Overview

Q. What is a DVT?
A. A DVT (Deep Vein Thrombosis) is a blood clot that forms in the leg veins, typically beginning in the calf veins.

Q.What is a PE?
A. A PE (Pulmonary Embolism) is caused by a blood clot, typically in the leg, groin, or pelvic veins (and occasionally in the upper extremity veins) which breaks free and travels to the lung arteries.

Q.What is the relationship between a DVT and a PE?
A. A DVT is often the source of a clot that travels to the lung arteries and becomes a PE.

Q.What fraction of people with a DVT get a PE?
The risk varies depending on the location of the clot. The risk for a PE increases the higher up in the leg the DVT occurs. For example, a calf DVT has a lower risk of breaking off and becoming a PE than a clot behind the knee or one in the groin or pelvic veins. Essentially, the larger the vein with the clot, the greater the risk of developing a PE.

Q.What fraction of people with a PE have an identifiable DVT?
A. One-third to two-thirds.

Q.What is the frequency of clots among men and women?
A. About equal.

Q. What is the rate of death in people who have a PE?
A. This depends upon age, health, and underlying medical conditions, as well as the cause of the PE.

Risk Factors

Q. What causes a DVT or a PE?
A. There are many known causes of clot formation. Prolonged bed rest or inactivity, such as a long plane ride, can cause reduced circulation in the legs, which provides the opportunity for clot formation. Major surgical procedures or physical trauma can also increase the risk.
Blood has several clotting factors, and an imbalance may lead to increased clot formation. There are genetic disorders known to contribute to clot formation. Pregnancy, oral contra-ceptives, and hormone replacement therapy also increase the risk of clots.
Two-thirds of all clots have no identifiable cause, and this is the subject of ongoing research. Two risk factors recently discovered are Factor V Leiden and an elevated homo-cysteine level.

Q. What is Factor V Leiden?
Factor V Leiden is a hereditary condition present in 15-20% of PE/DVT patients of European ancestry. A positive test for Factor V Leiden increases the risk of clots about three to four times compared to someone without it. In general, this risk is still small.
However, if you are taking oral contraceptives and you have Factor V Leiden, the risk of a clot increases dramatically (about 35-fold). If you have Factor V Leiden, the risk of clots also increases with age.
For Factor V Leiden patients who stop anticoagulant therapy after treatment, the risk for a second clot is about three times greater than for those without it.

Q. If I have Factor V Leiden, should family members be tested for it?
If family members are considering taking oral contraceptives or becoming pregnant, they may wish to be tested. Recommendations for family testing remain controversial.

Q. What is homocysteine?
A. Homocysteine is a byproduct of protein metabolism that promotes clotting via an unknown mechanism.
An elevated homocysteine level is treatable with folic acid, B6, and B12. This condition (hyperhomocysteinernia) is much less common than the Factor V Leiden mutation.

Q. Is age a risk factor for clots?
A. Increasing age is a risk factor for DVT and PE.

Q. Is cancer a risk factor for clots?
A. Yes, although having a clot does not necessarily mean you have cancer.

Q. Is there an increased risk of clots to other family members since I've had a PE or DVT?
A. If you have tested positive for Factor V Leiden, family members may also have this condition and be at a slightly higher risk for clots.
Most clots are caused by nongenetic factors such as surgery, bed rest, cancer, pregnancy, etc., none of which would indicate that family members have an increased risk.

Diagnosis

Q. How is a DVT diagnosed?
A. Most often, ultrasound is used to diagnose blood clots in the leg veins. This is a non-invasive test. If the results are not definitive, then venography (an invasive test using contrast dye) or MRI (magnetic resonance imaging) may be used.

