BMJ 2017;357:j2344 doi: 10.1136/bmj.j2344 (Published 2017 May 31)
Page 1 of 9
Practice
PRACTICE CLINICAL UPDATE
Diagnosis and management of deep vein thrombosis in pregnancy 1 2
Faizan Khan MSc epidemiology student , Christian Vaillancourt associate professor of emergency 1 2 3 medicine, emergency physician , Ghada Bourjeily associate professor of medicine, pulmonary 4 and critical care, obstetric medicine physician 1
Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada K1H 8L6; 2Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada; 3Department of Emergency Medicine, The Ottawa Hospital, Ottawa, ON, Canada; 4Warren Alpert Medical School of Brown University, The Miriam Hospital, Providence, RI, USA
Venous thromboembolism includes deep vein thrombosis (DVT) and pulmonary embolism. In DVT a blood clot forms in the lower extremities that may break off and travel to the lungs causing a pulmonary embolism. DVT is more common than pulmonary embolism during pregnancy1 and will constitute the focus of this clinical update. However, the prevalence, risk factors, and therapeutic options for DVT and venous thromboembolism in pregnancy are closely linked, and thus information regarding venous thromboembolism in pregnancy has also been covered where appropriate or when data regarding DVT are unavailable. Among pregnant women, pulmonary embolism is the most serious complication of DVT and remains one of the leading causes of maternal death in the developed world.2 Pregnancy related DVT is associated with a higher risk of embolic complications and of the post-thrombotic syndrome (chronic leg pain, intractable oedema, leg ulcers) than DVT in non-pregnant women.1 3 This article provides an update on the diagnosis and management of pregnant women with DVT.
How common is DVT in pregnancy? The risk of venous thromboembolism in pregnancy is about four times the risk among non-pregnant women of childbearing age4; it is highest in the third trimester5 6 and increases further in the first six weeks post partum.1-7 The incidence of DVT among pregnant women is around 1.1 per 1000 deliveries.5 The risk of pregnancy related DVT is approximately three times higher than pregnancy related pulmonary embolism.5
What is the pathophysiology of DVT in pregnancy? Pregnancy is associated with hypercoagulability. There is an increase in procoagulant and a decrease in anticoagulant and fibrinolytic activity in preparation for delivery as well as venous stasis.8 Vascular damage in the pelvis also occurs around labour and delivery. These changes are consistent with Virchow’s triad (hypercoagulability, venous stasis, and vascular damage) (fig 1⇓). In pregnancy the uterus can compress the left iliac vein and may explain why DVT is significantly more common on the left side in pregnancy (>80% of cases). DVT is more commonly diagnosed in the pelvic venous system in pregnancy (>60% of cases) compared with the non-pregnant population.9
How is DVT diagnosed in pregnancy? Clinical presentation Pregnant women with DVT most commonly present with discomfort (80-95%) and oedema (80-88%) in a lower extremity.10 Symptoms are more likely to be left sided. Isolated lower abdominal or pelvic pain may rarely be the presenting symptoms of a pelvic DVT.11 Clinicians must maintain a high level of suspicion for DVT in pregnant women and arrange diagnostic tests promptly to minimise the risk of embolic complications and of post-thrombotic syndrome (chronic leg pain, intractable oedema, and leg ulcers).1 12 In a case-control study, post-thrombotic syndrome was reported in 42% of women with pregnancy related DVT.3
Correspondence to: F Khan fkhan039@uottawa.ca For personal use only: See rights and reprints http://www.bmj.com/permissions
Subscribe: http://www.bmj.com/subscribe
BMJ 2017;357:j2344 doi: 10.1136/bmj.j2344 (Published 2017 May 31)
Page 2 of 9
PRACTICE
What you need to know • Diagnosis of deep vein thrombosis (DVT) in pregnant women can be difficult given that the Wells’score and D-dimer are not validated for use • Compression ultrasonography with Doppler examination of the iliofemoral region is the first line diagnostic tool • Anticoagulation with low molecular weight heparin is the preferred treatment for pregnant women with DVT, but optimal duration and dosing schedule remain unclear • Women with DVT related to pregnancy are at higher risk of embolic complications and of post-thrombotic syndrome than non-pregnant women • Management of DVT around labour and delivery involves balancing the risk of bleeding from anticoagulation with the risk of clot recurrence and the need for regional anaesthesia
Risk factors A previous unprovoked or oestrogen related (associated with oral contraceptive or pregnancy) venous thromboembolism is one of the strongest risk factors 1 13 for antepartum and postpartum venous thromboembolism. Others are shown in box 1. A recent systematic review and meta-analysis of 1003 patients showed that around 1 in 20 women (4.27% (95% confidence interval 1.20% to 7.30%), P=0.001) will experience a recurrent venous thromboembolism in a subsequent pregnancy.5
Investigations The approach to investigation of DVT differs in pregnancy. Figure 2⇓ shows a suggested approach.
