Doppler ultrasound in the diagnosis of venous thrombosis

Translational molecular imaging: Thrombosis imaging with positron emission tomography

A key focus of cardiovascular medicine is the detection, treatment, and prevention of disease, with a move towards more personalized and patient-centred treatments. To achieve this goal, novel imaging approaches that allow for early and accurate detection of disease and risk stratification are needed. At present, the diagnosis, monitoring, and prognostication of thrombotic cardiovascular diseases are based on imaging techniques that measure changes in structural anatomy and biological function. Molecular imaging is emerging as a new tool for the non-invasive detection of biological processes, such as thrombosis, that can improve identification of these events above and beyond current imaging modalities. At the forefront of these evolving techniques is the use of high-sensitivity radiotracers in conjunction with positron emission tomography imaging that could revolutionise current diagnostic paradigms by improving our understanding of the role and origin of thrombosis in a range of cardiovascular diseases.

Venous thromboembolism and anticoagulation in spinal cord lesion rehabilitation inpatients: A 10-year retrospective study

BACKGROUND

Venous thromboembolism (VTE) is a concern following the onset of spinal cord lesions (SCL).

OBJECTIVES

To assess the current efficacy and risks of anticoagulation after SCL and consider changes in thromboprophylaxis.

METHODS

This retrospective cohort study included individuals admitted to inpatient rehabilitation within 3 months of SCL onset. Main outcome measures were the incidence of deep vein thrombosis (DVT), pulmonary embolism (PE), bleeding, thrombocytopenia, or death, which occurred within 1 year of the SCL onset.

RESULTS

VTE occurred in 37 of the 685 patients included in the study (5.4%, 95% CI 3.7-7.1%, 2.8% PE), and in 16 of 526 patients who received prophylactic anticoagulation at rehabilitation (3%, 95% CI 1.6-4.5%, 1.1% PE, with at least 1 fatality). Of these 526, 1.3% developed clinically significant bleeding and 0.8% thrombocytopenia. Prophylactic anticoagulation, most commonly 40 mg/day, continued until a median period of 6.4 weeks after SCL onset (25% -75% percentiles 5.8-9.7), but in 29.7%, VTE occurred more than 3 months after SCL onset.

CONCLUSION

The VTE prophylaxis used for the present cohort contributed to a considerable but limited reduction of VTE incidence. The authors recommend conducting a prospective study to assess the efficacy and safety of an updated preventive anticoagulation regimen.

A Prospective Cohort Comparative Study of Rivaroxaban, Dabigatran, and Apixaban Oral Thromboprophylaxis in 2431 Hip and Knee Arthroplasty Patients: Primary Efficacy Outcomes and Safety Profile

BACKGROUND

Direct oral anticoagulants (DOACs) have promised superior efficacy to low molecular weight heparins in the prevention of venous thromboembolism (VTE) in total hip and knee arthroplasty. However, there are concerns about raised associated bleeding and wound problems with these agents. This study aims to evaluate and compare the efficacy and safety of the 3 DOAC drugs: rivaroxaban, dabigatran and apixaban.

METHODS

The primary outcome measures were rate of symptomatic VTE and major bleeding. Secondary outcome measures were wound healing problems and requirement for return to theater. A total of 2431 patients received one of the DOAC drugs as thromboprophylaxis following total hip arthroplasty (35 days) or total knee arthroplasty (14 days) between 2011 and 2015. Binary variables were compared between the 3 groups by using the chi-squared test or Fisher's exact test. Relative risks of selected primary and secondary end points were also calculated for the prespecified pairwise comparison.

RESULTS

The overall symptomatic VTE rate was 2%. Rivaroxaban had a statistically significant superior efficacy for overall VTE prevention (0.8% vs 2.6%) compared with dabigatran (P < .01) and apixaban (P < .01), and deep vein thrombosis prevention (0.3% vs 2.2%) over dabigatran (P < .01). The overall rate of major bleeding was 1.2% with no significant difference observed between the 3 studied drugs.

CONCLUSION

All 3 drugs had symptomatic VTE rates comparable with low molecular weight heparin from the published literature. Rivaroxaban appears to have superior efficacy in VTE prevention over apixaban and dabigatran. No statistical difference was observed for major bleeding with any of the 3 agents.

