Deep Venous Thrombosis
What is a blood clot?
A blood clot can form when the flow of blood in blood vessels changes or the clotting system of the blood vessels is abnormal. Blood clots in the veins are known as deep vein thrombosis (DVT). Pulmonary embolism (PE) is caused by the detachment (embolization) of a clot that travels to the lungs.
- Deep vein thrombosis: DVT can occur in any vein of the body, although most commonly occur in the legs. A leg DVT can be in a small vein or can span the entire leg. This can lead to swelling, pain and color changes of the leg.
- Pulmonary embolism: When pulmonary embolism occurs, it is usually small enough so that blood can flow around the clot and into the lungs. However, in some cases, the clot can be large enough to block much of the blood flow to the lungs. In severe cases, this can lead to heart failure and/or death.
Collectively, DVT and PE are known as venous thromboembolism (VTE)
Risk factors for VTE include:
- Family history of DVT or PE
- Blood clotting disorders
- Sitting for prolonged periods
- Recent surgery
- Current or recent pregnancy
- Current or previous cancer
- Certain medications including oral contraceptives or other hormone treatments
- Injury or trauma
- Excessive weight or obesity
Common symptoms for DVT include:
- Swelling of the limb
- Pain or tenderness in the limb
- Increased warmth or redness
- Fatigue or heaviness of the limb
- Surface veins may become more visible
Common symptoms for PE include:
- Shortness of breath
- Chest pain when taking a deep breath
- Cough, sometimes bloody or with a frothy pink quality
- Increased heart rate
VTE can be life threatening. If you suspect that you may have DVT or PE, you should notify your physician or go to the emergency room. Typically, an ultrasound of the legs is performed to detect DVT. If PE is suspected, a CT scan of the lungs may be performed. Once DVT or PE is diagnosed, a patient is typically started on blood thinners. If symptoms remain unabated or there is large clot burden to begin with, minimally invasive, image-guided treatments may be indicated.
Blood thinning medications
The main treatment for VTE is blood-thinning medication. Blood thinners are given to stop new clots from forming by disrupting the body’s blood clotting mechanism. New oral anticoagulants (NOAC) make dosing much easier for patients compared to traditional medications such as as warfarin or heparin. For patients who cannot receive blood thinners, who continue to form new blood clots despite blood-thinners, or have a particularly large amount of clot burden, an inferior vena cava (IVC) filter may be necessary to prevent large clots from passing to the lungs.
A venogram is a minimally invasive x-ray procedure that outlines the flow of blood in the veins by injecting contrast. It allows direct visualization, localization and quantification of clot within the vein(s). Often, a venogram is performed when mechanical clot-busting therapies are considered.
Using imaging guidance, specialized catheters are maneuvered within a blood clot. These catheters allow clot-dissolving medication, called tissue plasminogen activator (TPA), to be instilled directly into the clot. Typically, TPA is allowed to work for a short duration followed by thrombectomy, a procedure that allows mechanical disruption and removal of clot from the affected veins, thereby restoring blood flow in a shorter period of time.
At DESC, this combination therapy is used to treat acute DVT for more rapid restoration of circulation and improvement of patient symptoms.
Angioplasty and stenting
After removal of the blood clot, a narrowing in the vein that limits blood flow may be found. This narrowing is referred to as a stenosis, which are quite common in compression syndromes such as May-Thurner Syndrome (compression of the left iliac vein in the pelvis) and Paget-Schroetter Syndrome (compression of the axillary-subclavian veins in the arm). Compression syndromes are known causes of DVT. The stenosis can be treated by inflating a balloon across it, thereby making the vein larger. In some instances, a metal tube called a stent may need to be placed as a scaffold to widen and keep the vein open.
Inferior vena cava filter
For patients whom blood thinning medication or catheter-based interventions are not medically appropriate, a filtering device may be placed within the inferior vena cava
(IVC), the large vein in the abdomen that drains the blood from the pelvis and legs. The IVC filter acts like a small net, allowing for normal blood flow but capturing dislodged blood clots, preventing a PE. The filter can be removed once the blood clot has cleared or
when the patient can begin taking blood thinners to treat the clot.