Q. How is a PE diagnosed?
A. If a clot is suspected, a non-invasive test called a VQ (ventilation perfusion) scan is performed. This also is known as a lung scan.
If the VQ scan does not identify a clot, but one is still suspected, a pulmonary angiogram is performed. A catheter is threaded through a vein in the groin, passed through the heart, and into the pulmonary artery. Contrast dye is then injected and Xrays are taken to monitor the blood flow in the lung. The angiogram will give a definite diagnosis as to the presence of a clot.
Occasionally, an echocardiogram will show abnormalities in heart function, particularly in the right ventricle, as it meets resistance in pumping blood into the lungs.

Q. Is the VQ scan the best non-invasive method for detecting a PE?
A. It is the best current non-invasive technique for detecting a PE. Spiral CT (computed tomography) imaging is a new non-invasive technique being developed and has potential for replacing the VQ scan.

Q. Why did I get a chest X-ray?
A.To rule out pneumonia, another common cause of chest pain and breathing difficulty.

Q. Is it common for a PE to be misdiagnosed as a pulled muscle, pleurisy, anxiety, asthma, etc?
A. Yes. PE mimics many other diseases and is particularly difficult to diagnose.

Treatment

Q. How do you treat a DVT?
A. Initially, the patient is given Heparin, an anticoagulant, to prevent the formation of new clots. Additionally, if the patient is not pregnant, treatment with Coumadin is started. It takes about five days for the Coumadin to become fully effective, during which time the patient continues to get Heparin to prevent new clots from forming.

Q. What happens if a DVT is not treated?
A. The clot can grow and extend toward the heart, potentially break off, and cause a PE.

Q. How do you treat a PE?
A. It is treated very similarly to a DVT.

Q. What happens if a PE is not treated?
A. The heart may fail and death may occur.

Q. What is anticoagulation therapy?
A. Anticoagulation with Heparin or Coumadin increases the time it takes for blood to clot and reduces the chance of forming another DVT or PE.

Q. What is a therapeutic dose vs. a prophylactic dose?
A. A therapeutic dose of anticoagulants is given to treat an initial "active" clot. The therapeutic dose is higher than a prophylactic dose, which is given to someone who may be at a slightly increased risk for a new clot. For example, a pregnant woman with a prior history of clots may be prescribed a prophylactic dose of Heparin. This lower dose is intended to offset a minor risk of clot formation.

Q. What are the possible side effects of Heparin?
A. Bleeding is the most common side effect. Rare side effects of Heparin include a low platelet count or a rash. Thinning of bones is a potential side effect of Heparin when taken for many months.

Q. Do I need to take calcium while on Heparin?
A. Yes. A side effect of Heparin is calcium loss. Supplemental calcium should help offset this side effect.

Q. What is low molecular weight Heparin?
A. This is a new form of Heparin which requires only one or two injections a day rather than three of regular Heparin. The dose is based on body weight, reducing or eliminating the need for blood testing.

Q. How long does it take to get Heparin out of my system?
A. It takes 6 to 12 hours to get Heparin out of your system, but it can be reversed in 15 minutes, if necessary.

Q. What are the possible side effects of Coumadin?
A. Bleeding (most common by far), possible hair loss, and rash. The risk of spontaneous bleeding increases with age, a particular concern for older patients and those on anticoagulation therapy for life.
If taking either Heparin or Coumadin, you should take care to avoid falls and head injuries which could result in nausea, dizziness, drowsiness, or loss of consciousness (even briefly). Additional concerns are dark colored vomit or a dark stool. If you experience any of these conditions, contact your doctor as soon as possible.

Q. How long does it take to get Coumadin out of my system?
A. About five days.

Q. Do Coumadin and Heparin dissolve clots?
A. No, they prevent new clots from forming.

Q. What happens to a clot after anti coagulation therapy has begun?
A. Over time, the body will usually dissolve some, but not all, of the clot. The remainder of the clot embeds in the vessel wall and becomes scar tissue.