Non-invasive in vivo imaging of acute thrombosis: development of a novel factor XIIIa radiotracer

AIMS

Cardiovascular thrombosis is responsible a quarter of deaths annually worldwide. Current imaging methods for cardiovascular thrombosis focus on anatomical identification of thrombus but cannot determine thrombus age or activity. Molecular imaging techniques hold promise for identification and quantification of thrombosis in vivo. Our objective was to assess a novel optical and positron-emitting probe targeting Factor XIIIa (ENC2015) as biomarker of active thrombus formation.

METHODS AND RESULTS

Optical and positron-emitting ENC2015 probes were assessed ex vivo using blood drawn from human volunteers and passed through perfusion chambers containing denuded porcine aorta as a model of arterial injury. Specificity of ENC2015 was established with co-infusion of a factor XIIIa inhibitor. In vivo18F-ENC2015 biodistribution, kinetics, radiometabolism, and thrombus binding were characterized in rats. Both Cy5 and fluorine-18 labelled ENC2015 rapidly and specifically bound to thrombi. Thrombus uptake was inhibited by a factor XIIIa inhibitor. 18F-ENC2015 remained unmetabolized over 8 h when incubated in ex vivo human blood. In vivo, 42% of parent radiotracer remained in blood 60 min post-administration. Biodistribution studies demonstrated rapid clearance from tissues with elimination via the urinary system. In vivo,18F-ENC2015 uptake was markedly increased in the thrombosed carotid artery compared to the contralateral patent artery (mean standard uptake value ratio of 2.40 vs. 0.74, P < 0.0001).

CONCLUSION

ENC2015 rapidly and selectively binds to acute thrombus in both an ex vivo human translational model and an in vivo rodent model of arterial thrombosis. This probe holds promise for the non-invasive identification of thrombus formation in cardiovascular disease.

A systematic review showing the lack of diagnostic criteria and tools developed for lower-limb cellulitis

Background

Cellulitis can be a difficult diagnosis to make. Furthermore, 31% of patients admitted from the emergency department with suspected lower‐limb cellulitis have been misdiagnosed, with incorrect treatment potentially resulting in avoidable hospital admission and the prescription of unnecessary antibiotics.

Objectives

We sought to identify diagnostic criteria or tools that have been developed for lower‐limb cellulitis.

Methods

We conducted a systematic review using Ovid MEDLINE and Embase databases in May 2018, with the aim of describing diagnostic criteria and tools developed for lower‐limb cellulitis, and we assessed the quality of the studies identified using the Quality Assessment of Diagnostic Accuracy Studies‐2 tool. We included all types of study that described diagnostic criteria or tools.

Results

Eight observational studies were included. Five studies examined biochemical markers, two studies assessed imaging and one study developed a diagnostic decision model. All eight studies were considered to have a high risk for bias in at least one domain. The quantity and quality of available data was low and results could not be pooled owing to the heterogeneity of the findings.

Conclusions

There is a lack of high‐quality publications describing criteria or tools for diagnosing lower‐limb cellulitis. Future studies using prospective designs, validated in both primary and secondary care settings, are needed.

What's already known about this topic?

Diagnosing lower‐limb cellulitis on first presentation is challenging.

Approximately one in three patients admitted from the emergency department with suspected lower‐limb cellulitis do not have cellulitis and are given another diagnosis on discharge. Consequently, this results in potentially avoidable hospital admissions and the prescription of unnecessary antibiotics.

There are no diagnostic criteria available for lower‐limb cellulitis in the U.K.

What does this study add?

This systematic review has identified a key research gap in the diagnosis of lower‐limb cellulitis.

There is a current lack of robustly developed and validated diagnostic criteria or tools for use in clinical practice.

Linked Comment: https://doi.org/10.1111/bjd.18317.

https://doi.org/10.1111/bjd.18569 available online

Highly Elevated Quantitative D-Dimer Assay Values Increase the Likelihood of Venous Thromboembolism

Objectives  In patients with suspected venous thromboembolism (VTE), the D-dimer assay is commonly utilized as part of the workup. The assay is primarily used to determine whether to proceed with radiographic imaging. We compared D-dimer levels in patients suspected of having VTE. We hypothesized that higher D-dimer values predict a higher likelihood of subsequent VTE diagnosis.

