Patient Education Blog

Archive for the ‘Deep vein thrombosis (DVT)’ Category

DVT/ PE and Airline Travel

| Deep vein thrombosis (DVT), Pulmonary embolism, Venous clots | Comments Off on DVT/ PE and Airline Travel

Stephan Moll, MD writes… Can the person with a newly diagnosed DVT or PE safely fly, or should he/she wait for a few weeks before flying?  It appears o.k. to fly early.  There is no evidence that flying early after the diagnosis of DVT or PE leads to an increased risk of recurrent clots or breaking off of clots from a DVT to form a PE, as long as the patient is on adequate blood thinner treatment.

Airline travel and Blood Clots

  a) The person NOT on blood thinners

Airline travel is an established (mild) risk factor for DVT and PE in the patient who is NOT on blood thinners [ref 1,2]; the longer the travel, the higher the risk for clots [1]. Typically, multiple risk factors come together –overweight, hormone therapy (e.g. contraceptives), recent surgery, trauma, or hospital stay, cancer, genetic or acquired clotting disorders, and the immobility from the travel itself.  It has also been suggested that the decreased air pressure in the airplane cabin might lead to activation of the clotting system and an increased risk for DVT or PE, particularly in persons with one or more of the above underlying risk factors [ref 4].  However, neither have published data on this issue been consistent, nor is it clear whether such changes are really relevant for the traveller.

  b) The patient with VTE who is on blood thinners

  1. Is there an increased risk for recurrent DVT or PE or clot breaking off from a DVT?  It is not known whether the risk for recurrent clot or the risk for a DVT to break off to cause a PE is increased with airline travel in the patient who is on blood thinners.  Any potential activation of the clotting system by the decreased cabin pressure while flying is very likely counteracted by the fact that the patient is on a blood thinner.  Thus, an increased failure rate of blood thinners (i.e. progression of DVT or PE; increased risk of DVT leading to PE) is not likely.
  2. Is there worsened leg swelling in the patient with DVT?  The patient with acute DVT and leg swelling may experience somewhat more swelling during or after the flight – not because of worsening DVT, but because of increased fluid retention in the legs from the decreased air pressure in the cabin.  Many healthy people experience that, too. Also, the distances to walk and the prolonged standing in the airport may lead to increased leg swelling.  However, this is not expected to lead to worsening DVT or a new DVT.
  3. Is there worsened shortness of breath in the patient with PE?  The patient who has had a large PE or has other underlying lung disease (COPD, etc.) may have some worsening of shortness of breath during flying – not because of new PE, but because the airplane cabin contains slightly less oxygen than the air at sea level.

My Approach

In general, I discuss with the patient who has a new DVT or PE that…

  • it appears to be o.k. to fly immediately after the DVT or PE diagnosis, as long as the person is on full-dose blood thinners.
  • airline travel is not expected to lead to an increased risk of new DVT or PE or breaking off of clots from a DVT.
  • leg swelling in the person with DVT may temporarily worsen during and in the few days after airline travel due to the lower air pressure in the airline cabin.
  • shortness of breath in the person with a fairly large PE may be somewhat worse during airline travel due to the mildly decreased oxygen content in the airline cabin.
  • it may be worthwhile to delay a flight for at least a few days, to be sure that the patient is stable, no unexpected issues occur, and/or the patient has had time to adapt to this new, potentially life-modifying diagnosis and treatment.

As always, individualized medical decisions need to be made.


  1. Chandra D et al. Meta-analysis: Travel and risk for venous thromboembolism. Ann Intern Med 2009;151:180-190.
  2. Cannegieter SC. Travel-related thrombosis. Best Pract Res Clin Haematol. 2012 Sep;25(3):345-50.
  3. Schreijer AJ et al. Activation of coagulation system during air travel: a crossover study. Lancet 2006 Mar 11;367(9513):832-8.
  4. Schreijer AJ et al. Explanations for coagulation activation after air travel. J Thromb Haemost 2010 May;8(5):971-8.


I appreciate the discussions with Dr. Richard Moon, Medical Director, Center for Hyperbaric Medicine & Environmental Physiology, Duke University Medical Center, Dr. Claude Piantadosi, Interim Chief, Division of Pulmonary, Allergy and Critical Care Medicine, Duke University Medical Center, and Dr. Philip Blatt, Adjunct Professor of Internal Medicine and Hematology, Duke University Medical Center, Durham, NC.


