A blood clot in the lung, also called a pulmonary embolism, is a blockage of one or more divisions of the pulmonary artery. According to the Cleveland Clinic, a pulmonary embolism results from a clot that has formed somewhere in the body, for instance in the legs or pelvic area, and travels through the bloodstream to the lungs. A thrombus is a blood clot that has formed somewhere in the body and does not travel to the lungs. Many factors can contribute to the formation of blood clots.
Causes
Blood clots can occur when a person is bed-ridden due to illness or injury. According to the Centers for Disease Control and Prevention, surgery and injury can also cause a blood clot, particularly fractures of the long bones in the legs, hip and pelvic areas. Heart disease can also cause blood clots to form, as well as certain types of hormone replacement therapy, drugs used for birth control and drugs used in chemotherapy.
Warning Signs
The sudden onset of breathlessness is the most common symptom of a pulmonary embolism. According to the Centers for Disease Control and Prevention, other symptoms include chest pain, palpitations, coughing up blood-stained mucus, a slight fever and wheezing. If any of these occur, especially after surgery, chemotherapy, an accident or injury, a visit to the local emergency department may be necessary.
Non-Invasive Testing
Non-invasive testing can map the flow of blood through the veins with ultrasonic high-frequency sound and by measuring the electrical forces generated when the blood pushes against a clot. Chest x-rays often appear normal for individuals with a pulmonary embolism, although a physician may see signs of reduced blood flow through the affected lung. An electrocardiogram can sometimes distinguish a pulmonary embolism from other causes of breathlessness and chest pain, such as asthma or a heart attack.
Invasive Testing
To confirm a blood clot in a vein, doctors may perform a venous angiography. During this procedure, a physician will inject a contrast medium through which x-rays cannot pass, into the veins of a person's foot. This contrast medium outlines the veins on x-ray film, showing any possible abnormalities or clots.
A second, more invasive test is a pulmonary angiography. According to National Jewish Health, a trained physician will insert a catheter or small tube into a vein in a person's arm or groin and carefully guide it within the vessel until it reaches the pulmonary artery. The physician then injects contrast medium through the catheter and into the pulmonary artery. The contrast medium outlines the arteries, which appear white on an x-ray. If an embolism is present, the artery often appears to end abruptly at the point where the embolism or blood clot is located.
Treatment
When a doctor confirms or strongly suspects a pulmonary embolism, she will begin drug treatment immediately, often before receiving all of the test results. According to the Cleveland Clinic, treatment begins with the drug heparin, which keeps a person's blood from coagulating. Heparin will prevent further clotting, but it does not break down a clot that has already formed. Treatment with clot-dissolving drugs, such as streptokinase, will help dissolve existing blood clots. Once the individual's condition stabilizes, the physician will begin treatment with an anticoagulant drug, such as warfarin, after five to seven days of heparin therapy.
