Detection Of Deep Venous Thrombosis Research Articles

Surveillance Venous Duplex Is Not Clinically Useful after Total Joint Arthroplasty When Effective Deep Venous Thrombosis Prophylaxis Is Used

The early detection of deep venous thrombosis (DVT) and treatment with systemic anticoagulation to prevent pulmonary embolism (PE) are essential in the management of patients undergoing total joint arthroplasty (TJA). However, improvements in prophylactic measures have significantly decreased the occurrence of DVT in these patients. The purpose of this study was to determine whether routine postoperative duplex surveillance for DVT remains clinically useful. The medical records of all patients undergoing total knee or total hip arthroplasty between October 1997 and January 2002 at a University Hospital and its Veterans Affairs (VA) affiliate were reviewed. The type of operation and occurrence of complications (e.g., DVT, PE, and hemorrhage) were noted. All patients were treated postoperatively with both enoxaparin 30 mg b.i.d. and bilateral lower extremity sequential compression devices (SCDs). A venous duplex scan was performed prior to discharge. Three hundred ninety-eight patients underwent 441 TJAs for 149 hips and 292 knees. The average age was 65 years (range, 23-95). Venous duplex scans were performed within 1 week (median, 4 days) of operation. Initial inpatient scans revealed acute, ipsilateral DVT in five patients (1.3%). Three patients experienced documented PE-one as an inpatient and two after hospital discharge; both outpatients had negative inhospital duplex scans. One of the 398 patients did not have a duplex scan as an inpatient and returned 6 weeks later with a popliteal DVT. Complications included one upper gastrointestinal hemorrhage, and one patient died postoperatively of unknown causes. These data demonstrate that routine postoperative venous duplex scans rarely found DVT (5 of 398 patients) after TJA when effective prophylaxis was used. Furthermore, surveillance scanning did not enable reliable prediction of PE. Therefore, we conclude that postoperative inpatient surveillance duplex scans for DVT provide very minimal benefit and that a routine screening program is not clinically useful for patients managed with effective DVT prophylaxis.

Flow-independent magnetic resonance venography of the calf.

To show that flow-independent venography that exploit the intrinsic MR properties of blood to isolate vessels from surrounding structures can be used for depiction of peripheral veins and for detection of deep venous thrombosis (DVT). Sequence and parameters were first determined on a theoretical basis. The sequence was then optimized in volunteers (N = 4) for the depiction of the peripheral venous vessels. Qualitative evaluation of the normal venous anatomy was performed in five volunteers. The feasibility of diagnosing DVT of the calf with this method was evaluated with preliminary clinical studies. Excellent depiction of the venous anatomy was achieved in all volunteers with the optimized technique. Very small venous structures, such as superficial, muscular, and perforator veins, were clearly depicted because of the high spatial and contrast resolution capacities of the sequences. In all six patients, DVT findings diagnosed by duplex sonography were also seen on MR venography. Venous anatomy mapping and detection of lower-limb DVT appear feasible using flow-independent MR venograms.

Efecto del neumoperitoneo en la hemodinámica venosa durante la colecistectomía laparoscópica. Influencia de la edad de los pacientes y del tiempo de cirugía

Abdominal hyperpressure developed during laparoscopic cholecystectomy by the effect of pneumoperitoneum represents an obstacle to the venous return that may facilitate thromboembolic complications. The aim of this study was to establish the effect of pneumoperitoneum in venous hemodynamics during laparoscopy. Prospective study of 31 consecutive patients who underwent laparoscopic cholecystectomy. Venous occlusion plethysmography was performed preoperatively, after anaesthetic induction, after insufflation, before pneumoperitoneum release and at the end of surgery. Changes of plethysmography were compared with preoperative values and according to age, obesity, presence of varicose veins and pneumoperitoneum time. Bilateral lower limb venous Duplex scanning was performed at days 1, 7 and 30 to detect deep venous thrombosis (DVT). Average age was 56 years, 66.6% females, 40% obese, 16% with varicose veins and the pneumoperitoneum time was < 45 min in 22.5% patients. Capacitance decreased progressively during surgery and was significantly reduced with pneumoperitoneum. The maximum venous outflow in the first second was reduced significantly at the end of pneumoperitoneum. These reductions were more evident in older patients. Pneumoperitoneum produces plethysmographic changes on venous hemodynamics with a diminished venous return in lower limbs. Older patients have higher risk of thromboembolic complications, while obesity can also increase this risk. However, no DVT was demonstrated in this study.

