in 69 treatments (91%). The average treatment times of major and complete hemostasis were 17 and 25 seconds, respectively. After the treatment, 74% of the vessels in which complete hemostasis was achieved were patent with distal blood flow and 26% were occluded. The HIFU-treated vessels showed a consistent coagulation of the adventitia surrounding the vessels, with a remarkably localized injury to the vessel wall. Extensive fibrin deposition at the treatment site was observed.. HIFU may provide a useful method of achieving hemostasis for arteries and veins in a variety of clinical applications.

Topics: Animals; Arterial Occlusive Diseases; Blood Loss, Surgical; Carotid Arteries; Elastic Tissue; Female; Femoral Artery; Fibrin; Hemostasis, Surgical; Jugular Veins; Male; Regional Blood Flow; Swine; Time Factors; Transducers; Ultrasonic Therapy; Vascular Patency

Polyethylene glycol (PEG)-hirudin is a derivative of hirudin with a long plasma half-life. We have compared the efficacy of PEG-hirudin with unfractionated heparin (UH) in preventing arterial thrombosis. Arterial thrombus formation was induced ex vivo in 12 healthy human volunteers by exposing a tissue factor-coated coverslip positioned in a parallel-plate perfusion chamber to flowing nonanticoagulated human blood drawn directly from an antecubital vein at an arterial wall shear rate of 2600 s-1 for 3.5 minutes. PEG-hirudin, UH, or saline (as control) were administered ex vivo through a heparin-coated mixing device positioned proximal to the perfusion chamber. Platelet and fibrin deposition was quantified by immunoenzymatic measure of the P-selectin and D-dimer content of dissolved plasmin-digested thrombi, respectively. UH was administered to a plasma concentration of 0.35 IU/mL. This concentration prolonged the activated partial thromboplastin time from 32+/-1 seconds to 79+/-4 seconds (P<0.01). UH did not significantly prevent platelet deposition. However, fibrin deposition was reduced by 39% (P<0.05). PEG-hirudin in plasma concentrations of 0.5, 2.5, and 5 microg/mL prolonged the activated partial thromboplastin time to 48+/-2, 87+/-4, and 118+/-4 seconds, respectively. In contrast to UH, PEG-hirudin prevented both platelet and fibrin deposition in a dose-dependent manner with a >80% reduction at 5 microg/mL (P<0.01). Furthermore, the plasma level of PEG-hirudin required to significantly prevent fibrin deposition (0.5 microg/mL) corresponded to a much shorter prolongation of activated partial thromboplastin time (48+/-2 seconds) than that needed for UH (79+/-4 seconds). Thus, our results are compatible with the view that thrombin is greatly involved in recruitment of platelets in evolving thrombi, and that PEG-hirudin is an effective agent for preventing arterial thrombosis in a human ex vivo experimental model.

Topics: Antithrombin III; Arterial Occlusive Diseases; beta-Thromboglobulin; Blood Coagulation; Blood Coagulation Tests; Fibrin; Fibrin Fibrinogen Degradation Products; Fibrinolytic Agents; Glass; Half-Life; Heparin; Hirudins; Humans; P-Selectin; Peptide Hydrolases; Platelet Activation; Sodium Chloride; Thromboplastin; Thrombosis

Topics: Angiography; Arterial Occlusive Diseases; Collateral Circulation; Endothelial Growth Factors; Fibrin; Humans; Injections, Intramuscular; Ischemia; Leg; Lymphokines; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factors

Occlusive arterial disease causes alterations in blood rheology and levels of potential thrombotic and fibrinolytic mediators. The aim of this study was to investigate the effect of graft materials on these parameters in patients undergoing successful infrainguinal revascularization.. Some 186 consecutive infrainguinal grafts were observed for 12 months. Venous blood was sampled before operation and at 3, 6, and 12 months after surgery. Samples were assayed for thrombotic and rheological parameters. An area under the curve analysis was used to compare the effects of vein and synthetic grafting on these parameters in 99 patients whose grafts remained patent and free from stenosis.. Plasma levels of fibrin degradation products were significantly higher in patients with synthetic grafts (n = 46) than in those with autogenous vein grafts (n = 53) (median 274 versus 150 ng/ml; P < 0.001). There were no significant differences in plasma fibrinogen or any other parameters between the two groups.. Patients with a synthetic infrainguinal graft have a higher fibrin turnover than those with a vein graft. Further studies are required to determine whether this increase in fibrin turnover is an essential requirement to maintain patency of a synthetic infrainguinal graft.

