Generation of fibrinolytic activity by infusion of activated protein C into dogs.

Bovine-activated protein C, administered intravenously to dogs, increases the rate of lysis of whole blood clots. Protein C, bovine prothrombin, and diisopropylfluorophosphate-inactivated protein Ca do not increase the rate of lysis. Repeated infusions of protein Ca sustain rapid blood clot lysis, but neither elevate circulating fibrin-split products nor decrease circulating plasminogen levels. The administration of protein Ca results in the elevation of the levels of lysine-adsorbable plasminogen activator activity in the plasma. When partially purified concentrates of this activator are added to normal dog blood at the levels seen following protein Ca injection, the rate of clot lysis is similar to that seen after protein Ca injection. The addition of protein Ca to citrated whole blood in vitro, with the subsequent neutralization of protein Ca with antibodies, results in increased rates of lysis when plasma made from the treated blood is reinjected into the animal. The generation of fibrinolytic activity is dependent on both cellular and plasma components of blood. A model of protein Ca fibrinolytic activity has a minimum of two components: a secondary messenger formed by protein Ca action on blood cells and plasma, and the subsequent appearance of plasminogen activator in the animal in response to that messenger.

Relationship between protein C antigen and anticoagulant activity during oral anticoagulation and in selected disease states.

Protein C is a natural vitamin K-dependent plasma anticoagulant, deficiencies of which have been found in patients with recurrent thrombosis and warfarin-induced skin necrosis. To appreciate more fully the role of protein C in disease states and during oral anticoagulation, a new functional assay for protein C involving adsorption of plasma protein C on a Ca+2-dependent monoclonal antibody, elution, quantitative activation, and assessment of plasma anticoagulant activity, has been developed. When oral anticoagulation is initiated, the anticoagulant activity of protein C decreases to a greater extent than either the amidolytic or immunologic levels. During stabilized warfarin treatment, there is no correlation between either amidolytic or antigenic levels and the functional protein C activity, suggesting that measurement of protein C anticoagulant activity may be necessary to reflect adequately the anticoagulant protection afforded by this protein. In contrast, there was a strong correlation between anticoagulant and amidolytic and immunologic levels in liver failure and disseminated intravascular coagulation. Two patients with thromboembolic disease have been identified who exhibit a marked decrease in anticoagulant activity, but who have normal immunologic and amidolytic levels. Thus, this assay permits assessment of protein C in individuals who have received anticoagulant treatment and identification of a new class of protein C-deficient individuals.

Activation of protein C in vivo.

An endothelial cell-associated cofactor that greatly enhances the rate of protein C activation by thrombin has recently been described. The observation that the cofactor binds thrombin with unusually high affinity (K(d) = 0.5 nM) suggested that low level thrombin infusion into dogs might lead to the selective activation of protein C. Infusion of thrombin (1 U/min per kg body wt) into the jugular vein of dogs leads to the formation of a systemic anticoagulant activity within 5 min of starting the infusion. The plasma has a prolonged partial thromboplastin time and Factor X(a) clotting time, but there is no change in the thrombin clotting time. The systemic anticoagulant activity is identified as activated protein C for the following reasons: (a) anti-canine activated protein C IgG antibodies inhibit the anticoagulant activity; (b) the anticoagulant activity can be partially purified from the plasma of dogs infused with thrombin by barium citrate adsorption; (c) the anticoagulant has chromatographic properties on QAE Sephadex indistinguishable from those of activated protein C, and (d) the rate at which this anticoagulant is inhibited in citrated canine plasma is identical to that of canine activated protein C. The in vivo activation of protein C appears to be receptor mediated since it occurs at low thrombin concentration and since it can be progressively inhibited by simultaneous infusion of diisopropylphospho-thrombin with thrombin. The activation of protein C at low levels of thrombin is selective, since neither the platelet count nor the Factor V levels are altered. Thrombin infusion leads to an elevation in circulating plasminogen activator levels. This appears to be mediated through the activation of protein C since coinfusion of diisopropylphospho-thrombin with thrombin inhibits the increase in plasminogen activator levels. Pretreatment of dogs with dicumarol blocks both the formation of anticoagulant activity and the rise in plasminogen activator. When the dicumarol-treated dogs are supplemented with isolated protein C and thrombin is infused, the anticoagulant activity again appears and the circulating levels of plasminogen activator are again elevated. These studies illustrate that low levels of thrombin in vivo can activate protein C, which in turn can inhibit blood coagulation and initiate fibrinolysis by elevating circulating plasminogen activator levels.

