Why Chris Bosh could miss the rest of the NBA season with blood clots

Bosh was sent to the hospital after reporting for practice Thursday feeling "under the weather," according to head coach Erik Spoelstra. The team didn't reveal the nature of the testing, but the Herald reported that initial tests focused on Bosh's lungs. A Heat spokesman said initial testing was inconclusive.

Blood clots in the lungs can be dangerous and even deadly. These clots typically form in the legs as a deep venous thrombosis (DVT). Our blood naturally forms clots to allow our bodies to heal and stop bleeding after injuries. However, they can form unexpectedly and without any type of notice. This typically occurs in veins in the legs or arms as DVT. Often patients with this condition can develop leg swelling (sometimes painful), warmth, and a reddish or bluish discoloration.

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The major fear with this kind of condition is the possibility that a piece of the blood clots may break off and travel through the bloodstream and lodge themselves in the lungs, which can result in pulmonary embolism (PE). Symptoms associated with PE can include chest and/or back pain, acute shortness of breath, exhaustion or unexplained fatigue, dizziness, and even fainting. More troublesome are the patients that don't exhibit any symptoms with this condition, which means tragedy can strike without warning.

Pulmonary embolism is very common, affecting about 300,000 Americans each year. The condition is more common in people who are inactive but can often occur in athletes as well. Many people actually have genetic traits that predispose them to forming these types of clots. In addition to Bosh, several other professional athletes are known to have dealt with PE including the NHL's Kimmo Timonen, Jed Ortmeyer and Pascal Dupuis, the NFL's Jason Pinkston, Serena Williams, while Anderson Varejao and Mirza Teletovic have both been diagnosed with the condition in recent years.

​There are several risk factors that are unique to professional athletes in regards to blood clots.1–3 Strenuous exercise or trauma can cause damage to blood vessels and clots can form at those damage points. Immobilization after a strenuous workout or injury can allow blood to pool and form clots. Dehydration after exercise thickens blood and can allow clots to form. Air travel (especially prolonged flights) has long been known as a risk factor for blood clots. Part of this is due to the immobilization of sitting still for the flight and the blood pooling in the legs and not getting pumped back to the heart as easily because the leg muscles are not being used. Since professional athletes are forced to fly (often long flights) more than most of us during their respective seasons, this is a significant risk for them. 

In addition, athletes often suffer higher rates of injuries that require immobilization and/or surgery that can also increase their risk of blood clots and possible PE. Athletes may face a slightly increased risk of forming blood clots but this is mainly a problem for those rare athletes who have a genetic predisposition to forming clots. 

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There are medications that can be used to thin the blood in people who form DVTs or PEs. These are typically taken for several months after a clot is diagnosed, which is why Bosh's season could be in jeopardy if he's found to have the condition. When taking blood thinners, patients tend to bleed more when injured, which can be problematic for athletes in contact sports, like basketball. That's why you'll see athletes sidelined up to six months or more while they're being treated—arm or leg injuries tend to be more severe, but injuries to the head, chest, or abdomen can be fatal.

Dr. Peter C. Vitanzo is a sports medicine physician at the Rothman Institutewho also works with the Phillies, 76ers and several collegiate sports teams in the Philadelphia area.​ Dr. Barry E. Kenneally, also a sports medicine physician at the Rothman Institute, treats a wide variety orthopedic problems in athletes and non-athletes.