Superficial venous thrombosis: Ultrasound, analysis of clot location, and risk factor assessment are “fundamental”

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James Froehlich
James Froehlich

At THE VEINS at VIVA meeting (10–11 September 2017, Las Vegas, USA), James Froehlich, University of Michigan, Ann Arbor, USA, reviewed guidelines on the management of superficial venous thrombosis (SVT) and emphasised the importance of performing duplex ultrasound in the examination, assessing clot location and extent, considering the risk factors for recurrence and development of deep vein thrombosis (DVT), and discussing with the patient their options on the use of anticoagulants. 

The diagnosis of superficial venous thrombosis is usually based on physical examination and findings such as oedema (especially if acute and unilateral), history of immobility, erythema or tenderness of the superficial vein, and other risk factors such as varicose veins, DVT and previous episodes of SVT. Ultrasound, Froehlich said, is effective for SVT, “making it very easy to identify whether there is in fact a thrombosed vein”.

The superficial venous system is defined as the great saphenous vein and all its branches, and joins the deep system at the saphenous femoral junction, and the small saphenous vein, which joins the popliteal vein. Many of these branches can varicose and are subject to thrombosis. In the past, Froehlich told delegates, “my surgical colleagues thought that this was simple. You did a duplex ultrasound, and if the patient did not present with a superficial clot, we did not treat them. If they have a clot, you treated them, with the removal of the thrombophlebitic vein or use of anticoagulation, depending on your preference”.

The picture changed with the results of a study on the role of anticoagulants in SVT (N Engl J Med 2010; 363:1222– 32). In the study, patients who had a large SVT (>5cm in length) and/or one that was located near the saphenous junction were randomised to a prophylactic dose of anticoagulant (fondaparinux 2.5mg a day) and placebo. There was a significant improvement in the rates of pulmonary embolism, death and extensive venous thrombosis with fondaparinux.

These results led the 2012 CHEST guidelines to suggest that “in patients with SVT of the lower limb of at least 5cm in length, a prophylactic dose of fondaparinux or low molecular weighted heparin (LMWH) for 45 days should be used over no anticoagulation (Grade 2B)”. The guidelines also stated that fondaparinux 2.5mg daily was probably better than MLWH (Grade 2C).

“However, this still did not give us a lot of leeway or guidance in terms of whom to treat beyond this criteria of 5cm superficial clot,” Froehlich noted. In 2013, an international consensus statement was published in International Angiology and reiterated some of the points included in the CHEST guidelines. “The document stated that you have to perform an ultrasound (as some of these patients have DVT as well as the superficial clot), LMWH helps, there is good evidence for the use of fondaparinux. And it added the concept of location. If the thrombus is close to the saphenofemoral junction then these patients should be treated aggressively with anticoagulation or intervention. If it is distal below the knee then anticoagulation is probably not useful,” Froehlich said. “This document helped us by further incorporating location into this thinking.”

Earlier this year the CHEST guidelines were updated to include the concept of risk. For patients with SVT but at low risk of DVT, the guidelines suggest oral non-steroidal anti-inflammatory drugs rather than anticoagulation as first-line drug therapy (Grade 2B). If the patient is at increased risk of DVT it suggests the use of anticoagulation for 45 days, with fondaparinux, LMWH, direct oral anticoagulants (DOACs) and vitamin K antagonists appearing to be equally effective. The guidelines also state that “the decision to anticoagulate the patient when the thrombus approaches the deep venous system should be individualised, and either anticoagulation or serial duplex ultrasound may be appropriate. For SVT after radiofrequency or laser vein ablation, we suggest not routinely anticoagulating the patient (Grade 2C).”

Froehlich told THE VEINS delegates that “this raises an important point that should guide our thinking about venous thromboembolism in general, superficial and deep. We do not actually treat DVT; we give anticoagulants to prevent a new episode, or to prevent disease extension. If you keep that in mind, for both superficial and deep disease, then it helps to understand how these factors, such as risk, may be important”. He added that the risk factors for SVT are the same for venous thromboembolic disease: recent surgery/immobility, cancer, thrombophilia/birth control pill use, venous insufficiency/varicosities, history of venous thromboembolism, male sex, and length of clot/proximity to saphenous femoral junction.

He gave the University of Washington’s guideline as an example of a protocol that “incorporates this well”. The guidelines state that in the case of SVT, if the patient does not have risk factors, conservative therapy should be considered. The location and size of the clot should be assessed, and maybe low-dose prophylactic anticoagulation should be used. For those who have risk factors, Froehlich said, “there are still very few data to guide us in terms of anticoagulants”, and added, “We have to talk to our patients about risk, risk avoidance and interest and willingness to undergo anticoagulation treatment. Fondaparinux is low risk but clearly effective, and to come are other alternatives that have not been well studied such as prophylactic or low doses of DOACs, which are incredibly safe. We are still in a data-free zone here.”

Froehlich summarised his talk by saying that there are three things he considers fundamental when managing SVT. “You have to perform a duplex ultrasound scan, even if the SVT is obvious in the physical exam, because you have to know if there is also a deep clot. Then look at location and extent of clot as well as risk for the problem you are trying to avoid, which is extension or recurrence. And then you have to have a discussion with your patient—conservative treatment vs. these low dose prophylactic anticoagulants and whether or not removing or ablating that vein may prevent recurrent episodes in the future,” he said.

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