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Immunity, Inflammation and Disease Mar 2023Since publishing successful clinical trial results of mRNA coronavirus disease 2019 (COVID-19) vaccines in December 2020, multiple reports have arisen about... (Review)
Review
BACKGROUND AND OBJECTIVES
Since publishing successful clinical trial results of mRNA coronavirus disease 2019 (COVID-19) vaccines in December 2020, multiple reports have arisen about cardiovascular complications following the mRNA vaccination. This study provides an in-depth account of various cardiovascular adverse events reported after the mRNA vaccines' first or second dose including pericarditis/myopericarditis, myocarditis, hypotension, hypertension, arrhythmia, cardiogenic shock, stroke, myocardial infarction/STEMI, intracranial hemorrhage, thrombosis (deep vein thrombosis, cerebral venous thrombosis, arterial or venous thrombotic events, portal vein thrombosis, coronary thrombosis, microvascular small bowel thrombosis), and pulmonary embolism.
METHODS
A systematic review of original studies reporting confirmed cardiovascular manifestations post-mRNA COVID-19 vaccination was performed. Following the PRISMA guidelines, electronic databases (PubMed, PMC NCBI, and Cochrane Library) were searched until January 2022. Baseline characteristics of patients and disease outcomes were extracted from relevant studies.
RESULTS
A total of 81 articles analyzed confirmed cardiovascular complications post-COVID-19 mRNA vaccines in 17,636 individuals and reported 284 deaths with any mRNA vaccine. Of 17,636 cardiovascular events with any mRNA vaccine, 17,192 were observed with the BNT162b2 (Pfizer-BioNTech) vaccine, 444 events with mRNA-1273 (Moderna). Thrombosis was frequently reported with any mRNA vaccine (n = 13,936), followed by stroke (n = 758), myocarditis (n = 511), myocardial infarction (n = 377), pulmonary embolism (n = 301), and arrhythmia (n = 254). Stratifying the results by vaccine type showed that thrombosis (80.8%) was common in the BNT162b2 cohort, while stroke (39.9%) was common with mRNA-1273 for any dose. The time between the vaccination dosage and the first symptom onset averaged 5.6 and 4.8 days with the mRNA-1273 vaccine and BNT162b2, respectively. The mRNA-1273 cohort reported 56 deaths compared to the 228 with BNT162b2, while the rest were discharged or transferred to the ICU.
CONCLUSION
Available literature includes more studies with the BNT162b2 vaccine than mRNA-1273. Future studies must report mortality and adverse cardiovascular events by vaccine types.
Topics: Humans; 2019-nCoV Vaccine mRNA-1273; BNT162 Vaccine; COVID-19; COVID-19 Vaccines; Myocardial Infarction; Myocarditis; Pulmonary Embolism; Stroke; Thrombocytopenia; Thrombosis
PubMed: 36988252
DOI: 10.1002/iid3.807 -
International Journal of Nursing Studies Jan 2024The number of risk prediction models for deep venous thrombosis (DVT) in patients with acute stroke is increasing, while the quality and applicability of these models in... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND
The number of risk prediction models for deep venous thrombosis (DVT) in patients with acute stroke is increasing, while the quality and applicability of these models in clinical practice and future research remain unknown.
OBJECTIVE
To systematically review published studies on risk prediction models for DVT in patients with acute stroke.
DESIGN
Systematic review and meta-analysis of observational studies.
METHODS
China National Knowledge Infrastructure (CNKI), Wanfang Database, China Science and Technology Journal Database (VIP), SinoMed, PubMed, Web of Science, The Cochrane Library, Cumulative Index to Nursing and Allied Health Literature (CINAHL) and Embase were searched from inception to November 7, 2022. Data from selected studies were extracted, including study design, data source, outcome definition, sample size, predictors, model development and performance. The Prediction Model Risk of Bias Assessment Tool (PROBAST) checklist was used to assess the risk of bias and applicability.
RESULTS
A total of 940 studies were retrieved, and after the selection process, nine prediction models from nine studies were included in this review. All studies utilized logistic regression to establish DVT risk prediction models. The incidence of DVT in patients with acute stroke ranged from 0.4 % to 28 %. The most frequently used predictors were D-dimer and age. The reported area under the curve (AUC) ranged from 0.70 to 0.912. All studies were found to have a high risk of bias, primarily due to inappropriate data sources and poor reporting of the analysis domain. The pooled AUC value of the five validated models was 0.76 (95 % confidence interval: 0.70-0.81), indicating a fair level of discrimination.
