Secundum type atrial septal defect with prolonged PR interval and autosomal dominant mode of inheritance.

The affinity of some chromosomal anomalies for certain types of congenital heart disease is well known, e.g. atrioventricular defects in Down's syndrome and coarctation of the aorta in Turner's syndrome. Many reports on several types of congenital heart disease in close or more distant family relationships have aroused suspicion that genetic factors may be important also in other patients. Reports on the increased incidence of congenital heart diseases in the families of patients with some kind of congenital heart disease have stressed the genetic component (Emanuel, I970). A report on familial atrial septal defect postulated multifactorial mode of inheritance as the most probable explanation (Nora, McNamara, and Fraser, I967). Some cases of congenital heart disease, however, do not seem to fit into a pattern of multifactorial inheritance, e.g. the syndrome reported by Holt and Oram (I960). There are also reported cases of inherited simple atrial septal defect and the author has been able to find published reports of I5 families where isolated septal defect occurred in more than 2 cases in at least 2 generations (Amarashinghlam and Fleming, I967; Bizarro et al., I970; Campbell, I949; Campbell and Polani, I96I; Carleton, Abelmann, and Hancock, I958; Davidsen, I958; Ehlers and Engle, I966; Howitt, I96I; Kahler et al., I966; Nora et al., I967; Weil and Allenstein, I96I; Zetterqvist et al., I971; Zuckerman et al., I962). But really good evidence for a dominant mode of inheritance is found only in 8 families. In 6 of these families there was prolonga-