23 Cardiopulmonary Exercise Testing Paul Stephens Jr, Michael G Mcbride, Alexander R Opotowsky, Stephen M Paridon Abstract Regular exercise is an important part of a healthy lifestyle Healthy levels of physical fitness require regular participation in activities that generate energy expenditures significantly above the resting level Exercise testing has become an integral part of the evaluation of children and adults with congenital and acquired cardiovascular disease The cardiopulmonary exercise test is unique among cardiac tests which are typically performed when the patient is at rest The evaluation of the patient in the exercise physiology laboratory allows the clinician to assess the cardiovascular system in a state that is more likely to reflect that of the normal daily physical activities Keywords Isomerism; heterotaxy; asplenia; polysplenia; functionally univentricular; kawashima; fontan; Glenn; ciliary dyskinesia Regular exercise is an important part of a healthy lifestyle Physical activity in some developed countries has diminished for a variety of reasons as society has trended away from outdoor activities toward other types of activities, such as computer games and television, and jobs have become more sedentary Healthy levels of physical fitness require regular participation in activities that generate energy expenditures significantly above the resting level.1 Exercise testing has become an integral part of the evaluation of children and adults with congenital and acquired cardiovascular disease Although children are seldom sitting or lying quietly during waking hours, most of the testing available to the cardiovascular specialist is performed in such a resting state and sometimes in a sedated state The evaluation of the patient in the exercise physiology laboratory allows the clinician to assess the cardiovascular system in a state that is more likely to reflect that of the normal daily physical activities Optimal exercise performance requires continuous coordinated interaction between multiple organ systems.2 The roles of the heart and lungs are to provide adequate energy substrates to working skeletal muscle and to remove the end products of aerobic and anaerobic metabolism during exercise Most of the children whom we encounter in the exercise physiology laboratory have, or are