Exercise evaluation of patients with congenital heart disease in general and tetralogy of Fallot in particular has had much less impact on clinical care than that of adults with coronary heart disease. Of over 4000 references on tetralogy of Fallot in the literature since 1965, only 87 involve exercise. These studies were reported from 56 institutions, with 39 originating from the United States and Canada, 40 from Europe, and 8 from Japan. They involved 3157 patients, studied mostly after intracardiac repair (ICR). In reviewing these data one is struck by the wide range of different approaches to exercise testing. This is in part related to the different purposes of each exercise study, but it also relates to the lack of uniform standards for exercise testing in patients with congenital heart disease. The studies involved maximal treadmill exercise and maximal or submaximal cycle ergometer work, in the upright or supine position, utilizing 52 different work protocols, the most common being the Bruce treadmill protocol (employed 27 times). Despite this lack of standardization exercise evaluation has significantly contributed understanding of the natural history and pathophysiology of surgically corrected tetralogy of Fallot.
Work PerformanceThe majority of patients were asymptomatic when exercise tested, despite impaired exercise responses and significant residual cardiac pathology. This suggests that patient or parent assessment of physical work capacity does not correlate well with objective criteria of work performance, an impression confirmed in a study which specifically addressed this point [70]. Work capacity is best evaluated by maximal exercise. The data should be expressed as percentage of predicted known standards or simultaneously studied normal controls and/or in terms of the maximal oxygen uptake (VO 2max ), conventionally expressed in ml/min/kg body weight. For submaximal exercise tests only the determination of VO 2 at the ventricular anaerobic threshold (VAT) seems promising since VO 2 at VAT defines the limits of endurance performance and correlates well with VO 2max . Moreover, normal standards in children and adolescents have been reported [65].By objective criteria, work capacity remains markedly impaired after shunt palliation, with an average VO 2max of only 18 ml/min/kg [3,10]. In shunted patients work capacity is directly proportional to the magnitude of the systemic to pulmonary artery shunt and most limited in patients with the smallest pulmonary blood flow and the largest right-to-left shunt during exercise [24]. Following ICR there is marked improvement of the work capacity, which averaged 84.7 ± 8.8% in 20 studies (Tables 1 and 2). VO 2max averaged 36.4 ± 5.8 ml/min/kg in 45 studies, corresponding to 81% of 45 ml/min/kg, a reasonable estimate of VO 2max in untrained normal children and adolescents, as was also shown in 18 studies with normal controls (Table 2). Exercise performance varied considerably between studies. The poorest results after ICR were found in patients corrected as a...