Topics: Aged; Arterial Occlusive Diseases; Blood Vessel Prosthesis; Blood Viscosity; Female; Fibrin; Fibrin Fibrinogen Degradation Products; Fibrinogen; Graft Survival; Humans; Male; Middle Aged; Polytetrafluoroethylene; Vascular Patency

We developed a new model of embolic cerebral ischemia in the rat which provides a reproducible and predictable infarct volume within the territory supplied by the middle cerebral artery (MCA). The MCA was occluded by an embolus in Wistar rats (n = 71). An additional three non-embolized rats were used as a control. Cerebral blood flow (CBF) was measured by means of laser Doppler flowmetry (LDF) and perfusion weighted imaging (PWI) before and after embolization. The evolution of the lesion was monitored by diffusion weighted imaging (DWI). Cerebral vascular perfusion patterns were examined using laser scanning confocal microscopy. Infarct volumes were measured on hematoxylin and eosin (H&E) stained coronal sections. The lodgment of the clot at the origin of the MCA and the ischemic cell damage were examined using light microscopy. Regional CBF in the ipsilateral parietal cortex decreased to 43 +/- 4.1% (P < 0.05) of preischemic levels (n = 10). Confocal microscopic examination revealed a reduction of cerebral plasma perfusion in the ipsilateral MCA territory (n = 6). MRI measurements showed a reduction in CBF and a hyperintensity DWI encompassing the territory supplied by the MCA (n = 4). An embolus was found in all rats at 24 h after embolization. The infarct volume as a percentage of the contralateral hemisphere was 32.5 +/- 3.31% at 24 h (n = 20), 33.0 +/- 3.6% at 48 h (n = 13), and 34.5 +/- 4.74% at 168 h (n = 12) after embolization. This model of embolic focal cerebral ischemia results in ischemic cell damage and provides a reproducible and predictable infarct volume. This model is relevant to thromboembolic stroke in humans and may be useful in documenting the safety and efficacy of fibrinolytic intervention and in investigating therapies complementary to antithrombotic therapy.

Topics: Animals; Arterial Occlusive Diseases; Blood Gas Analysis; Blood Pressure; Brain Ischemia; Cerebral Infarction; Cerebrovascular Circulation; Disease Models, Animal; Embolism; Fibrin; Magnetic Resonance Imaging; Male; Microscopy, Confocal; Rats; Rats, Wistar

We investigated the relationships between the angiographic severity of peripheral arterial occlusive disease (PAOD) and haemostasis, fibrinolytic, and rheological variables in 219 patients with symptomatic peripheral arterial occlusive disease (PAOD). White cell count, fibrinogen, cross-linked fibrin degradation products (FDP), von Willebrand factor, and plasminogen activator inhibitor levels were all elevated in comparison with age-matched population controls (all p < 0.0001, Mann-Whitney U test), while fibrinogen (Spearman r = 0.30), von Willebrand factor (r = 0.40), and log (FDP) (r = 0.56), (all p < 0.0001) showed a strong correlation with the angiographic extent of PAOD. Multivariate analysis indicated that log (FDP) was a strong independent predictor of the angiographic severity of PAOD (p < 0.0001), in addition to increasing age (p < 0.0001), presence of tissue sepsis (p < 0.02), prior vascular surgery (p = 0.007), and other vascular pathology (p = 0.007). These results confirm that increases in fibrinogen, von Willebrand factor, plasminogen activator inhibitor and fibrin turnover, are strongly associated with the presence of symptomatic peripheral arterial disease, and suggest that there may be causal link between fibrin turnover, as determined by FDP levels, and the extent of peripheral arterial occlusive disease.

