J. W. Ten Cate

Comparison of subcutaneous low-molecular-weight heparin with intravenous standard heparin in proximal deep-vein thrombosis

In view of the potential of low-molecular-weight heparins (LMWH) to simplify initial therapy and allow outpatient treatment of proximal deep-vein thrombosis, we undertook a randomised comparison of fixed-dose subcutaneous LMWH with adjusted-dose intravenous standard heparin in the initial treatment of this disorder. Our main objectives were to compare the efficacy of these regimens for 6 months of follow-up and to assess the risk of clinically important bleeding. Of 170 consecutive symptomatic patients with venographically proven proximal deep-venous thrombosis, 85 received standard heparin (to achieve an activated partial thromboplastin time of 1.5 to 2.0 times the pretreatment value) and 85 LMWH (adjusted only for body weight) for 10 days. Oral coumarin was started on day 7 and continued for at least 3 months. The frequency of recurrent venous thromboembolism diagnosed objectively did not differ significantly between the standard-heparin and LMWH groups (12 [14%] vs 6 [7%]; difference 7% [95% confidence interval -3% to 15%]; p = 0.13). Clinically important bleeding was infrequent in both groups (3.5% for standard heparin vs 1.1% for LMWH; p greater than 0.2). We conclude that fixed-dose subcutaneous LMWH is at least as effective and safe as intravenous adjusted-dose heparin in the initial treatment of symptomatic proximal-vein thrombosis. Since there is no need for laboratory monitoring with the LMWH regimen, patients with venous thrombosis can be treated at home.

Association of idiopathic venous thromboembolism with single point-mutation at Arg506 of factor V

Abnormal coagulation factor V may underlie the thrombotic events associated with resistance to activated protein C (APC). We analysed 27 consecutive patients with documented idiopathic (recurrent) thromboembolism for the occurrence of point mutations within the APC sensitive regions of blood coagulation factor V. In 10 patients we observed a single basepair mutation resulting in a substitution of Arg506 to Gln. This mutation was significantly linked to in-vitro resistance to APC in these subjects. This mutation at Arg506 of factor V may form the molecular basis for the thrombotic events associated with APC resistance.

Diagnostic utility of ultrasonography of leg veins in patients suspected of having pulmonary embolism

