Stephan Moll, MD writes…
What Kind of Clot did You Have?
If you have had a blood clot in your legs or your lung (pulmonary embolism=PE), you will wonder how long you should stay on a “blood thinner”. The decision depends on a number of factors which will be discussed below.
- First, you and your doctor will want/need to know where in the extremity the clot was, as this influences management: Was it (a) a superficial clot (= superficial thrombophlebitis; surface clot) or was it a DVT (deep vein thrombosis; clot in the deep veins of the leg or pelvis)?
- If you had a DVT you will want to know: was it in the veins below the knee (=distal DVT) or in the veins in your thigh or pelvis (= proximal DVT). The anatomy of leg veins is shown here.
This blog entry will discuss management of leg DVT and of PE. Management of DVT of the arms and superficial thrombophlebitis will be discussed in separate blog entries.
Whether short-term or long-term “blood thinners” should be given depends on:
- (a) How high the risk of another clot is if the person comes off “blood thinners”, and (b) the risk of bleeding if the person remains on them. Thus, the decision to continue or discontinue “blood thinners” is a risk-benefit assessment: risk of a new clot off “blood thinners” versus risk of bleeding on “thinners”.
- In addition, it is important to take into consideration the patient’s preference, i.e. whether he/she minds being on a “blood thinner” (fluctuating or stable INRs?; frequency of clinic visits for INR monitoring; expense of the drug and clinic visits; impact of being on blood thinners on profession and hobbies; side effects).
If the risk of another clot is low, then short-term treatment for only 3 months is sufficient. This is long enough for the present clot to heal. However, if the risk for another DVT or PE is high, then treatment for more than 3 months is appropriate. This typically means long-term treatment, i.e. for several years. However, reevaluation in clinic once per year is appropriate to see whether continuation of the “blood thinner” is still the right thing to do.
Length of Treatment
A. Provoked leg DVT or PE
a) Provoked by a major temporary risk factor
3 months of “blood thinners” are typically all that is needed if a DVT (no matter whether distal or proximal) or PE was associated with a major transient risk factor, such as
- major surgery
- prolonged immobility (more than 3 days of bedridden state; cast or immobilizer after a bone fracture)
- major trauma
- long-distance airline travel (fights more than 12 hours).
Once off “blood thinners”, the risk for future DVT or PE is low. Less than 5 % (i.e. less than 1 out of 20) of these patients will develop another clot over the next several years [ref 1]. In this situation, no wok-up for a clotting disorder (thrombophilia) needs to be done, because the treatment would still only be 3 months, even if a thrombophilia was detected.
b) Provoked by a minor temporary/transient risk factor
Treatment decisions are more difficult if the DVT or PE was associated with a minor risk factor only, such as
- minor trauma
- minor surgery (e.g. arthroscopic surgery, plastic surgery)
- birth control pill, patch or ring or other estrogen therapy
- less than 12 hour airline travel.
In these patients treatment with “blood thinners” for 3-6 months may be all that is needed. However, the risk of another clot in this group of patients may be higher than in the group mentioned above who had a strong triggering factor. It is this “gray zone” group of patients with some intermediate risk of recurrence where length of treatment decisions are difficult. Presence of additional risk factors for recurrence (overweight, presence of postthrombotic syndrome, positive D-dimer test results, age > 65, strong thrombophilia) might argue for longer-term “blood thinners”, absence of such risk factors for discontinuation.
B. Unprovoked DVT or PE
If a DVT of PE occurs out of the blue, without any clear triggering factor, it is referred to as unprovoked or “idiopathic” DVT or PE. The length of “blood thinner” treatment in the case of leg DVT depends on where in the leg the DVT was – distal (below the knee) or proximal (behind the knee or in the thigh or groin).
a) Distal DVT (i.e. below the knee, in the calf). Length of treatment is typically 3 months only [ref 2].
b) Proximal DVT (pelvis, thigh, and/or behind knee) or PE
At least 3-6 months of “blood thinners” are typically recommended, with a preference for long-term (also referred to as “extended”) treatment, if the patient tolerates therapy well [ref 2,3]. There have been attempts to identify which of these patients have a higher and which have a lower risk of recurrence, i.e. in whom one can safely discontinue “blood thinners” and who clearly needs long-term therapy. Unfortunately, for some of these determinants, data from clinical studies are not very solid or too premature. Sometimes, different studies have provided discrepant results. This is a field of knowledge that is changing rapidly. Possible determinants of a higher risk for future clots are:
- Gender (men have a higher risk for recurrence than women)
- Presence of a strong clotting disorder – see table (Strong thrombophilias)
- Significant chronic leg swelling (postthrombotic syndrome)
- Positive D-dimer blood test obtained while the patient is still on the “blood thinner”
- Positive D-dimer blood test obtained 4 weeks after having come off the “blood thinner”
- A lot of left-over (residual) clot on follow-up Doppler ultrasound examination of the leg.
