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Embolism and thrombosis

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Embolism and thrombosis is "a collective term for pathological conditions which are caused by the formation of a blood clot (thrombus) in a blood vessel, or by blocking of a blood vessel with an embolus, undissolved materials in the blood stream."[1]

The United States Surgeon General has announced a call to action to prevent Deep Vein Thrombosis and Pulmonary Embolism.[2]



The risk of venous thromboembolism can be estimated with

One risk factor is hypercoagulability due to cancer. Cancer can be found in up to 10% of patients within one year of embolism or thrombosis.[4]


In a cohort study. the population attributable risk of venous thromboembolism was:[5]

In an older systematic review, the presence of Factor V Leiden (homozygotes or heterozygotes) but not prothrombin G20210A (heterozygoes; homozygotes not clear) increases risk of recurrence.[6]


The prevalence of malignancy is about:[7]

  • 3% of patients with first idiopathic venous thrombosis
  • 17% of patients with idiopathic, idiopathic venous thrombosis

The most common sites of cancer that is diagnosed at the time of, or later than the episode embolism and thrombosis of are:[8][9]


Clinical practice guidelines address this for patients in general[10] and for patients who are pregnant[11].


Embolism and thrombosis may be prevented by anticoagulation with anticoagulants. Clinical practice guidelines address this for patients in general[10] and for patients who are pregnant[11].

Dabigatran is given orally and may be as effective as warfarin and with less bleeding but increased dyspepsia for the treatment of embolism and thrombosis.[12]


Clinical practice guidelines address the management of severe forms of embolism and thrombosis which may require thrombolysis.[13]

Duration of treatment

This topic has been reviewed in a meta-analysis using individual patient data.[14]

Randomized controlled trials since 1995 of the duration of anticoagulation
  Patients Duration of
short course
Duration of
long course
Campbell, 2007[15] DVT or PE without prior episode within 3 years 3 mos 6 mos Prolonged tended to do slightly better
Schulman, 2003[16] DVT or PE. 13% had prior VTE. 6 mos 24 mos Prolonged did better
Kearon, 2004[17] First episode of VTE due to transient risk factor 1 mo 3 mos Prolonged did better
Ridker, 2003[18] Idiopathic VTE. 30% had prior VTE 6 mos 2.1 yrs Prolonged did better
Agnelli, 2001[19] First episode of idiopathic DVT 3 mos 1 yr Prolonged did better while anticoagulated, but after two years there was no difference
Kearon, 1999[20] First episode of idiopathic VTE. 3 mos 2 yrs Prolonged did better
Pinede, 2001[21] DVT or PE without prior episode within 3 years 6 wks for distal DVT;
3 mos for proximal or PE
12 wks for distal DVT;
6 mos for proximal or PE
Prolonged tended to do slightly better
Levine, 1995[22] Acute DVT with normal normal impedance plethysmogram (IPG) after 4 weeks 1 mo 3 mos Prolonged tended to do better

Clinical practice guidelines by the American College of Chest Physicians address the duration of anticoagulation for deep venous thrombosis and pulmonary embolism.[10] Although initial trials suggested lack of benefit from prolonged anticoaguation[23], trials since 1995 favor longer anticoagulation. In patients who have had recurrent DVTs (two or more), anticoagulation is generally "life-long." The Cochrane Collaboration and others have meta-analyzed the risk and benefits of prolonged anti-coagulation.[24][23]

Recommendations by the American College of Chest Physicians for the Duration of Therapy[10]
Setting Recommended duration
Single DVT due to transient risk factor 3 months
Single unprovoked DVT at least 3 months (longer if favorable risks for anticoagulation)
Second episode of unprovoked VTE long-term treatment
DVT in patients with cancer LMWH for the first 3 to 6 months of long-term anticoagulant therapy

Using D-dimer to determine duration of treatment

For more information, see: D-dimer.

Elevated d-dimer levels at the end of treatment predict recurrence.[25]

Using Ultrasonography to determine duration of treatment

Ultrasonography, using the following protocol may[26] or may not[27] help determine when to stop anticoaguation[26]:

"If veins had not recanalized, we invited patients to have further ultrasonography after 3 and 9 months in patients with secondary DVT and after 3, 9, 15, and 21 months in those with unprovoked DVT. Anticoagulation was discontinued when the veins had recanalized, along with further ultrasonography"

Reducing the risk of recurrence after an unprovoked deep venous thrombosis.[28] [29] [25] [30] [31]
  Treatment or test Risk if treated or test result is favorable Risk if not treated or test result is unfavorable Comments
Randomized controlled trial[28] Aspirin 100 mg daily for 2 years 6% per year 11.2% per year 0.5% major bleeding
Randomized controlled trial[29] Rivaroxaban for 6-12 months 1% over 6-12 months 7% over 6-12 months 0.7% major bleeding
Systematic review of a diagnostic test[25][31] Normal d-dimer 4% per year 9% per year
Systematic review of a diagnostic test[30] Recanalization of veins (no residual vein obstruction or RVO) Insignificant difference

Extending treatment with aspirin

Two trials have examined this idea.[32][28]

Randomized controlled trials of aspirin after discontinuation of anticoagulants.[32][28]
Trial Patients Intervention Comparison Outcome Results Comment
Intervention Control
ASPIRE, 2012[32] 822 patients
• first-ever, unprovoked venous thromboembolism
• completed initial anticoagulant
Aspirin 100 mg/day Placebo venous thromboembolism at 37 months 4.8% 6.5% relative risk ratio = 0.74 (95% CI: 0.52 to 1.05; P=0.09)
WARFASA, 2012[28] 502 patients
• first-ever, unprovoked venous thromboembolism
• completed initial anticoagulant
Aspirin 100 mg/day Placebo venous thromboembolism at 24 months 6.6% 11.2%

0.58 (95% CI: 0.36 to 0.93)


A systematic review of cohort studies found:[33]

  • During the initial 3 months of anticoagulation
    • Recurrent VTE = 3.4%
      • Recurrent fatal VTE was 0.4% (case-fatalityrate was 11.3%)
    • Major bleeding was 1.6%
      • Fatal major bleeding events was 0.2% (case-fatalityrate of 11.3%)
  • After anticoagulation
    • Recurrent VTE = 7.6% per 100 patient-years
      • Recurrent fatal VTE was 0.3% per 100 patient-years (case-fatality rate was 3.6%)

Elevated d-dimer levels at the end of treatment predict recurrence.[25]

The presence of Factor V Leiden but not prothrombin G20210A increases risk of recurrence.[6]


Among patients with cancer, anticoagulation does not help in the primary prevention of embolism and thrombosis.[34]

Rosuvastatin, a hydroxymethylglutaryl-coenzyme A reductase inhibitor (statin), may reduce embolism and thrombosis according to the Jupiter randomized controlled trial.[35]


  1. Anonymous (2019), Embolism and thrombosis (English). Medical Subject Headings. U.S. National Library of Medicine.
  2. The Surgeon General's Call to Action to Prevent Deep Vein Thrombosis and Pulmonary Embolism. Office of Public Health and Science (2008).
  3. Decousus H, Quéré I, Presles E, Becker F, Barrellier MT, Chanut M et al. (2010). "Superficial venous thrombosis and venous thromboembolism: a large, prospective epidemiologic study.". Ann Intern Med 152 (4): 218-24. DOI:10.1059/0003-4819-152-4-201002160-00006. PMID 20157136. Research Blogging.
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