VTE Prevention, Diagnosis, and Acute Lower-Extremity DVT

52.1Definition and presentation

Deep vein thrombosis is thrombus formation in the deep veins, usually of the lower limb; it is one manifestation of venous thromboembolism ESVS 2021. A proximal deep-vein thrombus can embolize to the pulmonary arteries to cause pulmonary embolism, the other manifestation of the venous thromboembolism spectrum. Proximal disease carries the greatest embolic risk.

Many deep vein thromboses are clinically silent and signs are non-specific, necessitating clinical probability scoring and objective testing ESVS 2021 · ASH 2018. Typical clinical features include: - Unilateral limb swelling (iliofemoral disease typically causes whole-limb swelling) - Pain or tenderness, often localized to the calf - Warmth - Erythema

52.2Pathophysiology

Venous thrombosis arises from Virchow's triad: stasis, endothelial injury, and hypercoagulability ESVS 2021 · Anderson & Spencer 2003. Thrombus typically forms in the valve pockets of the calf veins, where stasis and local hypoxia activate coagulation. Most calf thrombi resolve or stay confined; a minority propagate proximally into the popliteal, femoral, and iliac veins. This proximal extension drives pulmonary embolism and post-thrombotic syndrome Heit 2015.

Iliofemoral thrombosis carries the greatest post-thrombotic burden. Persistent outflow obstruction and valvular reflux produce ambulatory venous hypertension, which underlies chronic limb swelling, pain, and ulceration ESVS 2021. May-Thurner anatomy (compression of the left common iliac vein by the overlying right common iliac artery) predisposes to left-sided iliofemoral deep vein thrombosis, particularly in younger women.

Phlegmasia cerulea dolens is the extreme of the clinical spectrum: near-total venous outflow occlusion raises compartment pressures, compromises arterial inflow, and threatens limb viability ESVS 2021.

52.3Epidemiology and risk factors

Venous thromboembolism has a population incidence of roughly 1 to 2 per 1000 person-years and is the third most common acute cardiovascular syndrome after myocardial infarction and stroke Worcester 2006 · AHA 2024 · Heit 2015. Incidence rises steeply with age, from under 1 per 1000 per year in young adults to nearly 1 per 100 per year after age 80 LITE 2004.

High-risk and sex-specific risk factors include ESVS 2021 · Heit 2015: - Pregnancy and the puerperium (risk is particularly high in the postpartum period) - Estrogen-containing contraception and hormone therapy - Active cancer - Recent surgery or trauma - Immobility - Prior venous thromboembolism - Inherited thrombophilia - Advancing age

Hospitalized, post-operative, immobile, and oncologic patients carry the highest short-term risk, and many at-risk inpatients receive no guideline-recommended prophylaxis ENDORSE 2008.

52.4Risk assessment and prophylaxis

Every adult surgical, trauma, and acutely ill medical inpatient is assessed for both thrombotic and bleeding risk. In surgical and trauma patients, a Caprini score of 5 or more identifies high risk and warrants pharmacologic prophylaxis unless bleeding risk prohibits it ASH 2019 · Caprini · 2005. In acutely ill medical inpatients, a Padua score of 4 or more identifies candidates for pharmacologic prophylaxis, and the IMPROVE bleeding score identifies those in whom bleeding risk favors mechanical prophylaxis ASH 2018 · IMPROVE 2011 · Padua score 2010.

Low-molecular-weight heparin is the default agent; fondaparinux is an alternative ASH 2019 · ASH 2018. In acutely ill medical inpatients, enoxaparin prophylaxis reduced symptomatic venous thromboembolism versus placebo in MEDENOX (1999) MEDENOX 1999. The dose is reduced or antifactor-Xa monitored in severe renal impairment, at a creatinine clearance below 30 mL/min. Where bleeding risk is high or active bleeding precludes anticoagulation, intermittent pneumatic compression is the substitute, and it works only while the device is worn IMPROVE 2011.

Prophylaxis prevents thrombosis; bleeding risk determines the method. Assessment is repeated after reoperation, a bleeding event, a change in renal function, or a change in mobility ASH 2019 · ASH 2018.

52.5Diagnosis

Compression duplex ultrasonography is the first-line and reference standard diagnostic test for lower-extremity deep vein thrombosis ESVS 2021 · ASH 2018. Suspected deep vein thrombosis is assessed using pretest probability scoring (Wells score), D-dimer, and imaging.

In outpatients, a modified Wells score of 1 or less with a negative high-sensitivity D-dimer excludes deep vein thrombosis without imaging ESVS 2021 · ASH 2018 · Wells 2003. A higher Wells category or a positive D-dimer requires compression duplex ultrasonography.

D-dimer specificity is low in inpatients and in patients with cancer, pregnancy, or advanced age; a positive result in these groups is rarely discriminating ESVS 2021 · Wells 2003. In a post-operative or cancer inpatient with high clinical suspicion, diagnosis proceeds directly to compression duplex ultrasonography ASH 2018.

52.6Anticoagulation

Confirmed acute deep vein thrombosis is treated with prompt anticoagulation unless contraindicated. A direct oral anticoagulant is first-line for most patients and is preferred over low-molecular-weight heparin followed by a vitamin K antagonist in non-cancer patients without antiphospholipid syndrome, mechanical heart valves, severe renal impairment, or pregnancy CHEST 2021 · ESVS 2021 · ASH 2020.

Renal function, prior bleeding, recent surgery, antiplatelet co-therapy, age, and weight are reviewed before prescribing, utilizing bleeding-risk tools such as IMPROVE and GARFIELD-VTE as adjuncts GARFIELD-VTE 2019 · IMPROVE 2011.

