Pulmonary embolism (PE) is a common but very serious medical emergency that everyone should be aware of. In simplistic terms, a pulmonary embolism can be thought of as a ‘Lung attack’. In a heart attack, there is disruption of the blood supply which leads to cells of the heart dying. With a PE, there is disruption of the blood supply to the lungs leading to death of lung cells.

Blood is delivered to the lungs by the right heart which pumps blood into the pulmonary arteries which divide and subdivide and perfuse all the lungs. Here the blood collects oxygen and the then travels to the left heart where that oxygen rich blood is pumped to the brain and the rest of the body.

If a blood clot gets into the pulmonary arteries then it will block the passage of blood into the lungs and that part of the lung will die. In addition, there will be a sudden and significant reduction of the amount of oxygen collected by the blood and therefore there will be a profound drop in oxygen levels within the body. There will also be a significant reduction in the amount of blood getting into the left heart and this will cause the amount of blood going out of the left heart to drop markedly which can cause heamodynamic collapse and even death.

By far and away the commonest mechanism for PE is the development of blood clots in the legs (termed DVT) which then travel into the right heart, up to the lung and cause the PE in the lung. PE can also result from fat, air and cancer cells causing a blockage in the pulmonary vasculature.

How common is it?

The incidence is anywhere between 40115 people per 10000 per year for PE and 50160 people per 100000 per year for DVT.

The incidence is higher in men compared to women and in the US it is estimated that 100000 people die every year of a PE. This is likely to be an underestimate because when someone drops down dead suddenly, it is often assumed that the patient has died of a heart attack and a detailed autopsy may. Not be undertaken. It is likely that a bunch of these patients could have died due to a pulmonary embolism. A timely diagnosis is crucial because without treatment, up to 30% of patients will die but if timely treatment is delivered then that number drops to 8%.