Patent Foramen Ovale and Recurrent Stroke

Clinical management of patients with acute stroke and the approach used for secondary prevention depends upon clarification of pathogenesis. Although most strokes are a consequence of cerebrovascular disease, ≈15% to 20% of ischemic (nonhemorrhagic) strokes have been attributed to cardiogenic embolism.1 In practice, determination of the stroke mechanism is fraught with uncertainty, particularly when the possibility of thromboembolism emanating from atherosclerotic lesions in the aorta or cervical arteries is considered. When cardiogenic embolism is suspected, cardiac ultrasound is the principal method used to identify the potential source. The finding of left atrial enlargement has been shown to bear a significant relationship to the risk of stroke in a multivariate analysis of population-based data from the Framingham Heart Study2. The most frequent confounding variable is atrial fibrillation, occurring in >2 million patients in North America and in over half of all patients with cardiogenic embolism. Criteria for selection of patients with acute ischemic stroke for transesophageal echocardiography (TEE) to search for a potential cardiac source of embolism are controversial, particularly because cardiogenic embolism is often an uncertain diagnosis that is inferred merely on the basis of the finding of potential cardiac source. Even after extensive investigation, ≈40% of ischemic stroke patients have no clearly identifiable pathogenesis (cryptogenic stroke).3 In one study, 62% of patients younger than 60 years of age without an obvious source of cerebral infarction and 23% of those with arterial lesions had potential sources of cardiogenic embolism identified by TEE ( P =0.0007 for the difference).4 See p 2625 Among the cardiac anomalies detected by TEE that have been implicated as risk factors for stroke are patent foramen ovale (PFO) and atrial septal aneurysm (ASA).5,6⇓ The foramen ovale, a remnant of the fetal circulation, remains patent through adulthood in ≈1 in 4 …

Isolated Calf Vein Thrombosis: Comparison of MR Venography and Conventional Venography after Initial Sonography in Symptomatic Patients

Rationale and Objectives The authors performed this study to compare magnetic resonance (MR) venography and conventional venography in the diagnosis of deep venous thrombosis (DVT) in the calf after sonography. Materials and Methods Sonography was performed in 595 patients who were suspected of having lower-extremity DVT. Patients with positive above-knee duplex sonograms, allergy to iodinated contrast material, renal insufficiency, or cardiac pacemakers and patients who were obese were excluded. The remaining 73 patients were asked to undergo MR venography and conventional venography. All studies were to be performed within 48 hours of the clinical diagnosis and according to standard clinical practice. Images were interpreted by radiologists who were blinded to the results of other modalities. Two separate analyses were performed: one in which conventional venography was used as the standard of reference, and one in which the presence of at least two positive studies for thrombus was considered diagnostic. Results Although 36 patients agreed to participate in the study, only 14 underwent MR venography and conventional venography within 48 hours of the clinical diagnosis. With use of any two positive studies for confirmation, acute DVT was diagnosed in three patients. Conventional venography depicted two of the three cases, whereas sonography and MR venography each depicted all three. The findings were concordant in only five of the 14 patients. Conclusion Moderate discrepancy among modalities was demonstrated. This suggests radiologists should undertake comparisons among these three modalities for the detection of calf DVT. In patients with a high clinical suspicion, a second modality may be useful if the initial study is negative.

Enoxaparin treatment in high-risk trauma patients limits the utility of surveillance venous duplex scanning