Topics: Age Factors; Aged; Angiography; Arterial Occlusive Diseases; Blood Coagulation Factors; Blood Coagulation Tests; Female; Fibrin; Fibrin Fibrinogen Degradation Products; Fibrinogen; Fibrinolysis; Hemostasis; Humans; Intermittent Claudication; Ischemia; Leg; Male; Middle Aged; Reference Values; Rheology

Aortic aneurysms are characterized by the destruction of the extracellular matrix of the media, whereas occlusive disease involves excess matrix accumulation within the intima. Plasmin degrades extracellular matrix directly and indirectly by activation of latent metalloenzymes. To determine the expression of tissue- and urokinase-type plasminogen activators, immunoassay, fibrin autography, Northern analysis, and immunohistochemistry were performed on specimens of aneurysmal (n = 12), occlusive (n = 8), and healthy (n = 6) aorta.. Immunoassay of tissue-type plasminogen activator revealed 8.7 +/- 0.9 ng tissue-type plasminogen activator/mg extracted protein in aneurysmal aorta, 5.7 +/- 0.3 ng/mg in normal aorta, and 2.5 +/- 0.3 ng/mg in occlusive aorta (p < 0.05 for comparisons between all groups). No urokinase-type plasminogen activator antigen was detected by urokinase-type plasminogen activator immunoassay. Fibrin autography exhibited lytic activity at 64 kDa and 54 kDa attributable to tissue-type plasminogen activator and urokinase-type plasminogen activator. The vast majority of fibrinolysis was secondary to free tissue-type plasminogen activator and was greatest in aneurysmal disease and least in occlusive disease. There was only a small amount of lysis secondary to urokinase-type plasminogen activator. Expression of tissue-type plasminogen activator and urokinase-type plasminogen activators mRNA was comparable in aneurysmal and occlusive aortas. In contrast to occlusive disease, aneurysms had an inflammatory cell infiltrate characterized by the expression of urokinase-type plasminogen activator by specific mononuclear cells. Tissue-type plasminogen activator expression was evident in the intima of normal and diseased aorta and in the media of diseased aorta.. Differential expression of plasminogen activators within the arterial wall may contribute to the unique pathogenesis of aneurysmal and occlusive aortic disease.

Topics: Adult; Aged; Aorta, Abdominal; Aortic Aneurysm, Abdominal; Aortic Diseases; Arterial Occlusive Diseases; Autoradiography; Blotting, Northern; DNA Probes; Electrophoresis, Polyacrylamide Gel; Fibrin; Humans; Immunohistochemistry; Middle Aged; Plasminogen Activators

Fifteen patients (9 male, 6 female) undergoing peripheral vascular surgery were monitored during surgery for evidence of subclinical anticoagulation using the activated coagulation time (ACT), thromboelastography (TEG), and heparin titration monitoring. Assessments were made at 30-minute intervals before and after the occlusion clamp. Mean (+/- SD) ACT values preoperatively were 111 (17) seconds, and 10 minutes after 5,000 IU of heparin, the ACT was 264 (57) seconds (P < 0.001). Intraoperatively, there was a significant decline in ACT values at 30 minutes (ACT 228 [50] sec, P < 0.005) and 60 minutes (200 [46] sec, P < 0.001) postheparin. No significant difference in ACT was observed between samples drawn distally and proximally to the clamp. TEG profiles were abolished in all patients immediately following heparinization. However, in 2 patients nearly complete return of the TEG coagulation profile was observed prior to the termination of the procedure and was associated with ACT values less than 160 seconds. The heparin device was unable to accurately monitor heparin elimination at these low doses. Variability of patient response to heparinization necessitates the use of intraoperative monitoring of anticoagulation during peripheral vascular surgery.