The clinical diagnosis of pulmonary embolism is an insufficient basis for initiating long-term anticoagulant therapy [1, 2]. When objective tests are used, the diagnosis of pulmonary embolus is confirmed in only about 30% of patients in whom the condition is suspected [1, 2]. It is important to identify patients with pulmonary embolism because adequate anticoagulant treatment reduces morbidity and mortality from recurrent thromboembolic disease [3]. However, anticoagulant therapy carries a substantial risk for major bleeding [4]. Thus, it is equally important to identify patients without pulmonary embolism from whom anticoagulant therapy can be safely withheld. Lung scintigraphy remains the test of first choice for the diagnostic work-up of patients suspected of having pulmonary embolism. It has been conclusively shown that anticoagulant agents can be safely withheld from patients who have normal scans [5, 6]. In patients with segmental or larger perfusion defects and locally normal ventilation (that is, patients with high-probability lung scans), the diagnosis is sufficiently proven to warrant long-term anticoagulant therapy [1, 2, 7]. Unfortunately, the lung scan is neither normal nor high-probability in 40% to 60% of patients [1, 2, 7-9]. Further investigation is required because the prevalence of pulmonary embolism in this group is still approximately 20% to 40% [1, 2, 9, 10]. Pulmonary angiography is generally considered the definitive test, but this method is invasive and requires substantial technical resources and expertise for proper execution [9, 11]. Therefore, several alternate noninvasive methods that reduce the need for pulmonary angiography have been advocated; these include tests for the measurement of coagulation activation [12, 13], clinical decision rules [14, 15], and spiral computed tomography [16]. On the basis of the concept that pulmonary embolism and deep venous thrombosis are manifestations of the same disease, some investigators have evaluated the use of tests for the detection of venous thrombosis of the leg in the diagnostic work-up of patients suspected of having pulmonary embolism [17, 18]. To be clinically useful, such a test should be simple, readily available, and highly accurate. Compression ultrasonography has been shown to be reliable for detecting and excluding thrombosis in patients in whom deep venous thrombosis is clinically suspected [19-21]. However, in nonsymptomatic persons with a high risk for thrombosis (for example, patients who have recently undergone hip surgery), this test did not prove clinically useful, primarily because of an insufficient sensitivity [22-24]. We sought to determine the diagnostic value of compression ultrasonography in consecutive patients suspected of having pulmonary embolism. We then used our findings to assess the potential contribution of compression ultrasonography to the diagnostic management of symptomatic patients. Methods Patients Patients were eligible for the study if they were 18 years of age or older and underwent perfusion-ventilation lung scanning for a diagnostic work-up of pulmonary embolism at the Academic Medical Center in Amsterdam, the Netherlands. All patients were primarily referred because pulmonary embolism was clinically suspected (outpatients) or because they developed signs or symptoms of pulmonary embolism during hospitalization for another illness (inpatients). All patients were scheduled to undergo ultrasonography as soon as possible; this test was done independently of the other tests. All patients were prospectively followed for 6 months. The study protocol was approved by the institutional review board, and informed consent was obtained for all patients. Diagnostic Methods Perfusion lung scanning was done in all patients after the administration of 100 MBq of 99mTechnetium-labeled macroaggregates of albumin. Six views were routinely obtained: anterior, posterior, left and right lateral, and left and right posterior oblique. Lung scans were interpreted by using an anatomic-segment lung chart [25] and were considered normal if no perfusion defects were seen in any of the six projections. If segmental or larger defects were seen, ventilation lung scanning was done using 81mKrypton gas. Pulmonary embolism was considered to be excluded if the lung scan was normal and was considered to be proven if a high-probability scan (that is, a scan showing at least one segmental perfusion defect with locally normal ventilation [1, 7]) was obtained. Selective pulmonary angiography was attempted in all patients who had a nondiagnostic lung scan. Angiography involved a modified Seldinger approach with a 6.7F-braded, multiple side-holed, Grollman-type pig-tail catheter. The angiogram was classified according to standard definitions as normal, indicative of pulmonary embolism, or inadequate for interpretation [1, 2, 9]. B-mode gray-scale compression ultrasonography was done with a 7.5-MHz linear-array sonographic scanner. While the patient was in the supine position, the common femoral vein was visualized at the inguinal ligament; the adjacent artery was used as a reference point. The popliteal vein was scanned while the patient was in the prone or lateral decubitus position, and the transducer was placed posteriorly in the mid-popliteal fossa. For evaluation of the distal popliteal vein, the transducer was moved slowly from the popliteal fossa along the calf until the trifurcation of the calf veins was visualized. No attempt was made to visualize the calf veins. Ultrasonographic results were considered abnormal (that is, consistent with the presence of deep venous thrombosis) if a venous segment could not be completely compressed [19-21]. All patients underwent bilateral compression ultrasonography, which was done by an independent investigator who was not aware of the results of lung scanning or pulmonary angiography. Results of compression ultrasonography were not forwarded to the referring physician, and decisions about anticoagulant treatment were based on the results of lung scanning or pulmonary angiography. Statistical Analysis The rate of abnormal compression ultrasonography in patients in whom pulmonary embolism was proven (sensitivity) was calculated for all patients and for patients with the diagnosis of pulmonary embolism by using as a conjoint gold standard a high-probability lung scan or a non-high-probability lung scan plus a subsequent abnormal angiogram. We also determined the rate of abnormal ultrasonographic results in patients in whom pulmonary embolism was excluded by either a normal lung scan or a normal angiogram (1 specificity). Finally, the rate of abnormal results on compression ultrasonography was calculated for patients whose diagnosis of pulmonary embolism was uncertain because angiography could not be performed or because the result could not be interpreted. The possible contribution of compression ultrasonography to the diagnostic management of symptomatic patients was assessed by 1) calculating the number of lung scans and angiograms that could be avoided if compression ultrasonography yielded abnormal results and 2) determining the number of patients who would be inappropriately treated with anticoagulation because of false-positive ultrasonographic results. These calculations were done by applying the sensitivity and specificity of compression ultrasonography obtained in our study to a hypothetical population of 1000 patients suspected of having pulmonary embolism; the proportional distribution of lung scanning and angiography results were the same as those seen in our study. To minimize bias, all 397 patients (including the 40 patients in whom ultrasonography was not done) were used to calculate the necessary figures. We assumed that the prevalence of pulmonary embolism in the 30 patients without a diagnosis (those whose lung scan was nondiagnostic but who did not undergo pulmonary angiography) was 27%, as was seen in the remaining patients who had a nondiagnostic lung scan. Furthermore, the sensitivity and specificity of ultrasonography in these 30 patients were assumed to be similar to those obtained in the cohort of patients with a nondiagnostic lung scan in whom angiography was done. This resulted in an overall calculated prevalence of pulmonary embolism of 41.1%, with a high-probability lung scan in 30.2% of these patients and a nondiagnostic lung scan in 40.6%. Pulmonary embolism was considered to be present in 27% of patients who had a nondiagnostic lung scan (if angiography had been performed). Finally, we assumed that all patients with abnormal ultrasonographic results would be treated with anticoagulant agents without further testing. Results A total of 397 consecutive patients who were clinically suspected of having pulmonary embolism were enrolled (Figure 1). The mean age was 56 years (range, 18 to 92 years); 223 patients (56%) were women, and 206 (52%) were outpatients. Twenty-four percent of patients had cancer, 21% had recently had surgery, 12% had congestive heart failure, and 12% had a history of venous thromboembolism. No risk factor was seen in 26% of patients. The median interval between the onset of symptoms and diagnostic investigations was 2 days. Compression ultrasonography could not be done in 40 patients. Thirty of these patients had a normal perfusion lung scan; 22 of the 30 were outpatients for whom compression ultrasonography could not be arranged before they left. Compression ultrasonography was not performed in 4 patients who had a high-probability lung scan and 6 patients who had a nondiagnostic lung scan (angiography results were abnormal in 1 patient and normal in 2; angiography was not done in 3 patients). Treatment decisions in these 40 patients were made on the basis of lung scans and angiography results, as was done for the 357 patients in whom ultrasonography was performed. Figure 1. Flow diagram of test outcomes of 397 patients suspected of having pul