Objective: The value of surveillance venous duplex scanning for detecting unsuspected deep venous thrombosis (DVT) in trauma patients who are receiving enoxaparin prophylaxis is open to question. This study was undertaken to determine whether enoxaparin reduced the clinical utility of surveillance scanning and whether management of these patients was altered by findings of the scans. Methods: The medical records of trauma patients who met defined criteria for high DVT risk, admitted during 30 consecutive months, were reviewed. These patients received enoxaparin 30 mg every 12 hours for the duration of their admissions. Per protocol, surveillance lower extremity venous duplex scans were performed within 72 hours of enoxaparin administration and then weekly until patients were discharged from the hospital. The records were reviewed for thromboembolic events (DVT or pulmonary embolism [PE]), patient location and ambulatory status, therapeutic interventions (systemic anticoagulation, vena cava filter), and complications of enoxaparin therapy. Results: A total 241 patients underwent 513 venous duplex examinations (1-13 per patient). Eight patients had DVT on the initial scan; seven of these patients were asymptomatic. Five were treated with anticoagulation and/or vena cava filter placement. Of the 233 patients with initially negative duplex scan results, five patients (2%) developed clinically unsuspected lower extremity DVT while hospitalized. All of these five patients were in an intensive care unit. Three of the five patients had no change in treatment. Two of the five underwent anticoagulation, and one vena cava filter was placed. PE occurred in two hospitalized patients, one of whom was ambulatory, with negative duplex scan results. After hospital discharge, six other patients had symptomatic DVT or PE despite in-hospital scans with negative results. Complications associated with enoxaparin included hemorrhage (2) and thrombocytopenia (8). Conclusions: After initial negative scan results, repeat surveillance duplex scanning during hospitalization detected a low incidence (2%) of DVT in high-risk patients. Furthermore, the detection of unsuspected DVT altered the clinical management of less than 1% of the patients tested. Thus, after a venous duplex scan with negative results and initiation of enoxaparin prophylaxis, subsequent surveillance duplex examinations are not warranted in asymptomatic trauma patients. (J Vasc Surg 2001;34:447-52.)

Artery dissection and arterial thrombus aging: the role of noninvasive magnetic resonance imaging.

Magnetic resonance imaging (MRI) has the potential to study atherosclerotic lesions noninvasively, and it is considered a valid method for the detection of deep venous thrombosis. An organized/old thrombus is considered one of the most thrombogenic substrates. Therefore, noninvasive detection and differentiation between recent and old arterial thrombi is an important goal for diagnostic imaging. Aortic dissection was detected in a rabbit model of atherosclerosis after balloon injury using MR angiography and black-blood cross-sectional images (Figure 1⇓). A low-intensity signal area compatible with slow flow and/or fresh thrombus was seen …

Radiolabeled peptides in the detection of deep venous thrombosis

Venous thrombosis and pulmonary embolism are major clinical problems that result in significant morbidity and mortality. It is estimated that 600,000 cases of pulmonary embolism occur each year in the United States, resulting in the death of approximately 100,000 patients. Most of these pulmonary emboli arise from deep venous thrombosis (DVT). The clinical diagnosis of DVT is unreliable. Only a third of patients with a clinical suspicion of DVT have objective evidence of the disease, and half of patients with proven DVT do not have any clinical symptoms. Although ascending contrast venography is the present standard for the diagnosis of DVT, duplex ultrasonography, which is increasingly used in combination with color Doppler flow imaging, is accepted as a useful clinical afternative to contrast venography. Both contrast venography and ultrasonography are imaging procedures that detect changes in venous anatomy that are caused by the presence of an intraluminal thrombus that is sufficiently formed either to reduce vascular filling with contrast medium or to resist compression. However, these imaging procedures do not reflect the metabolic activity of the clot, and therefore, they may overestimate the presence of active clots. The sensitivity of ultrasonography is also limited by various disease-related and technical factors. An alternative approach to the diagnosis of acute DVT is to detect a molecular marker of acute DVT that is not present in old, organized DVT. Recent advances in biotechnology permit the use of highly specific synthetic peptide or small molecular markers, which are involved in the acute stages of DVT formation and can be labeled efficiently with 99mTc. 99mTc-apcitide, a glycoprotein (GP IIb/IIIa) receptor antagonist previously known as 99mTc-P280, has been approved recently by the Food and Drug Administration for the clinical detection of acute DVT. Two other agents are currently under clinical investigation: 99mTc-DMP 444, which is another GP IIb/IIIa receptor antagonist, and 99mTc-Fibrin-Binding Domain (FBD), a radio-labeled fibrin-binding domain of fibronectin. Different clinical studies have shown a high diagnostic accuracy with these synthetic 99mTc-labeled peptides in the detection of acute DVT. Although further studies are needed to fully appreciate all of the diagnostic potential of these radiopharmaceuticals, the clinical introduction of 99mTcapcitide scintigraphy will certainly be helpful in expanding the use of nuclear medicine in a specific field in which it used to play a relatively marginal role.

