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:
- shortness of breath
- sharp, stabbing chest pain, which may worsen with breathing
- rapid heart rate
- coughing up blood or blood-streaked sputum
- dizziness or fainting, caused by a sudden drop in blood pressure.
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:
- periodically flex and relax your leg muscles
- try to get up and walk around every half hour during long flights
- if you are driving, make stops every hour or so to walk and stretch
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:
- oral contraceptives
- hormone-replacement therapy
- raloxifene (Evista), which is used for osteoporosis
- tamoxifen (Nolvadex), which is used for cancer prevention and treatment.
A few other conditions or situations are associated with a higher-than-average risk of pulmonary embolism.
- Inflammatory bowel disease (such as Crohn’s disease or ulcerative colitis)
- Prenancy and Childbirth
- Heart disease
- Heart surgery
- Trauma to the legs
- Inflammation of a vein
- History of pulmonary embolism
- Sickle cell disease
- Lung disease
- Drug use
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