Topics: Aged; Aged, 80 and over; Aortic Diseases; Arterial Occlusive Diseases; Blood Coagulation; Blood Vessel Prosthesis; Female; Femoral Artery; Fibrin; Heparin; Humans; Iliac Artery; Male; Middle Aged; Monitoring, Intraoperative; Peripheral Vascular Diseases; Thrombelastography; Titrimetry; Whole Blood Coagulation Time

A number of thrombotic mediators have been related to peripheral arterial disease in both epidemiological and pathological studies.. We measured preoperative levels of fibrinogen, cross-linked fibrin degradation products (FDP), and the endothelial markers, von Willebrand factor (vWF), tissue plasminogen activator (tPA), and plasminogen activator inhibitor (PAI), in the venous blood of 43 claudicants undergoing percutaneous transluminal angioplasty (PTA). Samples were repeated 4 months later, and changes in the levels of thrombotic mediators were compared with ten controls undergoing angiography alone. Additional perilesional arterial samples were obtained from 11 of the patients.. Arterial sampling indicated that successful PTA led to an immediate fall in tPA levels and a rise in arterial vWF (p < 0.05), together with a trend toward a significant rise in cross-linked FDP levels. Only the increase in FDP following successful PTA (36 cases) (p < 0.05) was observed in 4-month postangioplasty venous samples, whereas all variables remained unchanged in cases of restenosis (4 patients) and in controls (all comparisons made by Wilcoxon matched pairs test).. These findings suggest that successful PTA in patients with intermittent claudication results in acute endothelial disturbance and increased fibrin turnover at the site of angioplasty and in sustained increases in fibrin turnover (as reflected by FDP levels). The observation that this increase in fibrin turnover is absent in cases of restenosis within 4 months of PTA merits further study to determine whether increases in fibrin turnover are necessary to maintain patency following PTA.

Topics: Angioplasty, Balloon; Arterial Occlusive Diseases; Constriction, Pathologic; Endothelium, Vascular; Female; Femoral Artery; Fibrin; Fibrin Fibrinogen Degradation Products; Humans; Iliac Artery; Intermittent Claudication; Male; Plasminogen Inactivators; Popliteal Artery; Tissue Plasminogen Activator; von Willebrand Factor

The efficacy of recombinant vampire bat salivary plasminogen activator (bat-PA) as a thrombolytic agent was compared with that of human tissue-type plasminogen activator (t-PA) in a canine model of arterial thrombosis. An occlusive thrombus was formed in the femoral artery by insertion of a thrombogenic copper coil; femoral arterial blood flow was monitored with a Doppler flow meter. Bat-PA and t-PA, when administered by 5-minute intravenous infusion (14 nmol/kg), reperfused seven out of eight and four out of eight dogs, respectively. The median reperfusion times in the bat-PA and t-PA groups were 24 and greater than or equal to 131 minutes, respectively. The mean reperfusion times (+/- SEM) in the recanalized bat-PA- and t-PA-treated dogs were similar (20 +/- 5 and 11 +/- 2 minutes, respectively, p = NS). Maximal blood flow after reperfusion was greater with bat-PA than with t-PA (80 +/- 10% and 41 +/- 15% of control flow, respectively, p less than 0.05). Furthermore, the median reocclusion time was markedly delayed in the bat-PA group relative to the t-PA group (131 versus 34 minutes, respectively, p less than 0.05). Plasma fibrinogen and plasminogen were not significantly depleted by the administration of t-PA or bat-PA. However, plasma alpha 2-antiplasmin activity was moderately depressed in the t-PA group relative to the bat-PA group (p less than 0.05). The clearance profile for t-PA was monoexponential, with a half-life (t1/2) of 2.4 +/- 0.3 minutes and a mean residence time of 3.5 +/- 0.4 minutes. The clearance profile for bat-PA was biexponential, with a t1/2 alpha of 0.9 +/- 0.2 minutes, a t1/2 beta of 20.2 +/- 2.7 minutes, and a mean residence time of 21.3 +/- 4.3 minutes. The steady-state volume of distribution displayed by bat-PA was 16-fold greater than that of t-PA. Zymography of serial plasma samples from the bat-PA-treated dogs failed to demonstrate the apparent generation of a complex between bat-PA and plasminogen activator inhibitor-1; the corresponding complex with t-PA was observed in plasma samples from the t-PA-treated dogs. The sustained recanalization and improved blood flow in the bat-PA group relative to the t-PA group and the avoidance of fibrinogenolysis by bat-PA, despite its prolonged mean residence time, suggest that bat-PA may be superior to t-PA as a thrombolytic agent.