Compression ultrasonography Compression ultrasonography combines real time imaging of the deep veins with venous compression (fig 3⇓) and is the first line diagnostic technique for the assessment of DVT in pregnancy. It should be undertaken as soon as possible in order to minimise the risk of pulmonary embolism.1 12 Doppler examination of the iliofemoral veins as part of the compression ultrasonography is recommended.1 12 The diagnostic accuracy of a single, whole leg, compression ultrasonography is not yet known. In one study, follow up of 226 pregnant and postpartum women with suspected DVT who had negative findings on a single compression ultrasonography examination, a DVT was missed in only 1.1% (95% confidence interval 0.3% to 4.0%) of them.17 These data need to be replicated in larger samples. In addition, in pregnant patients with a negative result on a single, complete leg compression ultrasonography but a persisting high level of clinical suspicion, or in cases of a negative compression ultrasonography with restricted views or incomplete imaging of the iliofemoral vessels, serial compression ultrasonography (repeat on day 3 and day 7) that includes examination of the iliac veins should be performed.12 The negative predictive value of serial compression ultrasonography showing no DVT has been demonstrated to be 99.5% (96.9% to 100%) in a prospective cohort study.18
Wells’ score
non-pregnant population.20 However, a physiological gradual increase in circulating D-dimer occurs in pregnancy; hence its measurement may result in false positive findings.21 D-dimer measurements may be helpful in the diagnosis of DVT in early pregnancy as levels would be close to pre-pregnancy levels.22 However, such a strategy has not been validated, and the use of D-dimer cannot yet be considered a safe strategy to exclude DVT in pregnancy.12
Magnetic resonance or contrast venography Magnetic resonance or contrast venography may be considered for pregnant women with negative results from single or serial compression ultrasonography in whom iliac DVT is suspected (especially if back and buttock pain). In practice, however, compression ultrasonography will often be sufficient because of the extensive nature of iliac vein clots.1 12
What are the treatment options for DVT in pregnancy? Managing and preventing DVT in pregnancy remains a challenge. Anticoagulation is the mainstay of treatment, with low molecular weight heparin being the preferred agent, although the optimal duration and dose remain uncertain. Management options in pregnancy are complicated by concerns for fetal safety, changes in drugs’ pharmacokinetics, and maternal bleeding around labour and delivery. Fetal haemorrhage or embryopathy, bioavailability, and risk of vaginal bleeding around delivery, as well the risk of bleeding from neuraxial analgesia interventions, all constitute a challenge in this population.
Anticoagulation Just as in the non-pregnant population, treatment with anticoagulants is first line treatment and should be initiated upon diagnosis in pregnant women with DVT to avoid complications, unless they are strongly contraindicated (such as in patients with a high risk of major bleeding, recent major surgery, or heparin induced thrombocytopenia).12
Low molecular weight heparin
The most common clinical prediction rule (Wells’ score)19 used for estimating the pre-test probability of DVT is not validated in pregnant women. It does not take into account pregnancy as a risk factor for DVT, nor the left sided predilection of pregnancy related DVT. Current evidence and guidelines do not support the use of pretest probability in the diagnosis of DVT in pregnancy.12
Low molecular weight heparin (LMWH) is the anticoagulant of choice in pregnancy as it does not cross the placenta or enter breast milk. LMWH has largely replaced unfractionated heparin as it has a better pharmacokinetic and safety profile among pregnant women.1 12 Monitoring plasma heparin levels with the anti-Xa assay is debated in pregnancy; guidelines recommend anti-Xa monitoring only in women with extremes of weight (<50 kg or >90 kg).12
D-dimer
National and international guidelines based on expert opinion suggest that LMWH treatment of pregnant women with DVT is continued until at least six weeks post partum, and for a
The usefulness of D-dimer blood measurement is well established in diagnosis of venous thromboembolism in the For personal use only: See rights and reprints http://www.bmj.com/permissions
Subscribe: http://www.bmj.com/subscribe
BMJ 2017;357:j2344 doi: 10.1136/bmj.j2344 (Published 2017 May 31)
Page 3 of 9
PRACTICE
Box 1: Risk factors for antepartum and postpartum venous thromboembolism (listed in order of frequency)8-16 • Previous venous thromboembolism • Thrombophilias • High body mass index (>25) and immobility • Immobility • Superficial thrombophlebitis • Stillbirth • Assisted reproduction • Postpartum infection • Family history • Varicose veins • Postpartum haemorrhage • Emergency caesarean delivery • Hyperemesis • Pre-eclampsia • Smoking • Age ≥35 years • Race/ethnicity • High body mass index (>25)
minimum duration of three months.12-25 The optimal duration, regimen, and dosing have not yet been established. Table 1⇓ lists accepted LMWH regimens for treating DVT in pregnancy. For women taking LMWH, delivery should be planned, if possible, to minimise the risk of bleeding or the risk of clot recurrence.