Acquired deficiencies of protein S. Protein S activity during oral anticoagulation, in liver disease, and in disseminated intravascular coagulation.

Protein S is a vitamin K-dependent plasma protein which serves as the cofactor for activated protein C. Protein S circulates in both an active, free form and in an inactive complex with C4b-binding protein. To elucidate the role of protein S in disease states and during oral anticoagulation, we developed a functional assay for protein S that permits evaluation of the distribution of protein S between free and bound forms and permits determination of the specific activity of the free protein S. In liver disease, free protein S antigen is moderately reduced and the free protein S has significantly reduced specific activity. In disseminated intravascular coagulation, reduced protein S activity occurs due to a redistribution of protein S to the inactive bound form. During warfarin anticoagulation, reduction of free protein S antigen and the appearance of forms with abnormal electrophoretic mobility significantly decrease protein S activity. After the initiation of warfarin, the apparent half-life of protein S is 42.5 h. In patients with thromboembolic disease, transient protein S deficiency occurs due to redistribution to the complexed form. Caution should be exercised in diagnosing protein S deficiency in such patients by use of functional assays.

Familial protein S deficiency is associated with recurrent thrombosis.

Recent studies have demonstrated that protein C deficiency is associated with recurrent familial thrombosis. In plasma, activated protein C functions as an anticoagulant. This anticoagulant response requires a vitamin K-dependent plasma protein cofactor, referred to as protein S. Since the anticoagulant activity of activated protein C is dependent on protein S, we hypothesized that patients lacking functional protein S might have associated thrombotic disease. Two related individuals with otherwise normal coagulation tests are described whose plasma is not effectively anticoagulated with activated protein C. Addition of purified human protein S to their plasma restores a normal anticoagulant response to activated protein C. We have developed a rapid one-stage clotting assay for protein S to quantitate the level of protein S in their plasma. Plasma is depleted of protein S by immunoadsorption with immobilized antiprotein S antibodies. The resultant plasma responds poorly to activated protein C, but is effectively anticoagulated in a dose-dependent fashion upon addition of purified protein S or small quantities of plasma. The affected individuals possess less than 5% protein S activity. Using Laurell rockets, protein S antigen was detected in the plasma but was at reduced levels of 13 and 18% in the two individuals. When the barium eluate of the patient plasma was chromatographed on quaternary aminoethyl Sephadex, a single peak of protein S antigen devoid of protein S anticoagulant cofactor activity was detected early in the chromatogram. In contrast, the barium eluate from normal donors separated into two peaks, one emerging early and also devoid of anticoagulant cofactor, and the second peak with anticoagulant activity emerging later. The first peak of protein S antigen, from both the normal donor and the patient, chromatographed in the region of the complement component C4-binding protein-protein S complex. These studies suggest that protein S deficiency may result in recurrent thrombotic disease.

On the role of phosphatidylethanolamine in the inhibition of activated protein C activity by antiphospholipid antibodies.

Phosphatidylethanolamine (PE) is an important membrane component for supporting activated protein C anticoagulant activity but has little influence on prothrombin activation. This difference constitutes a potential mechanism for selective inhibition of the protein C anticoagulant pathway by lupus anticoagulants and/or antiphospholipid antibodies. In this study, we demonstrate that the presence of PE augments lupus anticoagulant activity. In the plasma of some patients with lupus anticoagulants, activated protein C anticoagulant activity is more potently inhibited than prothrombin activation. As a result, in the presence of activated protein C and PE, these patient plasmas clot faster than normal plasma. Patients with minimal lupus anticoagulant activity are identified whose plasma potently inhibits activated protein C anticoagulant activity. This process is also PE dependent. In three patient plasmas, these phenomena are shown to be due to immunoglobulins. The PE requirement in the expression of activated protein C anticoagulant activity and the PE dependence of some antiphospholipid antibodies provide a mechanistic basis for the selective inhibition of the protein C pathway. Inhibition of activated protein C function may be a common mechanism contributing to increased thrombotic risk in certain patients with antiphospholipid antibodies.