Methods  We conducted a secondary analysis of a multinational, prospective observational study of low- to intermediate-risk adult patients presenting to the emergency department with suspicion of VTE. Demographic and clinical data were collected in a structured manner. Advanced imaging including ultrasound, computed tomography (CT) pulmonary angiography, and ventilation/perfusion scanning was obtained at the discretion of the treating physicians. Imaging was evaluated by board-certified radiologists in real time. D-dimer values' bins were evaluated using a logistic regression model.

Results  We evaluated 1,752 patients for suspected deep vein thrombosis (DVT), with 191 (10.4%) DVT positive. We evaluated 1,834 patients for suspected pulmonary embolism (PE), with 108 (5.9%) PE positive. Higher D-dimer values in both groups were associated with higher likelihood of subsequent VTE diagnosis, with D-dimer values > 3,999 ng/mL in both groups having the highest incidence of VTE. More than 50% of those patients were VTE positive.

Conclusions  Increasing D-dimer values predict increased likelihood of being found VTE positive in this patient population. Among those in the highest D-dimer category, > 3,999 ng/mL, over half of patients were VTE positive. Further research could determine additional nuance in D-dimer as a tool to work up suspected VTE.

Total Knee Arthroplasty in a Diagnosed Case of Deep Vein Thrombosis - Our Experience and Review of Literature

INTRODUCTION

Deep vein thrombosis (DVT) following total knee arthroplasty (TKA) and its associated complication, pulmonary thromboembolism (PTE) remains a challenge for orthopedic surgeons. There are wide ranges of predisposing factors which are both patient specific as well as procedure associated, responsible for DVT. PTE is a well-known fatal complication of DVT which may be life-threatening. Medical management and early mobilization are necessary for the management of DVT. Fatal PTE can be prevented by implantation of inferior vena cava (IVC) filter in at risk patients.

CASE REPORT

We are presenting a rare case report of 75-year-old female with severe osteoarthritis of the left knee with DVT of the left lower limb in which TKA was done in a prediagnosed case of DVT. IVC filter placement was done before TKA for prevention of fatal PTE, and medical management was done for DVT.

CONCLUSION

Prevention of fatal thromboembolism is of prime importance in the management of DVT. This can be achieved by implanting IVC filter. TKA is necessary for early pain free mobilization of the patient, which prevents progression of DVT and early recovery. IVC filter placement prevents fatal thromboembolism. Hence, treatment of both osteoarthritis of knee by TKA and DVT can be done simultaneously.

Evaluation of iron oxide nanoparticle micelles for magnetic particle imaging (MPI) of thrombosis

Magnetic particle imaging (MPI) is an emerging medical imaging modality that directly visualizes magnetic particles in a hot-spot like fashion. We recently developed an iron oxide nanoparticle-micelle (ION-Micelle) platform that allows highly sensitive MPI. The goal of this study was to assess the potential of the ION-Micelles for MPI-based detection of thrombi. To this aim, an in vivo carotid artery thrombosis mouse model was employed and ex vivo magnetic particle spectrometer (MPS) measurements of the carotid arteries were performed. In addition, we studied the effect of functionalization of the ION-Micelle nanoplatform with fibrin-binding peptides (FibPeps) with respect to nanoparticle thrombus uptake and hence thrombus detection. In vivo quantitative MR imaging pre- and post-ION-Micelle injection was performed as reference for visualization of ION-micelle uptake. ION-Micelles significantly decreased T₂ values in the thrombi with respect to pre-injection T₂ values (p < 0.01) and significantly increased ex vivo MPS thrombus signal with respect to the noninjured, contralateral carotid (p < 0.01). Functionalization of the ION-Micelles with the FibPep peptides did not result in an increased MPS thrombus signal with respect to the non-fibrin binding ION-Micelles. The lack of a significant increased thrombus uptake for the FibPep-ION-Micelles indicates that (non-fibrin-specific) entrapment of nanoparticles in the mesh-like thrombi is the key contributor to thrombus nanoparticle uptake. Therefore, (nontargeted) ION-Micelles might be of value for noninvasive MPI-based diagnosis, characterization and treatment monitoring of thrombosis.