Topics: alpha-Macroglobulins; Animals; Arterial Occlusive Diseases; Chiroptera; Dogs; Enzymes; Female; Femoral Artery; Fibrin; Fibrinogen; Fibrinolysin; Male; Plasminogen; Plasminogen Activators; Recurrence; Reperfusion; Salivary Glands; Thrombosis; Tissue Plasminogen Activator

Predictable vascular responses to burn injury can occur where blood vessels are occluded in and just beneath the site of trauma. The loss of vascular patency is linked to the development of ischemia in the surrounding skin. Several mechanisms may be responsible for this occlusion, and their identification will provide a logical means for prevention or reversal of the occlusion. The role of fibrin deposition was investigated here using a rat burn model. If an intravascular fibrin clot is a primary cause of early occlusion, the depletion of circulating fibrinogen should prevent its deposition. Ancrod, a pit viper venom trypsin-like proteinase, when given systemically, converts fibrinogen into a soluble product which does not clot. In studies here, the host is depleted of fibrinogen by intravenous injections of ancrod for 3 days before standard burn trauma. Burn injury in defibrinogenized rats resulted in greatly reduced local vascular occlusion. These results support the idea that vascular occlusion caused by burn injury is dependent on the deposition of fibrin. It is conjectured that the vascular occlusion of burn injury can be reversed by preventing or breaking down intravascular fibrin clots.

Topics: Ancrod; Animals; Arterial Occlusive Diseases; Burns; Fibrin; Ischemia; Male; Models, Cardiovascular; Rats; Rats, Inbred Strains; Skin; Vascular Patency

Topics: Ancrod; Arterial Occlusive Diseases; Drug Evaluation; Drug Therapy, Combination; Fibrin; Heparin; Humans

A prospective study was performed on 32 consecutive patients undergoing elective operations on the abdominal aorta. Dacron prosthetic grafts were used to replace resected abdominal aortic aneurysms or to bypass aorta-iliac occlusive disease. Complete coagulation studies were performed preoperatively, immediately postoperatively and 24 hours postoperatively. Twenty to 30 per cent of the patients had significant postoperative alterations in prothrombin time, partial thromboplastin time and platelet count. Fibrin monomer, fibrin split products and plasminogen were abnormal in 40 to 80 per cent of the patients postoperatively. Results of preoperative studies showed no significant abnormalities. One of the 32 patients had mild clinical evidence of disseminated intravascular coagulation postoperatively, which was treated with 5 units of heparin per kilogram per hour. Results of the study indicate that aortic grafting procedures frequently produce intravascular coagulation, either local or disseminated. In most patients, this is offset by activation of the fibrinolytic system. However, clinically significant sequelae may result, requiring prompt recognition and treatment.

