Cardiorespiratory response to exercise after repair of tetralogy of Fallot

We studied 24 patients who had a graded exercise test 1 to 16 years after correction of tetralogy of Fallot. Maximal oxygen consumption was subnormal in 19 of the patients. We found no relationship between age at repair, postoperative right ventricular pressure, right ventricular-to-pulmonary artery pressure gradient, or ratio of right ventricular and left ventricular pressure and degree of exercise intolerance. The stroke volume response to exercise was normal in only three of eight patients. Twenty-five percent of patients had arrhythmia just prior to, during, or after exercise. The arrhythmias were independent of the factors of age at repair, age at exercise, previous operation, presence of an outflow tract patch, or residual right ventricular outflow tract obstruction. The ventilatory responses to exercise were normal. Persistent exercise intolerance may be due, in part, to abnormal ventricular function.