Pulmonary embolism (PE) is a complication that results from a block in the main artery supplying the lungs, or one of its branches.
Most of the time, the block is due to a blood clot (thrombus) that has detached itself from the deep veins in the legs and traveled all the way to the lungs. Hence, this process is known as venous thromboembolism.
Thrombosis classically develops due to the following causes or factors
(A) Blood flow alterations –This can happen due to an injury or a surgery, pregnancy, indwelling venous catheters, obesity or even long -distance travel
(B) Factors affecting the blood vessel wall such as injury or dysfunction of the inner lining
(C ) Factors affecting clotting of blood such as hormonal factors or disease conditions for e.g. genetic or acquired thrombophilia (factor V mutation). These three factors collectively are known as Virchow’s triad.
Deep vein thrombosis (DVT) or pelvic vein thrombosis is the most common risk factor for PE. When the clot dislodges into the blood circulation, it reaches the lungs and blocks the lung artery or one of its main sub-arteries. This condition is known as venous thromboembolism (VTE).