Pulmonary embolism is a condition that occurs when an artery in your lung becomes blocked. In most cases, the blockage is caused by one or more blood clots that travel to your lungs from another part of your body.
Most blood clots originate in your legs, but they can also form in the veins of your arms, the right side of your heart or even at the tip of a catheter placed in a vein. In rare cases, other types of clots - such as globules of fat, air bubbles, tissue from a tumor or a clump of bacteria - also can lodge in your lungs' arteries.
Smaller clots prevent adequate blood flow to the lungs, sometimes causing damage to lung tissue (infarction). Large clots that completely block blood flow can be fatal.
You're especially at risk of pulmonary embolism if you must rest in bed or remain inactive for long periods of time. You're also at risk if you've had surgery, a stroke or heart attack, have chronic congestive heart failure or if you've fractured your hip or femur. In addition, people with cancer or chronic lung disease and women who use birth control pills are at increased risk.
The encouraging news is that a few simple measures, such as moving around during a long airplane flight, can go a long way toward preventing pulmonary embolism. In addition, treatment with medications that break up clots or prevent new clots from forming can greatly reduce the number of deaths from this serious condition.
Signs and symptoms
The signs and symptoms of pulmonary embolism can vary greatly, depending on how much of your lung is involved, the size of the clot and your overall health especially the presence or absence of underlying lung or heart disease. Common signs and symptoms include:
A number of other signs and symptoms also may occur with pulmonary embolism, including:
You have two lungs, one on either side of your heart. Each time blood passes through your heart, it travels to your lungs, where it picks up oxygen and releases carbon dioxide a waste product of metabolism.
Blood vessels known as arteries take the oxygen-rich blood to tissues throughout your body, while veins bring oxygen-poor blood back to the right side of your heart. Capillaries the smallest blood vessels connect the veins and arteries.
Blood is constantly being pumped from the right side of your heart to your lungs and back to the left side of your heart. As a result, clots that form in the veins and then break off can migrate through your bloodstream to the right side of your heart and then into the pulmonary arteries, potentially blocking an artery (pulmonary embolism). It can take less than 10 seconds for this whole process to occur. No one knows what causes fragments or even the whole clot to break off and migrate, and it's not possible to predict which clot will break off or when.
A blockage can occur in any small artery, but your lungs are especially vulnerable because all of the blood in your body passes through your lungs every time it circulates. In most cases, a number of clots will develop over a period of minutes or hours and spread to several parts of your lungs. It's unusual to have only one clot.
Your heart is composed of two upper and two lower chambers. The upper chambers (the right and left atrium) receive incoming blood. The lower chambers, the more muscular right and left ventricles, ...A blood clot in a leg vein can break loose and travel through the heart, lodging in a pulmonary artery. There, the clot blocks blood flow to a portion of the lung....The lungs are two spongy organs located in the chest. Air is carried through the trachea to the lungs via larger airways called the bronchi, which subdivide into smaller airways. At the end of the ...
Understanding blood clots
Most of these clots originate in a vein in your leg or pelvis. The affected vein may be near the surface of your skin (superficial thrombosis) or deep within a muscle (deep vein thrombosis, or DVT). Clots in superficial veins rarely present a problem and often clear on their own. But clots in the deep veins may detach and migrate through your bloodstream to your lungs. Not everyone who has DVT develops a pulmonary embolism.
A blood clot that forms and remains in a vein is called a thrombus. A clot that travels to another part of your body is an embolus. Occasionally other substances such as pieces of a tumor, globules of fat from fractured bones or air bubbles may enter your circulation and block arteries. Most clots in the legs begin in veins below the knee, and it's uncommon for these clots to break off and embolize. Eventually, these clots may extend up into the upper leg (thigh), and that's when they tend to be dangerous.
Most blood clots occur for one of the following reasons:
Although anyone can develop blood clots and subsequent pulmonary embolism together known as venous thromboembolism (VTE) you have a higher risk if you:
When to seek medical advice
See your doctor right away if you develop redness, swelling or tenderness over a vein in one of your legs. This may indicate a blood clot. Because other conditions can also cause these signs and symptoms, your doctor will order tests to confirm a blood clot before proceeding with any treatment. However, you can have DVT and have no symptoms.
Once a clot has reached your lungs, the situation can be life-threatening and you need immediate medical care. About 10 percent of people with pulmonary embolism die within the first hour, so prompt treatment is crucial. Pulmonary embolism is seldom fatal when diagnosed and treated promptly.
Although signs and symptoms of pulmonary embolism vary widely and often resemble those of other conditions, they commonly include sudden shortness of breath, chest pain and a cough that produces blood-streaked sputum.