CONCLUSION
Although the included studies reported a certain level of discrimination in the prediction models of DVT in patients with acute stroke, all of them were found to have a high risk of bias according to the PROBAST checklist. Future studies should focus on developing new models with larger samples, rigorous study designs, and multicenter external validation.
REGISTRATION
The protocol for this study is registered with PROSPERO (registration number: CRD42022370287).
Topics: Humans; Stroke; Risk Assessment; Venous Thrombosis; China; Multicenter Studies as Topic
PubMed: 37944356
DOI: 10.1016/j.ijnurstu.2023.104623 -
Acta Neurologica Scandinavica Jan 2022Cerebral venous thrombosis (CVT) is caused by partial or complete occlusion of the major cerebral venous sinuses or the smaller feeding cortical veins which predispose... (Meta-Analysis)
Meta-Analysis Review
Cerebral venous thrombosis (CVT) is caused by partial or complete occlusion of the major cerebral venous sinuses or the smaller feeding cortical veins which predispose to the risk of venous infarction and hemorrhage. Current guidelines recommend treating CVT with either low-molecular-weight heparin (LMWH) or unfractionated heparin (UFH) followed by an oral vitamin K antagonist (VKA) for 3-12 months. Direct oral anticoagulants (DOACs) have already established benefit over warfarin as a long-term treatment of symptomatic venous thromboembolic disorder like deep vein thrombosis (DVT), and pulmonary embolism (PE) given its equal efficacy and better safety profile. The benefit of DOACs over warfarin as a long-term anticoagulation for CVT has likewise been extensively studied, yet it has not been approved as first-line therapy in the current practice. We therefore performed a systematic review and meta-analysis of relevant studies to generate robust evidence regarding the safety and efficacy of DOACs in CVT. This meta-analysis demonstrates that the use of DOACs in CVT has similar efficacy and safety compared to VKAs with better recanalization rate.
Topics: Administration, Oral; Anticoagulants; Heparin; Heparin, Low-Molecular-Weight; Humans; Venous Thromboembolism; Venous Thrombosis
PubMed: 34287841
DOI: 10.1111/ane.13506 -
Critical Care Medicine Mar 2022Tranexamic acid is proposed as a treatment for gastrointestinal bleeding. The Haemorrhage Alleviation with Tranexamic Acid-Intestinal System trial evaluated extended-use... (Meta-Analysis)
Meta-Analysis
OBJECTIVES
Tranexamic acid is proposed as a treatment for gastrointestinal bleeding. The Haemorrhage Alleviation with Tranexamic Acid-Intestinal System trial evaluated extended-use (24 hr) high-dose tranexamic acid, prompting a reappraisal for tranexamic acid in gastrointestinal bleeding.
DATA SOURCES
We conducted a systematic review and meta-analysis of randomized controlled trials comparing tranexamic acid with usual care or placebo in adults with gastrointestinal bleeding. We searched MEDLINE, EMBASE, and CENTRAL (inception to September 2019).
DATA SELECTION
Two reviewers independently screened citations, extracted data, and assessed the risk of bias using the Cochrane risk of bias tool in duplicate. The main outcomes were mortality, bleeding, and adverse events.
DATA EXTRACTION
Studies were analyzed as high-dose IV tranexamic acid versus all other dosing strategies for tranexamic acid using fixed-effects models. We assessed certainty of evidence using the Grading of Recommendations Assessment, Development, and Evaluation approach.
DATA SYNTHESIS
Five randomized controlled trials evaluated extended-use high-dose IV tranexamic acid, seven evaluating low-dose IV or enteral tranexamic acid. Extended-use high-dose IV tranexamic acid did not reduce mortality (relative risk, 0.98%; 95% CI, 0.88-1.09; I2 = 63%; high certainty) or bleeding (relative risk, 0.92; 95% CI, 0.82-1.04; p = 0.17 and absolute risk differences, -0.7%; 95% CI, -1.5 to 0.3; high certainty) but resulted in a small increase in deep venous thrombosis (relative risk, 2.01; 95% CI, 1.08-3.72; I2 = 0%), pulmonary embolism (relative risk, 1.78; 95% CI, 1.06-3.0; I2 = 0%), and seizure (relative risk, 1.73; 95% CI, 1.03-2.93) with high certainty. Low-dose IV/enteral tranexamic acid did not reduce mortality (relative risk, 0.62; 95% CI, 0.36-1.09; I2 = 0%) but did reduce risk of rebleeding (relative risk, 0.5; 95% CI, 0.33-0.75; I2 = 9%) and need for surgery (relative risk, 0.58; 95% CI, 0.38-0.88; I2 = 11%), with moderate certainty.
