Venous thrombo-embolism and anticoagulation

Considerations

Venous thrombo-embolism (VTE) disease includes deep vein thrombosis (DVT) and pulmonary embolism. The incidence is 0.1 to 0.2% per annum in the general population. The risk increases with age. A pulmonary embolism may result in subtle or sudden incapacitation, including death and is likely to affect flight safety.

Thrombo-embolic disease has a high risk of recurrence of 5 -7% per year following a first episode, or about 50 times the risk of someone who has not suffered an episode of DVT. The risk is much higher following a recurrent episode. The risk decreases over time.

Since anticoagulation has its own risks, an episode of VTE currently treated with anticoagulants implies an increased risk to flight safety.

A provoked VTE episode means an occurrence in the presence of a temporary risk factor, for instance pregnancy, surgery, trauma or prolonged immobilisation.

An unprovoked or idiopathic VTE episode means an occurrence where no temporary clinical risk factor can be identified. DVTs due to malignancy and congenital coagulopathy are not idiopathic but should generally be considered as unprovoked when making treatment decisions.

Treatment is by anticoagulants. The American College of Chest Physicians (ACCP) Guidelines recommends the following anticoagulation treatment duration, taking into account the risk versus benefit of treatment.

Provoked distal DVT	3 months
Unprovoked isolated distal DVT	3 months, then evaluation of riskbenefit of extended therapy
Provoked proximal DVT	3 months
Unprovoked proximal DVT	At least 3 months, then evaluation of risk-benefit of extended therapy High risk of bleeding: 3 months Low/moderate risk: extended anticoagulation
Second provoked DVT	Low risk of bleeding: extended anticoagulation Moderate risk of bleeding: extended anticoagulation
DVT and active cancer	Low, moderate and high risk of bleeding: extended anticoagulation

The following parameters need considering since they do increase the risk of recurrence (J Fahrni and al; Assessing the risk of recurrent venous thromboembolism – a practical approach; Vascular Health and Risk Management 2015:11 451-459). The relative risk (RR) is between 1.5 and 2.8 depending on the parameter considered. These are:

Unprovoked proximal DVT
Obesity
Male sex
Positive D-dimer test
Residual thrombosis
Hereditary thrombophilia
Inflammatory bowel disease and
Antiphospholipid antibody.

Male sex and positive D-dimer test following anticoagulation have the highest relative risk (RR) of 2.8 and 2.6 respectively while Asian and Pacific Islander ethnicity decreases the risk, with a RR = 0.7.

Information to be provided

Following an episode of VTE:

Complete medical notes relating to the thrombo-embolic episode;
A recent D-dimer test if anticoagulants have been discontinued within the past 12 months;
A recent Ultra-Sound of the affected limb may be required;
A haematologist report may be required.

Disposition

An applicant who has suffered from a recent thromboembolic episode, currently treated with anticoagulants:

Should be considered as having a condition that is of aeromedical significance.

An applicant who has suffered a first thromboembolic episode more than 6 months ago and who is no longer requiring anticoagulants or is only requiring an anti-coagulant for prophylactic reasons may be considered as having a condition that is not of aeromedical significance if:

A D Dimer test is normal;
A follow up ultra-sound is showing resolution of the thrombus;
A thrombophilia screen, completed at least one month after cessation of anticoagulants is normal;
If taking prophylactic treatment with Warfarin, is assessed by following the guidelines, Use of Warfarin;
If taking prophylactic treatment with a novel oral anticoagulant (NOAC), is assessed by following the guidelines, Use of NOACs;
If the application is for a Class 1 certificate and the applicant is taking anticoagulants, a 'Not valid for single pilot air operations carrying passengers is imposed'.