VTE - the disease

1. What is thrombosis?
2. What is VTE?
3. Who is at risk of VTE
4. What are the signs and symptoms of VTE?
5. What is PE?
6. Which diseases are associated with VTE?
7. What are the long-term consequences of VTE?
8. Which risk factors can lead to the development of VTE?
9. How is VTE diagnosed?
References

1. What is thrombosis?
Sometimes clots can develop within blood vessels. These blood clots (thrombi) can develop within veins or arteries. This process is known as thrombosis. Thrombosis can be categorized into two types: arterial and venous.
 
Arterial thrombosis is usually caused by atherosclerosis. Atherosclerosis is a slow build-up of fatty deposits such as cholesterol to form a plaque, which causes the body’s arteries to become narrow. If a plaque eventually bursts or ruptures: the coagulation process is activated and a blood clot is formed within the artery, ultimately, this can cause a heart attack, stroke or peripheral arterial disease.

Venous thrombosis, known as venous thromboembolism (VTE), occurs when a blood clot forms in a vein. VTE can occur in different situations

• there is a venous stasis (blood flow within the vein is stopped)
• the blood is more likely to clot than normal (a state known as hypercoagulation)
• there is a vascular injury; the wall of the vein is damaged and/or torn

2. What is VTE?
VTE is a general term to describe the blocking of a blood vessel by a blood clot. This term includes both deep vein thrombosis (DVT) and pulmonary embolism (PE). DVT occurs when a blood clot blocks a deep vein, usually in the leg. PE is a potentially life-threatening complication and occurs when the blood clot escapes into the circulation and becomes lodged in the lungs. VTE is often a silent disease, and the first appearance can be fatal. It affects approximately 1.5 million Europeans each year¹ and 2.6 million² Americans. It kills far more people than AIDS, breast cancer, prostate cancer, and traffic accidents combined.³ VTE is the most common preventable cause of death in hospitalized patients and pregnant women.

3. Who is at risk of VTE?
VTE can occur in almost anyone, but there are some known risk factors and triggering events. Risk factors include cancer, certain heart or respiratory diseases, a history of DVT, advanced age (risk increases after 40 years of age), acute medical illness with restricted mobility, major surgery such as hip or knee replacement, trauma, an inherited or acquired predisposition to clotting, obesity, stroke, use of birth control pills or postmenopausal hormone replacement therapy. Events that may trigger VTE include immobility following major surgery, pregnancy and postpartum, infection, and long-distance travel.

4. What are the signs and symptoms of VTE?
VTE is generally a silent disease associated with a low frequency of clinical symptoms; the majority of DVT cases may be asymptomatic. If there are symptoms, they usually occur in just one leg and may include pain, tenderness and swelling of the leg and/or skin discolouration that is pale, blue, or a reddish-purple colour. Symptoms of PE, if they present before severe complications, include shortness of breath, rapid pulse, sweating, chest pain, and sudden collapse, and symptoms of DVT may also be present.

5. What is PE?
Anyone who experiences a DVT is at risk of PE. PE occurs when part or all of a blood clot breaks off from the wall of the vein, travels in the bloodstream into a lung vessel, and blocks a pulmonary artery or one of its branches. The blocked artery restricts blood supply to the lung. PE is often fatal, and is the most common cause of preventable hospital death.

6. Which diseases are associated with VTE?
A multitude of acute diseases are known to favour occurrence of VTE, including: some cardiac disease (acute myocardial infarction, heart failure, stroke and heart attack), infectious disease, active cancer, respiratory diseases (respiratory failure), neurological disorders (stroke, paraplegia), and even some rheumatic diseases or inflammatory bowel diseases.

7. What are the long-term consequences of VTE?
Many patients who are diagnosed and treated for VTE recover. However, there are two long-term complications associated with VTE that can cause substantial illness and a high economic burden. The first is post-thrombotic syndrome (PTS), which is a common complication of DVT. It results from damage to the valves in the deep veins following a DVT. This syndrome increases pressure in the veins of the lower calf and ankle and may cause pain, redness, and thickening of the skin; the skin may also look shiny or glossy. PTS can be debilitating and may lead to chronic leg ulceration. Approximately 30% of patients with VTE develop this syndrome within 8 years. The second long-term consequence is chronic thromboembolic pulmonary hypertension (PH) which is a relatively common, serious complication among those who survive PE. Patients may develop PH when pressure in the pulmonary blood vessels increases due to obstruction of these vessels by blood clots. If left untreated, PH impairs the transport of oxygen to the blood and stresses the heart, causing heart failure. Approximately 4% of patients develop this condition within 2 years of a PE. Costs of hospitalization, acute treatment, and long-term effects such as cardiac failure, post-stroke disability, or PTS also increase the economic burden of VTE.

8. Which risk factors can lead to the development of VTE?
Numerous risk factors can lead to the development of VTEs, including:

• advancing age  (risk commonly increases after 40 years of age), obesity, history of VTE, cancer, varicose veins
• predisposing transient risk factors can also include: pregnancy/post-partum, dehydration and prolonged bedrest

9. How is VTE diagnosed?
Two different types of tests are used to diagnose DVT and PE. Non-invasive ultrasound imaging (duplex colour scanner) is the gold standard for diagnosing DVT, but venography using contrast material and an X-ray is also used. A safer and more accurate method using magnetic resonance imaging has recently been developed. For the diagnosis of PE, the most frequently used non-invasive imaging test is the rapid-speed chest computed tomography (CT) scan. Imaging using ventilation/perfusion scan or a computerized tomography pulmonary angiogram can be performed. A simple blood test called a D-dimer test can also be used to diagnose DVT and PE but this test does not always produce reliable results.  Unfortunately on many occasions PE is still diagnosed after a patients’ death; this is due to the unpredictable evolution of the disease.

References

1. Cohen AT,et al. Thromb Haemost. 2007;98:756-64.
2. American Heart Association. Available from: www.americanheart.org. Accessed September 2005.
3. Eurostat statistics on health and safety 2001. Available from: http://epp.eurostat.cec.eu.int. Accessed September 2005