I assessed the accuracy of two clinical prediction rules, the d-dimer blood test and point of care ultrasound for diagnosing lower limb deep vein thrombosis. Emergency physicians were trained in ultrasound and prospectively scanned emergency department patients with suspected deep vein thrombosis. Accuracy of the Wells and AMUSE rules and the ultrasound result was compared to radiology-performed ultrasound and a 90-day clinical outcome. Univariate and multivariate analyses were performed assessing which factors were associated with the outcome. The sensitivity and specificity of the Wells score for the clinical outcome was 85.7% and 68.5%; the AMUSE score 85.7% and 54.4%. Ultrasound had a sensitivity of 91.7% and specificity of 91.7% for radiology-diagnosed thrombus and 78.6% and 95.0% for clinical outcome. The odds ratio of a positive outcome with a positive ultrasound was 65.1. After receiving the ultrasound training program, emergency physicians were unable to demonstrate sufficient accuracy to replace current diagnostic strategies.

This master thesis describes a journaling system for compression ultrasonography and a clinical assessment system for deep vein thrombosis (DVT). We evaluate Support Vector Machines (SVM) models with linear- and radial basis function-kernels for predicting deep vein thrombosis, and for facilitating creation of new clinical DVT assessment. Data from 159 patients where analysed, with our dataset, Wells Score with a high clinical probability have an accuracy of 58%, sensitivity 60% and specificity of 57% these figured should be compared to those of our base models accuracy of 81%, sensitivity 66% and specificity 84%. A 23 percentage point increase in accuracy.The diagnostic odds ratio went from 2.12 to 11.26. However a larger dataset is required to report anything conclusive. As our system is both a journaling and prediction system, every patient examined helps the accuracy of the assessment. / I denna rapport beskrivs ett journalsystem samt ett system för klinisk bedömning av djupvenstromboser.Vår modell baserar sig på en stödvektormaskin (eng. Support Vector Machine) med linjär och radial basfunktion för att fastställa förekomsten av djupa ventromboser samt att hjälpa till i skapandet av nya modeller för bedömning. 159 patientjournaler användes för att fastställa att Wells Score har en klinisk precision på 58%, 60% sensitivitet och specificitet på 57% somkan jämföras med våran modell som har en precision på 81%, 66% sensitivitet och specificitet på 84%. En 23 procentenheters ökning i precision.Den diagnostiska oddskvoten gick från 2.12 till 11.26. Det behövs dock en större datamängd för att rapportera något avgörande. Då vårt system både är för journalskapande och klinisk bedömning så kommer varje undersökt patient att bidra till högre precision i modellen.

Patients with inflammatory bowel disease (IBD) are known to have an increased propensity for thromboembolic events. Like any patient with a high risk of event recurrence, most of these patients can be managed successfully with long-term warfarin therapy. We present the case of a 66-year-old woman with Crohn's disease who, despite careful attention to the management of her international normalized ratio, developed a new deep vein thrombosis and required inferior vena cava filter placement in addition to ongoing warfarin therapy to prevent recurrent pulmonary emboli. This report serves as a reminder to physicians to have a low threshold for diagnosing thromboembolic events in patients with IBD, even if they are presumed to be adequately anticoagulated. Known and theoretical contributing factors to this increased clotting tendency are also reviewed.

Background: Recent studies have suggested that patients with idiopathic pulmonary fibrosis (IPF) may have a higher risk of venous thromboembolism (VTE) compared to general population even though the results were inconsistent. Objective: To investigate the risk of VTE among patients with IPF. Methods: Comprehensive literature review using MEDLINE and EMBASE database were performed to identify studies that compared the risk of VTE among patients with IPF to general population. Effect estimates from each study were combined together using random effect model, generic inverse variance method of DerSimonian and Laird. Results: Out of 510 retrieved articles, 5 studies met the inclusion criteria and were included in the meta-analysis. A significant risk of VTE in patients with IPF was observed with the pooled risk ratio of 2.11 (95% confidence interval, 1.28-3.48). The heterogeneity was moderate with I2 of 64%. Conclusion: An approximately 2-fold increased risk of VTE among patients with IPF was observed in this meta-analysis.

Kidney and inferior vena cava (IVC) abnormalities with extensive deep vein thrombosis (DVT) is a very rare cause of DVT and has a diverse clinical presentation. Computed tomography (CT) angiography is the gold standard for diagnosis and treatment including thrombectomy, thrombolysis and systemic anticoagulation. We present a rare case of active young healthy male admitted with acute onset of right lower extremity pain and swelling who was found to have extensive DVT on doppler ultrasound. CT abdomen showed extensive clot burden involving right common femoral vein extending into internal and external iliac veins associated with IVC hypoplasia and hypoplastic left kidney. Patient underwent urgent thrombectomy, catheter directed thrombolysis and was discharged home in stable condition on oral anticoagulation.