Inhibition of plasminogen activator inhibitor-1 activity results in promotion of endogenous thrombolysis and inhibition of thrombus extension in models of experimental thrombosis.

BackgroundWe investigated the effect of inhibition of plasminogen activator inhibitor-1 (PAI-1) activity by a murine monoclonal anti-human PAI-1 antibody (MAI-12) on in vitro thrombolysis and on in vivo thrombolysis and thrombus extension in an experimental animal model for thrombosis. Methods and ResultsThrombolysis, mediated by recombinant tissue-type plasminogen activator (rt-PA), was studied in an in vitro system consisting of fibrinogen, plasminogen, and thrombin. Addition of purified platelets during clot formation inhibited rt-PA-mediated thrombolysis in a dose-dependent manner. Platelet-dependent thrombolysis resistance could be completely neutralized by the monoclonal antibody MAI-12, supporting the notion that the observed resistance is due to PAI-1 released from α-granules of platelets. Subsequently, we monitored in vivo thrombolysis and thrombus extension of human whole blood thrombi that were allowed to form in rabbit jugular veins. During thrombus formation, either MAI-12 or an irrelevant antibody was incorporated. Thrombolysis and thrombus extension were simultaneously measured during endogenous thrombolysis or upon administration of different dosages of rt-PA. We observed that endogenous thrombolysis was enhanced in the presence of MAI-12 compared with the control antibody. Significantly, thrombus extension was partially prevented by MAI-12 and not by the control antibody irrespective of whether exogenous rt-PA was systematically administered ConclusionsThese observations further confirm the essential role of PAI-1 in the regulation of the thrombolytic system and support the exploration of adjunctive therapy based on inhibition of PAI-1 activity in thrombolytic strategies.

