COLUMBIA — Pulmonary embolisms, the type of blood clotting that claimed the life of MU freshman Tracy Fisher three weeks ago, kill more people annually in the United States than breast cancer and AIDS combined.
"People are still unaware this is a chronic disease," said Ousama Dabbagh, a pulmonary and critical care specialist at MU Health Care.
The Centers for Disease Control and Prevention estimates between 350,000 and 600,000 Americans have a deep vein thrombosis or pulmonary embolism every year; at least 100,000 people die each year of the blood disorder.
Deep vein thrombosis, or a blood clot, most often forms in the legs. If it breaks off, it is carried up and through the venous circulatory system, through the heart and into the left or right pulmonary arteries.
These arteries resemble the letter T, where the blood clot enters from the bottom of the the left or right lung and becomes lodged in one of the branches there. This stops blood flow and thus, oxygen.
That, Dabbagh said, is when a deep vein thrombosis becomes a pulmonary embolism.
"In a way, this looks like a lung attack," Dabbagh said. "At that time there is a high risk this patient will usually die right away, on the spot."
The clots form in many ways. According to Dabbagh, people with a history of active cancer are highly susceptible to pulmonary embolisms, and those most likely to form the clot are older than age 70.
"There's no argument about that," he said. "Risk for deep vein thrombosis increases with age."
The age of 40 is another statistical cutoff point, Dabbagh said, meaning those 40 and older are at greater risk than younger age groups.
Obese persons with a body mass index above 29 are also vulnerable to clotting, as are smokers.
Brian Walker, a respiratory therapist in Columbia, said some lifestyle choices weaken the heart and make a person more susceptible.
The weakened heart is forced to work against gravity, making clotting in the lower extremities such as the legs and pelvis more likely, he said. It is here, according to the National Institutes of Health, where most clots form.
Anyone with a prior history of deep vein thrombosis or pulmonary embolism is also at higher risk for suffering another clot, according to the CDC.
Cancer and pelvic and orthopedic surgery patients are vulnerable to developing blood clots as well, Dabbagh said, because of the locations of the operations as well as the long periods under anesthesia.
"Any surgery with anesthesia more than 60 minutes — meaning the patient is down in the operating room more than 60 minutes — carries a very high risk for thrombosis," Dabbagh said.
Longer post-surgery recovery periods might also play a role in causing the blood clots.
"After surgery they may stay in bed for a long time, and immobility is another risk factor for deep vein thrombosis and pulmonary embolism," he said.
That's why travel, which often entails long periods of sitting, can result in a pulmonary embolism in some people. According to the World Health Organization, travel lasting longer than four hours doubles the risk for developing a venous thromboembolism, which, most commonly manifests as deep vein thrombosis or pulmonary embolism.
One can decrease the risk of clotting by getting up to walk every two to three hours, raising and lowering the heels while keeping toes on the floor and avoiding caffeinated or alcoholic beverages, according to the CDC.
Pulmonary embolism in young people is rare, Dabbagh said, but when it happens there are some usual suspects.
Among them is the use of birth control or any other estrogen-containing product.
"All estrogen-containing products — by far all of them, no exceptions — they increase the risk of pulmonary embolism," Dabbagh said. "I would say it's very frequent that we see that, and in young patients they probably don't know that birth control pills may carry that risk."
Dabbagh also said that birth control can combine with other risk factors to make a person more prone to clotting.
"If somebody goes to surgery and they have birth control pills on board, then the risk is higher than surgery alone," he said.
Michael Burks, an obstetrician/gynecologist for Central Missouri Physicians for Women, said the risk of developing thromboembolic disorders among the general birth control-taking population is low.
"About 5 to 6 people out of 100,000 in the United States are going to develop a thromboembolic event," he said.
The risk is significantly higher in women age 35 and older who smoke and take birth-control pills.
"If you smoke at age 35, you should not be on birth control pills," Burks said.
The kind of contraceptive taken is also significant. Burks said contraceptive patches, which are placed directly onto the skin and enter the blood stream directly, increase the chances of clotting. The chances of clotting are lower with oral contraceptives because they have to go through the liver and intestine before entering the blood stream, he said.
Young people who suffer from pulmonary embolism but are not taking birth control might develop a clot because of a congenital disorder called Factor V Leiden thrombophilia. It is a genetic condition, among others, that increases the chance of developing blood clots.
Burks said that Factor V Leiden increases a person's chances of clotting by 35 times and that it is the most common hereditary factor to developing blood clots.
"That's typically what we find in those patients who have pulmonary embolism without any other risk factors," Dabbagh said.
Dabbagh also said that some patients might not show any risk factors.
"There are a lot of nuances, it really depends," Burks said.
Deputy Medical Examiner Eddie Adelstein forwarded questions regarding Fisher's autopsy report to forensic pathologist Ariel Goldschmidt, who couldn't be reached for comment.