Pulmonary embolism

Illustration of a blood clot traveling through the blood vessels until it gets stuck. A pulmonary embolism is often caused by a blood clot that forms somewhere else in the body, travels to the lungs and gets stuck there.

A pulmonary embolism is a clot of material (an embolus) that blocks blood from getting to the lungs. It is usually caused by a blood clot that starts somewhere else in the body and travels to the lungs. However, it can also be caused by clumped cancer cells, fat, or bone. Rarely, while giving birth, a woman can get a clot of amniotic fluid.

Symptoms

Symptoms of a pulmonary embolism start suddenly, as soon as the clot starts blocking blood flow to the lungs. Blood is supposed to pick up oxygen in the lungs and then carry that oxygen to the rest of the body. If blood cannot get through to the lungs, it cannot pick up oxygen or deliver it to the body. Every part of the body needs blood and oxygen to survive.

Often, the first sign of a pulmonary embolism is syncope (fainting), because the brain is not getting enough blood and oxygen. Other symptoms include:

• Chest pain that feels like a knife sticking into the chest. The pain is often worse when the person breathes in.
• Trouble breathing
• Hemoptysis (coughing up blood)
• Low oxygen saturation (because the body is not getting enough oxygen)

Saddle embolus

The worst kind of pulmonary embolism is caused by a saddle embolus. This kind of embolus blocks the pulmonary artery, which carries blood from the right side of the heart to the lungs. This makes it impossible for any blood to get through to the lungs. Since no blood can get out to the rest of the body, the person's blood pressure drops and they can go into shock. A saddle embolus is a very serious medical emergency. Many people with this type of embolus die.

Risk factors

Deep vein thrombosis - a blood clot in a large vein, like a leg vein - is a risk factor for pulmonary embolism

There are many risk factors that make it more likely for a person to get a pulmonary embolism. For example:

• Smoking
• A type of abnormal heart rhythm called atrial fibrillation ("A-fib")
• Recent surgery (after surgery, the body's blood clotting system works harder than usual, to help heal the body. If clots travel to the lungs, they can cause a pulmonary embolism)
• Being paralyzed, bedridden, or not able to move around very much
• Sitting in one place for a long time, like on a long airplane flight (this makes the blood pool in the legs; if a blood clot forms in the leg, it can travel through the blood vessels to the lungs)
• Recent fracture of one of the long bones in the leg (because having a broken leg makes it harder to move around; also, clots of fat from the bone marrow can escape from the broken bone and travel to the lungs)
• High levels of estrogen because of pregnancy or some birth control pills
• Having had a deep vein thrombosis (DVT) - a blood clot in a large vein - before
• Certain kinds of cancer (some kinds can cause extra blood clotting)
• Being overweight or obese

Treatment

There are a few treatments for pulmonary embolism. The choice of which treatments to use depends on how serious the pulmonary embolism is. Treatments include:

• Oxygen. Oxygen can be given through a special mask to make it easier for the person's body to get the oxygen it needs.
• Anticoagulants. These are medicines commonly called "blood thinners." Doctors may give a few blood thinners together. For example, they may give heparin because it works right away. They may also give warfarin (Coumadin), which takes a few days to start working, but which the patient can keep taking at home.
• Thrombolytics. These are medicines often called "clot busters" or "clot dissolvers." They can quickly dissolve (break up) a clot. However, they are usually given only if a pulmonary embolism is life-threatening, because they can cause bleeding.
• Removing the clot. Sometimes a doctor will thread a catheter (a flexible tube) up through a vein and into the lung. Once the doctor finds the clot, the catheter can be used to pull the clot out, or to give medicine to dissolve the clot. In very bad cases, surgery may be needed to remove a clot.

Pulmonary Embolism Media

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  A deep vein thrombosis as seen in the right leg is a risk factor for PE

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  A Hampton hump in a person with a right lower lobe pulmonary embolism

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  Ventilation-perfusion scintigraphy(A) After inhalation of 20 mCi of Xenon-133 gas, scintigraphic images were obtained in the posterior projection, showing uniform ventilation to lungs.*(B) After intravenous injection of 4 mCi of Technetium-99m-labeled albumin, scintigraphic images shown here in the posterior projection. This and other views showed decreased activity in multiple regions.

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  Selective pulmonary angiogram revealing clot (labeled A) causing a central obstruction in the left main pulmonary artery. ECG tracing shown at the bottom.

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  Electrocardiogram of a person with pulmonary embolism, showing sinus tachycardia of approximately 100 beats per minute, large S wave in Lead I, moderate Q wave in Lead III, inverted T wave in Lead III, and inverted T waves in leads V1 and V3.

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  Histopathology of a pulmonary artery from autopsy. It shows a fat embolism (seen as multiple empty globular spaces on this H&E stain since its processing dissolves fat). There is a bone marrow fragment in the middle, and multiple single hematopoietic cells in the blood, being evidence of fracture as the source of the embolism.

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  Used inferior vena cava filter.

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  On CT scan, pulmonary emboli can be classified according to the level along the arterial tree.

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  Segmental and subsegmental pulmonary emboli on both sides

• Ultrasound of the heart showing signs of PE

• Ultrasound of the heart showing signs of PE