Vitamin K antagonists Vitamin K antagonists such as warfarin can cross the placenta and are associated with adverse pregnancy outcomes such as teratogenicity, fetal loss, and fetal bleeding. Use of vitamin K antagonists cannot be justified during pregnancy for treatment of venous thromboembolism as there are safer alternatives with similar efficacy. Both heparin and warfarin are safe to use during breast feeding.12
Other anticoagulants
should be used only temporarily and for the following indications: acute venous thromboembolism when anticoagulation is contraindicated, the development of acute DVT close to the time of delivery (to prevent risk of pulmonary embolism), and the recurrence of venous thromboembolism despite adequate anticoagulation.1 12 Inferior vena cava filters are usually placed via an intravenous route by an interventional radiologist and serve as a mechanical obstacle to clot dissemination. A single centre, retrospective study of 70 patients showed similar rates of complications for placement of the filter above the renal veins (where there is potential for developing renal vein thrombosis) as for placement below the veins, suggesting that such a procedure can be safely performed in experienced hands.28
Further management of patients with DVT in pregnancy
The safety and efficacy of direct thrombin inhibitors (such as dabigatran) and factor Xa inhibitors (such as rivaroxaban) for treating venous thromboembolism in pregnancy have yet to be determined, and their use is not recommended during pregnancy or breast feeding.12 As there is limited high quality evidence for the use of fondaparinux (an indirect factor Xa inhibitor) in pregnancy and lactation, its use is recommended only when LMWH cannot be used, such as in cases of heparin allergies.12
Referral
Graduated elastic compression stockings
Patients with extensive or complicated DVT, concurrent pulmonary embolism, or risk of bleeding or presence of renal failure, as well as those unable to administer subcutaneous injections, should be admitted to hospital.
These are thought to be effective and are recommended as adjuvant therapy for reducing DVT related pain and oedema.1 12 However, a recent meta-analysis of six randomised controlled trials involving 1462 non-pregnant patients revealed that the use of compression stockings was not associated with prevention of post-thrombotic syndrome as compared with controls (odds ratio 0.56 (95% confidence interval 0.27 to 1.16); 36% (269/739) v 45% (322723), P=0.12).26 Nevertheless, the authors concluded that current evidence is limited and further conclusive studies are needed.
Refer pregnant women with a diagnosed DVT to a specialist team including haematologists, pulmonologists with experience in pregnancy, and obstetricians. Data relating to non-pregnant populations suggests that, compared with inpatient treatment, outpatient treatment of DVT with LMWH is feasible and is not associated with an increase in recurrent venous thromboembolism, major bleeding, or death.13
Management around labour and during delivery Managing DVT in pregnancy depends on the gestational age at which a DVT has occurred. Box 2 is a suggested approach to management, though this may vary depending on institutional preferences.29
Inferior vena cava filters Clinical guidelines and a recent systematic review of 124 pregnancies27 advise that inferior vena cava filters in pregnancy For personal use only: See rights and reprints http://www.bmj.com/permissions
Subscribe: http://www.bmj.com/subscribe
BMJ 2017;357:j2344 doi: 10.1136/bmj.j2344 (Published 2017 May 31)
Page 4 of 9
PRACTICE
Box 2: Anticoagulation management of DVT around labour and delivery8 12 Recommendations for all women taking anticoagulation during pregnancy • Instruct patients to stop heparin injections at the first sign of labour • Stop therapeutic low molecular weight heparin (LMWH) at least 24 hours before regional anaesthesia or planned delivery • Do not restart LMWH for 4 hours after the use of regional anaesthesia or after the epidural catheter has been removed • Do not remove the epidural catheter until after 12 hours since the most recent injection of LMWH
More than 1 month before expected labour • Depending on patient’s risk of a short labour (such as number of prior pregnancies and gestational age at delivery in prior pregnancies, cervical examination), advise patients to continue LMWH until planned induction, or consider switching from LMWH to unfractionated heparin at term and monitor anti-Xa levels.