Topics: Aged; Aorta, Abdominal; Aortic Aneurysm; Aortic Diseases; Arterial Occlusive Diseases; Blood Cell Count; Blood Coagulation Tests; Blood Platelets; Blood Vessel Prosthesis; Disseminated Intravascular Coagulation; Female; Fibrin; Fibrin Fibrinogen Degradation Products; Fibrinogen; Humans; Male; Middle Aged; Postoperative Complications; Prospective Studies; Prothrombin Time; Thromboplastin

Retinal changes in accelerated hypertension were studied in seventeen monkeys with experimental hypertension by means of ophthalmoscopy and colour and flourescence photography during life, and by injection and digest preparations and light and electron microscopy after the animals had been killed. Cotton-wool spots developed in all but three monkeys. The arteries became tortuous and dilated and the light reflex decreased in those animals that became hypertensive. The earliest abnormality was a development of many points of fluorescein leakage on terminal arterioles or small arteries. Such leaking points were always present in relation to cotton-wool spots but were not confined to such areas. Focal narrowing of arteries was not observed but arteriolar occlusion and retrograde filling of the distal segment was present in three animals. Superficial linear haemorrhages were noted in five animals. Light microscopy revealed cotton-wool spots which were identical to those observed in man with a collection of swollen axons containing densely staining pseudonuclei. Study of the arterioles by electron microscopy showed findings ranging from normality to extensive necrosis. Many precapillary arteries were constricted and some were virtually occluded. Degenerative changes were present in smooth muscle cells in the wall of many of the constricted arterioles. Many arteries also showed insudation into their wall of plasma which had seeped into the muscular coat displacing and sometimes entirely replacing the smooth muscle cells. Except for arterioles with advanced necrosis, there was no indication of how plasma insudation occurred. Two arterioles with extensive necrosis showed a break within the endothelial cell cytoplasm through which penetration of plasma proteins had probably occurred. The extravascular tissues showed collections of amorphous material, sone of it with the typical banded configuration of fibrin. The sequence of events proposed to explain these features is as follows: (1) The arterioles constrict as the pressure rises, most likely as a result of vascular autoregulation. This may head to occlusion of the precapillary arterioles and is associated with necrosis of vascular smooth muscle. (2) Dilatation then occurs with insudation of plasma into the unsupported wall through a damaged endothelium. This stage probably corresponds to the autoregulatory break-point and is evidenced clinically by focal leakage of fluorescein. (3) Progressive plasma insudation

Topics: Animals; Arterial Occlusive Diseases; Basement Membrane; Blood Flow Velocity; Blood Pressure; Capillaries; Dilatation; Fibrin; Fluorescein Angiography; Haplorhini; Hypertension, Malignant; Muscle, Smooth; Necrosis; Ophthalmoscopy; Reflex, Pupillary; Retina; Retinal Artery; Retinal Diseases; Urea

Topics: Adenosine Diphosphate; Anemia, Sickle Cell; Arterial Occlusive Diseases; Bilirubin; Blood; Erythrocytes; Fibrin; Humans; Platelet Adhesiveness; Platelet Aggregation; Veins

Topics: Arterial Occlusive Diseases; Batroxobin; Biological Assay; Blood Coagulation Tests; Chromatography, Agarose; Fibrin; Fibrin Fibrinogen Degradation Products; Fibrinogen; Humans; Male; Molecular Weight; Peptide Hydrolases; Staphylococcus; Thrombin

Topics: Arterial Occlusive Diseases; Erythrocytes; Female; Fibrin; Humans; Infarction; Leukocytes; Necrosis; Placenta; Pregnancy; Thrombosis

Topics: Adult; Aged; Animals; Anticoagulants; Arterial Occlusive Diseases; Blood Flow Velocity; Blood Viscosity; Enzyme Therapy; Female; Fibrin; Foot; Hemolysin Proteins; Humans; Injections, Intravenous; Leg; Male; Middle Aged; Necrosis; Pain; Regional Blood Flow; Snakes; Venoms

Topics: Arterial Occlusive Diseases; Blood Coagulation Disorders; Blood Coagulation Tests; Blood Platelets; Blood Transfusion; Factor XIII; Femoral Artery; Fibrin; Humans; Male; Microscopy, Electron; Middle Aged

Topics: Arterial Occlusive Diseases; Fibrin; Fibrinogen; Humans; Peripheral Vascular Diseases; Vascular Diseases