Thrombolysis and Reocclusion in Experimental Jugular Vein and Coronary Artery Thrombosis Effects of a Plasminogen Activator Inhibitor Type 1–Neutralizing Monoclonal Antibody

BACKGROUND Thrombolytic therapy for acute myocardial infarction is often complicated by reocclusion of the initially reperfused artery. Platelets have been shown to play an important role in this process. We determined the contribution of plasminogen activator inhibitor type 1 (PAI-1), stored in the alpha-granules of platelets, to thrombolysis resistance and to reocclusion. METHODS AND RESULTS In a rabbit jugular vein thrombosis model, the effect of a PAI-1-neutralizing monoclonal antibody (CLB-2C8) on thrombolysis and thrombus growth was assessed. The effect on reperfusion, reocclusion, and duration of vessel patency was studied in a canine model of coronary artery thrombosis superimposed on a high-grade stenosis and endothelial damage. In the rabbit jugular vein model, the intravenous administration of 1 mg/kg anti-PAI-1 antibody significantly enhanced the endogenous thrombolysis from 5.5 +/- 1.3% in the animals treated with a nonspecific monoclonal antibody (control) to 13.7 +/- 2.6% in the animals treated with the anti-PAI-1 antibody. Thrombus growth was reduced significantly, from 41.3 +/- 2.6% in the control animals to 22.8 +/- 2.8% in the animals treated with the anti-PAI-1 antibody. In combination with a single bolus injection of recombinant tissue-type plasminogen activator (rTPA; 0.25 mg/kg), the anti-PAI-1 antibody reduced thrombus growth significantly, from 21.5 +/- 2.7% in the animals treated with rTPA alone to 12.2 +/- 2.6% in the animals treated with rTPA and the antibody. No additional effect of the anti-PAI-1 antibody was observed on rTPA-induced thrombolysis. In the canine coronary artery thrombosis model, the administration of a suboptimal dose of rTPA (0.45 mg/kg) induced reperfusion in 7 of the 8 dogs after 19.5 +/- 8.2 minutes. Reperfusion was followed by reocclusion in all animals after 3.3 +/- 2.6 minutes. Administration of the anti-PAI-1 antibody in combination with rTPA significantly reduced time to reperfusion (8.1 +/- 5.2 minutes) and delayed the occurrence of reocclusion to 11.6 +/- 12.5 minutes. CONCLUSIONS Administration of the anti-PAI-1 antibody (CLB-2C8) results in increased endogenous thrombolysis and inhibition of thrombus growth in a venous thrombosis model in rabbits and facilitated reperfusion and reduction of reocclusion in a canine model of coronary artery thrombosis.

Review: Infectious Diseases and Coagulation Disorders

Infection, both bacterial and nonbacterial, may be associated with coagulation disorders, resulting in disseminated intravascular coagulation and multiorgan failure. In the last few decades a series of in vivo and in vitro studies has provided more insight into the pathogenetic mechanisms and the role of cytokines in these processes. Because of the growing interest in this field, the complexity of the subject, and the fact that many physicians must deal with a variety of infections, current data are reviewed on the association between infectious diseases and the coagulation system. Novel therapeutic intervention strategies that will probably become available in the near future are mentioned, along with those of special interest for infectious disorders for which only supportive care can be given.

