Cardiopulmonary exercise test (CPET); Congenital Heart Disease (CHD); Coronavirus disease 2019 (COVID-19); adult; artery; cardiology; cardiopulmonary exercise test; cardiopulmonary function; cardiovascular disease; child; clinical article; complication; conference abstract; congenital heart disease; congestive cardiomyopathy; controlled study; coronavirus disease 2019; Fallot tetralogy; female; forced expiratory volume; forced vital capacity; functional status; heart rate; heart tumor; human; male; mucocutaneous lymph node syndrome; observational study; outpatient care; peak oxygen uptake; pediatric patient; prospective study; rank sum test; school child; carbon dioxide; oxygen