1.

1. Studies of eight cases of congenital heart block, including the first published case of mitral atresia with congenital heart block, are presented.

2.

2. Review of the literature revealed that of the seventeen cases of congenital heart block reported with postmortem findings interventricular septal defect, with or without other anomalies, was the most common associated congenital lesion, being present in twelve cases, while patent ductus arteriosus was found in six and coarctation of the aorta in four cases as part of the malformation. Congenital heart block may occur in patients who show no clinical evidence of associated heart disease.

3.

3. The diagnostic value of the electrocardiogram in differentiating congenital from acquired heart block is stressed. The ventricular rate in congenital heart block is generally 40 to 80 beats per minute and the QRS complex is usually supraventricular in form. This is in contrast to the somewhat slower ventricular rate and idioventricular form of the QRS complex usually found in acquired heart block.

4.

4. Cardiac catheterization in two of our patients revealed that (a) when atrial contraction occurs during ventricular systole, the “a” waves were considerably higher than those recorded when atrial contraction occurs during ventricular diastole; (b) direct pulmonary artery, right ventricular and brachial artery pressures revealed the influence of the atrial contractions. The possible mechanisms of the hemodynamic observations are discussed.

5.

5. The prognosis of congenital heart block is primarily that of the associated heart disease, when present.