̨ÍåSWAG

This year, the sports pages have brought a serious health concern back into the spotlight.

NBA stars Victor Wembanyama and Damian Lillard both were sidelined during the regular season by deep vein thrombosis, or DVT, a type of blood clot. They joined a long list of athletes, including tennis legend Serena Williams, hockey great Zdeno Chára and basketball Hall of Famer Chris Bosh.

Dr. J. Sawalla Guseh, director of the cardiovascular performance program at Massachusetts General Hospital in Boston, said that athletes as a group aren't inherently at a higher risk for such clots than the overall population.

But clots are common, said Guseh, who also is an assistant professor of medicine at Harvard Medical School and team cardiologist for the NFL's New England Patriots and Major League Soccer's New England Revolution. And athletes are exposed to things that could increase their odds of developing one.

DVT refers to a clot that forms in the deep veins of the legs, arms or pelvis. If that clot travels to the lungs, it's called a pulmonary embolism, which can cause sudden death.

The two conditions are also referred to as venous thromboembolism, or VTE. According to ̨ÍåSWAG Heart Association statistics, almost 1.3 million VTE cases were tallied in U.S. inpatient settings in 2021, the most recent year for which data was available.

The risk of someone younger than 40 having a VTE is about 1 in 10,000, said Dr. Mary Cushman, a hematologist who is medical director of the Thrombosis and Hemostasis Program at the University of Vermont Medical Center in Burlington.

Athletes' cases tend to get extra attention, "because when your favorite team has a player who goes out because they have a DVT, everybody hears about it," said Cushman, who also is a professor of medicine and pathology at the University of Vermont.

The risks athletes face that can increase their chances of DVT include:

Injuries

Athletes get hurt. Sometimes, an injury can affect blood flow, causing clotting. If they need surgery, that also increases the risk of clots. "Knee surgery, for example, is common and comes with higher clot risk," Guseh said.

Having a broken leg immobilized in a cast can raise the risk, too. Veins in the leg require muscles, particularly in the calves, to push on them to help the blood go up, Cushman said. "And when you're immobilized, you can't do that. So blood tends to move slower. And when blood is sitting still, it likes to clot."

Sports-related motions

Clots can sometimes form in athletes who repeatedly pull their arms back to pitch a baseball or swing a tennis racket, Guseh said. "I won't say it's extremely common, but it's something that we see" in basketball, rowing, wrestling and other "arm" sports, he said.

The arteries and veins to and from the arms pass through the narrow area below the collarbone and above the first rib. This tunnel is called the thoracic outlet. Some people, Cushman said, have a smaller tunnel than others.

The condition goes by several names: effort thrombosis, Paget-Schroetter syndrome and thoracic outlet syndrome.

"Thoracic outlet syndrome can happen in anyone," Cushman said. "But in an athlete, it might be more common because they're building up the muscles in that area," narrowing the tunnel.

A college student carrying a heavy backpack or a mover lifting boxes might develop the same problem. "That's why it's called effort thrombosis," Cushman said. "You overused that arm, and it led to increased trauma in the local area that irritated the vein and caused it to clot."

Other issues related to physique

Some issues that have nothing to do with athletics might be more common in certain athletes, Cushman said. She has been involved in research showing that being taller may increase the risk of VTE – and basketball players are tall.

Having a high body mass index also raises the risk, Guseh said. BMI is used as a measure of obesity, but large, muscular athletes such as football players can also have a high BMI.

And anyone can have genetic differences that make them predisposed to clots, the doctors said.

Travel and other factors

Elite college and professional athletes would spend more time on long-haul flights than the general population, and such flights are associated with a slight increase in the risk of blood clots.

"We're talking flights more than four or six hours," Cushman said. "It's really a slight risk," probably related to being immobile and altitude effects from reduced air pressure during flights.

Dehydration related to such travel or exercise may thicken the blood, promoting clot development, Guseh said.

And young women who use estrogen-based contraceptives also are at higher risk, Cushman said.

Whatever the cause, the stakes of having a blood clot are high. According to the , about a quarter of the time, the first symptom of a pulmonary embolism is sudden death.

With DVT, leg or arm pain and swelling are the primary symptoms, Cushman said. It might be accompanied by areas of skin that turn pinkish or reddish.

Those signs, or warmth in a limb, especially in someone who has recently had surgery, would be considered an emergency until proven otherwise, Guseh said.

Pulmonary embolism symptoms can include chest pain, trouble breathing and sometimes lightheadedness or heart palpitations.

"A blood clot that enters the lungs will make you short of breath" and unable to do normal levels of exercise, Guseh said.

Clots are treated with blood thinners. But the length of treatment depends on the causes behind a clot, which is categorized as either provoked or unprovoked. A provoked clot is one from a known factor, such as an injury or surgery, Cushman said. An unprovoked clot is one with an unknown cause.

"People with provoked thrombosis have a pretty low risk of recurrence," Cushman said. Those patients can be taken off blood thinners after a few months. But with unprovoked clots, "those patients have to be considered for long-term treatment, and that's where it can get difficult."

For athletes in the past, Guseh said, developing a clot meant "pretty much your career is over." But doctors now consider where a clot developed and what a patient's priorities are.

"Some need months of treatment. Some need lifelong treatment. Others may not need any at all," said Guseh, who was co-author of an ̨ÍåSWAG Heart Association and ̨ÍåSWAG College of Cardiology on athletes with cardiovascular abnormalities that was published in Circulation in February. He said that unlike older blood thinners that required constant monitoring, new medications allow some people to stop their use during a period when they might be at higher risk of collision, trauma and bleeding – say, riding in the Tour de France or playing in an NBA playoff game.

Anyone can take steps to lower their VTE risk, Guseh said. Drink plenty of water, especially during and after travel or intense training. "On flights or long bus rides, get up every one to two hours, flex your calves, and avoid sitting still for long stretches." For people at high risk for clots, compression socks can help during long travel or recovery from surgery, he said.

And if you're injured, if your doctor allows it, "try to stay mobile. Even light walking can help reduce clot risk after minor injuries," Guseh said.

Cushman understands the importance of tailoring treatment to individuals, especially in high-level athletes.

An athletic career, she said, is relatively short. "So being forced to not play is really hard."