Air plethysmography: The answer in detecting past deep venous thrombosis

Purpose: In this study we assessed the accuracy of air plethysmography (APG) as a means of detecting earlier deep venous thrombosis (DVT), in comparison with venography, to develop a preoperative test for patients with varicose veins. Methods: In this retrospective analysis of prospectively acquired data, 202 patients referred with the clinical suspicion of chronic venous obstruction (224 lower limbs) and 41 patients (41 lower limbs) who had symptoms and signs suggestive of DVT, but had deep veins that appeared normal on venography, were studied with both venography and APG. Results: The results of venography were negative for past DVT in 169 legs and confirmed past DVT in 96 limbs. The DVTs were confined to the calf in 19 limbs and were found at popliteal level, more proximal, or both in 77 limbs. A total of 95% of the limbs that had earlier proximal DVT (73 of 77) were identified by means of an APG outflow fraction with occlusion of the superficial veins in the first second (OFs) of less than 28%. This is analogous to the Q wave of the electrocardiogram, which is a means of denoting the presence of myocardial infarction. The specificity rate of the method in the detection of past proximal DVT was 96%, the positive predictive value was 92%, and the negative predictive value was 98%. Conclusion: APG is a practical, inexpensive, easy-to-perform, accurate, noninvasive method for the diagnosis of hemodynamically significant (ie, proximal or extensive calf DVT) chronic venous obstruction that could replace venography. (J Vasc Surg 2001;33:715-20.)

Meta-analysis of thromboembolic prophylaxis after total knee arthroplasty

We performed a meta-analysis of the English literature to assess the efficacy of four common regimes for thromboembolic prophylaxis after total knee arthroplasty: aspirin, warfarin, low-molecular-weight heparin (LMWH) and pneumatic compression. We reviewed 136 articles and abstracts published between January 1980 and December 1997. Papers not using routine venography and a lung scan or angiography to detect deep-venous thrombosis (DVT) and pulmonary emboli (PE) respectively, were excluded. Of the 136 studies, 23 with 6001 patients were selected. The incidence of DVT was 53% (1701/3214) in the aspirin group, 45% (541/1203) in the warfarin group, 29% (311/1075) in the LMWH group, and 17% (86/509) in the pneumatic compression device group. Intermittent pneumatic compression devices and LMWH were significantly better than warfarin (p &lt; 0.0001) or aspirin (p &lt; 0.0001) in preventing DVT. The incidence of asymptomatic PE was 11.7% in the aspirin group (222/1901), 8.2% (101/1229) in the warfarin group and 6.3% (24/378) in the pneumatic compression group. No studies with LMWH used routine lung scans. Warfarin and pneumatic compression were significantly better than aspirin in preventing asymptomatic PE (p &lt; 0.05). The incidence of symptomatic PE was 1.3% (23/1800) in the aspirin group, 0.4% (2/559) in the warfarin group, 0.5% (2/416) in the LMWH group and 0% (0/177) in the pneumatic compression group. No statistically significant difference was noted between the above prophylatic regimes due to the very small incidence of symptomatic PE. Prophylaxis for thromboembolic disease in TKA may have to include a combination of some of the above regimes to incorporate their advantages.

Detection of deep venous thrombosis by DMP 444, a platelet IIb/IIIa antagonist: A preliminary report

Background. We report a method for detection of deep venous thrombosis with a technetium 99m-labeled peptide (DMP 444). The N-methyl-arginine-glycine-aspartic acid sequence on DMP 444 binds the glycoprotein IIb/IIIa receptor on activated platelets (inhibition constant [IC50] for fibrinogen binding = 6 nmol/L). Methods. DMP 444 (23 to 27 mCi) was injected into 11 patients with clinical suspicion of deep venous thrombosis, diagnostic confirmation by ultrasound, and a positive D-dimer test result. Planar images in the anterior and posterior projections were obtained at 10 to 40 minutes, 50 to 80 minutes, and 120 to 150 minutes after injection. Results. No clinically significant adverse effects were noted after DMP 444 administration. One patient (excluded from the analysis) withdrew consent, so image acquisition was not complete. By 10 to 40 minutes after injection, 8 of 10 patients demonstrated an area of increased activity that was clearly related to the abnormality noted on ultrasound. Most patients were taking warfarin (Coumadin) and heparin (n = 8) or heparin (n = 1) and warfarin (n = 1) alone at the time of the imaging. The average time from onset of symptoms to injection of DMP 444 was 5 days (range 1 to 18 days). Conclusion. These preliminary human studies indicate that DMP 444 is safe and may be of value in the diagnosis of deep venous thrombosis. (J Nucl Cardiol 2000;7:359–64.)

