[Study of the cardiorespiratory response and chronotropic function after correction of tetralogy of Fallot. Important role of residual pulmonary regurgitation].

Effort tolerance is reduced after correction of Tetralogy of Fallot. This prospective study investigated the cardiorespiratory response and the chronotropic function (mean follow-up 11.1 years) of 70 patients (43 boys and 27 girls) with an average age of 14.9 +/- 7.2 years (group 1) compared with 65 normal, sedentary subjects paired red for age and gender (group 2). All underwent exercise testing (Bruce protocol) with measurement of respiratory gases. Quantification of pulmonary regurgitation was performed by Doppler echocardiography. The chronotropic response to exercise was assessed by calculating the mean of slopes established by chronotropic metabolic relationship of Wilkoff. The cardiorespiratory response to exercise was abnormal in group 1: the duration of exercise (11.3 vs 13.6 min; p = 0.005), peak VO2 (35.5 vs 46 ml/min/kg; p < 0.001) and anareobic threshold (8.3 vs 9.2 min; p = 0.001) were decreased. Maximal heart rate (172 vs 190bpm; p < 0.001) and the mean of the metabolic-chronotropic slopes (0.68 vs 0.83; p < 0.001) were decreased in the patient group, showing abnormal chronotropic response to exercise. The latter seemed to be related to the severity of pulmonary regurgitation. The duration of exercise (10.6 vs 11.5 min; p = 0.001), peak VO2 (33 vs 37 ml/min/kg; p < 0.001), maximal heart rate (161 vs 177 bpm; p = 0.002) and the mean of the slopes of the metabolic-chronotropic relationship (0.59 vs 0.72; p < 0.001) were decreased in patients with moderate to severe pulmonary regurgitation. This study shows that significant pulmonary regurgitation is responsible for a poor cardiorespiratory response to exercise and for an abnormal chronotropic response which seems to be multifactorial but probably related to an adaptation favouring left ventricular filling during exercise.