Venous Thromboembolism (Deep Vein Thrombosis & Pulmonary Embolism)

What is venous thromboembolism?

A venous thromboembolism is a blood clot that blocks the flow of blood in a vein. “Thrombo” means blood clot, “embolism”, means a circulating particle that causes a blockage, and “venous” means in the veins. A VTE incorporates two kinds of blood clotting conditions:

How does it occur?

When your skin is cut or wounded, your blood partially solidifies, or coagulates, to keep you from bleeding too fast. On the surface of the skin, it forms a scab, but inside the body, it forms a clot. This is a normal, healthy response to injury, ‘injury’ from a medical intervention, like surgery, chemotherapy or inserting an IV or catheter, or infection, which irritates the blood vessel lining like a wound. When the wound/infection starts healing, the clot is supposed to dissolve, but sometimes it doesn’t, hence causing VTE. Blood clots can form even in the absence of a wound, and there are numerous factors that can lead to this. If it grows large enough, it can block the vein.

Causes

Common causes for VTE are:

• major surgery
• serious infection, such as COVID-19
• inflammation
• being immobilized for long periods
• long periods of restricted movement, such as long-distance travel
• an imbalance of blood-clotting proteins, which makes some people’s blood more prone to clot and less prone to dissolve clots (thrombophilia); this can be genetic or a side effect of a specific condition.
• cancer

Risk factors

There are numerous risk factors for developing VTE:

• Long-term hospitalisation. In the US, approximately 60% of all VTE cases develop within 90 days of hospitalisation.
• Recent major surgery, orthopaedic cast of a limb or paraparesis (partially unable to move your legs). The most common surgery associated with VTE are orthopaedic surgeries, especially knee and hip replacements.
• Age. It’s more common in older people. After the age of 40, the chance of VTE nearly doubles every 10 years.
• Sex. Women are at a greater risk for VTE due to:
  • pregnancy and up to 28 days post-partum
  • estrogen-based medication, including birth control pills and hormone replacement therapy
• Medical history. Several medical conditions increase the risk of VTE including:
  • blood clotting disorders, such as Factor V Leiden disease, polycythemia vera, and sickle cell disease.
  • cancer
  • metabolic conditions, like diabetes
  • heart conditions such as high blood pressure, congestive heart failure, and obstructive pulmonary disease
  • kidney diseases
  • obesity
  • infections such as COVID-19
  • HIV, especially early after initiation of antiretrovirals
  • tuberculosis (TB), especially after starting TB treatment
  • chronic heart and lung conditions, like congestive heart failure
  • chronic inflammation, like arthritis and irritable bowel syndrome (IBS)
• Prolonged travel (>6 hours).
• Prolonged immobility.
• Genetics and family history of VTE.
• Lifestyle factors. Smoking, obesity, and lack of exercise increase the risk of VTE.

Symptoms

* Signs of a PE can occur without previous signs of a DVT

Complications

Blood clots, especially those in the lungs, can block blood flow, resulting in hypoxia – the death of tissue due to a lack of oxygen. Large clots or blockages can cause organ damage, induce a coma, and ultimately lead to death. It’s estimated that about 1 in 10 people with deep vein thrombosis will have a pulmonary embolism (PE). A PE can also lead to heart failure, trouble breathing, and high blood pressure in the lungs (pulmonary hypertension). It’s estimated that sudden death occurs in 1 in 4 people with a PE.

When a clot is embedded in your leg or arm for too long, it can damage the vein or its valves, causing it not to work properly. This is called post-thrombotic syndrome or chronic venous insufficiency. The long-term effects of a blood clot – pain at the area, swelling, darkening of the skin color, skin sores, and varicose veins – may only show up years later.

The clot can also cause an extreme buildup of fluid in a major vein and in the veins around it. This is called Phlegmasia Cerulea Dolens (PCD). As the fluid builds, the skin whitens and eventually starts to turn blue. This causes blisters on the skin, burning or tingling in the skin, and weakness in your muscles.

When VTE is detected and treated early, these complications can often be avoided.

Diagnosis

VTE/DVT is diagnosed by reviewing your medical history, doing a physical exam, imaging, and blood tests to detect clotting activity and oxygen levels in your blood.

A DVT is diagnosed using:

• Blood tests. A D-dimer test measures levels of a substance that is released when blood clots dissolve. Blood tests also measure oxygen levels in your blood and screen for inherited clotting disorders.
• Doppler ultrasound (also known as the vascular or duplex ultrasound). This is used for visualizing the blood flow through the veins.
• MR venography. Magnetic resonance imaging uses pulses of radio-frequency waves to detect blood clots in the pelvis, abdomen, and chest.
• Contrast venography. This is a traditional X-ray that uses a contrast dye to be injected into your vein to make it show up in images.

If PE is suspected, your doctor may start by putting a pulse oximetry sensor on one of your fingers to measure oxygen levels in your blood. Low oxygen levels could be caused by PE or by another lung or heart condition.

For PE, tests might include:

• CT pulmonary angiography (CTPA). This takes images of your blood vessels in your lungs and is the standard test for PE.
• Pulmonary angiography. A tube is inserted into one of the large veins and then threaded up into your chest area to deliver contrast dye, after which X-rays are taken. While invasive, it does offer definitive results.
• Ventilation-perfusion (V/Q) scan. This measures air and blood flow in the lungs.
• Chest X-ray. This is used for diagnosing other possible causes of your symptoms, including lung and heart conditions.

Treatment

VTE’s are treated using medication and surgical procedures.

Medication

• Blood thinners (anticoagulants) prevent blood clots from growing or forming, and are administered as a pill, a shot, or through an IV. The type of blood thinners used will depend on your medical history, the cause of the clot, and how long you need to take it for. The anticoagulants warfarin, apixaban, dabigatran, and rivaroxaban are typically prescribed.
• Thrombolytics are used to dissolve the blood clot(s) and are used for large blood clots, or a pulmonary embolism. They are administered through an IV.

Surgical procedures

• Catheter-assisted blood clot removal is used for emergencies; under anesthesia, a flexible tube is used to remove a clot from your lung or leg.
• Vena cava filter is a device used for people who can’t take blood thinners; it filters the blood and ‘catches’ blood clots before they move to the lungs.

Living and managing

If you have a VTE, ensure that:

• you take medications as prescribed; if you notice excessive bleeding – a side effect of blood thinners – stop taking them and contact your doctor immediately.
• you have follow-up care
• you move regularly and stay active
• you drink enough water
• you quit smoking

Prevention

If you are at high risk of developing VTE, preventative measures try to reduce clotting and promote blood circulation. Here are several suggestions that could assist in preventing blood clots:

• Take anticoagulants (blood thinners) as prescribed.
• Stretch and move around as soon as possible after surgery.
• Wear compression stockings or use a sleeve/boot to help with blood flow.
• Check for signs of clotting in your legs, such as redness and swelling.

When traveling:

• Stand up and walk around every 1 to 2 hours.
• Change positions frequently while sitting.
• Wear compression stockings.
• Move your knees and ankles often.
• Wear loose clothing.
• Avoid drinking alcohol.
• Stay hydrated.