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Venous thromboembolism

Developed in collaboration with CASA Medical.

This guideline refers to venous thromboembolism (VTE), which includes deep vein thrombosis (DVT) and pulmonary embolism (PE). These are conditions where blood clots develop inside the veins (DVT), and where the clots may move through the venous system and lodge in the lungs (PE).

VTE is caused by issues with the content of a person’s blood, the structure of the veins and the way their blood flows. These causes include genetic diseases of the blood and clotting processes, prolonged immobilisation, surgical procedures, and some cancers.

Symptoms of DVT can range from mild pain and swelling of the affected limb through to chronic pain and changes in blood flow. Symptoms of PE can be severe and life-threating, including shortness of breath, chest pain, coughing up blood, and sometimes sudden death.

Treatment relates to managing the underlying cause if possible and using anti-clotting agents (also known as anticoagulants or “blood thinners” such as warfarin and direct-acting oral anticoagulants) to prevent clots from developing and spreading. Anticoagulant medication is associated with well recognised hazards (e.g. bleeding) which must be considered as a separate risk to aviation safety.

Pilot and controller information

Stop flying or operating and report to ME or CAA for any of the following:

  • New diagnosis of VTE
  • On commencement of anticoagulant treatment
  • Any bleeding complications of treatment (significant bruising, nosebleeds, blood in any body fluids)
  • Directed to do so by your treating doctor
  • Develop new or increased symptoms of chest pain, difficulty breathing or limb swelling
  • Recurrence of VTE
  • If on a DOAC medication, if any dose is omitted don’t fly until you have taken a dose
  • If on warfarin
    • INR is outside the safe range (≥ 1.8 and ≤ 3.5)
    • A point of care device records a reading outside the safe range, the INR needs to be verified with formal laboratory INR
    • Commencement of other medications or diet that may interfere with anticoagulant activity

When medical certification is reinstated, long term multi-crew/proximity restriction and surveillance may be required.

Aeromedical Implications

Effect of aviation on the condition

  • Hypobaric hypoxia: PE reduces the flow of blood through the lungs, so a person with PE is far more sensitive to hypoxia than someone with normal lungs.
  • Prolonged sitting and immobility: these reduce the way blood flows through the veins, which is one factor that may make people in the aviation environment more likely to experience DVT. This is usually of more concern in people who also have other issues that increase their risk of VTE. 

Effect of the condition on aviation

  • Overt incapacitation
    • Acute respiratory distress due to reduced blood flow through the lungs and reduced oxygen transfer within the lungs.
    • Dyspnoea (shortness of breath) impairs speech and communication.
    • Distraction due to severe chest pain caused by clots lodging in the lungs.
    • Thromboembolic stroke due to movement of blood clots into the circulation of the brain.
    • Sudden death due to disruption of the cardiac system caused by large pulmonary embolism.
  • Subtle incapacitation
    • Pain and swelling in affected limbs from peripheral thrombosis
    • Respiratory symptoms – chest pain, dyspnoea, cough
    • Hypoxia due to impaired lung function (reduced blood flow and oxygen transfer caused by blockages from blood clots), leading to cognitive impairment

Approach to medical certification

Based on the condition

  • Provoked – identifiable transient cause such as surgery, trauma, pregnancy, immobility. These are modifiable risk factors which can be managed, reducing the likelihood of a further event in future.
  • Unprovoked – coagulopathic risk factors such as inherited disorders of coagulation, cancer or autoimmune disease. These factors mean the condition is more likely to happen again, requiring long-term treatment.
  • Location, extent and resolution of clots - large, extensive and severe clots are likely to require a longer period of anticoagulation and may require longer to recover and return to normal function.
  • Multiple episodes – people who have multiple previous VTE episodes are more likely to continue to have episodes and will require more surveillance and a more detailed aeromedical risk assessment.
  • Presence of comorbidities and complications – these factors may require closer surveillance and a more detailed aeromedical risk assessment.
    • Heart failure
    • Pulmonary hypertension
    • Patent foramen ovale
    • Thromboembolic stroke (see CPG “Stroke”)

Based on treatment

  • Certification is likely to be supported if the condition (and any related underlying causes and complications) is managed according to current national clinical best practice
  • The certificate-holder must demonstrate adherence to ongoing anticoagulation – refer to the relevant clinical practice guidelines and surveillance requirements.

Risk assessment protocol - Information required

New cases

A report from haematologist and other treating specialist (as indicated) detailing:

  • Confirmed diagnosis and pathogenesis of the VTE
    • Provoked or Unprovoked DVT/PE (if provoked, detail risk factors)
    • Pre-disposing and related co-morbidities
  • Clinical status
    • Location and extent of venous thrombosis
    • Symptoms and their severity
    • Presence of cardiopulmonary and other complications
  • Investigations conducted (as clinically indicated)
    • Diagnostic and surveillance imaging results
    • Coagulopathy assessment tests such as PT, PTT, Protein S and C, Factor V Leiden
    • For pulmonary embolus:
      • Sea level pulse oximetry
      • Imaging results, including chest CTPA result
      • Echocardiogram
      • If indicated, a functional assessment of respiratory capacity (eg 6-minute walk test)
  • Management
    • Treatment – short or long term anticoagulation
    • Response to treatment (resolution of PE)
    • Effective management of sequelae and comorbidities
    • Adherence to treatment
      • Serial INR results (at least monthly) or proof of DOAC adherence as applicable
    • Side-effects of anticoagulation
  • Follow-up plan including duration of anticoagulation, specialist review intervals and requirement for interval scans

Renewal

A report from treating doctor or haematologist and other treating specialist (as indicated) detailing:

  • Clinical status
    • Symptom update
    • Recurrences
    • Presence of comorbidities
  • Investigations conducted as clinically indicated (e.g., interval scan)
  • Management
    • Adherence to treatment
      • Serial INR results or proof of DOAC adherence as applicable
    • Side-effects of treatment (bleeding complications)
  • Follow-up plan including duration of anticoagulation, specialist review intervals and requirement for interval scans 

ME Aeromedical decision-making guide

VTE or PE is not of safety relevance or aeromedical significance if the following criteria are met.

ME must review Tick 
Renewal only – VTE episode previously assessed by CAA Aviation Medicine
Treating specialist or GP finds condition is stable on current management and no changes recommended
No evidence of recurrence of VTE
No symptoms related to VTE and its treatment
If on DOAC evidence of compliance of use
If on Warfarin:
80% INRs ≥ 1.8 and ≤ 3.5
No concerns re interactions eg St John’s Wort, Alcohol, Current antibiotic use
No coagulation disorders
Eg PT, PTT, Protein S and C, Factor V Leiden
ME considers safe to certify

An AMC referral to CAA Aviation Medicine team is required if an applicant’s condition does not meet the above criteria and the applicant consents to their condition being considered under flexibility to the CAR 67 rules.

ME letters

VTE medical certification letter [DOCX 22 KB]

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