Apixaban (AMPLIFY, 2013) and rivaroxaban (EINSTEIN-DVT, 2010) are single-drug regimens with an initial intensified dose: apixaban 10 mg twice daily for 7 days then 5 mg twice daily, and rivaroxaban 15 mg twice daily for 21 days then 20 mg once daily AMPLIFY 2013 · EINSTEIN-DVT 2010. Edoxaban (HOKUSAI-VTE, 2013) and dabigatran (RE-COVER, 2009) require at least 5 days of parenteral anticoagulation before the oral drug HOKUSAI-VTE 2013 · RE-COVER 2009. In acute venous thromboembolism, apixaban and edoxaban were non-inferior to warfarin for recurrence with less bleeding ASH 2020.

52.7Endovascular and surgical treatment

Most acute lower-extremity deep vein thrombosis is treated with anticoagulation alone ESVS 2021 · ASH 2020. Thrombus removal is considered for acute iliofemoral deep vein thrombosis with severe symptoms (marked whole-limb swelling, disabling pain limiting ambulation) or a threatened limb (phlegmasia cerulea dolens), in patients with low bleeding risk and good life expectancy ATTRACT 2017.

When intervention is chosen, endovascular techniques are first-line: catheter-directed thrombolysis, pharmacomechanical thrombolysis, and mechanical thrombectomy ESVS 2021 · ATTRACT 2017 · CaVenT 2012. An underlying iliac vein stenosis or May-Thurner compression is treated with venous stenting under intravascular ultrasound guidance to prevent re-thrombosis. Open surgical thrombectomy is reserved for failure of, or contraindication to, endovascular therapy. An inferior vena cava filter is placed only when anticoagulation is contraindicated by active major bleeding in a patient with acute proximal deep vein thrombosis or pulmonary embolism; a retrievable filter is preferred and is removed once anticoagulation can safely resume CHEST 2021 · ASH 2020.

The trial evidence is restrictive. In ATTRACT (2017), pharmacomechanical thrombolysis did not reduce post-thrombotic syndrome at 24 months and caused more major bleeding; an iliofemoral subgroup showed a modest reduction in moderate-to-severe post-thrombotic syndrome ATTRACT 2017. In CaVenT (2012), additional catheter-directed thrombolysis reduced post-thrombotic syndrome by 14 percentage points at two years, at a bleeding cost, a benefit sustained at five years CaVenT 5-year 2016 · CaVenT 2012.

52.8Cancer-associated VTE

Cancer-associated venous thromboembolism is treated with either low-molecular-weight heparin or a direct oral factor Xa inhibitor. Low-molecular-weight heparin was established as superior to warfarin by CLOT (2003) and supported by CATCH (2015) ASH 2020 · CATCH 2015 · CLOT 2003.

Edoxaban, rivaroxaban, and apixaban are non-inferior to low-molecular-weight heparin for recurrence, but edoxaban (HOKUSAI Cancer, 2018) and rivaroxaban (SELECT-D, 2018) increased bleeding in gastrointestinal and genitourinary tumors ASH 2020 · HOKUSAI Cancer 2018 · SELECT-D 2018.

Apixaban (Caravaggio, 2020) was non-inferior to dalteparin for recurrence without the gastrointestinal-bleeding excess, making it a reasonable oral option even in luminal malignancy ASH 2020 · Caravaggio 2020. The choice between low-molecular-weight heparin and an oral factor Xa inhibitor turns on tumor type, drug interactions with systemic therapy, platelet count, and tolerance of injections; anticoagulation continues while the cancer is active.

52.9Duration, compression, and secondary prevention

Treatment duration follows the classification of the index event: venous thromboembolism provoked by a transient risk factor is treated for 3 months; unprovoked venous thromboembolism is treated for at least 3 months with extended therapy considered; cancer-associated disease continues while the cancer is active CHEST 2021 · ESVS 2021 · ASH 2020.

For extended therapy, a reduced-dose direct oral anticoagulant is effective. In EINSTEIN CHOICE (2017), rivaroxaban 20 mg or 10 mg once daily reduced recurrent venous thromboembolism versus aspirin without increasing major bleeding EINSTEIN CHOICE 2017. The DASH and HERDOO2 scores estimate recurrence risk after a first unprovoked event and structure the decision to stop or extend DASH 2012 · HERDOO2 2008. Bleeding risk is re-evaluated whenever therapy is extended, particularly around staged operations, wounds, and antiplatelet therapy GARFIELD-VTE 2019 · IMPROVE 2011.

Graduated compression therapy (30-40 mmHg stockings and intermittent pneumatic compression) relieves acute pain and swelling and is used in the acute phase ESVS 2021. Routine elastic stockings are not recommended solely to prevent post-thrombotic syndrome. SOX (2014) found no reduction in post-thrombotic syndrome, recurrence, or quality of life with active versus placebo stockings, a result confirmed in pooled analysis Cochrane 2014 · SOX 2014. However, selected patients with residual venous obstruction or persistent symptoms benefit from stockings Kahn 2014.

52.10Areas of controversy

The role of catheter-directed thrombolysis in iliofemoral deep vein thrombosis is contested: ATTRACT (2017) was negative overall, while its iliofemoral subgroup and the earlier CaVenT (2012) trial suggest benefit, and patient selection remains individualized ESVS 2021 · ATTRACT 2017 · CaVenT 2012. Optimal duration after a first unprovoked event is unsettled, with risk-prediction tools informing rather than settling the stop-or-extend decision DASH 2012 · HERDOO2 2008. The preferred anticoagulant in cancer-associated disease continues to move toward direct oral anticoagulants, with the choice still dependent on tumor type ASH 2020 · Caravaggio 2020 · SELECT-D 2018.