Pulmonary is a term used when referring to something affecting, occurring in, or related to the lungs. When a blood clot (thrombus) detaches from the wall of the vein in which it has formed, it is carried in the blood through the vasculature. Subsequently, the thrombus can pass through the right ventricle of the heart, which forces it into the pulmonary circulation (circulation to the lungs), where it can get stuck. This is known as a pulmonary embolism (PE). The development of a thrombus and its detachment and journey to a pulmonary artery are different aspects of the same pathological process, known as thromboembolism.

The figure shows how a thrombus can cause obstruction of a pulmonary vessel and acute disruption of blood supply to the lung.

The size of the blood clot has an impact on the subsequent consequences. If it is small, it may remain unnoticed or manifest as mild shortness of breath. Larger clots can cause shortness of breath, chest pain, or even circulatory collapse. The latter condition is life threatening and requires immediate medical intervention.

Although common symptoms of a PE include breathlessness and bloody mucus, not all patients present with these symptoms. Doctors employ an assessment score that has been shown to accurately assess the chance of having a PE on the basis of a number of measurements.

Having a PE is a medical emergency. Although PE can be diagnosed quickly and effectively treated, in some cases, death can occur quickly. Therefore, guidelines for doctors recommend that patients waiting for a test for PE are given treatment even before the diagnosis is confirmed. About one in ten people with an untreated DVT develops a severe pulmonary embolism.


PE is a very serious condition, which can have severe consequences including damage to the right ventricle of your heart (ventricular failure), hypertension, and death.

A serious, long-term condition called pulmonary hypertension produces shortness of breath, dizziness, and fainting and occurs in around one in 25 patients with PE after 2 years [4].


DVT might not cause any further problems, but potential complications associated with DVT can be serious and unpleasant and include:

  • Pulmonary embolism (PE) (see the next section)—when part of the blood clot breaks off and blocks blood flow to a lung
  • Recurrence of venous thromboembolism (DVT or PE)
  • A condition called post-thrombotic syndrome that develops in up to one half of patients after symptomatic DVT and is the most common complication of DVT
    • Typical features include chronic pain, swelling, a feeling of heaviness, and skin changes in the affected leg and fluid retention
    • The symptoms are usually worse with activity; for example, standing and walking
    • About 5-10% of cases with post-thrombotic syndrome will be severe and may induce unpleasant leg ulceration [3]