Deep Vein Thrombosis (DVT)
Deep Vein Thrombosis Overview
Deep vein thrombosis (DVT) occurs when a blood clot (thrombus) develops in one or more of the deep veins of the legs, pelvis, or arms.
Blood clots can form in superficial veins (otherwise known as superficial thrombophlebitis) and in the deep veins. Blood clots in superficial veins rarely cause serious problems, however clots in deep veins require immediate medical attention.
Veins that lie deep near the center of the leg are surrounded by strong muscles. When they contract, they force deoxygenated blood back to the lungs and heart. In a healthy vessel, one-way valves prevent the backflow of blood between the contractions. Through repeated contractions, the blood is ultimately returned from the legs to the heart.
The development of clot in the legs can result in serious morbidity, and can even be fatal. Clots in the legs can break off and travel through the bloodstream to the heart and lungs as a pulmonary embolism (PE). Large pulmonary emboli can cause critical strain on the heart resulting in cardiac arrest.
Beyond the risk of migration, thrombus in the legs can cause severe swelling and pain in the leg, which can be permanent. In rare cases, the clot itself can threaten the viability of the affected limb.
Blood clots in deep veins can develop when the circulation of blood slows down due to injury, illness, or inactivity. Blood can accumulate or “pool” which leaves a perfect setting for a clot to form.
Risk factors for deep vein thrombosis include:
- Coagulation abnormalities
- Injury to the lining (endothelium) of the veins
- Previous or current cancer
- Inflammatory diseases and some autoimmune diseases
- Pregnancy or post-partum
- Hormone therapy or oral contraceptives
- Over the age of 40
- Recent injury or surgery
- Antiphospholipid syndrome
- Immobility, such as bed rest or sitting for extended periods of time
- Previous or family history of DVT
- Heart failure
- Polycythemia vera
- Nephrotic syndrome
- IV drug use
- Foreign bodies (e.g., central venous catheters)
While deep vein thrombosis can occur without any symptoms, some signs that can occur are:
- Warm feeling in the affected limb
- Discoloration of the skin (blueish or reddish)
- Distension of superficial veins at the skin
- Pain or tenderness in the affected limb when pressure is applied
Acute Deep Vein Thrombosis Overview
Acute DVT refers to clot that is two weeks or less in age. Acute DVT causes more immediate, severe symptoms than chronic DVT. Historically, anticoagulation alone was the mainstay of therapy. However, current research suggests a benefit to early and more aggressive removal of the clot, particularly when the clot is in the larger, more central veins.
Chronic Deep Vein Thrombosis Overview
Chronic deep vein thrombosis occurs when a clot has been in the vein for an extended period. Chronic clot becomes more organized and adherent to the wall of the vein, leaving the vein scarred. Unlike acute DVT, which can be readily dissolved or removed, chronic DVT is not amenable to catheter or surgical based removal. With chronic DVT, the body naturally recanalizes small channels within the blocked vein allowing partial drainage. However, the valves in the veins become damaged, which coupled with the narrowed lumen of the affected vein results in poor venous drainage. Patients with damaged veins often develop post-phlebetic syndrome, whereby the leg is chronically swollen and frequently painful.
Anticoagulation is the mainstay of treatment for patients with acute DVT. This prevents further propagation of the clot and allows the body to naturally break up existing clot. In some cases, this may not be adequate and further intervention is required. In severe cases, surgical exposure of the vein with manual removal of clot can be performed. More commonly, however, patients are offered catheter-based procedures for clot removal. A variety of devices exist for removing fresh clot. These include devices and catheters that deliver clot dissolving drugs, devices that mechanically aspirate clot, and other devices that macerate and remove clot. In addition, balloons and stents are frequently employed to dilate the vein and re-establish the lumen.
For patients with chronic DVT, the clot becomes organized and web-like and is therefore not amenable to removal. Instead, attention is directed to creating a lumen within the occluded vein for drainage using a combination of balloons and stents.