Fondaparinux combined with intermittent pneumatic compression vs. intermittent pneumatic compression alone for prevention of venous thromboembolism after abdominal surgery: a randomized, double-blind comparison.

BACKGROUND: The benefit of combined mechanical and pharmacologic methods for venous thromboembolism prevention after abdominal surgery has not been clearly established. OBJECTIVES: To compare the efficacy and safety of fondaparinux in conjunction with intermittent pneumatic compression vs. intermittent pneumatic compression alone in this context. PATIENTS AND METHODS: This was a randomized, double-blind, placebo-controlled superiority trial. Patients aged at least 40 years undergoing abdominal surgery were randomized to receive either fondaparinux 2.5 mg or placebo s.c. for 5-9 days, starting 6-8 h postoperatively. All patients received intermittent pneumatic compression. The primary efficacy outcome was venous thromboembolism up to day 10. The main safety outcomes were major bleeding and all-cause mortality. Follow-up lasted 32 days. RESULTS: Of the 1309 patients randomized, 842 (64.3%) were evaluable for efficacy. The venous thromboembolism rate was 1.7% (7/424) in the fondaparinux-treated patients and 5.3% (22/418) in the placebo-treated patients (odds ratio reduction 69.8%; 95% confidence interval 27.9-87.3; P = 0.004). Fondaparinux significantly reduced the proximal deep vein thrombosis rate from 1.7% (7/417) to 0.2% (1/424; P = 0.037). Major bleeds occurred in 1.6% (10/635) and 0.2% (1/650) of fondaparinux-treated and placebo-treated patients, respectively (P = 0.006), none being fatal or involving a critical organ. By day 32, eight patients (1.3%) receiving fondaparinux and five (0.8%) receiving placebo had died. CONCLUSIONS: In patients undergoing abdominal surgery and receiving intermittent pneumatic compression, fondaparinux 2.5 mg reduced the venous thromboembolism rate by 69.8% as compared to pneumatic compression alone, with a low bleeding risk as compared to placebo.

Traces of factor VIIa modulate thromboplastin sensitivity to factors V, VII, X, and prothrombin.

BACKGROUND: Thromboplastin reagents are used to conduct prothrombin time (PT) clotting tests to monitor oral anticoagulant therapy and screen for clotting factor deficiencies. Thromboplastins made from purified, recombinant tissue factor are generally more sensitive to changes in plasma factor (F) VII levels than are thromboplastins prepared from tissue extracts. This may be problematic as FVII's short plasma half-life can result in day-to-day fluctuation during oral anticoagulant therapy. We hypothesized that trace contamination of tissue-derived thromboplastins with FVII(a) blunts sensitivity to plasma FVII levels. METHODS: Traces of purified FVIIa were added to thromboplastin reagents prepared using recombinant human tissue factor and the effect on sensitivity to individual clotting factors was quantified in PT clotting assays. RESULTS AND CONCLUSIONS: Adding 5-100 pm FVIIa not only decreased thromboplastin sensitivity to plasma FVII, it surprisingly increased sensitivity to plasma levels of FV, FX and prothrombin. In addition, traces of FVIIa interacted with changes in the salt content and phospholipid composition of recombinant thromboplastins to further modulate their sensitivities to individual clotting factors. These results help explain how thromboplastin reagents of differing composition exhibit differing sensitivities to individual clotting factor levels. Implications of our results for monitoring oral anticoagulant therapy and other uses of the PT assay are discussed.

Phospholipid composition controls thromboplastin sensitivity to individual clotting factors.

BACKGROUND: Tissue factor is the active ingredient in thromboplastin reagents used to perform prothrombin time (PT) clotting tests to monitor oral anticoagulant therapy and to screen for clotting factor deficiencies. Thromboplastins are complex mixtures prepared from extracts of brain or placenta, although newer thromboplastins contain recombinant tissue factor incorporated into phospholipid vesicles. Thromboplastins can vary widely in their sensitivity to reductions in the levels of vitamin K-dependent clotting factors. A system to compensate for this, the International Sensitivity Index (ISI) and International Normalized Ratio (INR), has revolutionized the monitoring of oral anticoagulant therapy. The INR system is also sometimes used to monitor coagulopathies in patients with sepsis or liver failure, applications for which it was not originally designed and for which it has not been rigorously validated. OBJECTIVES: To better understand thromboplastin performance, we systematically investigated which properties of recombinant thromboplastins influence their sensitivities to changes in the levels of specific clotting factors. RESULTS: We now report that relative sensitivities to changes in the plasma levels of factors V, VII, X (FV, FVII, FX) and prothrombin are differentially influenced by a recombinant thromboplastin's content of phospholipid and sodium chloride. Furthermore, thromboplastins of similar ISI values may exhibit quite different sensitivities to each of these clotting factors. CONCLUSIONS: Differing sensitivities of thromboplastin reagents to individual clotting factor levels have implications for monitoring of oral anticoagulant therapy and interpreting results of the PT assay.