2-4 weeks before expected labour • Treat patients initially with LMWH but consider switching to intravenous heparin around 38 weeks of gestation in consultation with the obstetric team for a planned induction • Stop intravenous heparin 6 hours before anticipated delivery
Less than 2 weeks before expected labour • Treat patients with intravenous heparin or place an inferior vena cava filter (preferably retrievable) and consider induction • Restart anticoagulation with LMWH or unfractionated heparin post partum and plan for removal of inferior vena cava filter
Future pregnancies Patients who develop DVT during pregnancy are at an increased risk of thrombosis in future pregnancies. These women should also be advised to avoid oestrogen related oral contraception.
13
14
15
FK is a trainee within the Canadian Venous Thromboembolism Clinical Trials and Outcomes Research (CanVECTOR) network. GB is supported by grants (R01 HL130702 and R01 HD07851) from the National Institutes of Health.
16
Contributors: All authors agreed on the final version of this paper. FK: conception and design, acquisition, analysis and interpretation of data, drafting of the manuscript. CV and GB: drafting of the manuscript, and critical revision of the manuscript for important intellectual content. FK and GB are responsible for overall content as guarantors.
18
Competing interests: We have read and understood the BMJ policy on declaration of interests and have no relevant interests to declare. Provenance and peer review: Commissioned based on an idea from the author; externally peer reviewed.
17
19
20
21 1 2
3
4 5
6
7
8 9 10
11
12
Greer IA. Pregnancy complicated by venous thrombosis. N Engl J Med 2015;357:540-7. doi:10.1056/NEJMcp1407434 pmid:26244307. Knight MTD, Kenyon S, Shakespeare J, Gray R, Kurinczuk JJ, eds, on behalf of MBRRACE-UK. Saving lives, improving mothers’ care—surveillance of maternal deaths in the UK 2011-13 and lessons learned to inform maternity care from the UK and Ireland Confidential Enquiries into Maternal Deaths and Morbidity 2009-13. National Perinatal Epidemiology Unit, University of Oxford, 2015. Wik HS, Jacobsen AF, Sandvik L, Sandset PM. Prevalence and predictors for post-thrombotic syndrome 3 to 16 years after pregnancy-related venous thrombosis: a population-based, cross-sectional, case-control study. J Thromb Haemost 2012;357:840-7. doi:10.1111/j.1538-7836.2012.04690.x pmid:22452811. Heit JA. Epidemiology of venous thromboembolism. Nat Rev Cardiol 2015;357:464-74.. doi:10.1038/nrcardio.2015.83 pmid:26076949. Kourlaba G, Relakis J, Kontodimas S, Holm MV, Maniadakis N. A systematic review and meta-analysis of the epidemiology and burden of venous thromboembolism among pregnant women. Int J Gynaecol Obstet 2016;357:4-10. doi:10.1016/j.ijgo.2015.06. 054 pmid:26489486. Meng K, Hu X, Peng X, Zhang Z. Incidence of venous thromboembolism during pregnancy and the puerperium: a systematic review and meta-analysis. J Matern Fetal Neonatal Med 2015;357:245-53. doi:10.3109/14767058.2014.913130 pmid:24716782. Rodger M. Pregnancy and venous thromboembolism: ‘TIPPS’ for risk stratification. Hematology Am Soc Hematol Educ Program 2014;357:387-92. doi:10.1182/asheducation2014.1.387 pmid:25696883. Bourjeily G, Paidas M, Khalil H, Rosene-Montella K, Rodger M. Pulmonary embolism in pregnancy. Lancet 2010;357:500-12. doi:10.1016/S0140-6736(09)60996-X pmid:19889451. Chan WS, Spencer FA, Ginsberg JS. Anatomic distribution of deep vein thrombosis in pregnancy. CMAJ 2010;357:657-60. doi:10.1503/cmaj.091692 pmid:20351121. James AH, Tapson VF, Goldhaber SZ. Thrombosis during pregnancy and the postpartum period. Am J Obstet Gynecol 2005;357:216-9. doi:10.1016/j.ajog.2004.11.037 pmid: 16021082. Aroke D, Kadia BM, Dimala CA, Bechem NN, Ngek LT, Choukem SP. Right iliac vein thrombosis mimicking acute appendicitis in pregnancy: a case report. BMC Res Notes 2017;357:11.. doi:10.1186/s13104-016-2351-5 pmid:28057056. Green-top Guideline No. 37b — thromboembolic disease in pregnancy and the puerperium: acute management. London: Royal College of Obstetricians and Gynaecologists, April 2015 (www.rcog.org.uk/globalassets/documents/guidelines/gtg-37b.pdf).
