A deep vein thrombosis (DVT) involves the formation of a clot in the deep veins of the lower calf. The clot generally begins very low in the leg and grows in an upward direction to extend up to and past the knee. Some DVTs can rise to the level of the upper thigh, pelvis and even the lower abdomen. DVTs are considered dangerous because a piece of the clot can break off, travel up the patient’s vena cava and enter the patient’s lungs, resulting in a pulmonary embolism (PE).
A pulmonary embolism (PE) is dangerous because it can cut off the circulation to the lung vasculature, resulting in sudden cardiovascular collapse and often, sudden death within minutes. Of the 80 out of 100,000 people in the US who have a DVT each year, fifteen percent will develop a DVT. Of cases of sudden death, 3 percent are due to a PE.
In essence, the DVT generally comes first. People prone to a DVT include travelers who travel long distances and times without the ability to get up and move one’s legs. The moving of the legs triggers increased circulation in the legs, reducing the chance of a DVT. Travelers on long haul airline flights also get dehydrated from the dry air and lack of fluid intake, and are at an even higher risk than those traveling by other mechanisms.
Individuals who are obese, pregnant or elderly put themselves at higher risk for a DVT. Women who take birth control pills or estrogen replacement therapy are also at greater risk. In addition, those who have certain types of cancer secrete prothrombic agents that increase the chances of clotting within the body.
When a person develops a DVT, he or she might be asymptomatic. Alternatively, he or she may have symptoms, including redness or discoloration of the calf, pain in the back portion of the calf and an increase in swelling of the affected lower leg. Doctors can elicit a positive Homan’s sign by dorsiflexion (tipping upward toward the head) of the foot and asking the patient if they have increased pain in the posterior calf.
Furthermore, the doctor can check a d-dimer blood test—a test that determines the breakdown products of the clotting process. This can tell the doctor if there is clotting within the body. Imaging studies that prove the clotting is coming from a DVT include a Doppler ultrasound of the legs and a deep vein venogram, which employs the use of intravenous contrast dye and x-rays to determine the contour of the deep veins.
In treating a DVT, the doctor may order an IV infusion of TPA, also called tissue plasminogen activator. It is able to break up clots effectively and efficiently. It is reserved for severe cases of DVT. Lesser cases include treating the patient with intravenous heparin and pills consisting of Coumadin. The IV heparin works immediately to thin the blood. The clot breaks up through natural processes.
Coumadin takes longer to work effectively but, when it does work within a few days, the heparin can be stopped and the patient remains on Coumadin at home for a minimum of three months. Patients who have had multiple DVTs or a PE, may have to remain on Coumadin for longer periods of time and perhaps indefinitely.
As mentioned, when a blood clot from a DVT breaks off and travels to the lungs, it is called a PE. Doctors can prevent a DVT from becoming a PE by inserting a vena cava filter into the abdominal vena cava, thus preventing the clot from traveling past the filter.
When a PE does occur, the results can be catastrophic. If a clot straddles the opening to the pulmonary vessels of the lungs, it is called a “saddle embolism” and almost always results in death. Smaller clots will break off and settle in the smaller portions of the lungs.
The patient with a smaller PE will exhibit shortness of breath, anxiety, and chest pain that worsens with breathing deeply. Furthermore, the doctor will notice extra breath sounds heard with the stethoscope and will find low oxygen levels in the bloodstream. He can order a d-dimer test that can show if clotting is happening inside the body.
Imaging studies for proving a PE include a CT scan of the abdomen with IV contrast dye or an MRI of the chest. These tests can actually prove or disprove the presence or absence of a PE. A PE is considered a medical emergency and quick treatment is recommended.
Treatment includes eliciting the services of a vascular surgeon to perform a pulmonary embolectomy. The pulmonary embolectomy involves going into the vascular system and removing the clot directly. This can be a lifesaving procedure.
In addition, the doctor may order TPA in order to break up the clot. It works within minutes to dissolve any clot that is blocking the lung vasculature. If a person with a PE is completely stable, the doctor may order a trial of IV heparin and oral Coumadin, both of which are powerful blood thinners. They help the blood remain thin enough so the body can produce the enzymes necessary to dissolve the clot in a more natural way.
Coumadin, as mentioned, takes several days with which to work so it is taken along with the IV heparin until it can successfully thin the blood on its own. At that point, if the patient is otherwise healthy, the Coumadin is taken alone for at least three months.