- Strong family history of unprovoked DVT or PE.
- In addition, patients who had a PE more likely have a PE as a recurrence and have a higher risk of dying from the recurrent clot, compared to patients who “only” had a DVT.
The image (How long to treat) shows how I approach the length of “blood thinner” therapy decision in 2011. In men with an unprovoked DVT or PE, I have a tendency to recommend long-term “blood thinners”, particularly if the clot was a PE. In women who had a DVT or PE, it would be reasonable to consider discontinuation of “blood thinners”, if the woman is of normal weight, does not have postthrombotic syndrome, is less than 65 years old , and has a negative D-dimer.
C. Recurrent DVT or PE
If a patient has had 2 or more clots long-term “blood thinners” are not automatically needed. The decision how long to treat still depends on what triggered each of the episodes of DVT or PE.
- The patient who had 2 episodes of DVT or PE, each associated with a major transient risk factors, such as surgery, will not need to be on long-term “blood thinners; he/she “just” needs very good DVT prophylaxis in the future after major surgeries.
- However, the person who has had 2 episodes of unprovoked (idiopathic) DVT or PE, clearly shows that he/she “likes” to clot. In that person, long-term “blood thinners are clearly needed.
What does “Long-Term” Therapy Mean?
It means treatment for many years to come, but reevaluation once per year, to see whether continuation of “blood thinner” therapy is still the right thing to do in this patient. Things to consider and discuss with your thrombosis doctor at such an annual follow-up visit are:
- How have you tolerated the “blood thinner” in the last year? Have you had bleeding problems or any new clots?
- If you are on warfarin, have your INRs (blood test to measure how “thin” your blood is) been up and down and unsteady/fluctuating, or very steady? How often do you need to get your INR tested?
- What new studies have come out that might tell us who is at low risk for a future blood clot and who is at higher risk if off “blood thinners”?
- Is it unacceptably expensive for you to be on a “blood thinner” or getting it monitored?
- Do you mind being on a “blood thinner” and what is your own preference regarding
- being on it or not?
- Have new “blood thinners” been FDA approved and are they now available? Might they be suitable for you to switch to?
- Are there any DVT or PE studies that you could enroll into? To stay up-to-date you can sign-up for the monthly Clot Connect Newsletter, check the “research to participate in” section (in development) of the Clot Connect website or check the NIH clinical trials website.
Does having a thrombophilia (clotting disorder) mean that I should be on long-term “blood thinners”?
Decisions on how long to treat a patient with “blood thinners” are often independent on whether a thrombophilia is present or not. The decision is typically primarily based on the circumstances of the first clot (DVT or PE), i. e. whether it was triggered by a temporary risk factor or whether it was unprovoked (= idiopathic). If the clot was triggered by a major temporary risk factor, such as major surgery, then 3 months of therapy are sufficient. This is also true, if a mild clotting disorder, such as heterozygous factor V Leiden or heterozygous prothrombin (=factor II) 20210 mutation, is found. In patients with unprovoked (idiopathic) DVT or PE on the other hand, long-term “blood thinners” are often recommended, and this recommendation is the same, no matter whether a thrombophilia is present or not.
One of the few times that finding a thrombophilia really makes a difference in the “blood thinner” treatment of a patient is in the following two scenarios: (a) If a patient had a DVT or PE associated with a mild risk factor (such as birth control pill), the finding of a strong thrombophilia (see table) may lead to long-term therapy with “blood thinners”; whereas finding of no thrombophilia or only a mild thrombophilia (such as heterozygous – i.e. one variant gene - factor V Leiden or heterozygous II20210 mutation) may lead to discontinuation of “blood thinners” after 3-6 months; (b) in the patient with unprovoked DVT or PE who does not tolerate warfarin, very much dislikes being on it, or is thought to have a lowish risk of recurrence (women with DVT only) – see the image (How long to treat): in these patients the finding of a STRONG thrombophilia would be a reason to continue “blood thinners”, while the finding of no or only a mild thrombophilia might lead to discontinuing them.