<p>The effect of direction thrombin inhibition on acute deep vein thrombosis (DVT) stability has not been defined and could contribute to pulmonary embolism (PE) risk. Direct thrombin inhibitors (DTIs) effectively inhibit free and clot-bound thrombin, which could potentiate thrombus instability through disruption of platelet, fibrin, and FXIIIa stabilizing mechanisms. This could manifest as increased thrombus embolization. A clinically relevant mouse model of DVT stability could further our understanding of venous thrombosis pathophysiology and define the effect of direct thrombin inhibition on PE. We hypothesized that acute DTI administration would decrease acute DVT stability and potentially increase PE risk. Platelets were labeled <em>in vivo</em>, femoral vein thrombosis was induced using FeCl₃, and lepirudin (8U/g) was administered <em>after</em> clot formation. Using intravital videomicroscopy (IVM), real time embolization was quantified as a measurement of thrombus stability. Thrombus stability increased in the control group and decreased in the lepirudin-treated group over two hours. The decrease in α₂-antiplasmin (α₂-AP) content within lepirudin-treated thrombi, compared to control thrombi, could possibly contribute to the observed decrease in thrombus stability. Continued growth and embolization established the dynamic nature of formed thrombi. In both groups, emboli were detected in the pulmonary artery circulation. Therefore, we successfully developed a mouse model of venous thrombus stability, which imitated the clinical progression of DVT to PE. DTI administration in the acute DVT setting could decrease thrombus stability, demonstrated through increased embolization and PE. This model could be useful in examining the effect of other antithrombotics and risk factors settings on DVT stability.</p> / Master of Science (MSc)

Over seven million Americans suffer from Chronic Venous Insufficiency (CVI), a painful and debilitating disease that affects the superficial and deep veins of the legs. Problems associated with CVI include varicose veins, bleeding, ulcerations, severe swelling, deep vein thrombosis, and pulmonary embolism, which may lead to death. The presence of CVI results from damaged (incompetent) one-way vein valves in leg veins. These valves normally allow forward flow of blood to the heart, and prevent blood from pooling at the feet. However, incompetent valves allow reflux of blood, causing clinical problems. There are few effective clinical therapies for treating CVI. Vein valve transplantation is a surgical option for treatment. However, it is often difficult to find suitable donor valves. Very few prosthetic valves developed in the past have demonstrated sufficient clinical or mechanical functionality. Persistent problems include thrombus formation, leaking valves, and valves that do not open at physiologic pressure gradient. The primary objective of this research was to develop a clinically relevant functional prosthetic vein valve. The novel prosthetic valve is flexible, biocompatible, has low thrombogenecity, and is easy to manufacture. It was designed to address well-defined consumer needs and functional design requirements. The valve was required to 1) withstand 300 mmHg of backpressure with leakage less than 1.0 mL/min, 2) open with a pressure gradient less than 5 mmHg, and 3) meet criteria 1 and 2 after 500,000 cycles of operation. The valve met these design requirements in bench testing. The valve can open with a pressure gradient of 2.6 0.7 mmHg, and can withstand 300 mmHg with leakage less than 0.5 mL/min. The valve remained functional after opening and closing over 500,000 times. The valve presented in this research is operationally functional, and is a potential solution for treating venous incompetence in CVI patients.

Chronic Venous Insufficiency (CVI) is a condition in present in almost 27% of adults in which an insufficient amount of blood is pumped back to the heart due to damaged or poorly apposed one-way valves in the leg veins. During forward flow, vein valves allow blood to return to the heart while posing very little resistance to the flow. During gravity-driven reverse flow, normal valves close and prevent blood from flowing backward through the valve. Incompetent, or damaged, vein valves cannot prevent this reverse flow and lead to a pooling of blood at the feet. CVI is a painful disease presents itself in various ways, including varicose veins, ulcerations of the lower extremities, and severe swelling. Current therapies and treatments include compressive stockings, destruction or removal of affected veins, valve repair, and valve transplants. The implantation of prosthetic vein valves is a future treatment option that does not require an invasive surgery, human donor, or lengthy hospital stay. While no prosthetic vein valves are currently commercially available, this thesis describes the design, verification, and validation of a novel prosthetic vein valve. Verification tests include CFD simulations, functional tests, mechanical tests, and in vitro thromogenicity tests. The validation of the device was done through an animal study in sheep external jugular veins. CFD analysis verified that shear rates within the valve support its lower thrombogenicity as compared to a previous vein valve. Benchtop tests demonstrate superiority in short-term patency over a previous polymer valve. In a sheep study, patency was shown at 6 weeks, surpassing many autograft valves and showing great potential to meet the goal of 3 month patency in sheep.