Numerical model of deep venous thrombosis detection using venous occlusion strain gauge plethysmography.

Strain gauge plethysmography (SGP) is a non-invasive method used in the detection of deep venous thrombosis (DVT). The technique is based on the measurement of calf volume changes in response to venous occlusion by a thigh cuff, the volume changes reflecting the rates of arterial inflow and venous outflow. A numerical model of the blood circulation within the limb and the response of this to a SGP test has been derived, based on treating the different parts of the circulatory system in the leg as resistance and capacitance elements. The simulation results were compared with clinical studies and support the ability of SGP to detect non-occlusive clots of more than 50-60% of the lumen, as well detecting calf vein occlusion. The non-linear behaviour of the venous compliance with intra-luminal pressure appears to be a particularly important factor within the model. In addition, increases in venous tone due to post-operative venospasm were shown to be a potential source of false positive results.

Lower‐extremity Doppler for Deep Venous Thrombosis—Can Emergency Physicians Be Accurate and Fast?

Clinical diagnosis of lower-extremity (LE) deep venous thrombosis (DVT) requires confirmation by an imaging study before committing the patient to anticoagulation therapy. Studies have shown that demonstrating compressibility of leg veins under ultrasound is accurate for ruling out DVTs when performed by vascular specialists. Although LE Doppler has become the preferred test for diagnosing DVTs, it is not always available 24 hours per day. To evaluate the accuracy and speed with which emergency physicians (EPs) could perform LE color duplex ultrasonography for the detection of DVT. Patients presenting to an urban community emergency department (ED) between August 1, 1998, and March 3, 1999, were enrolled into this prospective study. The EPs, who underwent brief and standardized training, scanned patients at high risk for DVT with leg pain, swelling, or both. Physicians performed color duplex ultrasound examinations with compression at the common femoral and popliteal veins. The time until completion of the ED scan was recorded with a standardized method. The vascular laboratory performed a complete duplex ultrasound examination within eight hours. One hundred twelve patients were enrolled in the study, with 34 positive for DVT. The median examination time was 3 minutes 28 seconds (95% CI = 2 min 45 sec to 4 min 2 sec; IQR 3 min 9 sec). Times ranged from 1:02 to 18:20 minutes. The ED results had a high correlation with vascular laboratory studies, giving a kappa of 0.9 and a 98% agreement (95% CI = 95.4% to 100%). Emergency physicians can perform LE duplex ultrasound examinations accurately and quickly.

High Prevalence of Detectable Deep Venous Thrombosis in Patients With Acute Pulmonary Embolism

Because specific studies are unavailable, the exact prevalence of detectable "residual" deep venous thrombosis (DVT) in patients with acute pulmonary embolism (PE) is unknown. Review of clinical records and radiologic documents of consecutive patients. Pulmonary diseases and radiology departments at a university hospital. All patients hospitalized in the Department of Pulmonary Diseases with a diagnosis of acute PE during a 5-year period (1984 to 1988). During this period, the diagnosis of PE was based exclusively on pulmonary angiography, and bilateral lower limb venography was routine in patients with proven acute PE. Among 228 consecutive patients with angiography-proven PE, 213 underwent bilateral lower limb venography within 48 h of the diagnosis. Venography demonstrated DVT in 174 patients (81.7%; 95% confidence interval, 76.5 to 86.9%), including 128 patients (60%) with proximal DVT. Signs or symptoms of DVT were present in only 72 patients (42%) with DVT. The prevalence of detectable DVT was significantly lower in patients with recent pelvic surgery or delivery (6 of 12, 50%) than in the other patients, whatever their individual risk factors (p < 0.05). The mean pulmonary vascular obstruction was significantly lower in patients with normal venography than in patients with detectable DVT (37.6 +/- 20.9% vs 48.4 +/- 21.7%; p = 0.007). Lower limb venography demonstrates a high prevalence (82%) of residual DVT in patients with angiography-proven PE. These data should be taken into account in the diagnostic and therapeutic management of patients with suspected or proven PE.

