Definition
A pulmonary embolism (PE) is a blockage of one or more branches of the pulmonary artery by a substance that has travelled through the bloodstream (embolus), usually a thrombus (blood clot). Other, less common emboli include:
- Amniotic fluid → e.g. during labor
- Fat → from long bone fractures
- Air → from IV lines, trauma, or decompression sickness
This leads to impaired perfusion of lung tissue, ventilation–perfusion mismatch, and strain on the right heart.
Etiology
Main sources of thrombi:
- Deep veins of the lower limbs → due to phlebothrombosis or thrombophlebitis
- Venous plexuses around uterus/prostate
- Right atrium → especially in atrial fibrillation/flutter (blood stasis)
- Right ventricle → in dilated cardiomyopathy or ventricular aneurysm
Virchow’s Triad – Key Factors in Thrombosis
These three conditions significantly increase the risk of thrombus formation.
Symptoms
Onset is sudden, and severity depends on embolus size and location.
Symptom Distribution:
- Peripheral emboli often cause pain but don’t usually lead to severe hypoxia Central emboli are frequently painless but can be fatal
- The blockage of the pulmonary a. or one of its main branches causes sudden death.