Thesis submitted in fulfilment of the requirements for the degree of Doctor of Technology: Radiography in the Faculty of Health and Wellness Sciences at the Cape Peninsula University of Technology 2013 / Background. Ultrasound has until recently been regarded as a sophisticated examination reserved for tertiary health care. In reality it is well suited to the district or primary health-care situation. A DVT (deep vein thrombosis) is an important complication of the treatment of TB and this can lead to more devastating sequelae such as a pulmonary embolus. Many DVTs are clinically silent, making the diagnosis difficult. Method. This study was a prospective, longitudinal observational study. The study documented the incidence of DVTs and their onset, assessed certain aspects in an attempt to identify some risk factors, and noted the most common position of the DVT in a TB population. The feasibility of a sonographer-led ultrasound clinic for the diagnosis of DVTs was also assessed. This was achieved by screening the in-patient population at a district TB hospital. The participants received up to four routine duplex Doppler compression ultrasound examinations of the venous system of the lower extremities on week 0, week 4, week 8 and week 14. In addition a single abdominal ultrasound was performed at week 0. Results The incidence of DVTs in this TB population was 15.3%. A median of day 10 from commencing TB treatment was identified as the most common day to develop a DVT. The popliteal vein was the most frequent position for a DVT. Several statistically significant factors were identified, including a decreased ambulatory status, TB regimen and the use of anticoagulants. Only 52% of the DVTs were clinically symptomatic. The clinical evaluation for a DVT diagnosis in this study population had a sensitivity of 52.4% and a specificity of 65.3%. The positive predictive value (PPV) was 21.7%. Of the abdominal ultrasound reports there were 75.5% (281) abnormal reports, 22.5% (n = 90) normal reports and 4.5% (n = 18) with no report. Conclusion This body of work has shown how an effective ultrasound service can be provided at a district level TB hospital successfully administered by a trained ultrasonographer. This also facilitated a screening service to diagnose both symptomatic and asymptomatic deep vein thromboses in newly diagnosed tuberculosis patients. This study confirmed a higher rate of DVT in newly diagnosed TB patients than has been previously seen. It also provided detail on additional risk factors. The study illustrates the poor performance of clinical signs and symptoms as a trigger for further investigation for the confirmation of a DVT. Given the frequency and impact of the embolic complications of DVT, this study provides a strong justification for further research into routine serial ultrasonic screening and/or prophylactic antithrombolytics in newly diagnosed TB patients. As well as the DVT ultrasound scans there was the ancillary service offered by the research sonographers. This included an abdominal scan that detected abdominal pathology in 75% of the scans performed. An ultrasound scan is not pathognomonic but it does provide significant insight into the extent of some of the abdominal pathologies seen in TB patients. The information provided from this study gives a good indication of the problem that DVTs present in this population and the complexities of the disease TB. It is hoped that the results from this study will better equip the medical team in the non-tertiary situation to be vigilant for the presence of a DVT and educate them on the usefulness of the ultrasound scan.

Background: Guidelines recommend the use of multiple pharmacologic agents and/or mechanical compressive devices for prevention of venous thromboembolism, but preference for any specific agent is no longer given in regard to safety or efficacy. Objective: To compare postoperative bleeding rates in patients receiving enoxaparin, rivaroxaban, or aspirin for thromboprophylaxis after undergoing elective total hip arthroplasty or total knee arthroplasty. Methods: This retrospective cohort analysis evaluated patients who received thromboprophylaxis with either enoxaparin, rivaroxaban, or aspirin. All data were collected from the electronic medical record. The primary outcome was any postoperative bleeding. Results: A total of 1244 patients were included with 366 in the aspirin, 438 in the enoxaparin, and 440 in the rivaroxaban arms. Those who received aspirin or enoxaparin were less likely to experience any bleeding compared to those patients who received rivaroxaban (P <.05). There was also a lower rate of major bleeding in these groups, but the differences were not significant. Conclusions: Aspirin and enoxaparin conferred similar bleeding risks, and both exhibited less bleeding than patients who received rivaroxaban.