If a large blood clot blocks the artery in the lung, blood flow may be completely stopped, causing sudden death. A smaller clot reduces the blood flow and may cause damage to lung tissue. However, if the clot dissolves on its own, it may not cause any major problems.

Symptoms of pulmonary embolism usually begin suddenly. Reduced blood flow to one or both lungs can cause shortness of breath and a rapid heart rate. Inflammation of the tissue covering the lungs and chest wall (pleura) can cause sharp chest pain.

Without treatment, pulmonary embolism is likely to recur.

Complications of pulmonary embolism

Complications of pulmonary embolism may include:

• Cardiac arrest and sudden death.
• Shock.
• Abnormal heart rhythms.
• Death of part of the lung, called pulmonary infarction.
• A buildup of fluid (pleural effusion) between the outside lining of the lungs and the inner lining of the chest cavity.
• Paradoxical embolism.
• Pulmonary hypertension.

Doctors will consider aggressive steps when they are treating a large, life-threatening pulmonary embolism. Death caused by pulmonary embolism usually occurs within 30 minutes of the onset of symptoms.⁴

Chronic or recurring pulmonary embolism

Blood clots that cause pulmonary embolism may dissolve on their own. However, if you have had pulmonary embolism, you have an increased risk of a repeat episode if you do not receive treatment. If pulmonary embolism is diagnosed promptly, treatment with anticoagulant medicines (usually heparin and warfarin) may prevent new blood clots from forming.

The risk of having another pulmonary embolism caused by something other than blood clots varies. Substances that are reabsorbed into the body, such as air, fat, or amniotic fluid, usually do not increase the risk of having another episode. Cancer increases the risk of blood clots.

Having multiple episodes of pulmonary embolism can severely reduce blood flow through the lungs and heart. Over time, this increases blood pressure in the lungs (pulmonary hypertension), eventually leading to right-sided heart failure and possibly death.