CONCLUSIONS
Extended-use high-dose IV tranexamic acid does not improve mortality or bleeding outcomes and increases adverse events. Low-dose/enteral tranexamic acid may be effective in reducing hemorrhage; more evidence is required to demonstrate its safety.
Topics: Antifibrinolytic Agents; Gastrointestinal Hemorrhage; Humans; Length of Stay; Secondary Prevention; Tranexamic Acid
PubMed: 34709209
DOI: 10.1097/CCM.0000000000005362 -
Radiology Feb 2021Background The association of pulmonary embolism (PE) with deep vein thrombosis (DVT) in patients with coronavirus disease 2019 (COVID-19) remains unclear, and the... (Meta-Analysis)
Meta-Analysis
Background The association of pulmonary embolism (PE) with deep vein thrombosis (DVT) in patients with coronavirus disease 2019 (COVID-19) remains unclear, and the diagnostic accuracy of D-dimer tests for PE is unknown. Purpose To conduct meta-analysis of the study-level incidence of PE and DVT and to evaluate the diagnostic accuracy of D-dimer tests for PE from multicenter individual patient data. Materials and Methods A systematic literature search identified studies evaluating the incidence of PE or DVT in patients with COVID-19 from January 1, 2020, to June 15, 2020. These outcomes were pooled using a random-effects model and were further evaluated using metaregression analysis. The diagnostic accuracy of D-dimer tests for PE was estimated on the basis of individual patient data using the summary receiver operating characteristic curve. Results Twenty-seven studies with 3342 patients with COVID-19 were included in the analysis. The pooled incidence rates of PE and DVT were 16.5% (95% CI: 11.6, 22.9; = 0.93) and 14.8% (95% CI: 8.5, 24.5; = 0.94), respectively. PE was more frequently found in patients who were admitted to the intensive care unit (ICU) (24.7% [95% CI: 18.6, 32.1] vs 10.5% [95% CI: 5.1, 20.2] in those not admitted to the ICU) and in studies with universal screening using CT pulmonary angiography. DVT was present in 42.4% of patients with PE. D-dimer tests had an area under the receiver operating characteristic curve of 0.737 for PE, and D-dimer levels of 500 and 1000 μg/L showed high sensitivity (96% and 91%, respectively) but low specificity (10% and 24%, respectively). Conclusion Pulmonary embolism (PE) and deep vein thrombosis (DVT) occurred in 16.5% and 14.8% of patients with coronavirus disease 2019 (COVID-19), respectively, and more than half of patients with PE lacked DVT. The cutoffs of D-dimer levels used to exclude PE in preexisting guidelines seem applicable to patients with COVID-19. © RSNA, 2020 See also the editorial by Woodard in this issue.
Topics: Humans; Computed Tomography Angiography; COVID-19; Fibrin Fibrinogen Degradation Products; Pulmonary Embolism; SARS-CoV-2; Venous Thrombosis; Multicenter Studies as Topic
PubMed: 33320063
DOI: 10.1148/radiol.2020203557 -
Scandinavian Journal of Surgery : SJS :... Jun 2021Acute mesenteric venous thrombosis accounts for up to 20% of all patients with acute mesenteric ischemia in high-income countries. Acute mesenteric venous thrombosis is...
BACKGROUND AND AIMS
Acute mesenteric venous thrombosis accounts for up to 20% of all patients with acute mesenteric ischemia in high-income countries. Acute mesenteric venous thrombosis is nowadays relatively more often diagnosed with intravenous contrast-enhanced computed tomography in the portal phase than at explorative laparotomy No high-quality comparative studies between anticoagulation alone, endovascular therapy, or surgery exists. The aim of the present systematic review was to offer a contemporary overview on management.
