Blood Clots: Pulmonary Embolism
Basics
Pulmonary embolism is a sudden blockage of one of the blood vessels in the lungs. It is usually caused by a blood clot from the leg that travels through the body and the heart before reaching the lungs. Figure 01
Large clots can seriously affect the lung's ability to transfer oxygen to the blood, resulting in shortness of breath, chest pain, and a rapid heart rate. These symptoms indicate an emergency situation, and cause sudden death in about one-third of the cases.
Pulmonary emboli are a serious risk to older people, and are more likely to occur in those who have been immobilized for long periods; for example, in those recovering from leg or hip surgery.
Pulmonary embolism can be fatal if not detected and treated quickly. Fortunately, treatment is life-saving in almost all cases.
People who have sudden life-threatening symptoms of pulmonary embolism have a death rate of 30% if not treated promptly. With rapid diagnosis and treatment, mortality rates drop to only 3%.
Figure 01. Pulmonary embolism
Causes
The vast majority of emboli are caused by blood clots that arise from veins in the legs.
About 80% of emboli arise from leg veins, although they can also arise in other blood vessels. Under certain circumstances, blood tends to form clots in the deep veins, the larger veins located inside the leg (not the visible veins). This is a condition known as deep venous thrombosis. (Thrombosis is the formation of a blood clot, or thrombus. Once it has lodged in a blood vessel, it is referred to as an embolus.) Deep venous thrombosis tends to occur:
Emboli can result from substances other than blood.
Emboli can also arise from a piece of fat or bone marrow that has escaped from the inside of a fractured long bone. In very rare cases, a piece of a malignant tumor can break off, invade the bloodstream, and cause pulmonary embolism. Air emboli from catheters or IV drug use can also cause pulmonary embolism, as can emboli from parasite eggs (such as those in schistosomiasis), or from amniotic fluid released during labor.
An embolus can cause part of the lung to die.
An embolus can be large enough to cut off the blood supply to surrounding lung tissue. If the blood is stopped for long enough, the tissue in the area dies.The area of dead tissue is known as an infarction.
Symptoms
Symptoms vary depending on the size of the blockage. Tiny emboli may cause no symptoms; however, large emboli can be life-threatening.
Many people have no symptoms from a pulmonary embolus. A small blockage may not cause enough damage to affect lung function significantly.
A large blockage, on the other hand, can cause:
Blood clots in the deep veins of the legs (deep vein thrombosis) can lead to pulmonary embolism. Therefore, it is important to recognize the symptoms of deep vein thrombosis, as treatment for this disease can prevent pulmonary embolism.
Deep venous thrombosis often manifests as swelling and pain in the calf muscle. Pain increases with walking, when applying pressure to the leg muscles, or when pointing the toes and foot upward. Redness and a warm feeling may be apparent. If the thrombosis is in the thigh, a swollen leg may be the only sign. However, many patients will have no visible leg abnormalities.
Risk Factors
Pulmonary emboli affect approximately 5 out of 10,000 people in the US each year. Incidence increases with age and being overweight or obese.
Prolonged inactivity is a major risk factor.
Prolonged bedrest, such as occurs during hospitalization or recuperation, is a clear risk factor for pulmonary emboli. In hospital situations, patients deemed at high risk are often put on blood thinners as a precautionary measure, and patients are encouraged to walk around and increase activity as soon as possible. Inactivity, such as occurs during many hours of sitting in a car or airplane, also places individuals at risk. If you have to spend a lot of time sitting still during travel, try the following things to keep your blood moving:
Injury or surgery to the legs or hips increases risk.
People who are recovering from hip or knee replacements and those who have had a traumatic injury, such as a fracture of the hip or femur (long leg bone), are at high risk for pulmonary embolism. The long period of inactivity necessary for recuperation, as well as damage to the blood vessels, further increases the likelihood of clot formation. Doctors often place such patients on blood-thinning therapy as a precautionary measure.
Some hereditary disorders make blood clotting more likely.
Many components of the blood are involved in clot formation and breakdown. Some inherited conditions involve deficiencies or defects of such factors, making clots more likely to occur. For example, some people are resistant to a protein called activated protein C (factor V Leiden), which makes them more likely to develop blood clots and progress to pulmonary embolism.
Some medications are associated with a risk for pulmonary embolism.
Medications associated with a slightly higher-than-average risk for pulmonary embolism include:
A few other conditions or situations are associated with a higher-than-average risk of pulmonary embolism.
