Acute Pulmonary Embolism

The process that ends in a PE usually begins when a blood clot forms in one of the large veins of the legs. This is called a deep vein thrombosis, or DVT. If this blood clot becomes dislodged it can flow (the medical term is 'embolize') back from the leg, through the heart and become wedged in one of the blood vessels (pulmonary arteries) of the lungs. This is called a PE. While the vast majority of PEs are caused by blood clots, it is worth noting that in rare cases they are caused by tumors, air, fat or amniotic fluid.

PE is an important public health problem. It is estimated that there are between 500,000 and 600,000 cases of acute PE in the U.S. each year, leading to an estimated 50,000 to 200,000 deaths.(1)(2)(3)(4)(5) This makes PE the third most common cause of cardiovascular death in the U.S., behind only heart attack and stroke.

PE can strike anyone but people at particularly high risk include older individuals, cancer patients, people who recently had surgery or trauma, pregnant women, women on oral contraceptives or estrogen containing hormone replacement therapy, and people with certain genetic or inflammatory disorders. The most obvious symptoms of PE are shortness of breath and chest pain. Unfortunately, these symptoms can be subtle and overlap with many other diagnoses. As a result, physicians will typically test 10-20 patients for every case of PE they diagnose.(6)(7) Fortunately, in the past few years the tests available for diagnosing PE have improved dramatically, as have the treatments.

PE [is] the third most common cause of cardiovascular death in the U.S., behind only heart attack and stroke.

This article will discuss factors that put people at risk for developing PE, the tests used for diagnosis and common treatments.

Physicians usually use their experience to determine a patient's pretest probability of PE11,(12)(13) though researchers have developed decision aids to help with this process.(16)(17)(18)(19)(20)(21)(22) The most well known of these is called the "Wells Score." It includes seven items related to risk factors, physical examination findings and the physician's clinical impression.(14) Studies have shown that the Wells Score is accurate at predicting PE.(15) A score of less than 2 means a pretest probability of PE of about 4%; a score less than 4 means a pretest probability of PE of about 5-8%; and a score more than 6 means a pretest probability of PE of about 33-60%.