Congenital complete atrioventricular block: problems of clinical assessment.

The diagnosis of congenital complete atrioventricular block usually offers little difficulty. There remains, however, the problem of interpreting certain clinical findings, including systolic and diastolic murmurs and cardiomegaly, which are sometimes falsely suggestive of an associated congenital heart lesion. The clinical, radiologie, and electrocardiographic findings in 27 children with congenital complete heart block have been analyzed in terms of the hemodynamic abnormalities found at cardiac catheterization in 12 of these patients. THE diagnosis of congenital complete atrioventricular block usually offers little difficulty. It requires only electrocardio-graphic verification of the mechanism of an abnormally slow heart rate that has been recognized in utero or early infancy and has occurred without any known toxic or infectious etiology. There frequently remains, however, the problem of the interpretation of clinical findings that are suggestive of an associated congenital cardiac lesion. Auscultation, in particular, has long been confusing, and it has been a common view that the systolic murmur heard in most patients with congenital heart block is indicative of a ventricular septal defect. Earlier studies also suggested that an underlying structural defect, usually in the ventricular septum, was responsible for the interruption in normal atrioventricu-lar conduction.1' 2 More recently, Campbell and Thorne3 and Wood4 have demonstrated that this relationship has undoubtedly been overemphasized. The purpose of this communication is to present the clinical and hemodynamic findings in a group of children with congenital complete atrioventricular block and to analyze certain perplexing aspects of the clinical profile in relation to the hemodynamic abnormalities. Clinical, electrocardiographic, and radiologic examinations are available in 27 children, observed at the Children's Medical Center during the past 8 years (1949-57). These patients had electrocar-diographic evidence of complete heart block without history of associated infection (diphtheria, rheumatic fever, virus) or intoxication (digitalis). Phonocardiograms with simultaneous electrocar-diograms or pulse tracings were obtained on selected patients by means of a dual channel photographic oscillograph. Right heart catheterization according to methods previously described' was performed in 12 of these patients with special attention directed to the detection of small left-to-right shunts. In 3 patients 2 intracardiac cathe-ters were inserted to provide simultaneous blood sampling from the superior vena cava or right atrium and the main pulmonary artery, and in all patients multiple blood samples were obtained from the superior vena cava, right atrium, right ventricle, and pulmonary artery. In the children on whom ventilatory measurements and oxygen consumption could not be obtained the cardiac …