CORE Metadata, citation and similar papers at core.ac.uk Provided by Elsevier - Publisher Connector 376 lACC Vol. 6, No.2 August 1985:376-82 PEDIATRIC CARDIOLOGY A Possible Increase in the Incidence of Congenital Heart Defects Among the Offspring of Affected Parents VERA ROSE, BSc, MB, BS, FRCP(C) , REYNOLD JOHN MORLEY GOLD, MB, BCHIR, PHD, FCCMG, GAIL LINDSAY, RN, MSN, BScN, MARYLIN ALLEN, RN, PHN Toronto, Ontario, Canada The incidence of congenital heart disease in the children dence than that reported in most comparable studies. of219 probands was determined. Each of these probands The difference is highly significant statistically and there• had one of four selected defects: atrial septal defect, fore is likely to be genuine. The cause of the high re• coarctation of the aorta, aortic valve stenosis or complex currence is probably environmental. dextrocardia. Of their children, 8.8% had substantial (J Am Coli CardioI1985;6:376-82) congenital cardiac defects. This is a much higher inci- The successful medical and surgical treatment of congenital first degree relatives of those affected with it therefore offers heart disease has increased the importance of its early di• evidence as to whether the disease is polygenic. agnosis and this in tum has contributed to the growing Nora et al. (4) were the first to undertake family studies interest in the risk of cardiac defects in the offspring of to determine whether the actual incidence of congenital heart affected parents. Although a few cases of congenital heart disease in first degree relatives corresponds to that predicted disease are known to be caused by environmental agents, by this model. The recurrence risks published for first degree for example, viruses, drugs and maternal infections, there relatives were in a range of I to 5% which, given the pop• are many examples of familial recurrence suggesting that ulation incidence rates, are in good agreement with the genes contribute substantially to its origin. It is well known figures that Edwards' theory predicts. For this reason, the that chromosomal anomalies account for only a small pro• concept that the inheritance of congenital heart disease is portion of cases of congenital heart disease and it is believed, of a polygenic nature gained wide acceptance. Another rea• on less secure grounds, that the contribution of single gene son for accepting the polygenic model is that the observed (Mendelian) disorders is also small. It was therefore sug• sex distribution of congenital heart disease conforms with gested (1,2) that congenital heart disease might be polygenic the distribution predicted by the model. If a given polygenic or multifactorial, that is, caused by the interaction of a large disease occurs more frequently in one sex than in the other, number of genes with or without some contribution from theory predicts and observation confirms that children are environmental factors. more likely to inherit the disease from a parent of the less A method of testing the polygenic model is available. frequently affected sex. This has been found true of some Edwards (3) calculated the incidence of disease to be ex• types of congenital heart disease (see Discussion). The po• pected in first degree relatives of subjects affected with a lygenic model has, however, encountered certain difficul• polygenic disease and has shown that it is approximately ties. First, it has been found that the recurrence risk is the square root of p, where p is the frequency of the disease somewhat higher for children than for siblings of affected in the general popUlation. A knowledge of the incidence of probands (5), but the polygenic model predicts that their a given disease both in the general population and in the risks would be the same. Furthermore, Whittemore et al. (6) reported a 16.1 % recurrence risk for congenital heart disease in a prospective study of 482 pregnancies of 233 From the Division of Cardiology, Department of Paediatrics and De• affected mothers over a period of 15 years. This figure is partment of Medical Genetics, University of Toronto, Ontario, Canada. This study was supported by Grant 6606-1600-41(53) from Health and considerably higher than that reported by Nora et al. (4) Welfare, Ottawa, Ontario, Canada. Manuscript received December 26, and is also too high to be readily explained on the basis of 1984; revised manuscript received March 12, 1985, accepted March 29, polygenic inheritance. 