The Risk-of-Recurrence and Risk-of-Bleeding Calculator
It would be nice to have a web-based calculator into which one could enter a patient’s clinical details about the first clot, the patient’s risk factors for recurrent clot as well as for bleeding, so that the calculator would spit out a risk-benefit assessment whether this patient should remain on “blood thinners’ or come off. At present there are not enough data from good, solid, prospective clinical trials to make such a calculator reliable, but increasingly such data are being published [ref 6,7]. At some point in the future such a calculator will likely become reality.
Existing Guidelines for the Treatment of DVT and/or PE
Well respected treatment guidelines have been published for health care professionals 1,2, developed by a panel of national and international experts who reviewed all published clinical trial data and came up with evidence based treatment recommendations.
- The comprehensive ACCP (American College of Chest Physicians) guidelines are highly valued[ref 2]. They are brought up-to-date every 3-4 years.
- A very solid, yet less comprehensive guideline (does not cover DVT of the mid-thigh, or distal leg; does not cover superficial thrombophlebitis) was published in 2011 by the American Heart Association[ref 3].
- For many health care providers, these guidelines are a little cumbersome to use in clinical practice, due to their extensiveness and complexity. Solid down-to-the-point, practical “How-to” summaries have, therefore, been published [ref 4,5].
Key Points for the Patient
- Know whether you had a superficial clot (superficial thrombophlebitis) or a deep vein clot (DVT).
- If you had a DVT, know whether it was below the knee (=distal) or behind and/or above the knee (=proximal DVT).
- If you are not sure what kind of clot you have/had and where in the leg it was, print out this leg vein anatomy drawing and ask your health care professional to mark where your clot is/was.
- Know the risk factors that triggered your clot.
- Ask your health care professional how long he/she thinks you should be on “blood thinners”.
- Ask whether obtaining a D-dimer would be helpful, a thrombophilia work-up, a repeat Doppler ultrasound of the leg to look for residual clot.
- Find out whether there are any clinical studies you could participate in.
- If you are on long-term “blood thinners”, rethink once per year with your physician whether you should still be on it. Inquire about new studies published, new “blood thinner” drugs available.
Patient Questions /Examples - Explanations
Question #1: “I have been told that I need to be on blood thinner for life. I have factor V leiden….Is this the truth????????”
Answer #1: The questions you should ask your doctor are clear: (a) did I have a proximal DVT or PE, or only a distal DVT? (b) what were the triggering factors for my clot (immobility, surgery trauma, long-distance travel, etc)?, (c) what clotting work-up was done beside of factor V Leiden?, (d) do I have one or two abnormal genes for factor V Leiden, i.e. am I heterozygous or homozygous?. Once you have this information, you often have an inkling on whether it is appropriate to be on long-term “blood thinners” or not, based on published guidelines and, hopefully, the preceeding discussion in this Clot Connect blog entry. You should also ask your physician: (e) What is my risk of recurrent clot if I am off “blood thinners”?, (f)) how long should I be on “blood thinners”?, and you might ask: (g) is it worthwhile for me to be referred to a Thrombosis Center for specialist input?.
- Iorio A et al. Risk of recurrence after a first episode of symptomatic venous thromboembolism provoked by a transient risk factor: a systematic review. Arch Intern Med. 2010 Oct 25;170(19):1710-6. Review.
- Kearon C et al. Antihrombotic therapy for VTE disease. Antithrombotic therapy and prevention of thrombosis, 9th ed: American College of Chest Physicians evidence-based clinical practice guidelines. Chest 2012;141(2)(Suppl):e419S-494S.
- Jaff MR et . Management of massive and submassive pulmonary embolism, iliofemoral deep vein thrombosis, and chronic thromboembolic pulmonary hypertension. AHA A scientific statement from the American Heart Association. Circulation 2011;123(16):1788-830.
- Bauer K. Duration of anticoagulation: applying guidelines and beyond. Am Soc Hematol Education Program Book 2010;210-215.
- Goldhaber SZ et al. Optimal duration of anticoagulation after venous thromboembolism. Circulation 2011;123:664-667.
- Rodger MA et al. Identifying unprovoked thromboembolism patients at low risk for recurrence who can discontinue anticoagulant therapy. CMAJ 2008;179:417-426.
- Eichinger S et al. Risk assessment of recurrence in patients with unprovoked deep vein thrombosis or pulmonary embolism: the Vienna prediction model. Circulation. 2010 Apr 13;121(14):1630-6
Disclosure: I have no relevant financial conflict of interest with this blog entry.
Last updated: Feb 1st, 2013