Diagnosis
Pulmonary embolism is a sudden blockage of one of the blood vessels in the lungs. It is usually caused by a blood clot from the leg that travels through the body and the heart before reaching the lungs. Figure 01
Large clots can seriously affect the lung's ability to transfer oxygen to the blood, resulting in shortness of breath, chest pain, and a rapid heart rate. These symptoms indicate an emergency situation, and cause sudden death in about one-third of the cases.
Pulmonary emboli are a serious risk to older people, and are more likely to occur in those who have been immobilized for long periods; for example, in those recovering from leg or hip surgery.
Pulmonary embolism can be fatal if not detected and treated quickly. Fortunately, treatment is life-saving in almost all cases.
People who have sudden life-threatening symptoms of pulmonary embolism have a death rate of 30% if not treated promptly. With rapid diagnosis and treatment, mortality rates drop to only 3%.Figure 01. Pulmonary embolism
The vast majority of emboli are caused by blood clots that arise from veins in the legs.
About 80% of emboli arise from leg veins, although they can also arise in other blood vessels. Under certain circumstances, blood tends to form clots in the deep veins, the larger veins located inside the leg (not the visible veins). This is a condition known as deep venous thrombosis. (Thrombosis is the formation of a blood clot, or thrombus. Once it has lodged in a blood vessel, it is referred to as an embolus.) Deep venous thrombosis tends to occur:
Emboli can result from substances other than blood.
Emboli can also arise from a piece of fat or bone marrow that has escaped from the inside of a fractured long bone. In very rare cases, a piece of a malignant tumor can break off, invade the bloodstream, and cause pulmonary embolism. Air emboli from catheters or IV drug use can also cause pulmonary embolism, as can emboli from parasite eggs (such as those in schistosomiasis), or from amniotic fluid released during labor.
An embolus can cause part of the lung to die.
An embolus can be large enough to cut off the blood supply to surrounding lung tissue. If the blood is stopped for long enough, the tissue in the area dies.The area of dead tissue is known as an infarction.
Symptoms vary depending on the size of the blockage. Tiny emboli may cause no symptoms; however, large emboli can be life-threatening.
Many people have no symptoms from a pulmonary embolus. A small blockage may not cause enough damage to affect lung function significantly.
A large blockage, on the other hand, can cause:
Blood clots in the deep veins of the legs (deep vein thrombosis) can lead to pulmonary embolism. Therefore, it is important to recognize the symptoms of deep vein thrombosis, as treatment for this disease can prevent pulmonary embolism.
Deep venous thrombosis often manifests as swelling and pain in the calf muscle. Pain increases with walking, when applying pressure to the leg muscles, or when pointing the toes and foot upward. Redness and a warm feeling may be apparent. If the thrombosis is in the thigh, a swollen leg may be the only sign. However, many patients will have no visible leg abnormalities.
Pulmonary emboli affect approximately 5 out of 10,000 people in the US each year. Incidence increases with age and being overweight or obese.
Prolonged inactivity is a major risk factor.
Prolonged bedrest, such as occurs during hospitalization or recuperation, is a clear risk factor for pulmonary emboli. In hospital situations, patients deemed at high risk are often put on blood thinners as a precautionary measure, and patients are encouraged to walk around and increase activity as soon as possible. Inactivity, such as occurs during many hours of sitting in a car or airplane, also places individuals at risk. If you have to spend a lot of time sitting still during travel, try the following things to keep your blood moving:
Injury or surgery to the legs or hips increases risk.
People who are recovering from hip or knee replacements and those who have had a traumatic injury, such as a fracture of the hip or femur (long leg bone), are at high risk for pulmonary embolism. The long period of inactivity necessary for recuperation, as well as damage to the blood vessels, further increases the likelihood of clot formation. Doctors often place such patients on blood-thinning therapy as a precautionary measure.
Some hereditary disorders make blood clotting more likely.
Many components of the blood are involved in clot formation and breakdown. Some inherited conditions involve deficiencies or defects of such factors, making clots more likely to occur. For example, some people are resistant to a protein called activated protein C (factor V Leiden), which makes them more likely to develop blood clots and progress to pulmonary embolism.
Some medications are associated with a risk for pulmonary embolism.
Medications associated with a slightly higher-than-average risk for pulmonary embolism include:
A few other conditions or situations are associated with a higher-than-average risk of pulmonary embolism.
Pulmonary embolism can be difficult to diagnose. First, your doctor must suspect pulmonary embolism on the basis of your symptoms.