Clinically suspected pulmonary embolism: use of bilateral lower extremity US as the initial examination--a prospective study.

To determine the prevalence of deep venous thrombosis (DVT) and evaluate the use of symptoms and risk factors as selection criteria in the patient population undergoing lower extremity ultrasonography (US) as an initial examination for suspected pulmonary embolism (PE). One hundred eighty-two consecutive patients referred for bilateral lower extremity US as the first examination for suspected PE were evaluated prospectively for predisposing factors and symptoms of DVT. Patients were placed into four groups: group 1, no symptoms or risk factors; group 2, both symptoms and risk factors; group 3, only risk factors; group 4, only symptoms. The prevalence of DVT detected at lower extremity US in each group was determined. There were 89 patients in group 1, 12 in group 2, 43 in group 3, and 38 in group 4, with a DVT prevalence of 0%, 25%, 14%, and 24%, respectively. There was no significant difference in DVT prevalence between groups with symptoms or risk factors but a significant difference between these groups and the group lacking both symptoms and risk factors. Lower extremity US as the initial examination in patients suspected of having PE should be used only in those patients who have symptoms or risk factors for DVT. This would substantially decrease the number of examinations performed without a decline in DVT detection.

The use of power doppler ultrasound in the diagnosis of isolated deep venous thrombosis of the calf

While ultrasound has been well accepted as an accurate test for the diagnosis of both femoral and popliteal deep venous thrombosis (DVT), its role in the detection of calf DVT has been less clear. There have been variable results between studies in the accuracy of colour Doppler or compression sonographic techniques in demonstrating calf DVT. Many of these studies have suffered from high rates of technically inadequate examinations. Power Doppler (colour Doppler energy) has a higher sensitivity than conventional colour Doppler. It should therefore allow the detection of slow venous flow in patent vessels, that may not be demonstrated by conventional colour Doppler. This should decrease the number of technically inadequate examinations as well as decreasing the false-positive rate of the test. A prospective blinded reader study was undertaken comparing power Doppler to the gold standard venography, in the diagnosis of isolated calf deep venous thrombosis (DVT). Both examinations were successfully performed in 50 patients, in whom proximal DVT had been excluded by compression ultrasonography. Fifteen patients had positive evidence of an isolated calf DVT on the gold standard technique, venography. Power Doppler demonstrated a sensitivity of 100%, a specificity of 79%, a positive predictive value of 71% and a negative predictive value of 100%, in detecting an isolated calf DVT. There were no technically inadequate ultrasound examinations. Where venous flow is demonstrated, power Doppler is a highly accurate test in excluding a calf DVT. The specificity of the test, however, is limited, as the absence of flow does not always signify a DVT.

CT-phlebography. A new method for the diagnosis of venous thrombosis of the upper and lower extremities

Spiral CT venography is a new method in vascular imaging, which is an accurate tool for the evaluation of deep venous thrombosis in the evaluation of deep venous thrombosis in the lower and upper extremity. 102 lower extremities and 12 upper extremities were evaluated for deep vein thrombosis using spiral-CT-venography. The results were compared with findings of ascending venography, color coded duplex sonography and clinical follow up. Spiral CT venography of the lower extremity showed a sensitivity of 100% and a specifity of 96%. The quality of venous opacification with CT venography compared with ascending venography was superior in all venous segments. Spiral CT venography is a valuable tool for the detection of deep venous thrombosis. Advantages of the method are the reduction of the amount of contrast material necessary for opacification and the detection of perivascular soft tissue alterations. The application of CT venography is limited due to higher costs and radiation dosage.