Afibrinogenemia and hypobetalipoproteinemia in a kindred.

A 3-year-old boy with minor bleeding problems had no plasma fibrinogen measured by both clottable assay and immuno-precipitation. Low normal fibrinogen levels were present in the mother and father. Markedly decreased plasma cholesterol and apolipoprotein B levels were found in the father, proband's brother, and the paternal side of the kindred. The proband and his mother had normal plasma total cholesterol and apolipoprotein B levels. These findings are compatible with autosomal dominant transmission of hypobetalipoproteinemia and autosomal recessive transmission of afibrinogenemia. Two members of the father's family had plasma cholesterol levels below the fifth percentile but elevated levels of fibrinogen (6.0 and 4.4 g/L). Both have symptomatic coronary heart disease. Finding coronary heart disease with very low cholesterol but elevated fibrinogen levels is consistent with fibrinogen levels being an independent risk factor for coronary heart disease.

Predictive value of compression ultrasonography for deep vein thrombosis in symptomatic outpatients: clinical implications of the site of vein noncompressibility.

BACKGROUND: Compression ultrasonography has a high negative predictive value for deep vein thrombosis in symptomatic outpatients. Limited data are available on factors influencing positive predictive value. The objective of this study was to evaluate the positive predictive value of compression ultrasonography according to the anatomic site of vein noncompressibility. METHODS: We performed a prospective cohort study of 756 consecutive outpatients with suspected first-episode deep vein thrombosis. Compression ultrasonography was performed at the initial visit: results were abnormal if a noncompressible segment was identified or normal if all segments were fully compressible. Venography was performed in patients with abnormal compression ultrasonography results. Positive predictive value was determined according to the site of noncompressibility: common femoral vein only, popliteal vein only, or both sites. Venography was the reference standard for the presence of deep vein thrombosis. RESULTS: Positive predictive value was 16.7% (95% confidence interval, 0.4%-64.1%) for noncompressibility isolated to the common femoral vein compared with 91.3% (95% confidence interval, 72.0%-98.9%) for the popliteal vein only and 94.4% (95% confidence interval, 72.7%-99.9%) for both sites (P<.001). Of 15 patients with isolated noncompressibility of the common femoral vein, 8 (53%) had pelvic neoplasm or abscess compared with 2 (5%) of 42 with noncompressibility of the popliteal vein only and 6 (13%) of 47 with noncompressibility of both sites (P<.001). CONCLUSIONS: The positive predictive value of noncompressibility isolated to the common femoral vein is too low to be used alone as the diagnostic end point for giving anticoagulant therapy. Noncompressibility isolated to the common femoral vein is a diagnostic marker for pelvic disease.

Selective removal of plasma low density lipoprotein with the HELP system: biweekly versus weekly therapy.

PURPOSE: Biweekly (once every 2 weeks) heparin-induced extracorporeal low-density lipoprotein (LDL) precipitation (HELP) therapy was evaluated for safety and efficacy in selectively reducing LDL cholesterol levels compared with weekly HELP therapy. PATIENTS AND METHODS: Biweekly treatments were given to high-risk, diet/drug resistant hypercholesterolemic patients (n = 23) after 6 months of weekly HELP therapy. Lipids, lipoprotein cholesterol, apolipoproteins A-I and B, and fibrinogen were measured on plasma samples before and after treatment. RESULTS: Mean plasma volume treated was 2.8 l and mean treatment duration 1.7 h. Therapy complications were minimal. In 98% of 268 biweekly HELP treatments, LDL cholesterol levels were reduced by > 30%. For patients completing 6 months of biweekly therapy following 6 months' weekly therapy (n = 23), mean LDL cholesterol levels were reduced 138.5 mg/dl (111.2 mg/dl weekly) with a time-averaged decrease from mean pre-apheresis levels of 33% for biweekly therapy (39% weekly). Mean total cholesterol (161.2 mg/dl biweekly versus 132.9 weekly) and apolipoprotein B (104.6 mg/dl versus 92.6) levels were also reduced with each treatment. Mean HDL cholesterol was reduced only 6.1 mg/dl (6.3 mg/dl weekly). CONCLUSIONS: Biweekly HELP treatments can safely reduce LDL cholesterol levels as consistently as weekly HELP treatments. However, the higher pre-treatment LDL cholesterol levels with biweekly treatments may produce less therapeutic benefit than with weekly therapy.