MATERIALS AND METHODS
Eleven relevant published original studies with series of at least ten patients were retrieved from a Pub Med search between 2015 and 2020 using the Medical Subject Heading term "mesenteric venous thrombosis."
RESULTS
When MVT is diagnosed early, immediate anticoagulation with either unfractionated heparin or subcutaneous low-molecular-weight heparin should commence. Surgeons need to be aware of the importance to scrutinize the computed tomography images themselves for assessment of secondary intestinal abnormalities to mesenteric venous thrombosis and the risk of bowel resection and worse prognosis. Progression toward peritonitis is an indication for explorative laparotomy and assessment of bowel viability. Frank transmural small bowel necrosis should be resected and bowel anastomosis may be delayed for several days until second look. Meanwhile, intravenous full-dose unfractionated heparin should be given at the end of the first operation. Postoperative major intra-abdominal or gastrointestinal bleeding occurs rarely, but the heparin effect can instantaneously be reversed by . Patients who do not improve during conservative therapy with anticoagulation alone but without developing peritonitis may be subjected to endovascular therapy in expert centers. When the patient's intestinal function has recovered, with or without bowel resection, switch from parenteral unfractionated heparin or low-molecular-weight heparin therapy to oral anticoagulation can be performed. There is a trend that direct oral anticoagulants are increasingly used instead of vitamin K antagonists. Up to now, direct oral anticoagulants have been shown to be equally effective with the same rate of bleeding complications. Patients with no strong permanent trigger factor for mesenteric venous thrombosis such as intra-abdominal cancer should undergo blood screening for inherited and acquired thrombophilia.
CONCLUSION
Early diagnosis with emergency computed tomography with intravenous contrast-enhancement and imaging in the portal phase and anticoagulation therapy is necessary to be able to have a succesful non-operative succesful course.
Topics: Anticoagulants; Heparin; Humans; Mesenteric Ischemia; Mesenteric Veins; Venous Thrombosis
PubMed: 33118463
DOI: 10.1177/1457496920969084 -
Journal of Vascular Surgery. Venous and... Nov 2022Hospital-acquired venous thromboembolism (VTE, including pulmonary embolism [PE] and deep vein thrombosis [DVT]) is a preventable cause of hospital death. The Caprini... (Review)
Review
OBJECTIVE
Hospital-acquired venous thromboembolism (VTE, including pulmonary embolism [PE] and deep vein thrombosis [DVT]) is a preventable cause of hospital death. The Caprini risk assessment model (RAM) is one of the most commonly used tools to assess VTE risk. The RAM is operationalized in clinical practice by grouping several risk scores into VTE risk categories that drive decisions on prophylaxis. A correlation between increasing Caprini scores and rising VTE risk is well-established. We assessed whether the increasing VTE risk categories assigned on the basis of recommended score ranges also correlate with increasing VTE risk.
METHODS
We conducted a systematic review of articles that used the Caprini RAM to assign VTE risk categories and that reported corresponding VTE rates. A Medline and EMBASE search retrieved 895 articles, of which 57 fulfilled inclusion criteria.
RESULTS
Forty-eight (84%) of the articles were cohort studies, 7 (12%) were case-control studies, and 2 (4%) were cross-sectional studies. The populations varied from postsurgical to medical patients. There was variability in the number of VTE risk categories assigned by individual studies (6 used 5 risk categories, 37 used 4, 11 used 3, and 3 used 2), and in the cutoff scores defining the risk categories (scores from 0 alone to 0-10 for the low-risk category; from ≥5 to ≥10 for high risk). The VTE rates reported for similar risk categories also varied across studies (0%-12.3% in the low-risk category; 0%-40% for high risk). The Caprini RAM is designed to assess composite VTE risk; however, two studies reported PE or DVT rates alone, and many of the other studies did not specify the types of DVTs analyzed. The Caprini RAM predicts VTE at 30 days after assessment; however, only 17 studies measured outcomes at 30 days; the remaining studies had either shorter or longer follow-ups (0-180 days).
CONCLUSIONS
The usefulness of the Caprini RAM is limited by heterogeneity in its implementation across centers. The score-derived VTE risk categorization has significant variability in the number of risk categories being used, the cutpoints used to define the risk categories, the outcome being measured, and the follow-up duration. This factor leads to similar risk categories being associated with different VTE rates, which impacts the clinical and research implications of the results. To enhance generalizability, there is a need for studies that validate the RAM in a broad population of medical and surgical patients, identify standardized risk categories, define risk of DVT and PE as distinct end points, and measure outcomes at standardized follow-up time points.
