A disturbance in the chronotropic response to exercise has well documented following surgical repair of a congenital heart defect. Observations of a similar dysfunction following correction of simple atrial as well as ventricular septal defect suggest that its occurrence might be linked to a common denominator in the surgical procedures. Since cardiopulmonary bypass (CPB) is used for all initacardiac surgeries, the contribution of this factor to the abnormal response was examined. Three groups of patients von; evaluated: VSDop: operated on for a ventricular septal defect, CPB required; VSDnon-op: spontaneous closure of a congenital 73D, no surgery; and PDAoperated on for a patent ductus arteriosus, no CPB required. They were compared io a control group of healthy adolescents (C). The main, finding was that of lower submax final and maximal heart rates in VCDop disc in any other group. These results suggest that placement of cannulae resulting from-CPB could alter the control of heart rate during exercise and contribute to the abnormal chronotropic response following intracardiac repair of a congenital heart defect.
Hélène Perrault, André Davignon, Gail Grief, Anne Fournier and Claude Chartrand
Hélène Perrault, Maria Tzovanis, Dominique Johnson, André Davignon, Claude Chartrand, Abdelkader Mokrane and Réginald A. Nadeau
This study compares the autonomic responses of 9 adolescents (mean ± SEM: 17±1 years) successfully operated for tetralogy of Fallot (TOF) in early childhood and 8 age-matched healthy controls (CTRL) using R-R and blood pressure variability. Continuous ECG and BP recordings were obtained during spontaneous and controlled respiration (CR) at 0.20 Hz as well as after an 85° head-up tilt (HUT) and during steady-state cycling at heart rates of 100 and 120 bpm, selected to reflect partial and complete cardiac vagal withdrawal. TOF exhibited total R-R variance and HF power (ms2) lower than CTRL under both spontaneous (938 ± 322 vs. 1,714 ± 296) and CR (1,541 ± 527 vs. 4,725 ± 1,207; p < .05), which may be indicative of a lower cardiac vagal activity. HUT decreased the R-R HF component, which remained lower in TOF than CTRL and increased the diastolic BP LF component in TOF but not in CTRL. Exercise decreased the R-R HF power more in TOF than CTRL. The exaggerated diastolic BP and limited heart rate responses to tilting and the more marked vagal withdrawal at Ex120 in TOF may be suggestive of a disturbance in the cardiac sympathetic response. Further studies are needed to confirm these observations on larger groups of young adults successfully operated for TOF.