Distribution of thrombosis in patients with symptomatic deep vein thrombosis. Implications for simplifying the diagnostic process with compression ultrasound

BACKGROUND: Two different diagnostic strategies are used to perform compression (real-time) ultrasound for the diagnosis of clinically suspected deep-vein thrombosis. One is to examine the entire proximal venous system from common femoral to distal popliteal vein; the other is a limited examination of only the common femoral and the entire popliteal vein. The latter strategy, which is less time-consuming and requires less expensive equipment, is based on a strong impression from prospective studies using limited compression ultrasound that proximal vein thrombi always involve the common femoral or popliteal vein. This impression, which is supported by the demonstrated safety at long-term follow-up of not treating patients whose limited compression ultrasound is normal at presentation and then repeated within the next week, has not been tested in a formal study. Therefore, we reviewed a large series of venograms performed in consecutive patients with clinically suspected venous thrombosis to determine the distribution of venous thrombosis in symptomatic patients. METHODS: Venograms were performed using 150 mL of radiographic contrast material. Before the study, a panel of experts agreed on the standardized criteria for the assessment of venograms. Venograms were adjudicated blindly for the presence of deep vein thrombosis and to determine the distribution of proximal vein thrombosis and isolated calf-vein thrombosis, the size of proximal thrombi, and whether they were occlusive or nonocclusive. Subsequently, the duration of symptoms was related to the venographic findings. RESULTS: Five hundred sixty-two venograms from consecutive patients with a first episode of clinically suspected deep vein thrombosis were adjudicated. Of these, 20 (3.6%) were inadequate for interpretation. In the remaining 542, venous thrombosis was demonstrated in 189 instances (prevalence, 35%; 95% confidence interval, 31% to 39%) and were located in the proximal veins in 166 (88%; 95% confidence interval, 82% to 92%) venograms. Isolated calf-vein thrombosis was present in the remaining 23 (12%; 95% confidence interval, 8% to 18%) venograms. Proximal with concurrent calf thrombosis was detected in 164 (99%) of the 166 patients. Proximal thrombi involved only the popliteal vein in 16 (10%); the popliteal and superficial femoral veins in 70 (42%); and the popliteal, superficial, and common femoral vein in eight (5%); whereas thrombi involving the entire proximal deep venous system were detected in 58 (35%) venograms. Isolated thrombosis of the superficial femoral, common femoral, and iliac vein was not observed. Proximal venous thrombi were occlusive in 146 (88%) patients. No relation between the duration of symptoms and the extent or the occlusiveness of venous thrombi could be demonstrated. CONCLUSIONS: Most symptomatic patients have extensive occlusive proximal vein thrombosis at the time of presentation. Thrombi isolated to the superficial femoral or iliac vein were not observed in this large sample of consecutive patients. Our data support the use of the relatively simple, inexpensive, and rapid compression ultrasound method that limits the examination of the proximal veins to the common femoral and popliteal veins.     

Accuracy of clinical assessment of deep-vein thrombosis

The clinical diagnosis of deep-vein thrombosis is generally thought to be unreliable. From experience, we hypothesised that this widely held view might be incorrect. We developed a clinical model and prospectively tested its ability in three tertiary care centres to stratify symptomatic outpatients with suspected deep-vein thrombosis into groups with high, moderate, or low probability groups of deep-vein thrombosis. We evaluated our clinical model in combination with venous ultrasonography to determine the potential for an improved and simplified diagnostic approach in patients with suspected deep-vein thrombosis. All patients were clinically assessed to determine the probability for deep-vein thrombosis before they had ultrasonography and venography. All tests were performed and interpreted by independent observers. In 529 patients, the clinical model predicted prevalence of deep-vein thrombosis in the three categories: 85% in the high pretest probability category, 33% in the moderate, and 5% in the low category. There was no statistical difference in the performance of the model in the three centres. The model demonstrated excellent interobserver reliability (Kappa = 0.85). There were important differences with ultrasonography between the high and low pretest probability groups for both positive predictive values (100% (95% CI, 94-100%) vs (63% [35-85%], respectively). Thus, use of the clinical model combined with ultrasonography would decrease the number of false positive and negative diagnosis if venography were done when the ultrasound result and pretest probability were discordant. The diagnostic process could be simplified by excluding those patients with low pretest probability and normal ultrasound results from serial testing.     

Deep-vein thrombosis

Deep-vein thrombosis is an important complication of several inherited and acquired disorders, but may also occur spontaneously. Prevention of recurrent venous thrombosis and pulmonary embolism is the main reason for accurate diagnosis and adequate treatment. This seminar discusses only symptomatic deep-vein thrombosis. The diagnosis can be confirmed by objective tests in only about 30% of patients with symptoms. Venous thromboembolic complications happen in less than 1% of untreated patients in whom the presence of venous thrombosis is rejected on the basis of serial ultrasonography or ultrasonography plus either D-dimer or clinical score. Initial anticoagulant treatment (intravenous or subcutaneous heparin) should continue until oral anticoagulant treatment, started concurrently, increases the international normalised ratio above 2.0 for more than 24 h. The optimum duration of oral anticoagulant treatment is unresolved, but may be guided by the presence of temporary or persistent risk factors or presentation with recurrent venous thromboembolism.     