Topics: Humans; Pulmonary Embolism; Retrospective Studies; Risk Assessment; Risk Factors; Venous Thromboembolism; Venous Thrombosis
PubMed: 35926802
DOI: 10.1016/j.jvsv.2022.05.003 -
Stroke Oct 2022High level evidence for direct oral anticoagulants (DOACs) in patients with cerebral venous thrombosis is lacking. We performed a systematic review and meta-analysis to... (Meta-Analysis)
Meta-Analysis
BACKGROUND
High level evidence for direct oral anticoagulants (DOACs) in patients with cerebral venous thrombosis is lacking. We performed a systematic review and meta-analysis to assess the efficacy and safety of DOACs versus vitamin K antagonists in patients with cerebral venous thrombosis.
METHODS
This systematic review was registered in PROSPERO (CRD42021228800). We searched MEDLINE (via Ovid), EMBASE, CINAHL, and the Web of Science Core Collection between January 1, 2007 and Feb 22, 2022. Search terms included a combination of keywords and controlled vocabulary terms for cerebral venous thrombosis, vitamin K antagonists/warfarin, and DOACs. We included both randomized and nonrandomized studies that compared vitamin K antagonists and DOACs in 5 or more patients with cerebral venous thrombosis. Where studies were sufficiently similar, we performed meta-analyses for efficacy (recurrent venous thromboembolism and complete recanalization) and safety (major hemorrhage) outcomes, using relative risks (RRs).
RESULTS
Out of 10 665 records identified, we screened 254 as potentially eligible. Nineteen studies (16 observational studies [n=1735] and 3 randomized controlled trials [n=215]) met the inclusion criteria. All 3 randomized controlled trials had some concerns, and all 16 observational studies had at least moderate risk of bias. When compared with vitamin K antagonist treatment, DOAC had comparable risks of recurrent venous thromboembolism (relative risk [RR], 0.85 [95% CI, 0.52-1.37], I=0%), major hemorrhage (RR, 0.70 [95% CI, 0.40-1.21], I=0%), intracranial hemorrhage (RR, 0.58 [95% CI, 0.30-1.12]; I=0%), death (RR, 1.14 [95% CI, 0.54-2.43], I=1%), and complete venous recanalization (RR, 0.98 [95% CI, 0.87-1.11]; I=0%).
CONCLUSIONS
This systematic review and meta-analysis suggest that in patients with cerebral venous thrombosis, DOACs, and warfarin may have comparable efficacy and safety. Given the limitations of the studies included (low number of randomized controlled trials, modest total sample size, rare outcome events), our findings should be interpreted with caution pending confirmation by ongoing randomized controlled trials and large, prospective, observational studies.
Topics: Administration, Oral; Anticoagulants; Fibrinolytic Agents; Hemorrhage; Humans; Intracranial Thrombosis; Prospective Studies; Venous Thromboembolism; Venous Thrombosis; Vitamin K; Warfarin
PubMed: 35938419
DOI: 10.1161/STROKEAHA.122.039579 -
Blood Advances Apr 2020Deep vein thrombosis (DVT) of the lower extremities can be associated with significant morbidity and may progress to pulmonary embolism and postthrombotic syndrome.... (Meta-Analysis)
Meta-Analysis
Deep vein thrombosis (DVT) of the lower extremities can be associated with significant morbidity and may progress to pulmonary embolism and postthrombotic syndrome. Early diagnosis and treatment are important to minimize the risk of these complications. We systematically reviewed the accuracy of diagnostic tests for first-episode and recurrent DVT of the lower extremities, including proximal compression ultrasonography (US), whole leg US, serial US, and high-sensitivity quantitative D-dimer assays. We searched Cochrane Central, MEDLINE, and EMBASE for eligible studies, reference lists of relevant reviews, registered trials, and relevant conference proceedings. Two investigators screened and abstracted data. Risk of bias was assessed using Quality Assessment of Diagnostic Accuracy Studies-2 and certainty of evidence using the Grading of Recommendations Assessment, Development and Evaluation framework. We pooled estimates of sensitivity and specificity. The review included 43 studies. For any suspected DVT, the pooled estimates for sensitivity and specificity of proximal compression US were 90.1% (95% confidence interval [CI], 86.5-92.8) and 98.5% (95% CI, 97.6-99.1), respectively. For whole-leg US, pooled estimates were 94.0% (95% CI, 91.3-95.9) and 97.3% (95% CI, 94.8-98.6); for serial US pooled estimates were 97.9% (95% CI, 96.0-98.9) and 99.8% (95% CI, 99.3-99.9). For D-dimer, pooled estimates were 96.1% (95% CI, 92.6-98.0) and 35.7% (95% CI, 29.5-42.4). Recurrent DVT studies were not pooled. Certainty of evidence varied from low to high. This systematic review of current diagnostic tests for DVT of the lower extremities provides accuracy estimates. The tests are evaluated when performed in a stand-alone fashion, and in a diagnostic pathway. The pretest probability of DVT often assessed by a clinical decision rule will influence how, together with sensitivity and specificity estimates, patients will be managed.