Because pulmonary embolism is associated with many symptoms, it is easily confused with several other conditions, such as heart attack, pneumonia, congestive heart failure, or even panic attacks.
Even if your doctor suspects pulmonary embolism, it is often difficult to detect.
Several diagnostic tests are available. They include:
Other tests may be given to rule out other possible causes of your symptoms.
Other conditions, such as such as pneumonia, heart attack, asthma, or pulmonary hypertension, may produce symptoms similar to those of pulmonary embolism. Some of the tests used to detect or rule out these conditions include:
Doctors may concentrate on trying to diagnose deep venous thrombosis, as this condition is the most likely cause of pulmonary embolism.
Tests for deep venous thrombosis include:
Figure 02. Chest x-ray
If you are confined to bed, wear compression stockings to decrease the incidence of deep venous thrombosis.
Compression stockings are available to promote circulation. They work by intermittently filling with air and squeezing the legs.
Avoid long periods of immobilization.
People traveling long distances should keep their legs uncrossed, stretch their legs often, and get up and walk around at least every hour.
Prevention and Screening
If you are confined to bed, wear compression stockings to decrease the incidence of deep venous thrombosis.
Compression stockings are available to promote circulation. They work by intermittently filling with air and squeezing the legs.
Avoid long periods of immobilization.
People traveling long distances should keep their legs uncrossed, stretch their legs often, and get up and walk around at least every hour.
Treatment
Pulmonary embolism is life-threatening and must be treated at once.
If any of the following symptoms occur suddenly, seek medical attention immediately:
These symptoms can also indicate life-threatening conditions other than pulmonary embolism.
Signs of deep venous thrombosis in the leg warrants immediate medical attention because of the danger that a pulmonary embolism can occur.
If you think you may have a clot in your leg, call your doctor for an appointment the same day or go to an emergency room if your doctor is unavailable. Symptoms include marked swelling or pain in one leg, most often in the calf muscle area, and less frequently in the thighs. Discomfort usually increases with walking. Redness may not be apparent if affected veins are deep.
If you are taking warfarin (Coumadin)--a medication used to prevent clots from forming or from getting larger—you should take precautionary measures with your diet and activities.
Your doctor is the best source of information on the drug treatment choices available to you.
You will be given oxygen to help your body maintain normal concentrations.
Clot-trapping filters can help in some circumstances.
If you cannot take blood-thinning medications, a special fine-meshed screen that acts as a trap for thrombi can be inserted into the main vein (the vena cava) that leads from the legs to the heart. This device is like a screen tent that lodges permanently in a leg vein. It funnels clots to the tip of the tent, allowing blood to pass by, and keeping the clot from reaching the lungs. Once the clot is trapped, the body will naturally dissolve the clot through a process called lysis.
For a very large embolism, a surgery known as pulmonary embolectomy can be performed to remove the blockage.
Although women can safely breastfeed while taking warfarin (Coumadin), they should generally not take the drug in the first trimester of pregnancy. Pregnant women can take heparin. If you require coumadin and you are considering pregnancy, talk to your doctor first.
Pulmonary embolism can be fatal if it is not detected and treated quickly. Fortunately, treatment is life-saving in almost all cases.
If not treated promptly, people with life-threatening pulmonary embolism have a death rate of 30%. With rapid diagnosis and treatment, this rate drops to 3%.
Although most people recover completely after a pulmonary embolism, some lung damage may remain.
About 10% of patients are left with permanent damage to part of their lung. Remaining damage is especially likely if lung disease was present before the embolism. Lung damage may result in shortness of breath that occurs more often than before, possibly requiring oxygen supplementation.
Once you have had a pulmonary embolism, you have an increased risk of having another.
If you are predisposed to blood clots, you may need to take warfarin for the rest of your life to minimize the risk for having an embolism.
People on warfarin must have their blood tested regularly.
Warfarin can be dangerous: a dose that is too high increases your risk for bleeding and stroke. Careful monitoring is required to ensure that the levels of the drug are not too high. However, the medication's activity in the blood is not simply dose-related—it also varies with diet, other medications, illness, activity levels, and even prolonged hot weather.
To monitor the medication, you will need a type of blood test called a prothrombin time (“pro-time” or PT test), which provides an indication of blood clotting activity. If the prothrombin time is too low—indicating that clots will occur faster—a higher dose is needed. If the prothrombin time is too high—indicating that clots will take longer to form—a shot of vitamin K is given to boost the body's manufacture of clotting factors. To find the right level, prothrombin time must be checked every week when you first start therapy, and it will be checked once a month throughout therapy.