Limitations of compression ultrasound for the detection of symptomless postoperative deep vein thrombosis

Compression ultrasonography is regarded as the non-invasive gold-standard to detect deep vein thrombosis (DVT) in patients presenting with symptoms. However, its use as a screening method in symptom-free postoperative patients at high risk of developing DVT remains controversial. In 100 consecutive patients who had undergone craniotomy, we compared the results of bilateral compression ultrasonic measurements of the results of bilateral compression ultrasonic measurements of the entire legs with the outcomes of contrast venography. Proximal DVT was detected in 13 patients, 5 of whom also had an abnormal ultrasonic result (sensitivity 38%, 95% CI 8-69%). Only 5 of the 9 patients with an abnormal ultrasound result for the proximal veins had proximal DVT (positive predictive value, 56%, 18-94%). Calf sonograms were evaluable in 71 of the 91 patients with bilaterally normal ultrasound results for the proximal veins. Of the 16 patients with calf DVT, ultrasound was abnormal in 8 (sensitivity 50%, 25-75%). Overall, ultrasound detected 13 of the 26 patients with proximal or isolated calf DVT (sensitivity 50%, 29-71%). The positive predictive value for the whole leg examination was 41% (24-60%). Most thrombi missed by ultrasound were non-occlusive and smaller than 5 cm. We conclude that compression ultrasound is not useful for screening for DVT in symptom-free postoperative high-risk patients.

SEROCONVERSION TO HTLV-III IN HAEMOPHILIAC GIVEN HEAT-TREATED FACTOR VIII CONCENTRATE

Since 1983 when commercial heat-treated factor VIII concentrates became available in the Netherlands 35 seronegative hemophilia patients receiving these products have been included in a prospective study focused on human T-lymphotropic virus type III (HTLV-III) seroconversion. Heating of these concentrates is assumed to reduce the risk of transmission of HTLV-III infection. 2 seroconversion have been recorded in this series; however 1 patient was also receiving nonheated products and was not investigated further. The other patient was a 27-year old man with severe hemophilia A who had been on heat-treated factor VIII home treatment for 2 years when he presented with fatigue and slight fever. He had an unexplained lymphadenopathy of 3 months duration multifocal lymphatic enlargements and splenomegaly. Antibody to HTLV-III was confirmed by immunoblotting. 2 earlier ser were antibody-negative. Although the symptoms receded the HTLV-III antibody titer rose to 7140. The concentrate used by this patient was of US origin. All other routes of infection were excluded. This is the 2nd reported cases of seroconversion in a hemophiliac given heat-treated factor VIII.

Reduction of contact activation related fibrinolytic activity in factor XII deficient patients. Further evidence for the role of the contact system in fibrinolysis in vivo.

In this study the contribution of activation of the contact system to activation of the fibrinolytic system in vivo was investigated in healthy volunteers and in factor XII deficient patients. The plasminogen activating activity in plasma from healthy volunteers after infusion of desamino D-arginine vasopressin (DDAVP) was only partially blocked (for 77%) with specific antibodies to tissue-type plasminogen activator and urokinase type plasminogen activator. The residual activity could be quenched by a monoclonal antibody that inhibits factor XII activity and was not present in patients with a factor XII deficiency. The formation of plasmin upon the DDAVP stimulus as reflected by circulating plasmin-alpha 2-antiplasmin complexes was lower in factor XII deficient patients than in healthy volunteers. Activation of the contact system occurred after DDAVP infusion in healthy volunteers and was absent in factor XII deficient patients. These results indicate that DDAVP induces a plasminogen activating activity that is partially dependent on activation of the contact system and that contributes to the overall fibrinolytic activity as indicated by the formation of plasmin-alpha 2-antiplasmin complexes. This fibrinolytic activity is impaired in factor XII deficient patients which may explain the occurrence of thromboembolic complications in these patients.

The influence of the body temperature on the EEG of the rat

Abstract Experiments on curarised rats suggest that: 1. 1. The body temperature affects the electrical activity of the cerebral cortex. 2. 2. The electroencephalogram remains virtually unaltered at rectal temperatures between 32°–39°Cdg C. 3. 3. When the temperature is reduced below about 30° C. the amplitude of the EEG also gradually decreases. The electrical activity of the brain virtually disappears at a body temperature of 18°–20° C. 4. 4. A rise of the body temperature to 40°–41° C. increases the general amplitude of most electrical components. 5. 5. When the body temperature rises above 41° C. the amplitude of the EEG diminishes relatively rapidly. At a temperature of 44°–45° C. the electrical activity of the brain disappears.