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Archive for the ‘Special situations’ Category

Acute DVT/ PE and Airline Travel

| Deep Vein Thrombosis (DVT), Pulmonary Embolism, Special situations | Comments Off on Acute DVT/ PE and Airline Travel

Stephan Moll, MD writes… Can the patient with acute DVT or PE safely fly, or should he/she wait for a few weeks before embarking on airline travel?  It appears safe to fly early: There is no evidence that flying early after the diagnosis of VTE leads to an increased risk of recurrent VTE or embolization from a DVT, as long as the patient is on adequate anticoagulation.

Airline travel and Thrombosis

  a) The person NOT on anticoagulation

Airline travel is an established (mild) risk factor for DVT and PE in the patient who is NOT on anticoagulation [1,2]; the longer the travel, the higher the risk for thrombosis [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 hypobaric atmosphere in the airplane cabin might lead to coagulation activation and an increased risk for VTE, particularly in persons with one or more of the above underlying risk factors for VTE [ref 4], but neither have data on this issue been consistent, nor is it clear whether such changes are clinically relevant.

  b) The patient with VTE who is on anticoagulation

  1. Is there an increased risk for recurrent DVT or PE or embolization from a DVT?  It is not known whether the risk for recurrent VTE or the risk for a DVT to embolize is increased with airline travel in the patient who is on anticoagulation for a previous VTE.  Any potential coagulation activation by the hypobaric cabin environment is likely counteracted by the fact that the patient is on anticoagulation.  Thus, an increased anticoagulation failure rate (i.e. progression of DVT or PE; increased risk of DVT leading to PE) is not likely.  And while the reduction in ambient cabin pressure per se leads to a small reduction in a patient’s partial pressure of oxygen (PO2) and this may lead to mild vasodilatation and an increase in cardiac output, this is not likely to increase the risk of embolization from a DVT.
  2. Do patients with DVT develop increased leg swelling while flying?  The patient with acute DVT (or postthrombotic syndrome) and leg swelling may experience somewhat more leg swelling during or after the flight – because of leg edema from an increase in capillary permeability in the hypobaric cabin environment, not because of DVT progression.  Also, the distances to walk and the prolonged standing in the airport may lead to worsened leg edema.  However, this is not expected to lead to progressive or recurrent DVT.
  3. Do patients with PE develop increased shortness of breath while flying?  The patient who has a large PE or has other underlying hypoxic lung disease (COPD, etc.) may have some worsening of shortness of breath during flying – not because of new PE, but because the cabin’s environment is mildly hypoxic.

Background Data

Rules by the International Air Transportation Association (IATA) limit the decrease in cabin pressure in commercial aircraft to an equivalent altitude of 8,000 ft (564 mmHg, 0.74 ATA), although most planes maintain their pressures at an equivalent altitude of around 5,000 ft (632 mmHg, 0.83 ATA).  Thus, the predicted decrease in a patient’s arterial PO2 is small, and would be clinically significant only for people with pre-existing hypoxemia.

My Approach

In general, I discuss with the patient who has an acute DVT or PE and wants to fly soon that…

  • he/she can fly, even immediately after the VTE diagnosis, as long as he/she is on full-dose anticoagulation.
  • that airline travel is not expected to lead to an increased risk of recurrent VTE or embolization from a DVT.
  • leg swelling in the patient with DVT may temporarily worsen during and in the few days after airline travel due to the hypobaric pressure in the airline cabin.
  • shortness of breath in the patient with a 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.


  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


Contraceptive Use While on Anticoagulants is Safe

| Anticoagulants, Bleeding, Uncategorized, Women and blood clots | Comments Off on Contraceptive Use While on Anticoagulants is Safe

Stephan Moll, MD writes… Interesting and clinically relevant publication this week [ref 1].  It is well known that estrogens and certain progestin preparations increase the risk for venous thromboembolism (VTE).  A woman on an anticoagulant may have heavy menstrual bleeds and hormonal therapy – such as estrogen-progestin contraceptives – may be considered to decrease the bleeding.

The newly published study Read the rest of this entry »

Thrombophilia – Information Handout for Patients

| Acquired risk factors, Antiphospholipid antibodies, APC resistance, Clots in unusual locations, Deep Vein Thrombosis (DVT), Factor V Leiden, Homocysteine, MTHFR, Inherited, Protein C deficiency, Protein S deficiency, Prothrombin 20210 mutation, Pulmonary Embolism, Thrombophilias, Uncategorized, Venous Clots, Whom to test, Women and blood clots | Comments Off on Thrombophilia – Information Handout for Patients

Stephan Moll, MD writes… An information article on various aspects of thrombophilia, written for patients and family members, was published today – available here – as a Vascular Disease Patient Information Page in the journal Vascular Medicine.  It addresses (a) in which patient with venous thromboembolism to consider thrombophilia  testing, (b) what tests might be appropriate to do, (c) how the test results might influence length of anticoagulation therapy (d), what contraceptives are safe to use in women with a history of DVT or PE or thrombophilia, and (e)  in which family members to consider thrombophilia testing.  This article can be used as an education handout for patients in clinic or the hospital who have DVT, PE, venous thrombosis in unusual locations, or an established thrombophilia.


Disclosures:  None

Last updated: April 1st, 2015

Commercial Airline Pilots and VTE

| Special situations, Uncategorized | Comments Off on Commercial Airline Pilots and VTE

Stephan Moll, MD writes… Interesting study: Are commercial airline pilots at increased risk of venous thromboembolism (VTE) [ref 1]?  One might think so, as air travel is an established, although only weak, risk factor for VTE [ref 2,3].  This study found, however, that the risk of VTE is NOT increased in airline pilots. Read the rest of this entry »

How Long is the Post-Partum Period in Respect to Thrombosis Risk?

| Uncategorized, Women and blood clots | Comments Off on How Long is the Post-Partum Period in Respect to Thrombosis Risk?