Topics: Humans; Lower Extremity; Pulmonary Embolism; Sensitivity and Specificity; Ultrasonography; Venous Thrombosis
PubMed: 32227213
DOI: 10.1182/bloodadvances.2019000960 -
JAMA Nov 2020Incidence rates for lower extremity deep vein thrombosis (DVT) range from 88 to 112 per 100 000 person-years and increase with age. Rates of recurrent VTE range from...
IMPORTANCE
Incidence rates for lower extremity deep vein thrombosis (DVT) range from 88 to 112 per 100 000 person-years and increase with age. Rates of recurrent VTE range from 20% to 36% during the 10 years after an initial event.
OBSERVATIONS
PubMed and Cochrane databases were searched for English-language studies published from January 2015 through June 2020 for randomized clinical trials, meta-analyses, systematic reviews, and observational studies. Risk factors for venous thromboembolism (VTE), such as older age, malignancy (cumulative incidence of 7.4% after a median of 19 months), inflammatory disorders (VTE risk is 4.7% in patients with rheumatoid arthritis and 2.5% in those without), and inherited thrombophilia (factor V Leiden carriers with a 10-year cumulative incidence of 10.9%), are associated with higher risk of VTE. Patients with signs or symptoms of lower extremity DVT, such as swelling (71%) or a cramping or pulling discomfort in the thigh or calf (53%), should undergo assessment of pretest probability followed by D-dimer testing and imaging with venous ultrasonography. A normal D-dimer level (ie, D-dimer <500 ng/mL) excludes acute VTE when combined with a low pretest probability (ie, Wells DVT score ≤1). In patients with a high pretest probability, the negative predictive value of a D-dimer less than 500 ng/mL is 92%. Consequently, D-dimer cannot be used to exclude DVT without an assessment of pretest probability. Postthrombotic syndrome, defined as persistent symptoms, signs of chronic venous insufficiency, or both, occurs in 25% to 50% of patients 3 to 6 months after DVT diagnosis. Catheter-directed fibrinolysis with or without mechanical thrombectomy is appropriate in those with iliofemoral obstruction, severe symptoms, and a low risk of bleeding. The efficacy of direct oral anticoagulants-rivaroxaban, apixaban, dabigatran, and edoxaban-is noninferior to warfarin (absolute rate of recurrent VTE or VTE-related death, 2.0% vs 2.2%). Major bleeding occurs in 1.1% of patients treated with direct oral anticoagulants vs 1.8% treated with warfarin.
CONCLUSIONS AND RELEVANCE
Greater recognition of VTE risk factors and advances in anticoagulation have facilitated the clinical evaluation and treatment of patients with DVT. Direct oral anticoagulants are noninferior to warfarin with regard to efficacy and are associated with lower rates of bleeding, but costs limit use for some patients.
Topics: Age Factors; Biomarkers; Factor Xa Inhibitors; Fibrin Fibrinogen Degradation Products; Humans; Life Style; Lower Extremity; Medical Illustration; Postthrombotic Syndrome; Predictive Value of Tests; Risk Factors; Sex Factors; Symptom Assessment; Thrombectomy; Thrombophilia; Ultrasonography; Vena Cava Filters; Venous Thromboembolism; Warfarin
PubMed: 33141212
DOI: 10.1001/jama.2020.17272