Q. Can a clot go to my brain? Or heart?
A. Blood from the veins returns to the heart via the right atrium. The blood then flows into the right ventricle, where it is pumped into the pulmonary arteries of the lungs. This is how a clot from elsewhere in the body can end up in the pulmonary arteries as a PE.
Some individuals are born with a tiny connection in the heart between the right and left atria. Through this connection, a clot entering the heart can travel from the right to the left atrium, where blood flows into the left ventricle and is then pumped into the aorta. From there the clot could go to the brain or other parts of the body. This is called "paradoxical embolism" and is extremely rare.

Q. What happens if a clot goes to the brain?
A. A stroke.

Q. How long should I stay on Coumadin?
A. This depends on your medical history and the number of risk factors for clotting. Typically, anticoagulation therapy continues for six months after the first clot. If clotting recurs, prolonged anticoagulation may be prescribed.

Q. Why can't I just take aspirin?
A. Aspirin is only a mild anticoagulant compared to Heparin or Coumadin.

Q. What should I do if I forget to take my Coumadin one night?
A. Skip it, and tell your doctor when you have your next blood test, because your INR or PT readings may be lower than usual because of the missed dose.

Q. What is an INR?
A. International Normalized Ratio or standardized prothrombin time (PT). This is a measure of how long it takes for blood to clot.

Q. How is my Coumadin dose adjusted?
A. The Coumadin dose is adjusted so that the INR stays within its designated range.

Q. Should I be upset if my INR or PT is not consistently stable?
A. No. It is very common to have an INR or PT that changes frequently.

Q. How frequently should blood be checked?
A. It depends on the stability of the INR or PT readings. Typically, your doctor will begin with twice-weekly or weekly blood tests, which can be adjusted to longer intervals if the readings are consistent.

Q. Should I take generic, rather than the more expensive brand-name Coumadin?
A. No, not unless recommended by your doctor.

Q. Can I test my blood at home?
A. Yes, equipment is now available to test the INR or PT at home. These small testing devices operate similarly to the blood sugar testers used by diabetics. A small drop of blood is obtained from a finger-stick and is put on a test cartridge. The cartridge is then inserted into the machine, and within a few seconds, the PT and INR readings are displayed.
Depending on the circumstances, some insurance companies will cover the expense.

Q. Should I wear a medical alert bracelet?
A. This is recommended if you are on anticoagulants. If you become unconscious, it is very important for emergency medical personnel to know that you are taking anticoagulants. Ask your pharmacist or doctor for an order form.

Q. How long should I stay out of work after I'm discharged from the hospital?
A. Recovery time varies. Check with your doctor prior to returning to work.

Q. What is chronic venous insufficiency?
A. Venous insufficiency, caused by damaged valves in the veins, allows blood to flow backward and then pool in the lower leg. Symptoms of chronic venous insufficiency include swelling, calf pain, and skin color changes.

Q. Why do some people who have had a DVT develop venous insufficiency and others don't?
A. The severity of the DVT and the extent of valve damage are the key factors in the development of venous insufficiency. Preexisting conditions, such as varicose veins, also increase the probability that venous insufficiency will develop after DVT.

Q. What helps prevent or alleviate the symptoms of chronic venous insufficiency?
A. Wearing prescription strength graduated compression stockings helps. Aerobic exercise, such as walking or bicycling, also increases circulation in the legs.

Q. Who wears graduated compression stockings?
A. Someone who has a DVT often wears graduated compression stockings to help stimulate blood circulation and reduce swelling in the legs. Wearing compression stockings on a long-term basis reduces venous insufficiency by one half.
Compression stockings need to be properly fitted with precise measurements. If the stockings feel too loose or too tight, see your doctor. Stockings need to be replaced every 3-4 months. Less tight stockings for night use are also available.
You should not have pain or numbness when wearing stockings.

Q. Does venous insufficiency always get worse with age?
A. No, not necessarily.

Follow-up Care

Q. What about that swelling/pain/ache still have?
A. If you have had a DVT, it is common to have residual swelling in the leg after the initial treatment. Graduated compression stockings help increase blood flow in the legs and reduce the swelling.
After a PE, shortness of breath and mild pain or pressure in the area affected by the PE are common. Pain may occur in response to physical activity or taking a deep breath and may be present for months or years after the PE. Shortness of breath should decrease with time and exercise.