Stephan Moll, MD writes… A recent NEJM study (ref 1) examined whether the risk for thrombosis in women persists beyond the first 6 weeks after delivery.  It found that an increased risk persists for at least 3 months after delivery, although the absolute risk was low after the first 6 weeks.  This is of clinical relevance, as the post-partum period has traditionally often been defined as the 6 weeks after delivery and, if post-partum anticoagulation prophylaxis is considered, it is typically given for 6 weeks only (ACOG – ref 2). Read the rest of this entry »

Klippel-Trenaunay Syndrome, DVT and PE

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Stephan Moll, MD writes…  Klippel-Trenaunay Syndrome (KTS) is a rare congenital disorder of capillary, venous and lymphatic malformations and a localized disturbed growth of bone and/or soft tissue (see photographs)[ref 1].  Patients with KTS are at significantly increased risk for DVT, PE and superficial thrombophlebitis.  KTS affects only one side of the body, typically the leg or the arm, sometimes both. It can also involve the trunk and face and inner organs.  Chronic pain and swelling of leg and arm can be a problem.  The swelling may lead to skin breakdown (ulcers).   A patient support group for KTS exists with an informative website.


DVT and PE in Patients with Klippel-Trenaunay Syndrome

Superficial thrombophlebitis, DVT and PE are not uncommon in patients with KTS: (a) a study of 49 patients with KTS showed that 11 (22.5 %) had DVT and PE problems [ref 2]; (b) a study of 47 children with KTS showed DVT or PE in 11 % and superficial thrombophlebitis in 53 % [ref 3]; and (c) a study of 68 patients reported a history of DVT or PE in 17 %, and of superficial thrombophlebitis in 48 % of patients [ref 4].

 The recurrence rate of blood clots and the best treatment are not known. Open questions are:

  • Do patients need to be on long-term warfarin after a first episode of DVT or PE?
  • Should patients with DVT or PE  be treated with warfarin or low molecular weight heparin rather than with warfarin?
  • Would the new oral anticoagulants Pradaxa® (Dabigatran) or Xarelto® (Rivaroxaban) be effective choices?
  • In the patient with DVT, should an IVC filter be placed to prevent PE?
  • What is the risk of recurrence of DVT or PE during pregnancy and how should pregnant women with KTS be managed? [ref 5]


How are KTS patients best treated?

  1. Awareness, Prophylaxis: As quite a few patients with KTS develop superficial thrombophlebitis, DVT or PE, patients should know the symptoms and risk factors of blood clots, so they recognize them quickly and seek medical attention and rapidly get diagnosed and treated.  They also need good DVT prophylaxis in risk situations, such as at times of surgery and hospitalization. Women need to know about their risk of VTE with contraceptives and pregnancy.
  2. Anticoagulant choice:  A 2005 publication [ref 6] reviewed all published cases of PE in individuals with KTS (10 patients are listed in the analysis), summarizing that several patients had recurrent DVT or PE in spite of being on warfarin (Coumadin®, Jantoven®).  The authors of the article, therefore, concluded that “if DVT or PE is diagnosed, then these patients should receive therapy with low molecular weight heparin”.  However, it has not been studied whether low molecular weight heparin is truly more effective in preventing blood clots.  At present, it appears fair to conclude, that there is some risk for recurrence of VTE, even while the patient is on adequate doses of warfarin.  However, because of a lack of studies, publications and extensive experience, there are no established and accepted guidelines on treatment. Individual decisions need to be made
  3. IVC filter: It is not clear whether patients with KTS who have had a VTE may benefit from having an IVC filter placed. Individual decisions need to be made.
  4. Risk for bleeding: Lastly, since venous malformations  may also be seen in the inner organs, such as the intestine, some patients with KTS have an increased risk for bleeding, putting the patient at increased risk for bleeding if  long-term anticoagulants are used.



    1. Tian XL et al: Identification of an angiogenic factor that when mutated causes susceptibility to Klippel-Trenaunay syndrome. Nature 2004;427:640-645.
    2. Baskerville PA et al: Thromboembolic disease and congenital venous abnormalities. Phlebologie 1987;40:531-536. 
    3. Samuel M et al: Klippel-Trenaunay syndrome: clinical features, complications and management in children. Br J Surg 1995:82:757-761.
    4. Douma RA et al. Chronic pulmonary embolism in Klippel-Trenaunay syndrome. J Am Acad Dermatol 2012;66:71-77.
    5. Güngor Gündoğan T et al. Klippel-Trenaunay syndrome and pregnancy. Obstet Gynecol Int 2010:706850. Epub 2010 Dec 19.
    6. Hiras, EE et al: Pulmonary thromboembolism associated with KTS. Pediatrics 2005;116:e596-e600.


Last updated: May 25th, 2012


Recovery After a DVT or PE

| Athletes and blood clots, Deep Vein Thrombosis (DVT), Pulmonary Embolism, Therapy, Uncategorized | Comments Off on Recovery After a DVT or PE

Stephan Moll, MD writes…  A discussion for patients of questions commonly asked after a DVT are discussed here, in Clot Connect’s patient blog, such as:

  • How quickly can I expect improvement?
  • How active can I be after a DVT or PE?
  • When can I go back to doing sports?
  • When is it safe to fly again after a DVT or PE? Read the rest of this entry »