Time course of oxygen uptake and heart rate during Bruce treadmill test in patients following surgery for tetralogy of Fallot.

Exercise performance was examined in 14 patients with a prior history of surgical repair for tetralogy of Fallot. Using a Bruce protocol, we evaluated the time course of oxygen uptake and heart rate in these patients and compared them with a standard curve obtained from 63 sex- and age-matched healthy children. Five of the 14 patients had unusual findings. The heart rate increased rapidly in four of them, while the oxygen uptake increased gradually (95% confidence lower limit). It is hypothesized that a reduction in stroke volume during exercise was responsible for these abnormal findings. The remaining unusual finding was in a patient who was known to have myocardial fibrosis and vacuolization. In this particular case, the time course of oxygen uptake and heart rate were both below the 95% coefficient of variation from the beginning to the end of exercise. In patients who have undergone surgical repair for tetralogy of Fallot, the analysis of oxygen uptake time course and the heart rate may provide valuable information for the long-term follow-up.