Cardiopulmonary Exercise Testing Combined with Stress Echocardiography for the Evaluation of Coronary Insufficiency in Children at Risk

Background: In adults, stress echocardiography is used for identifying patients at risk for myocardial ischemia (MI). In pediatric cardiology, stress echocardiography is rarely performed, even though MI represents a threat in children after arterial switch operation (ASO) or after Kawasaki disease (KD). Several cardiopulmonary exercise testing (CPET) parameters have been proposed for identifying coronary insufficiency in clinically silent patients, however, this has never been evaluated in children. This study combines stress echocardiography with CPET to identify new diagnostic modalities for children at risk for MI.

Methods: We recruited children and adults from our database after ASO or KD. All undertook a cardiopulmonary exercise test either on a tilt–recline ergometer or on a treadmill with intermittent echocardiography depending on their size. Echocardiography consisted of strain measurements. In addition to the standard cardiopulmonary exercise parameters, the behavior of the O₂ pulse before and after the end of exercise was evaluated, as a slope and a duration of a plateau if one was observed.

Results: Forty-three children, adolescents, and adults (21 ASO, 10 KD, and 13 controls) participated in this study. The patients showed a slightly lower cardiopulmonary function (18.4 vs. 25.2 mL/kg/min) at the first ventilatory threshold and peak exercise (39.6 vs. 45.9 mL/kg/min). The only other significant difference was the slope of the O₂ pulse in the 30 seconds following the end of exercise, which is supposed to decline rapidly after the termination of exercise (−4.9) but was more like a plateau in patients after ASO (−2.4). One ASO patient had decreased strain values during exercise (−13 at rest and −16.3 at peak exercise), an O₂ pulse plateau after exercise, and was later diagnosed with a filiforme stenosis of the ramus circumflexus.

Conclusion: Cardiopulmonary exercise testing in combination with stress echocardiography is feasible in children as young as 7 years of age. The new protocol which consisted of an echocardiographic examination of the standing child throughout the test allows for better image quality and a more thorough investigation. The combination of the two methods enabled us to establish a new parameter, namely the slope of the O₂ pulse after termination of exercise which could represent a good CPET parameter for evaluating coronary insufficiency, especially in patients who are not experiencing symptoms.