[Functional studies in children and adolescents with congenital complete heart block (author's transl)]

In 5 children and adolescents with congenital complete heart block functional studies were performed at rest and during submaximal and maximal work load. With reference to height standards the mean values of aerobic capacity and maximal cardiac output were reduced to 86% and 81%, respectively, whereas stroke volume during maximal oxygen uptake was elevated to 150%. Ventricular rate increased from a mean value of 50 min-1 at rest to a mean maximal value of 112 min-1 by the factor 2.2, atrial rate from 84 min-1 at rest by the factor 2.3 to 192 min-1 at maximum. The mean value of maximal arteriovenous oxygen difference was 14.5 ml/100 ml, the mixed venous oxygen content at maximal oxygen uptake was 4.3 ml/100 ml. The results show that compensation of the reduced ventricular rate not only at rest but also during work was mainly achieved by the increase of stroke volume. The compensatory elevation of stroke volume was, within certain limits, the greater, the more maximal ventricular rate was reduced. As an additional but considerably less effective compensatory mechanism the arteriovenous difference could be evaluated, whose maximal value was about 10% higher than normal.