In vivo molecular imaging of thrombosis and thrombolysis using a fibrin-binding positron emission tomographic probe

BACKGROUND

Fibrin is a major component of arterial and venous thrombi and represents an ideal candidate for molecular imaging of thrombosis. Here, we describe imaging properties and target uptake of a new fibrin-specific positron emission tomographic probe for thrombus detection and therapy monitoring in 2 rat thrombosis models.

METHODS AND RESULTS

The fibrin-binding probe FBP7 was synthesized by conjugation of a known short cyclic peptide to a cross-bridged chelator (CB-TE2A), followed by labeling with copper-64. Adult male Wistar rats (n=26) underwent either carotid crush injury (mural thrombosis model) or embolic stroke (occlusive thrombosis model) followed by recombinant tissue-type plasminogen activator treatment (10 mg/kg, IV). FBP7 detected thrombus location in both animal models with a high positron emission tomographic target-to-background ratio that increased over time (>5-fold at 30-90 minutes, >15-fold at 240-285 minutes). In the carotid crush injury animals, biodistribution analysis confirmed high probe uptake in the thrombotic artery (≈0.5%ID/g; >5-fold greater than blood and other tissues of the head and thorax). Similar results were obtained from ex vivo autoradiography of the ipsilateral versus contralateral carotid arteries. In embolic stroke animals, positron emission tomographic-computed tomographic imaging localized the clot in the internal carotid/middle cerebral artery segment of all rats. Time-dependent reduction of activity at the level of the thrombus was detected in recombinant tissue-type plasminogen activator-treated rats but not in vehicle-injected animals. Brain autoradiography confirmed clot dissolution in recombinant tissue-type plasminogen activator-treated animals, but enduring high thrombus activity in control rats.

CONCLUSIONS

We demonstrated that FBP7 is suitable for molecular imaging of thrombosis and thrombolysis in vivo and represents a promising candidate for bench-to-bedside translation.

Risk factors of venous thromboembolism in thai patients

Venous thromboembolism (VTE) has been reported to be less common among Thais than Caucasians. Whether this observation reflects genetic or environmental factors, or both, is uncertain. To identify genetic and acquired risk factors of Thai patients with VTE, we enrolled in the study 105 consecutive Thai patients (34 men, 71 women) who had an objectively confirmed history of VTE. A complete clinical summary was obtained from each patient, with emphasis on personal and family history of VTE, as well as circumstantial vascular risk factors (surgery, immobilization, pregnancy, postpartum condition, trauma, oral contraceptive use, and malignancy). Of the 105 patients, 19% were found to have a malignancy. The mean age at the time of the first thrombotic episode was 52.1 years (range, 29-76 years), compared with 42.6 years (range, 17-82 years) for the patients without malignancy. Of the 85 patients without malignancy, 12.3% had protein S deficiency, 8.9% had protein C deficiency, 4.7% had antithrombin deficiency, 10.4% had antiphospholipid antibody, 30.4% had an elevated factor VIII level, 26.8% had an elevated factor XI level, 5.3% had hyperhomocysteinemia, and 16.5% were on oral contraceptives before the thrombotic episode. Factor V Leiden, the G20210A prothrombin gene mutation, and homozygosity for the C677T methylenetetrahydrofolate reductase (MTHFR) gene variant were not found. The VTE in 7.1% of the patients was considered to be secondary to recent surgery, trauma, and/or immobilization. Compared with studies of Caucasian patients, there were significant differences in the risk factors for VTE, with protein S deficiency and protein C deficiency being more common in the Thai patients. In contrast, factor V Leiden, the G20210A prothrombin gene mutation, and the C677T MTHFR gene mutation are not genetic risk factors among Thai patients with VTE. Malignancy and the use of oral contraceptives were the most common acquired risk factors for VTE in the Thai patients.

A profile of lower-limb deep-vein thrombosis: the hidden menace of below-knee DVT

AIMS

To describe the anatomical site and laterality of deep-vein thrombosis (DVT) in symptomatic patients using contrast venography (CV), and to assess age, sex distribution, and accuracy of pre-test clinical suspicion of DVT.

METHODS

One thousand, five hundred and seventy-two patients undergoing CV because of a clinical suspicion of DVT at a large teaching hospital from October 1995 to March 2003 were prospectively studied.