In vitro studies of a new thrombus-specific ultrasound contrast agent

Ultrasound is used as a primary diagnostic technique for the detection of deep venous thrombosis. The purpose of this study is to describe the development of a new thrombus-specific ultrasound contrast agent: The linear hexapeptide (lysine-glutamine-alanine-glycine-aspartate-valine) was synthesized and coupled to a lipid moiety. The targeted lipid was then incorporated into the lipid blend for the contrast agent Aerosomes (ImaRx, Tucson, AZ, USA). The lipid blend was used to entrap perfluorobutane microbubbles. The microbubbles were sized and studied in vitro for acoustic stability, binding to blood clot, and ultrasound enhancement in vitro of blood clot. The results showed the mean size of the specific ultrasound contrast agent (MRX-408) was about 2.0 μm. The microbubbles appeared as smooth spherical structures. Microscopy showed that the targeted bubbles bound to blood clot whereas control, nontargeted bubbles did not bind to blood clot. In vitro acoustic study showed similar stability of the microbubbles compared with control microbubbles. The targeted microbubbles enhanced blood clot in vitro whereas nontargeted microbubbles did not enhance clot. Thus this promising new thrombus-specific ultrasound contrast agent could potentially improve detection of thrombosis by ultrasound and might be useful for distinguishing between new and old thrombosis. In vivo studies are in progress.

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

The standard diagnostic approach in patients suspected of having pulmonary embolism starts with perfusion-ventilation lung scanning. If the resulting scan is not diagnostic, pulmonary angiography should be done. The use of tests for deep venous thrombosis has been advocated as an adjunct to establishing the diagnosis of pulmonary embolism, but no prospective studies have provided adequate information about the value of these tests. To determine the accuracy and potential clinical utility of compression ultrasonography in the diagnosis of pulmonary embolism. Prospective cohort study with blinded assessment of ultrasonographic results. Teaching hospital. 397 consecutive inpatients and outpatients in whom pulmonary embolism was clinically suspected. Sensitivity and specificity of compression ultrasonography. Perfusion-ventilation scanning and angiography were the conjoint gold standard for determining the presence or absence of pulmonary embolism. Also calculated were the number of angiograms and lung scans avoided and the number of patients unnecessarily treated when compression ultrasonography was included in the diagnostic strategy. The overall sensitivity of compression ultrasonography for deep venous thrombosis in patients with pulmonary embolism was 29% (95% CI 22% to 37%); the specificity was 97% (CI, 94% to 99%). Adding ultrasonography to the diagnostic approach before lung scanning would avoid approximately 14% of lung scans and 9% of angiograms but would lead to unnecessary treatment of 13% of patients who have an abnormal ultrasonographic result (2% to 4% of all those receiving anticoagulation). When compression ultrasonography is done only in patients with a nondiagnostic lung scan, 9% of angiographies are prevented at the cost of unnecessarily treating 26% of patients who have an abnormal ultrasonographic result (2% of all patients receiving anticoagulation). The diagnostic value of compression ultrasonography for the detection of deep venous thrombosis in patients suspected of having pulmonary embolism is limited; the gain in diagnostic efficiency obtained through the use of ultrasonography may be offset by a loss in diagnostic accuracy.

The accuracy of color Doppler flow imaging for the detection of symptomatic deep venous thrombosis in Chinese patients.

To evaluate the ability of color Doppler flow imaging (CDFI) to detect deep venous thrombosis (DVT), which is difficult to diagnose clinically, 67 limbs of 60 patients who presented with clinical signs strongly indicative of DVT during the period between June 1988 and June 1992, were examined. The iliac, common femoral, and superficial femoral veins were assessed with the patient in the supine position, and the popliteal vein was examined with the patient prone. Gentle but firm compression with the transducer probe was used to test for the presence of DVT. Ascending contrast venograms were also obtained within 24 h after the ultrasound procedure, with venography being used as the standard for comparison with CDFI. DVT was identified in 63 limbs by contrast venography and in 62 limbs by CDFI. The sensitivity and specificity of CDFI were 98.4% and 100%, respectively, while the positive and negative predictive values were 100% and 80%, respectively. The thromboses were classified into three patterns: the filling type, the local type, and mural thrombus, detected in 63%, 27%, and 10%, of the limbs respectively, with the filling type being the most common in this series. The results of our study illustrated that CDFI is highly sensitive and specific for detecting symptomatic DVT and that it should be gradually substituted for venography in such patients.