Question: I have just gotten out of the hospital after being treated for a pulmonary embolism. Is it known what causes this condition?

Dr. Hibberd's answer:
When a blood clot dislodges and passes up our veins into the circulation of our lungs, it is said to have embolised, hence the term pulmonary embolism. It is a blockage in one or more arteries in your lung, and often presents in a shower of small clots to one or both lungs or from one massive clot that can cause everything from mild or no symptoms to massive cardiac arrest. Pulmonary embolism results in blocked or impaired circulation, stresses the heart, sometimes causing arrythmias or even cardiac arrest.
Pulmonary embolism impairs the ability of the lung to receive blood, so you lose its gas exchange functions and cannot oxygenate your blood effectively.
In most cases, pulmonary embolism is caused by blood clots that travel to your lungs from another part of your body, most commonly, your legs. Pulmonary embolism is a complication of deep vein thrombosis (DVT), which is clotting in the deep veins farthest from the surface of the body, not from the superficial veins. Pulmonary embolism can occur in otherwise healthy people.
Pulmonary embolism may be life-threatening, but immediate treatment with anticlotting medications can greatly reduce the risk of death. Long term anticoagulation with coumadin is recommended most usually for 6 months, and sometimes a venous filter is recommended to avoid longer term coumadin exposure than necessary.
Taking measures to prevent blood clots in your legs can help protect you against the life-threatening complication of pulmonary embolism.
Waist high compression stockings steadily squeeze your legs, helping your veins and leg muscles move blood more efficiently. Pneumatic compression uses thigh-high or calf-high cuffs that automatically inflate with air every few minutes to massage and squeeze the veins in your legs and improve blood flow. Increasing moving about can also prevent pulmonary embolism. If you intend to travel, walk around in the airplane and move your limbs while you are seated by flexing, extending and rotating your ankles, or press your feet against the seat in front of you, or try rising up and down on your toes. Do not sit with your legs crossed for long periods of time.