Molten Carbonate Fuel Cell electrochemistry modelling

A Fuel Cell (FC) is an electrochemical device which produces electric energy in DC. In order to support design control for the electrical system connected to it, it is necessary to work out a suitable representation of the fast dynamics involved. Therefore, in this work, a mathematical model, based on first principles and including both dynamical equations and algebraic relations, is described for electrochemical reactions, with the related formation of potential differences and anion and cation accumulation phenomena, in a Molten Carbonate Fuel Cell (MCFC). The model is formally consistent and it has been validated against experimental results, such as steady-state power and voltage versus current curves.     

Radial MV networks voltage regulation with distribution management system coordinated controller

The connection of a great number of distributed generation (DG) plants may cause a critical voltage regulation problem in actual medium voltage (MV) radial distribution networks. After a synthetic survey of different strategies reported in literature to solve this problem, a proposal for an active management of the distribution system which makes use of an innovative controller that coordinates the on load tap changer (OLTC) action with the regulation of reactive exchanges between DG plants and feeders, is presented.     

Compression ultrasonography for diagnostic management of patients with clinically suspected deep vein thrombosis: prospective cohort study

OBJECTIVE: To evaluate the safety of withholding anticoagulant treatment from patients with clinically suspected deep vein thrombosis but normal findings on compression ultrasonography. DESIGN: Compression ultrasonography was done with a simplified diagnostic procedure limited to the common femoral vein in the groin and the popliteal vein extending down to the trifurcation of the calf veins. Patients with normal ultrasonography findings at presentation were retested 1 week later. MAIN OUTCOME MEASURE: The incidence of venous thromboembolic complications during follow up for 6 months in patients in whom anticoagulant treatment was withheld on the basis of normal results on two ultrasonography tests 1 week apart. SETTING: University research centres in four hospitals. RESULTS: A total of 1702 patients were included in the study. Abnormal results on compression ultrasonography at presentation or at 1 week were found in 400 and 12 patients, respectively, for a prevalence of deep vein thrombosis of 24%. None of the patients were lost to follow up. Venous thromboembolic complications during the week of serial testing occurred in a single patient and in eight patients during 6 months' follow up, resulting in a cumulative rate of venous thromboembolic complications of 0.7% (95% confidence interval 0.3% to 1.2%). The mean number of extra hospital visits and additional tests required per initially referred patient was 0.8. CONCLUSION: It is safe to withhold anticoagulant treatment from patients with clinically suspected deep vein thrombosis who have a normal result on compression ultrasonography at the time of presentation and at 1 week.     

Effects of mental health and reactance-reducing information on offenders' compliance with court-mandated psychiatric evaluations.

Using psychological reactance theory, we examined the effects of 3 educational interventions on the appointment-related behaviors of offenders who were mandated by court to participate in psychiatric evaluations. A posttest-only control group design was used to determine the effects of type of information received on 120 probationers' preappointment requests for additional information, appropriate cancellation of appointments, and compliance with referrals. Ss were provided minimal information, basic mental health information, reactance-reducing information, or a combination of basic mental health and reactance-reducing information. Results indicate that type of information received affected Ss' compliance. The theoretical and practical implications are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Recurrence of venous thromboembolism in patients with familial thrombophilia

BACKGROUND: Treatment of patients with deep vein thrombosis and an antithrombin or protein C or S deficiency is based on case reports and personal experience. OBJECTIVE: To systematically assess the risk for recurrence of venous thromboembolism after a first episode in patients with these deficiencies, a literature review and retrospective family cohort study were performed. METHODS: For the literature review, the annual incidence of a first recurrent venous thromboembolism was assessed for each deficiency by dividing the number of venous thromboembolic events by the number of years at risk. For the family cohort study, 1- and 5-year cumulative incidences of first recurrence were calculated based on medical histories taken in relatives of consecutive patients in whom venous thromboembolism and a deficiency were diagnosed. RESULTS: For the literature review, the annual incidence of a first recurrent venous thromboembolism in patients with antithrombin or protein S deficiency ranged from 13% to 17% and 14% to 16%, respectively. For the family cohort study, the 1- and 5-year cumulative incidences of recurrent venous thromboembolism were 10% (95% confidence interval, 1%-19%) and 23% (95% confidence interval, 10%-36%), respectively. Warfarin sodium (Coumadin) prophylaxis was associated with 2 venous thromboembolic events in 141 years at risk (1.4% per year), in contrast with 19 events in 709 years at risk (2.7% per year) without prophylaxis (difference, -1.3%; 95% confidence interval, -3.5% to 1.0%). CONCLUSIONS: The annual incidence of recurrent venous thromboembolism is high during the first years following a first episode, but seems to decline thereafter. Therefore, our results challenge current practice of prescribing lifelong warfarin therapy after a first or second episode of venous thromboembolism in patients with antithrombin or protein C or S deficiency.