Disclosure: None

Last updated:  July 12th, 2017

Antiphospholipid Syndrome: Can the New Oral Blood Thinners Be Used?

| Anticoagulants, Antiphospholipid antibodies, Deep vein thrombosis (DVT), Edoxaban, Eliquis, Eliquis - Apixaban, Pradaxa - dabigatran, Pulmonary embolism, Savaysa - Edoxaban, Venous clots, Xarelto - Rivaroxaban | Comments Off on Antiphospholipid Syndrome: Can the New Oral Blood Thinners Be Used?

Stephan Moll, MD and Damon Houghton, MD write … Antiphospholipid syndrome (APS) is an acquired clotting disorder.  Patients with APS may have DVT or PE that requires treatment with blood thinners. Warfarin (Coumadin®, Jantoven®), and sometimes the injectable heparin drugs (enoxaparin = Lovenox®; dalteparin = Fragmin®; tinzaparin = Innohep®; etc.), have traditionally been used in patients with APS.  A question that comes up is whether one of the new oral blood thinners (apixaban = Eliquis®; dabigatran = Pradaxa®; edoxaban = Savaysa®; rivaroxaban = Xarelto®) can be used instead of warfarin or a heparin drug.  These drugs are collectively referred to as direct oral anticoagulants (DOACs).

It is not known at this point whether DOACs are equally, more or less effective as/than warfarin in patients with APS.  Data from clinical trials directly comparing DOACs with warfarin are not yet available.  Given the absence of data, no formal recommendations or guidelines exist on this topic.  It is an individualized decision between a physician and patient with APS whether to use warfarin or a DOAC for the treatment of DVT or PE.

Published Data

Multiple cases of patients with APS treated with a DOAC have been published. All of these (i.e. a total of 122 patients) have recently been summarized [ref 1]: Sixteen percent (i.e. one of every 6 patients) had a recurrent clot on a DOAC.  As this is a high rate of DOAC failure, the authors caution about the use of DOACs in APS.  However, two things need to be considered: (a) it is also known that warfarin has a high failure rate [references 2,3]; and (b) due to the nature of case report publications (potential bias; absence of control group), no strong or meaningful conclusion is really possible as to how DOACs compare to warfarin in the treatment of DVT and PE in patients with APS

Ongoing Studies

Several studies on APS and the use of DOACs are ongoing.  Details of the following studies can be found at

  1. NCT02157272: A Prospective, Randomized Clinical Trial Comparing Rivaroxaban with Warfarin in High Risk Patients With Antiphospholipid Syndrome (TRAPS)
  2. NCT02295475: Apixaban for the Secondary Prevention of Thromboembolism Among Patients With the AntiphosPholipid Syndrome (ASTRO-APS)
  3. NCT02116036: Rivaroxaban for Antiphospholipid Antibody Syndrome (RAPS)

Our practice

This is what we discuss with the patient with APS who needs to be on a blood thinner:

  1. I highlight that no solid data exist regarding the use of DOACs in APS, and that it is not known whether the DOACs are as effective as warfarin, less effective or more effective.
  2. I discuss the fact that some patients with APS develop new clots in spite of being on warfarin and that recurrent clots may also occur on a DOAC.

If we decide to use a DOAC, then our preference is typically to use a twice daily dosed blood thinner (Eliquis® or Pradaxa®) rather than a once daily dosed drug (Xarelto® or Savaysa®).  The thought behind this is that a twice daily dosed drug leads to more steady drug levels throughout the day and that this may lead to a more effective blood thinning effect.  However, this is a theory unproven, and whether this truly leads to a lower risk of recurrent clots than being on a once daily drug is not known.  A recent publication of a case report with discussion of drug metabolism also favors a twice daily rather than a once daily dosed drug in patients with APS [ref 4].  Ultimately, the most effective medication is likely the one that is taken as prescribed; therefore, a patient’s preference regarding the feasibility and practicality of a once daily versus twice daily medication is also an important consideration.


  1. Dufrost V et al. Direct oral anticoagulants use in antiphospholipid syndrome: Are these drugs an effective and safe alternative to warfarin? A systematic review of the literature. Curr Rheumatol Rep 2016;18:74.
  2. Crowther M et al. A Comparison of two intensities of warfarin for the prevention of recurrent thrombosis in patients with the antiphospholipid antibody syndrome. N Engl J Med 2003;349:1133-8.
  3. Finazzi G et al. A randomized clinical trial of high-intensity warfarin vs. conventional antithrombotic therapy for the prevention of recurrent thrombosis in patients with the antiphospholipid syndrome (WAPS) J Thromb Haemost 2005;3: 848–853.
  4. Schofield JR et al. Dosing considerations in the use of the direct oral anticoagulants in the antiphospholipid syndrome. J Clin Pharm Ther. 2017 Jun 27. doi: 10.1111/jcpt.12582. [Epub ahead of print].


