Understanding blood clot complications in teens


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Research is under way to learn why returning to exercise after pulmonary embolism treatment is difficult for many young patients.

Having a blood clot can lead to shortness of breath and decreased physical activity long after treatment, lowering a child’s or teen’s quality of life – and the rates of pediatric blood clots are increasing.

In the U.S., 1 in every 200 hospitalized children develops a blood clot. The most common types of clots are deep vein thrombosis (DVT), which usually occur in a deep vein in the lower body or arm, and pulmonary embolism (PE), the result of a DVT traveling to the lungs and blocking an artery, decreasing the lungs’ ability to provide oxygen to the body.

Common risk factors for blood clots in children and teens include:

  • Prolonged hospitalization due to illnesses that require IV lines in large veins and/or extended immobilization
  • Obesity, which may slow circulation in the legs
  • Birth control pills that contain estrogen, which can increase clotting activity in blood proteins

More pediatric blood clots are found today because more health care providers are looking for them. We also have better imaging equipment and can identify PEs that would have gone undetected in the past. And with improving medical treatments for so many chronic health conditions, young patients with serious illnesses are living longer – and spending more time in hospitals.

While recent research has helped us better understand why blood clots occur in young patients, studies also have raised more questions:

  • Are kids “deconditioned” after hospitalization?
  • Can blood thinners make children less likely to be active?
  • Do symptoms arise from the heart, lungs, or muscles?

My colleagues and I in the Department of Pediatrics are on a mission to find answers. With support from a National Institutes of Health (NIH) grant, we’re nearly one year into a five-year clinical study on why blood clot symptoms linger after treatment and how we might prevent complications from pediatric blood clots through comprehensive care.

Evaluating what happens after a blood clot

Initially, a blood clot is a medical emergency. Left untreated, it can become life-threatening. If your child experiences symptoms, such as chest pain, lightheadedness, shortness of breath, and pain or swelling in a leg or arm, get medical help right away.

Blood thinning medications are the standard treatment for clots, and many studies have focused on whether these drugs can effectively prevent future blood clots. While recurrence is uncommon in young patients, chronic symptoms such as shortness of breath and exercise intolerance are common.

Until now, the widely held belief has been that kids are simply deconditioned when they return to sports or physical activities. But that’s not the case for most patients.

The participants in our clinical trial have had a recent diagnosis within 60 days. They are 8 to 21 years old and had no other health conditions before their diagnosis. Over three days of testing at rest and during activity, we evaluate blood flow in their lungs, heart, and the muscle where their blood clot first occurred:

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In our clinical trial, we test participants at rest and during activity over three days to evaluate blood flow in their lungs, heart, and the muscle where their blood clot first occurred.
  • Day 1: Lungs. We perform pulmonary function tests to measure lung functions and air flow and how well oxygen moves in and out of the blood. We also perform a cardiopulmonary exercise test, a specialized stress test where the patient pedals a stationary bike and we monitor their heart rhythm, blood pressure, and oxygen levels.
  • Day 2: Heart. An MRI of the patient’s heart provides a detailed image of its structure and blood flow through surrounding vessels at rest. Then we ask patients to use an MR ergometer – a pair of bicycle pedals they push while lying down. As their heart rate increases, we take images of the heart to compare with the images taken at rest.
  • Day 3: Muscle. At our Advanced Imaging Research Center, patients get an MRI of the muscle where the clot developed, also at rest and with exercise. We look at energy use in the muscle and compare images of the muscle and surrounding blood vessels at rest and during exercise.

In the past, PE researchers have examined the body at rest only. Because we focus on the body’s reaction to movement, we can determine which physical difficulties participants experience most and why they are occurring.

If an adult experiences a significant cardiovascular problem or has trouble reacclimating to activity, they’ll likely be referred to a rehab program that includes exercise training. No protocol like that exists for pediatric blood clots, and I expect our research will lead to future studies of exercise training once we understand the “why” of complications.

We are actively enrolling participants around the country in our ongoing PE study. Review eligibility requirements.

Future focus areas: Education and psychology

As an academic medical center, UT Southwestern is an international leader in cardiovascular research and patient care. Our providers and scientists consistently look for ways to improve our patients’ lives through education.

I’m partnering with colleagues to develop a standard of care that ensures hospitalized patients and their providers get instructions for monitoring and responding to risk factors and symptoms of blood clots. This will help us prevent them from progressing or occurring in the first place.

We also have much to learn about the emotional and psychological effects of blood clots in young patients. Similar to a heart attack, a PE can be a life-changing event. How many patients are triggered by fear or worry when they experience chest pain or shortness of breath several months or even years after a PE diagnosis? Only more research can tell – and help us develop successful treatment options.

If your child stays three days or longer in a hospital, discuss your child’s risk of blood clots with their health care provider – the more we all communicate, the better we can act quickly to prevent and treat pediatric blood clots.

To visit with a specialist about personalized treatment for pediatric patients recovering from blood clots, call 214-645-8300 or request an appointment online.