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Pulmonary Thromboembolism: Symptoms, Causes, Treatment and Risk Factors

Pulmonary thromboembolism or pulmonary embolism is a potentially fatal disease. It occurs when parts of a thrombus break loose from somewhere in the venous area, migrate, and become lodged in the pulmonary arteries. In most cases, the emboli come from deep vein thrombosis of the extremities.

The result is an oxygen defect in the lungs and is one of the main medical emergencies. Furthermore, its diagnosis isn’t easy, as there are few signs that can guide the doctor.

Experts estimate that the incidence of pulmonary thromboembolism is 1 case per 1000 inhabitants per year. However, the true figure is probably higher. According to the data from Endovascular Today, during 2019, around 1 million cases were diagnosed in US with a mortality rate of 8-9%.

Causes of Pulmonary Thromboembolism

In most cases, approximately 95% of them, the thrombus or clot forms in the veins of the lower limbs. Then, it migrates into the pulmonary artery.

It can also be air-based or fat-based. In the first case, we’re dealing with a gaseous embolus and in the second case with a fatty embolus. This occlusion mainly affects the lungs and the heart:

  • An area of the lungs doesn’t receive venous blood, which is poor in oxygen, and therefore cannot oxygenate it. This fact will have a negative impact on the oxygen that will later reach the rest of the patient’s organs and tissues.
  • The heart will continue to pump blood to the lungs, but with the occlusion it will encounter an obstacle. In turn, the pressure will increase inside the pulmonary artery. This weakens the right ventricle of the heart, which is the heart chamber that sends blood without oxygen to the lungs.

Risk factors

There are several risk factors that favor the onset of pulmonary thromboembolism. The most important are:

  • Lower extremity fractures or recent surgeries
  • Prolonged bed rest or immobilization
  • Long trips (more than 8 hours)
  • States of hypercoagulability
  • Cancer and chemotherapy treatment
  • Obesity
  • Tobacco habit

Symptoms of pulmonary thromboembolism

The clinical manifestations of pulmonary thromboembolism are unspecific. This is why early diagnosis is difficult. That being said, some symptoms that could appear are the following:

  • Suffocating sensation: Small emboli that don’t cause symptoms can produce this sensation. This may be the only symptom when there’s no pulmonary infarction.
  • Accelerated breathing: Accompanied by anxiety and agitation.
  • Acute chest pain: Especially when the person takes deep breaths.
  • Dizziness and fainting or convulsions.
  • Cyanosis or sudden death: These symptoms can appear in cases where patients have more than one large occluded pulmonary vessel.
  • Cough, blood-tinged sputum, and fever.

People with recurrent pulmonary thromboembolism often progressively develop certain symptoms over weeks, months, or years. These include a chronic feeling of suffocation, swelling of the ankles or legs, and weakness.


Treatment in the acute phase of pulmonary thromboembolism aims to stabilize the patient, relieve symptoms, resolve vascular obstruction, and prevent further episodes.

Normally, doctors achieve these objectives with the administration of intravenous anticoagulant drugs. They administer this treatment during the first 5-10 days, the drug of choice for the treatment of pulmonary thromboembolism being heparin.

Treatment differs in the case of more critical patients or those who for some reason cannot receive anticoagulant medication. These cases require other treatments such as fibrinolysis in order to accelerate the dissolution of the clot. A filter can also be placed in the vena cava to prevent new thrombi from migrating into the lung.

Finally, once the patient is at home, they’ll be given oral anticoagulant drugs. The most commonly used is known as Sintrom. Generally, its administration is indicated for a minimum period of 3 months.

In patients who present a greater risk of pulmonary thromboembolism, this quarterly period usually extends and lasts a lifetime.

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