DVT

Summary


Identification of DVT with POCUS is an ideal skill for the anesthesiologist, emergency physician, and critical care physician.

It is essential that the physician understands that absence of compression and presence of echogenic material are both treated as a DVT.

The exam extends from the proximal leg to the beginning of the calf veins. There are many pitfalls that clinicians must understand when performing the POCUS evaluation of DVT.

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Upper Extremity DVT


Upper Extremity DVTs have a number of differences than lower extremity DVTs. Most importantly, upper extremity DVTs are more technically challenging to diagnose. The evaluation of an upper extremity DVT is considered outside the scope of practice of POCUS.

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Whole leg ultrasound vs. POCUS


It is common to misunderstand the difference between whole-leg ultrasound, 2-region ultrasound, 3-region ultrasound, and extended compression ultrasound.

It is essential that physicians new to the POCUS evaluation of a DVT perform compression ultrasound in as many areas as possible. This extended compression ultrasound establishes good practice patterns.

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Valves


It is not uncommon to visualize valves within the deep venous system. Here is an example of a valve opening. Grey-scale flow can be seen as the blood moves from one area to another. This is a normal finding. Presence of valves or grey-scale flow does not indicate pathology.

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Incomplete compression


It is critical to apply adequate force to cause complete coaptation of the vein. Incomplete compression of the vein will create a false positive. This is one of the biggest failures of individuals new to DVT imaging.

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Lymph Nodes


Lymph nodes can be misinterpreted as a DVT.
Image the structure in transverse and longitudinal planes. Add color flow doppler to the structure to identify typical blood flow of a lymph node.

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Medical Management


Proximal DVT without history of cancer

  • Novel oral anticoagulant (NOAC)) preferred over a vitamin K antagonist (coumadin) (Grade 2B recommendation)
  • Coumadin preferred to low-molecular weight heparin (LMWH) (Grade 2C recommendation)
  • Duration of treatment: 3 months for 1st clot (Grade 1B recommendation)

Proximal DVT with cancer (“cancer-associated thrombosis”)

  • LMWH preferred to coumadin or NOAC (Grade 2C recommendation)
  • Duration of treatment: 3 months for 1st clot (Grade 1B recommendation)

Isolated Distal (calf) DVT

  • Up to 25% will propagate proximally in admitted patients but no robust evidenced in ambulatory patients discharged home
  • Absence of severe symptoms and no risk factors for extension
    • Serial imaging over 2 weeks preferred to anticoagulation (Grade 2C recommendation)
    • No established role for providing antiplatelet therapy (i.e. aspirin) alone in these cases but a reasonable intervention
  • Presence of severe symptoms or risk factors for extension
    • Anticoagulation preferred to serial imaging (Grade 2C recommendation)
    • Anticoagulation choices same as for proximal DVT (Grade 1B recommendation)

Superficial Thrombophlebitis

  • Saphenous vein clots above the knee can spread into deep venous system via the saphenous-femoral junction
  • Initial treatment with NSAIDs, warm compresses and compression stockings
  • Repeat US in 2-5 days and start anticoagulation if clot extending

Catheter-Directed Thrombolysis (CDT)

  • No substantial benefits in most patients with proximal DVT
  • Likely increases risk of major bleeding
  • Possible benefit in post-thrombotic syndrome in patients with iliofemoral DVT and a low risk of bleeding

References:
1) Kearon C, Akl EA, Ornelas J, Blaivas A, Jimenez D, Bounameaux H, Huisman M, King CS, Morris TA, Sood N, Stevens SM, Vintch JRE, Wells P, Woller SC, Moores L. Antithrombotic Therapy for VTE Disease: CHEST Guideline and Expert Panel Report. Chest. 2016 Feb;149(2):315-352.
2) Decousus H et al. Fondaparinux for the treatment of superficial-vein thrombosis in the legs. N Engl J Med 2010; 363:1222-1232.
3) Bashir R et al. Comparative outcomes of catheter-directed thrombolysis plus anticoagulation vs anticoagulation alone to treat lower-extremity proximal deep vein thrombosis. JAMA Intern Med. 2014;174(9):1494-1501.

Medical Decision Making


A negative POCUS evaluation for DVT always requires follow up in 5-14 days because the calf is not evaluated.

There is a low probability that an isolated calf vein DVT can propagate proximally into the popliteal or femoral region. The follow up DVT evaluation in 5-14 days will detect if a missed calf vein DVT migrated to the proximal leg.

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Interpretation – Popliteal Region


In the popliteal region, the popliteal vein is often superficial to the popliteal artery. Notice how the physician is compressing with enough pressure to cause moderate collapse of the popliteal artery. However, the popliteal vein does not collapse. Additionally, there is heterogeneous material visualized in the popliteal vein.

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Image missingThe video shows the ultrasound view of the drawing above.

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This clip comes from the popliteal region. It occurs distal to the split of the first calf vein, the peroneal vein. Note the physician compresses the popliteal artery, but the popliteal vein does not compress. This lack of compression is concerning for a DVT

Interpretation – Mid Thigh


The video below demonstrates a DVT present in the femoral vein in the mid thigh. Notice how the physician attempts to compress the femoral vein. The thick-walled artery can be seen with moderate collapse, but the vein barely changes in size.

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