1985. Address for reprints: Vera Rose, MD, Division of Cardiology, The The principal purpose of the present study is to reexamine Hospital for Sick Children, Toronto, Ontario, Canada, M5G IX8. the polygenic model. We determined the incidence of con- © 1985 by the American College of Cardiology 0735-1097/85/$3.30 JACC Vol. 6. No.2 ROSE ET AL. 377 August 1985:376-82 CONGENIT AL HEART DEFECT IN OFFSPRING genital heart disease in subjects whose father or mother of a 2 year period. First, we attempted to contact them by suffered from aortic stenosis, atrial septal defect, coarctation phone or letter, or both, at their last address. In many cases, of the aorta or complex dextrocardia. The four defects cited either the subject or parent or someone who knew his or were chosen, first, to test the sex effect (aortic stenosis, her whereabouts was available. Failing this, we contacted atrial septal defect and coarctation); second, to expand the the subject's last reported family physician, explained the data where these are sparse (coarctation and aortic stenosis); study, and asked for information about the family. If this and third, to check reports of parental consanguinity (dex• also failed, we sought additional information from the public trocardia). Studies of offspring of patients with congenital health authorities of the region in which the patient was last heart disease have been few. Nora and Nora (7) published known to reside and the Motor Vehicle License Bureau of the results of personal examination of at least 100 children Ontario, having obtained special permission to secure in• of affected parents and the total number of affected offspring formation from this source. The subjects who were included was small, particularly for probands with coarctation of the in the study constitute the probands. aorta and aortic stenosis. Both defects are more common in History, pregnancy and offspring data. All probands male subjects. On the other hand, atrial septal defect occurs and, in most cases, their spouses and children were seen at more frequently in female subjects and we included this the Cardiac Outpatient Department at The Hospital for Sick defect to assess whether the risk to offspring is greater when Children in Toronto. Additional family history was taken the proband parent is of the more rarely affected sex. In all from both the proband and the spouse. Information was the lesions we selected, with the exception of dextrocardia, sought about any congenital heart defect or other type of it was expected that sufficient numbers of affected subjects birth defect in the parents and siblings of the proband and would have survived and become parents at the time of the spouse. The information was encoded on a form and sub• study. The suggestion that parental consanguinity occurs in sequently entered into a computer file. When heart disease patients with dextrocardia led to the suggestion that this was reported in one of the first degree relatives of the pro• malformation is transmitted as an autosomal recessive trait band or of the proband's spouse, we sought confirmatory (8,9). Although we suspected that the number of subjects evidence from appropriate sources. In addition, for each with dextrocardia of child-bearing age would be small, we pregnancy, a detailed history was taken and similarly en• included this defect to assemble more data. coded on a form. On this form were recorded the marital A subsidiary aim of this study was to gather data that status, length of gestation, complications, drugs adminis• would be useful in counseling prospective parents with con• tered during the pregnancy and outcome of the pregnancy, genital heart disease. Accordingly, we sought the following including type of delivery, birth weight and status of the information: I) incidence of congenital heart disease in off• offspring. Each child was examined by one of us (V.R.) to spring of parents affected with well defined congenital heart the extent necessary to establish that no cardiac defect was disease; 2) pregnancy risk in probands and spouses of pro• present or to identify the type that was present. All the bands with congenital heart disease; 3) concordance between children examined in the study had an electrocardiogram. diagnosis of offspring and parent; 4) sex ratio of both chil• An echocardiogram was obtained when findings suggested dren and parents affected with a given defect; 5) the fre• a probable cardiac defect. Cardiac catheterization was per• quency of consanguinous marriage; 6) the contribution of formed when necessary. single gene disorders; 7) maternal and paternal age effects; and 8) risk of other congenital defects. Results Proband Data Methods The outcome of the search procedure described above is Study patients. The congenital heart defects selected set forth in Table 1. Initially, we identified 921 pro bands for this study were: aortic stenosis, atrial septal defect se• who belonged to the selected diagnostic categories. Of these cundum, coarctation of the aorta and dextrocardia with com• 921, 380 were excluded because they had no children, 34 plex cardiac involvement. Probands were identified as fol• had died and 22 did not wish to participate. There were 266 lows: the records of the Division of Cardiology at The Hospital probands who lived too far away, that is, outside the Prov• for Sick Children were searched for all subjects who were ince of Ontario, or who could not be traced.