“…There are several published reports of haemodynamic studies after open heart surgery in patients with Fallot's tetralogy, and some of these include exercise data (Gotsman, 1966;Shah and Kidd, 1966;Bristow et al, 1970;Epstein et al, 1973;Bjarke, 1975;Mocellin et al, 1975Mocellin et al, , 1976. The following report differs from these others in one or more ways: studies were made during exercise on a large number of subjects including those with and without various residual defects; measurements were made during maximal exercise; haemodynamic measurements included intracardiac pressures, arterial and mixed venous blood gas tensions, and cardiac output (by indicator dilution method), during submaximal and maximal exercise in the supine position.…”