[Exercise test in isolated anomalies of auriculo-ventricular conduction in children and adolescents. Value in idiopathic auriculo-ventricular blocks and ventricular pre-excitation syndromes].

Abnormal atrioventricular conduction in children and adolescents without obvious underlying cardiac disease poses the problem of long term prognosis. This study of 45 patients aged 8 to 18 years with congenital atrioventricular block (30 cases) or ventricular pre-excitation (15 cases), was undertaken to determine the value of exercise testing, a physiological adrenergic stress test, in the assessment of these patients. Our results show that exercise testing was valuable in determining the site of atrioventricular block: during exercise the degree of block increased in two patients, justifying electrophysiological investigations which showed infrahisian block in one case; when the block was stable or improved on exercise, the atropine test, performed in 21 cases, gave concordant results in 18 cases (the same change with atropine and exercise): the block was nodal in all these patients. A concordant response to exercise and atropine, improving the degree of block, indicates suprahisian block and endocavitary investigation would not seem to be necessary. On the other hand, when the degree of block increases or remains the same during exercise and/or the atropine test, the site of block cannot be predicted and endocavitary investigation and Holter monitoring may be required. In patients with ventricular pre-excitation, exercise testing provides information on the relative values of the effective refractory periods of the normal and accessory pathways: in the 10 cases in which endocavitary studies were undertaken, the exercise electrocardiogram changed in the expected manner (disappearance of the pre-excitation wave on exercise in patients with accessory pathways with longer refractory periods than the normal pathway and persistence of pre-excitation when the accessory pathway refractory period was shorter).(ABSTRACT TRUNCATED AT 250 WORDS)