RESULTS

Thrombi were demonstrated in 511 (32.5%) of all CV studies. Isolated, below-knee thrombi were identified in 29.4% of positive studies. There was a left-sided predominance of DVT (ratio 1.24:1) that was most evident in the elderly and in more proximal veins.

CONCLUSION

Almost a third of positive cases were shown to be isolated, below-knee thrombi. These are thrombi that are more difficult to detect by non-invasive means. A left-sided predominance of DVT is evident.

Systematic review and meta-analysis of the diagnostic accuracy of ultrasonography for deep vein thrombosis

BACKGROUND

Ultrasound (US) has largely replaced contrast venography as the definitive diagnostic test for deep vein thrombosis (DVT). We aimed to derive a definitive estimate of the diagnostic accuracy of US for clinically suspected DVT and identify study-level factors that might predict accuracy.

METHODS

We undertook a systematic review, meta-analysis and meta-regression of diagnostic cohort studies that compared US to contrast venography in patients with suspected DVT. We searched Medline, EMBASE, CINAHL, Web of Science, Cochrane Database of Systematic Reviews, Cochrane Controlled Trials Register, Database of Reviews of Effectiveness, the ACP Journal Club, and citation lists (1966 to April 2004). Random effects meta-analysis was used to derive pooled estimates of sensitivity and specificity. Random effects meta-regression was used to identify study-level covariates that predicted diagnostic performance.

RESULTS

We identified 100 cohorts comparing US to venography in patients with suspected DVT. Overall sensitivity for proximal DVT (95% confidence interval) was 94.2% (93.2 to 95.0), for distal DVT was 63.5% (59.8 to 67.0), and specificity was 93.8% (93.1 to 94.4). Duplex US had pooled sensitivity of 96.5% (95.1 to 97.6) for proximal DVT, 71.2% (64.6 to 77.2) for distal DVT and specificity of 94.0% (92.8 to 95.1). Triplex US had pooled sensitivity of 96.4% (94.4 to 97.1%) for proximal DVT, 75.2% (67.7 to 81.6) for distal DVT and specificity of 94.3% (92.5 to 95.8). Compression US alone had pooled sensitivity of 93.8 % (92.0 to 95.3%) for proximal DVT, 56.8% (49.0 to 66.4) for distal DVT and specificity of 97.8% (97.0 to 98.4). Sensitivity was higher in more recently published studies and in cohorts with higher prevalence of DVT and more proximal DVT, and was lower in cohorts that reported interpretation by a radiologist. Specificity was higher in cohorts that excluded patients with previous DVT. No studies were identified that compared repeat US to venography in all patients. Repeat US appears to have a positive yield of 1.3%, with 89% of these being confirmed by venography.

CONCLUSION

Combined colour-doppler US techniques have optimal sensitivity, while compression US has optimal specificity for DVT. However, all estimates are subject to substantial unexplained heterogeneity. The role of repeat scanning is very uncertain and based upon limited data.

Utility of portable continuous-wave Doppler examination in screening for postoperative deep vein thrombosis

BACKGROUND

Early and accurate diagnosis of post-surgical deep vein thrombosis (DVT) can be difficult and time-consuming, even with duplex ultrasonography. Portable continuous-wave Doppler ultrasonography may be useful in screening patients for postoperative DVT. Further confirmation of Doppler-positive cases by duplex ultrasound might then be more cost-effective.

METHODS

All major post-surgical patients from the departments of general surgery, orthopaedic surgery and colorectal surgery were screened on the third postoperative day for DVT by assessing the quality of the flow signal ("whoosh") obtained by placing the probe over the femoral vein and subsequently over the popliteal vein, both with a distal squeeze, as well as assessment of phasic flow with respiration. An absent or attenuated "whoosh" was judged to be suspicious for DVT and required formal duplex ultrasonography. The first 800 consecutive patients were studied to determine the sensitivity, specificity and accuracy of portable Doppler ultrasonography for DVT screening.

RESULTS

Twenty-four cases of DVT were diagnosed, comprising seven cases in the proximal veins and 17 cases in the calf veins. The sensitivity of Doppler ultrasonography was 12.5% and the specificity was 96.8%. The positive and negative predictive values were 10.7% and 97.3%, respectively.

CONCLUSIONS

Portable Doppler ultrasonography does not have adequate accuracy to be used as a quick screening tool for DVT.