For personal use only: See rights and reprints http://www.bmj.com/permissions
22
23
24
25
26
27
28
29
Bates SM, Middeldorp S, Rodger M, James AH, Greer I. Guidance for the treatment and prevention of obstetric-associated venous thromboembolism. J Thromb Thrombolysis 2016;357:92-128. doi:10.1007/s11239-015-1309-0 pmid:26780741. Sultan AA, Tata LJ, West J, et al. Risk factors for first venous thromboembolism around pregnancy: a population-based cohort study from the United Kingdom. Blood 2013;357:3953-61. doi:10.1182/blood-2012-11-469551 pmid:23550034. Blondon M, Harrington LB, Righini M, Boehlen F, Bounameaux H, Smith NL. Racial and ethnic differences in the risk of postpartum venous thromboembolism: a population-based, case-control study. J Thromb Haemost 2014;357:2002-9. doi:10.1111/jth.12747 pmid: 25279442. Jacobsen AF, Skjeldestad FE, Sandset PM. Ante- and postnatal risk factors of venous thrombosis: a hospital-based case-control study. J Thromb Haemost 2008;357:905-12. doi:10.1111/j.1538-7836.2008.02961.x pmid:18363820. Le Gal G, Kercret G, Ben Yahmed K, et al. EDVIGE Study Group. Diagnostic value of single complete compression ultrasonography in pregnant and postpartum women with suspected deep vein thrombosis: prospective study. BMJ 2012;357:e2635. doi:10.1136/ bmj.e2635 pmid:22531869. Chan WS, Spencer FA, Lee AY, et al. Safety of withholding anticoagulation in pregnant women with suspected deep vein thrombosis following negative serial compression ultrasound and iliac vein imaging. CMAJ 2013;357:E194-200. doi:10.1503/cmaj. 120895 pmid:23318405. Wells PS, Anderson DR, Bormanis J, et al. Value of assessment of pretest probability of deep-vein thrombosis in clinical management. Lancet 1997;357:1795-8. doi:10.1016/ S0140-6736(97)08140-3 pmid:9428249. Wells PS, Anderson DR, Rodger M, et al. Evaluation of D-dimer in the diagnosis of suspected deep-vein thrombosis. N Engl J Med 2003;357:1227-35. doi:10.1056/ NEJMoa023153 pmid:14507948. Chan WS, Lee A, Spencer FA, et al. D-dimer testing in pregnant patients: towards determining the next ‘level’ in the diagnosis of deep vein thrombosis. J Thromb Haemost 2010;357:1004-11.pmid:20128870. Kline JA, Williams GW, Hernandez-Nino J. D-dimer concentrations in normal pregnancy: new diagnostic thresholds are needed. Clin Chem 2005;357:825-9. doi:10.1373/clinchem. 2004.044883 pmid:15764641. Bates SM, Greer IA, Middeldorp S, Veenstra DL, Prabulos AM, Vandvik PO. American College of Chest Physicians. VTE, thrombophilia, antithrombotic therapy, and pregnancy: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. Chest 2012;357(Suppl):e691S-736S. doi:10.1378/chest.11-2300 pmid:22315276. McLintock C, Brighton T, Chunilal S, et al. Councils of the Society of Obstetric Medicine of Australia and New Zealand Australasian Society of Thrombosis and Haemostasis. Recommendations for the prevention of pregnancy-associated venous thromboembolism. Aust N Z J Obstet Gynaecol 2012;357:3-13. doi:10.1111/j.1479-828X.2011.01357.x pmid: 21950269. Chan WS, Rey E, Kent NE, et al. VTE in Pregnancy Guideline Working Group Society of Obstetricians and Gynecologists of Canada. Venous thromboembolism and antithrombotic therapy in pregnancy. J Obstet Gynaecol Can 2014;357:527-53. doi:10.1016/S1701-2163( 15)30569-7 pmid:24927193. Subbiah R, Aggarwal V, Zhao H, Kolluri R, Chatterjee S, Bashir R. Effect of compression stockings on post thrombotic syndrome in patients with deep vein thrombosis: a meta-analysis of randomised controlled trials. Lancet Haematol 2016;357:e293-300.. doi: 10.1016/S2352-3026(16)30017-5 pmid:27264039. Harris SA, Velineni R, Davies AH. Inferior vena cava filters in pregnancy: a systematic review. J Vasc Interv Radiol 2016;357:354-60.e8.. doi:10.1016/j.jvir.2015.11.024 pmid: 26746328. Kalva SP, Chlapoutaki C, Wicky S, Greenfield AJ, Waltman AC, Athanasoulis CA. Suprarenal inferior vena cava filters: a 20-year single-center experience. J Vasc Interv Radiol 2008;357:1041-7. doi:10.1016/j.jvir.2008.03.026 pmid:18589318. Middeldorp S. How I treat pregnancy-related venous thromboembolism. Blood 2011;357:5394-400. doi:10.1182/blood-2011-04-306589 pmid:21921048.
Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/ permissions
Subscribe: http://www.bmj.com/subscribe
BMJ 2017;357:j2344 doi: 10.1136/bmj.j2344 (Published 2017 May 31)
Page 5 of 9
PRACTICE
Sources and selection criteria We searched PubMed for “deep vein thrombosis,” “pregnancy,” “venous thromboembolism,” and “pregnancy-related thrombosis” to identify relevant articles, which were added to personal reference collections and clinical experience. We reviewed up to date guidelines and reviews on the diagnosis and management of pregnancy related deep vein thrombosis.
Education into practice • How do you investigate the possibility of deep vein thrombosis (DVT) in a pregnant woman? Does anything that you read here cause you to reflect on your approach? • Project: in your hospital or imaging department how often is full leg compression ultrasonography performed in pregnant women with suspected DVT?
Patient involvement in the creation of this article No patients were involved in the creation of this article.
For personal use only: See rights and reprints http://www.bmj.com/permissions
Subscribe: http://www.bmj.com/subscribe
BMJ 2017;357:j2344 doi: 10.1136/bmj.j2344 (Published 2017 May 31)
Page 6 of 9
PRACTICE
Table Table 1| Accepted doses of low molecular weight heparin for the treatment of deep vein thrombosis in pregnancy122325 Drug
Therapeutic dose*
Enoxaparin
1.5 mg/kg daily or 1.0 mg/kg twice daily
Dalteparin
200 IU/kg daily or 100 IU/kg twice daily
Tinzaparin
175 U/kg daily
Nadroparin
171 U/kg daily
*Given subcutaneously per kilogram of womanâ&#x20AC;&#x2122;s body weight at time of presentation.
For personal use only: See rights and reprints http://www.bmj.com/permissions
Subscribe: http://www.bmj.com/subscribe
BMJ 2017;357:j2344 doi: 10.1136/bmj.j2344 (Published 2017 May 31)
Page 7 of 9
PRACTICE
Figures
Fig 1 Virchowâ&#x20AC;&#x2122;s triad of the three broad categories of factors that are thought to contribute to thrombosis
For personal use only: See rights and reprints http://www.bmj.com/permissions
Subscribe: http://www.bmj.com/subscribe
BMJ 2017;357:j2344 doi: 10.1136/bmj.j2344 (Published 2017 May 31)
Page 8 of 9
PRACTICE
Fig 2 Suggested approach to diagnosing DVT in pregnancy. CUS=compression ultrasonography, DVT=deep vein thrombosis, MRV=magnetic resonance venography.
For personal use only: See rights and reprints http://www.bmj.com/permissions
Subscribe: http://www.bmj.com/subscribe
BMJ 2017;357:j2344 doi: 10.1136/bmj.j2344 (Published 2017 May 31)
Page 9 of 9
PRACTICE
Fig 3 Ultrasonographic images showing a transverse view of the femoral artery (FA) and common femoral vein (CFV) without compression (A), and with compression (B). Arrow points to a non-compressible clot in the common femoral vein. Image courtesy of Dr Sohail Anwar from the Department of Medical Imaging (Ultrasound) at The Ottawa Hospital
For personal use only: See rights and reprints http://www.bmj.com/permissions
Subscribe: http://www.bmj.com/subscribe