Put a seemingly timid child with congenital heart disease (CHD) on a treadmill, attach electrodes to their chest and place a mask over their mouth and nose to measure gas exchange, and it's amazing what you can learn about their cardiovascular and pulmonary health. That's the premise behind Children's of Alabama's new Cardiometabolic Exercise Testing Lab, which opened this summer. The lab was made possible through the generosity of Gene and Leslie Cash in loving memory of their daughter Kelly Cash.
"Exercise capacity can be highly predictive of the risk of complications related to CHD, including developing heart failure," said pediatric cardiologist Camden Hebson, M.D., who runs the lab. "Given that the heart and lungs are usually the limiting factors on the extent of exercise capacity, stress testing is a wonderful way to evaluate how well patients are supported."
In contrast, evaluating a child at rest, as with an EKG and echocardiogram, "is like evaluating the quality of a car when it's in the shop versus taking it out on the road and seeing how well it drives," he said.
While the test mimics the traditional stress test, the use of the mask to measure oxygen consumption (VO2) and CO2 elimination is particularly important, Hebson said.
"These become the key variables to say from a quantitative standpoint how well the heart and lungs support you as you exercise," he said.
Children who have been living with a heart condition for years may underappreciate the severity of their symptoms, he said. The exercise test, however, provides objective data that can demonstrate problems and allow intervention.
"Many patients become accustomed to how they feel with exercise, yet with stress testing we can identify limitations early on and thus intervene in a timelier manner," he said.
The test also enables serial assessments to assess function over time.
In some instances, he said, a patient's symptoms are attributed to cardiovascular function, but the stress test can show it was related to pulmonary function instead.
Sometimes that's hard to tease out because we're always focused on the heart. Exercise testing offers a way to make that connection."
Camden Hebson, M.D., pediatric cardiologist
Children as young as 7 years old can complete the test, he said, and those that can't walk or run on the treadmill can use a bike. The key point is that "they need to be comfortable enough to come in and wear a mask, EKG leads, etc., while exercising," he said.
To take some of the fear and anxiety out of the experience, the team has decorated the room to look more inviting with posters of sports figures and decals. They even added a scoreboard where kids can write their "code name" and see how they compare to others taking the test. The goal, Hebson said, is to make the lab look less like a clinic or hospital setting and more like a place to have fun.
The test itself takes about 15 minutes, with another 30 minutes for the setup and explanations. It is typically covered by insurance.
Hebson, nursing staff, and parents are always in the room. As he noted, "We try to make it the least stressful as possible, even though it's a stress test."