Venous thromboembolism disease (VTE)

Venous thromboembolism occurs in two major forms: phlebitis, or deep venous thrombosis, and pulmonary embolism. More than 70% of cases of pulmonary embolism (PE) are the result of the migration of blood clots, or emboli, caused by a deep vein thrombosis (DVT) in the lower limbs, that is, the obstruction of veins by a thrombosis (blood clot). The severity of a pulmonary embolism is directly linked to the extent of the pulmonary vascular obstruction. Three main factors contribute to the formation of clots: changes in the vessel walls, hypercoagulability of the blood, and localized slowing of blood flow.

Impact on public health

It is estimated that approximately four million people are affected by venous thromboembolism in industrialized countries. Anyone may develop a deep venous thrombosis but there are risk factors: prolonged immobility, long trips, pregnancy, the use of oral contraceptives, obesity, old age, estrogen therapy, family history, a recent traumatism or surgery. Other aggravating factors are heavy smoking and alcoholism.

Diagnosis

Any clinical suspicion of VTE must be confirmed by additional tests and biological analyses (see below) since the symptoms are not specific. Medical imaging is generally based on non-invasive tests. However, pulmonary angiography, the reference test for diagnosing PE, has a non-negligible risk of death (0.1%) and of major complications (1.5 %). It is just as important to diagnose VTE as it is to rule it out in order not to administer an anticoagulant treatment to a patient who does not need it (the diagnosis of VTE is only confirmed in 20 to 25% of patients with clinical symptoms).
- Clinical signs:
o DVT: localized pain and swelling with warm skin at the affected site; low-grade fever. The unilateral nature (on one side of the body only) of these non-specific symptoms is an indication of DVT.
o PE: chest pain, rapid breathing, sweating, cyanosis (blue coloration of the lips and extremities) and a sensation of breathlessness.
- Additional tests:
o DVT: Doppler ultrasonography is used to localize the thrombosis and to assess the hemodynamic repercussions.
o PE: electrocardiographic abnormalities in 70% of cases, generally not significant. Pulmonary radiography generally abnormal. A normal perfusion lung scan rules out PE. In serious cases, echocardiography and thoracic spiral CT angiography are necessary.
- Biological analyses: The oxygen concentration in the blood is deficient in approximately three patients out of four with PE (blood gas analysis). The presence of phlebitis and pulmonary embolism can be almost totally excluded if the D-dimer level (fibrin degradation product, part of the clot) is normal. These rapid tests make it possible to obtain results, with a sensitivity and negative predictive value close to 100%, in just 30 minutes. Diagnostic strategies using the measurement of D-dimers have proven to be effective. Moreover, they make it possible to avoid additional tests and therefore limit the overall cost of diagnosis.