Decrease in endothelial cell-dependent protein C activation induced by thrombomodulin by treatment with cyclosporine.

The use of cyclosporine has been associated with an increased incidence of thrombosis and endothelial cell perturbation. To explore possible mechanisms involved, we examined the effects of CSA on the activation of protein C by thrombomodulin. Cultured bovine aortic endothelial cell monolayers were incubated for 24 hr with a wide range of CSA concentrations. After removal of CSA and incubation with thrombin and purified protein C, thrombomodulin-dependent protein C activation was measured with an S-2238-based kinetic chromogenic assay. As compared to control, a significant fall in thrombomodulin activity occurred after 24-hr incubation with 100 (70.8 +/- 15.8%, P less than 0.05), 1000 (64.9 +/- 16.6%, P less than 0.05), or 10,000 (28.9 +/- 12.3%, P less than 0.05) ng/ml of CSA. A comparable inhibition of thrombomodulin activity was also observed in cultured renal artery endothelial cells (67.5 +/- 12.6%, P less than 0.05), after 24-hr incubation with 5000 ng/ml CSA. In cells incubated with 5000 ng/ml of CSA for 4 hr, thrombomodulin activity fell by almost 15% (85.6 +/- 8.3%, P less than 0.05) and tended to plateau between 7 hr (73.8 +/- 12.7%, P less than 0.05), and 24 hr of incubation (72.7 +/- 8.9%, P less than 0.05). These results indicate that CSA produces a time- and dose-dependent reduction in thrombomodulin activity of cultured endothelial cells, downregulating the protein C anticoagulant pathway, thereby increasing the risk of thrombosis.

Monitoring low-dose warfarin therapy by a central laboratory and implications for clinical trials and patient care. The Coumadin Aspirin Reinfarction (CARS) Pilot Study Group.

The central laboratory provides International Normalized Ratio results in close agreement with the local laboratory for monitoring the anticoagulant effect of low-dose warfarin. A central laboratory may have practical advantages for patients in rural areas that lack laboratory facilities for anticoagulant monitoring.

Weekly treatment of diet/drug-resistant hypercholesterolemia with the heparin-induced extracorporeal low-density lipoprotein precipitation (HELP) system by selective plasma low-density lipoprotein removal.

Heparin-induced extracorporeal low-density lipoprotein (LDL) precipitation (HELP) weekly therapy was evaluated for safety and efficacy in selectively reducing LDL cholesterol levels. Weekly treatments (25) were given to high-risk hypercholesterolemic patients (n = 33) with screening LDL cholesterol levels > 160 mg/dl despite prior diet and drug therapy. Lipids, lipoprotein cholesterol, apolipoproteins A-l and B, and fibrinogen were measured on plasma samples before and after treatment. Mean plasma volume treated was 2.66 liters and mean treatment duration 1.7 hours. Therapy complications were infrequent and were primarily vascular access problems or hypotension. Treatment goals were > 30% LDL cholesterol reduction with each treatment. In 98% of 686 HELP treatments, LDL cholesterol levels were reduced > or = 30%. Mean LDL cholesterol levels were reduced 111.0 mg/dl (54%) with a time-averaged decrease of 39% over a 25-week course. Mean HDL cholesterol was reduced only 6.2 mg/dl (15%). Total cholesterol (134.4 mg/dl; 47% decrease) and apolipoprotein B (88.7 mg/dl; 53% decrease) levels were also reduced. Fibrinogen decreased 158.2 mg/dl (58%) without bleeding complications. HELP therapy can safely and selectively remove plasma LDL cholesterol, producing consistent reductions in LDL cholesterol, total cholesterol and apolipoprotein B levels.