Disclosure: Dr. Moll has consulted for Janssen Pharmaceuticals and Boehringer-Ingelheim. Dr. Houghton has no disclosures.

Last updated: July 5th, 2017

IVC Filters, May-Thurner Syndrome, Pelvic Vein Stents

| Anatomy, Deep vein thrombosis (DVT), IVC filters, Postthrombotic syndrome, Therapy | Comments Off on IVC Filters, May-Thurner Syndrome, Pelvic Vein Stents

Stephan Moll, MD writes… An article for patients discussing (a) IVC filters (inferior vena cava filters; also often referred to as “Greenfield filters”), (b) narrowing of the main left pelvic vein (referred to as May-Thurner syndrome) and (c) stents in veins in the pelvis has just been published (  Color images are included helping explain what these conditions are.

Reference:  Carroll S, Moll S. Circulation. 2016;133:e383-e387


Last updated: Feb 18th, 2016

Study for Patients with Previous Leg DVT and Chronic Leg Symptoms

| Deep vein thrombosis (DVT), Postthrombotic syndrome, Trials | Comments Off on Study for Patients with Previous Leg DVT and Chronic Leg Symptoms

Stephan Moll, MD writes…  A clinical research study is being conducted in the U.S. for the treatment of chronic deep vein thrombosis (DVT) with post-thrombotic syndrome (PTS) and is open for enrollment.  It is referred to as ACCESS-PTS.  Read the rest of this entry »

Catheter-Associated Blood Clots of Arm and Neck in Patients With Cancer

| Clots in unusual locations, Deep vein thrombosis (DVT), Venous clots | Comments Off on Catheter-Associated Blood Clots of Arm and Neck in Patients With Cancer

Stephan Moll, MD writes… Patients with cancer may have catheters in veins in their upper chest, neck or arm (central venous catheter,  port), to enable chemotherapy, fluids or blood products to be given. These catheters increase a patient’s risk for developing an arm or neck clot (DVT) leading to arm or neck swelling, pain, and may be warmth and reddish discoloration. Typically, blood thinners are used in this situation to prevent the clot from getting bigger or breaking off and traveling to the lung to cause a lung clot (pulmonary embolism; PE). Limited data exist how to best manage these catheter-associated DVTs.

This week (Feb 18th, 2014) a guidance document on the prevention and management of catheter-associated upper extremity and neck  DVT was published by one of the respected medical societies (International Society for Thrombosis and Haemostasis; ISTH) [ref 1].

A summary of the conclusions and treatment recommendations for health care professionals has been published on Clot Connect here.



Zwicker JI et al. Catheter-associated deep vein thrombosis of the upper extremity in cancer patients: guidance from the SSC of the ISTH. Feb 18th, 2014 (pre-published on the web) – link to abstract here.


Disclosures:  I have no relevant financial disclosures.

Last updated:  Feb 20th, 2014

New Publication: Eliquis (Apixaban) is Effective and Safe in DVT and PE

| Deep vein thrombosis (DVT), Eliquis - Apixaban, Pulmonary embolism, Trials, Venous clots | Comments Off on New Publication: Eliquis (Apixaban) is Effective and Safe in DVT and PE

Stephan Moll, MD writes…

An important study (called AMPLIFY trial) was published today in the New England Journal of Medicine [ref 1].  In a large study of patients with acute DVT or PE, Eliquis (apixaban) was as effective as warfarin and caused less major bleeding. Read the rest of this entry »

Aspirin Prevents Recurrent DVT and PE

| Aspirin, Deep vein thrombosis (DVT), Pulmonary embolism, Therapy | Comments Off on Aspirin Prevents Recurrent DVT and PE

 Stephan Moll, MD writes… An important study was published on May 23rd, 2012 in the New England Journal of Medicine [ref 1], showing that aspirin decreases the risk of recurrent clots (DVT and PE) in patients who have had a previous unprovoked (= idiopathic) clot and who have completed 6 to 18 months of blood thinner therapy. Aspirin did not lead to an apparent increase in risk of major bleeding Read the rest of this entry »

Recovery After a DVT or PE

| Athletes and blood clots, Deep vein thrombosis (DVT), Pulmonary embolism, Therapy | Comments Off on Recovery After a DVT or PE

Stephan Moll, MD writes…   Some patients may only have mild symptoms when diagnosed with a deep vein thrombosis (DVT) or pulmonary embolism (PE) and may feel normal again within a few days after initiation of blood thinners.  Patients with more extensive clots and more pronounced symptoms may take several weeks to get back to normal Read the rest of this entry »