Pulmonary Embolism: Symptoms, Causes, Risk Factors, Diagnosis, Treatment & Prevention

Last Updated on May 5, 2023 by Shabnam Sengupta

An embolism is a condition where a foreign body blocks an artery that supplies blood and oxygen to different organs of the body. This can be a blood clot, cholesterol from an atherosclerotic plaque or even air. Pulmonary embolism refers to the condition in which the embolism causes obstruction of the pulmonary arteries (arteries to the lung).

Pulmonary embolism is a serious condition that can lead to death if not promptly treated. It is one of the causes of sudden death. It is not a disease on its own but can be a complication of various conditions. A lot of hospitalised patients also develop this condition.

In pulmonary embolism, blood clots block one or more arteries that carry blood from the heart to the lungs. These arteries carry blood that is low in oxygen in order to collect oxygen from the lungs. 

When these arteries are blocked, the blood does not reach the lungs and does not receive oxygen. If these are the smaller arteries, only some of the blood is absent of oxygen, but the greater the size of the artery, the more severe the lack of oxygen and the complications due to it. Sometimes, the clot can be large enough to block the largest arteries and results in the failure of the heart to pump blood against the pressure of the clot and can result in sudden death.

Signs and Symptoms

The symptoms of pulmonary embolism depend on the severity of the blockage.

The classical symptoms of a sudden pulmonary embolism are:

1. Sharp pain in the chest
2. Shortness of breath of sudden onset
3. Decreased oxygen levels in the blood

But pulmonary embolism can also present as:

1. Gradual onset difficulty in breathing
2. Productive cough
3. Coughing up blood
4. Breathing associated with a whistling sound (wheeze)
5. Pain in the chest or abdomen
6. A fast heart rate, sometimes with a flutter
7. Fainting
8. Anxiety, sweating

Causes

The most common cause of obstruction in pulmonary arteries are clots that break off from blood clots in the large deep veins of the legs as seen in deep vein thrombosis. These clots form in patients with a high risk of clotting or in those with a greater risk of stasis of blood in the legs.

Risk Factors of Pulmonary Embolism

1. Genetic conditions: Some genetic conditions can have an increased risk of blood clots and tend to run in families 
2. Major surgery after which patients are immobilised for long durations
3. Pregnancy
4. Hormone replacement therapy and oral contraceptive use
5. In those who are already at higher risk, long travel involving prolonged sitting can predispose them to pulmonary embolism
6. Varicose veins
7. Heart diseases where there is an increased risk of clot formation
8. Covid-19 infection
9. Malignancy
10. Recreational drug abuse
11. Certain medications

Diagnosis

The recognition of pulmonary embolism on the basis of signs and symptoms can be done in a very few cases.

Therefore, when your doctor perceives that the patient is at a higher risk for pulmonary embolism, they may perform certain tests to help in the diagnosis of this condition.

1. Blood tests:
   1. To check for disorders with an increased risk of blood clots
   2. To test for clotting ability of the blood
   3. To test for signs of existing clots like the D-Dimer test.
   4. Blood gas analysis to look for levels of oxygen in the blood
   5. Troponin levels
2. Pulmonary angiography:
   1. A contrast material is injected, and imaging is done with X-Rays
3. CT Pulmonary Angiography:
   1. This is the best test to identify pulmonary embolism.
   2. Contrast material is injected into the patient’s bloodstream and imaging of pulmonary vessels is performed.
   3. Blood vessels that are obstructed can be identified using this method.
4. Chest X-Ray may be performed.
5. ECG to look for changes that are seen in pulmonary embolism.
6. Echocardiography
7. Duplex ultrasonography
8. Ventilation-perfusion scanning: Better in children than in adults, and in cases where CT scan is not an option due to some medical reasons.

Complications

The worst and most dangerous complication of pulmonary embolism is death. The complications vary on the basis of the size of the clot, the size of the obstruction of pulmonary artery and the degree of obstruction of the vessels.

1. A massive pulmonary embolism that occurs in the larger pulmonary arteries can result in a collapse of the body’s blood circulation and can lead to death.
2. Low oxygen levels can damage organs as they require oxygen for their functioning.
3. An increase in pressure in the lungs due to obstruction of blood flow leads to an increased pressure of the heart to pump blood to the lungs
4. If this occurs in the long term, this can lead to pulmonary hypertension and an increase in blood pressure in the lungs. This can be harmful to the lungs (and the heart) in the long term.

Treatment

Treatment in patients with pulmonary embolism or its symptoms is based on the severity of the blockage. 

1. Thrombolysis: This is the process of dissolving clots that are already present using certain medications called thrombolytics. These medications are very important in the treatment of severe pulmonary embolism, especially in those with a large fall in blood pressure. But due to the risks of these medications, it is not used in less severe pulmonary embolism. Your doctor will decide whether the risk is worth the benefit of using these drugs.
2. Anticoagulation: This prevents the formation of new clots or the increase in the size of existing clots. The most commonly used drugs are unfractionated and low molecular weight heparin and fondaparinux and warfarin.
3. Catheter-assisted or surgical embolectomy: This method is for patients who do not respond to thrombolysis. It is also for patients on whom thrombolysis cannot be used.
4. Vena cava filters: These are filters that are inserted in the inferior vena cava that prevent emboli from reaching the lungs. 

Long term treatment

1. Compression stockings: These are tight stockings that prevent or reduce the collection of blood in the deep veins of the legs, decreasing the risk of clot formation.
2. Anticoagulation
3. Monitoring the clotting ability of the blood

Prevention of Pulmonary Embolism

1. Since pulmonary embolisms can occur in hospitalised patients, your doctor will take necessary precautions to prevent the formation of clots in the legs.
2. These precautions include anticoagulant drugs.
3. Physical activity is useful in preventing the formation of clots in the legs.
4. Compression stockings: In patients with an increased risk of pulmonary embolism, compression stockings are advised.
5. Frequently moving legs and flexing the ankles or walking around when travelling is helpful.

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