Q. After having a DVT or a PE, what is the likelihood of developing another one?
The majority of patients do not suffer a recurrence. However, their risk is higher than for the general population. The degree of increased risk depends upon individual circumstances such as location of the clot, number of prior clots, and underlying medical conditions.

Q. If I have a DVT in a particular place in the calf, does scarring predispose this site for a new DVT?
A. Yes.

Q. What are the warning signs of a new DVT?
A. Swelling and pain. It often feels like a persistent "charlie horse," or cramping in the calf. A sensation of fullness/pressure/swelIing/tightness occurs, especially when going from sitting to standing. It is also described as an odd pulling sensation or tingling that doesn't go away.

Q. How do I know it isn't simply a pulled muscle?
A pulled calf muscle usually gets better in a day or two.

Q. Once you've had a DVT, should you have follow-up ultrasounds?
A. No, not unless a new DVT is suspected.

Q. What are the warning signs of a new PE?
A. Shortness of breath, fainting, or chest pains (particularly pains that worsen with coughing or change in position) are the three most worrisome signs.

Q. If I'm no longer taking anticoagulants, and I suspect a new clot, should I take Coumadin until I can seek medical attention?
A. No. Contact your doctor.

Q. What tests should I have after I stop taking Coumadin?
A. None.

Q. Should I take aspirin after stopping Coumadin?
A. Only if your doctor prescribes it.

Q. Is it necessary to be weaned gradually off Coumadin?
A. No.

Q. Taking Coumadin reassured me, since I thought I couldn't get another clot while taking Coumadin. Now that my doctor says it is no longer necessary, I feel reluctant and scared to stop taking Coumadin. Is this worrying normal?
A. Yes. This concern is common and you should discuss these feelings with your doctor.
If you are more than 40 years old, and if your DVT or PE occurred in the absence of trauma, surgery, or cancer, you may be eligible to participate in a clinical trial called PREVENT that is studying optimal duration of anti-coagulation. You may phone (617-732-7139) or E-mail Dr. Goldhaber for more information.

Q. If I have cancer, should I take prophylactic anticoagulants?
A. Discuss this with your doctor.

Q. Once I've had a PE or DVT, if I'm ever hospitalized, should I tell the doctors?
A. Yes, immediately.

Q. Should I tell my dentist I'm on anticoagulants?
A. Definitely tell the dentist when you make the appointment. Every dentist handles the issue of anticoagulants differently.

Q. Is it OK to exercise?
A. Moderate exercise such as walking or swimming is recommended.
A return to your normal exercise routine depends on your physical condition before the clot and the severity and location of your clots.

Q. How important is exercise in rehabilitation for a PE or DVT?
A. It is essential, within the constraints of your physical condition. Exercise increases circulation, reduces symptoms of venous insufficiency, and will make you feel invigorated. Aerobic exercise may increase lung function after a PE.

Q. I had a DVT. Should I refrain from crossing my legs?
A. Yes. Crossing your legs interferes with circulation.

Q. How long should I sit at one time?
A. No more than two hours at a time.

Q. Is it OK to travel?
A. Yes. In an automobile, stop every hour or so and walk for several minutes. On a plane, try to sit where you can stretch your legs (aisle seat, exit aisle, bulkhead seats, business class, etc.). Periodically, get up and walk the aisle(s) for several minutes. It is also a good idea to wear compression stockings when traveling.
 
Drug and Food Interactions

Q. Does Coumadin interact with other drugs, including over-the-counter medications?
A. Many drugs interact with Coumadin. Ask your pharmacist to check any prescription or over-the-counter medication for such interactions. Recently, acetaminophen (Tylenolâ) was reported to increase the risk of bleeding among patients taking Coumadin. Antibiotics such as BactrimÒ cause a drastic increase in the INR/PT.
You should generally not take any product containing aspirin, unless approved by your doctor.

