Comparison of cardiovascular adjustments to exercise in adolescents 8 to 15 years of age after correction of tetralogy of Fallot, ventricular septal defect or atrial septal defect

Surgical correction of tetralogy of Fallot (TF) has generally been associated with a reduced maximal exercise tolerance, possibly related to the ventriculotomy inherent to the intracardiac repair procedure. This study documents the exercise hemodynanties of a group of patients operated on for TF who showed similar clinical and functional characteristics, and compares these responses to those of age-matched patients operated on for an isolated ventricular septal defect (VSD) or atrial septal defect (ASD) in an attempt to better understand the role of the ventriculotomy in the exercise limitation. Thirty patients, ages 12 to 19 years, operated on before 5 years of age for complete repair of TF (n = 13), VSD (n = 7) or ASD (n = 10) and 10 agematched control subjects underwent a progressive maximal cycling test to determine the maximal oxygen uptake (VO 2 max), and completed submaximal cycling at intensities of 33 and 66% VO 2 max, respectively, to determine the cardiac output (CO 2-rebreathing). No significant differences in VO 2 max were observed (TF = 37.6 ± 10; VDS = 34.0 ± 9.2; ASD = 36.5 ± 7; controls = 41.3 ± 6.0 ml/kg/ min). The maximal heart rate, however, remained lower in all patient groups in comparison with control subjects (p ≤ 0.05) (TF = 178 ± 14; VSD = 172 ± 17; ASD = 179 ± 16; controls = 191 ± 12 beats/min). Moderate submaximal exercise evaluations revealed a subnormal cardiac index in all patient groups, independent of the type of surgery (66% VO 2 max was TF = 5.39 ± 1.0; VSD = 5.36 ± 1.3; ASD = 5.69 ± 0.7; controls = 6.75 ± 1.1 liters/min/m 2). Although no significant differences in stroke index could be calculated between the patient groups or the control subjects, a significant chronotropic limitation was found in all patient groups (66% VO 2 max was TF = 133 ± 15; VSD = 133 ± 12; ASD = 146 ± 17; controls = 159 ± 12 beats/min). These observations suggest that, despite their normal maximal exercise tolerance, patients who underwent early correction for TF, VSD or ASD show a similar chronotropic limitation in response to submaximal and maximal exercise, independent of the type of surgery performed. It thus appears that the ventriculotomy per se may not provide a complete explanation for the circulatory disturbances observed during exercise after corrective surgery for a congenital heart defect. A satisfactory explanation for the exercise chronotropic limitation observed after intracardiac repair of a congenital heart defect remains to be p