Fibrinogen levels in women having coronary angiography.

Fibrinogen has emerged as a risk factor for coronary artery disease in men that equals cholesterol in importance. It is known to play an important role in reparative processes, and evidence is accumulating that fibrinogen/fibrin accumulates at the site of minimal vascular injury. Fibrinogen contributes significantly to blood viscosity and its adherence to endothelium may mediate progression of atheromatous lesions. This study was designed to examine a number of markers of risk in a consecutive series of cardiology patients undergoing coronary catheterizations over a 15-month period. This article examines the level of fibrinogen in relation to the number of reported coronary stenoses and disease severity in a series of Caucasian female patients (n = 101). Women were classified as diseased if they had at least 1 lesion > or = 25% in the coronary anatomy and nondiseased if they had no lesions > or = 25%. The number of reported lesions correlates significantly with fibrinogen levels (r = 0.36, p = 0.0002). Women with fibrinogen levels > or = 283 mg/dl had a 3.2-fold increased risk (95% confidence interval 1.2 to 9.1) of having at least 1 stenosis > or = 25% after adjusting for age and diabetic status. Smoking and body mass index did not differ by disease status and thus did not confound the finding. Mean fibrinogen levels showed a progressive positive association with increasing clinically defined vessel involvement (stenosis > or = 50%).

Activated factor VII levels in patients with angiographically confirmed coronary artery disease.

We have examined factor VIIa levels in consecutive consenting patients undergoing coronary angiography (n = 702) to determine if levels are related to the presence of coronary arterial narrowing and to the degree and extent of that narrowing. Both men and women with clinically defined coronary artery disease (> or = 50% stenosis in at least 1 vessel) had factor VIIa levels that were similar to men and women with less stenosis or normal coronary arteries.

Safety and anticoagulation effect of a low-dose combination of warfarin and aspirin in clinically stable coronary artery disease. Coumadin Aspirin Reinfarction (CARS) Pilot Study Group.

The hypothesis that the combination of low-dose aspirin and warfarin therapy is more effective than aspirin alone in secondary prophylaxis after myocardial infarction is to be examined in the Coumadin Aspirin Reinfarction Study. This pilot study addressed the safety and anticoagulation effect of a fixed, low-dose combination in 114 patients (aged 64 +/- 8 years, 85% men) with stable coronary artery disease receiving 3 mg of warfarin plus 80 mg of aspirin daily for 8 weeks. The international normalized ratio (INR) was measured within 72 hours of initial therapy, and weekly. Of the 110 patients with evaluable INRs, 87 patients (79%) maintained the 3 + 80 mg combination, 19 (17%) had the dose reduced to 1 mg warfarin + 80 mg aspirin, and 4 (4%) discontinued therapy because of a confirmed INR of > or = 4.5. At steady state, patients had INRs of 1.48 +/- 0.41 (3 + 80 mg group) and 1.21 +/- 0.23 (1 + 80 mg group), and inter- and intra-patient variability (estimated by the mean of the between- and within-patient SDs at steady state) was 0.49 +/- 0.08 and 0.13 +/- 0.14, respectively. There was no apparent effect of age on INR distribution. Microscopic hematuria was the most frequent (20%) adverse clinical event, but was unrelated to the INR. Three patients required discontinuation of therapy because of bleeding events (persistent hematuria and epistaxis). A fixed low-dose combination of warfarin and aspirin results in a predictable and stable increase in the INR in a large proportion of patients with coronary artery disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Coumarin-induced skin necrosis. Incidence, mechanisms, management and avoidance.

Coumarin-induced tissue necrosis is a complication of oral anticoagulant therapy characterised by necrosis of the skin and underlying tissue. This occurrence of microvascular thrombosis associated with the administration of an anticoagulant has perplexed the medical and pharmaceutical community since the condition was first recognised in 1943. While the condition is rarely seen, it is of major clinical interest and raises a number of questions concerning pathological mechanisms and patient management. Although some cases occur in patients with hereditary disorders predisposing to thrombosis, the condition remains a mystery in terms of which patients will develop the condition, why the skin and underlying fatty tissues are the target of the microvascular thrombosis, and what the proper approach to a patient with coumarin-induced necrosis should be both in terms of acute management and long term anticoagulant therapy.