Q. Does diet affect the INR/PT reading?
A. Yes. Consuming foods high in Vitamin K will affect your INR/PT reading. Common foods containing vitamin K are leafy greens, broccoli, spinach, and canola oil. You should eat approximately the same amount of these daily and your Coumadin dosage will be regulated to account for this.
Most importantly, your diet should be consistent. Alert your doctor before you change your diet significantly.

Q. Does alcohol affect the INR or PT reading?
A. Sometimes. Even when alcohol does not affect the PT/INR, it may increase the likelihood of bleeding. Binge drinking should always be avoided.

Q. May I take vitamin E supplements while on Coumadin?
A. Vitamin E is a mild anticoagulant, and doses in excess of 400 units should be avoided.

Women's Health

Q. Will anticoagulation therapy cause changes in menstruation?
A. Usually not.

Q. What happens if I get pregnant while taking Coumadin?
A. Stop taking Coumadin, and tell your doctor immediately. You will be switched to Heparin.

Q. Why can't Coumadin be taken during pregnancy?
A. Coumadin passes through the placenta to the fetus and can cause major birth defects during weeks 6 to 12 of gestation.

Q. Does Heparin hurt the baby?
A. No, because it does not pass through the placenta to the fetus.

Q. How is Heparin taken during pregnancy?
A. Either by periodic injections or with an IV hooked to a small pump that can be worn like a "fanny pack".

Q. Will Heparin increase the risk of bleeding during delivery?
A. Heparin is not given during delivery.

Q. What if I need a Cesarean section?
A. A C-section, like any major surgical procedure, is a risk for blood clots.

Q. How long after delivery will I stay on anticoagulants?
A. For at least six weeks after delivery.

Q. Is it safe to breastfeed while on Coumadin?
A. Yes.

Q. Can I take hormone replacements containing estrogen?
A. This is generally not recommended for anyone who has had a history of clots because hormone replacement therapy increases the risk of a DVT or PE. You should discuss this with your doctor.

Special Situations

Q. When is a clot dissolving medicine like Tissue Plasminogen Activator (TPA) administered?
A. TPA is approved for treatment of a massive PE within 14 days of the onset of symptoms. It is not approved for treatment of a DVT.

Q. Do blood clots need to be removed through a catheter?
A. Not usually. If a clot is particularly large or life-threatening, a catheter may be used to remove it.

Q. Are blood clots removed surgically?
A. Only in rare situations.

Q. When is the placement of a filter recommended?
A. If you have had repeat PEs despite anticoagulation, your doctor may recommend a filter. The filter is inserted in the vein leading to the heart and catches clots before they travel to the heart and lungs. If a clot is caught by the filter, the vein is large enough to allow blood to flow around the clot.

Q. Do filters stay in permanently?
A. Yes.

Q. If I have a filter, do I still take Coumadin or Heparin?
A. Usually, the placement of a filter does not change the anticoagulant therapy regimen.

Major Research Areas

Epidemiology: defining precisely the risk of an initial or recurrent PE or DVT in specific patient populations.

Diagnosis: determining the role of spiral chest CT (computed tomography) scanning and MRI (magnetic resonance imaging) for detecting PE; improving the accuracy of diagnosis of isolated calf vein thrombosis (clots) and of recurrent DVT.

Treatment: evaluating low molecular weight Heparins and studying which patients are optimally treated at home or with abbreviated hospital stays; determining which populations of PE patients should receive thrombolytic (clot dissolving) therapy; determining the optimal duration of anticoagulation (in the PREVENT Trial).
To discuss your potential eligibility for the PREVENT trial, you may E-mail Dr. Goldhaber at: szgoldhabe@BlCS.BWH.harvard.edu

Prevention: optimizing anticoagulant regimens including low molecular weight heparins, especially in patient populations where high DVT rates persist, as in Neurosurgical and Medical Intensive Care Units.