[Ergometry in childhood. Normal values and use in paediatric cardiology (author's transl)]

In children with congenital heart disease ergometry may be used to measure cardiovascular performance capacity as well as to obtain detailed studies of the functional capacity of different aspects of the cardiovascular system by measuring various parameters during exercise and, thus, rendering a more complete preoperative or postoperative evaluation and possibly contributing to establishment of an indication for surgery. The direct method for measuring cardiovascular performance capacity is the determination of aerobic capacity. All indirect methods such as the W170 (the physical working capacity at a heart rate of 170 beats/min) permit only a rough estimation of working capacity. Since reliable normal values for aerobic capacity of representative samples of boys and girls in different age groups have not been rigidly established, plausible standard values have been estimated in relation to sex, age and body height from previously published data. Subsequently, maximal values for cardiac output have been calculated for all age groups based on a maximal arteriovenous oxygen difference of 13.5 ml/100 ml and, based on a mean maximal heart rate of 200 beats/min, the respective values for stroke volume during exercise have been calculated. In consideration of the fact that equal percentages of aerobic capacity correspond to equal values of arteriovenous oxygen difference, relationships between oxygen uptake and cardiac output were derived for boys and girls of different age groups. The respective regression lines run parallel to a regression valid for male adults which was derived from the values of Ekblom et al. [7] and is based on the formula Q[l/min] = 5.1 + 5.8 VO2[l/min]. In order to permit comparison independent of sex and age, the cardiac output values at rest and during exercise were corrected by subtracting the respective age-related intercepts. The resulting regression line representing normal values independent of sex and age has the formula: Qcorr[l/min] = 5.8 VO2[l/min]. Of particular clinical relevance in these young patients is that the question of feasibility of participation in school physical education classes can generally be answered. Children with congenital heart disease incurring severe hemodynamic compromise have frequently undergone corrective surgery in the pre-school age and the functional results can be assessed accordingly; in children with cyanotic heart disease in whom either no surgery or only a palliative procedure has been performed, ergometry may document severe hemodynamic derangement in spite of a seemingly bland history.