The evolution of specific genetic and environmental counseling in congenital heart diseases.

Abstract

The approach to genetic and environmental counseling in congenital heart disease has evolved during the past decade in the direction of greater specificity. At present about 8% of cases are predominantly genetic and about 2% are predominantly environmental in etiology. In the remaining 90% there is an important genetic-environmental interaction. Within this latter group (multifactorial inheritance) it should be possible to segregate and identify further etiologic subsets of predominantly environmental or predominantly genetic influences. It is imperative that high-risk patients in any etiologic mode be recognized as such. General guidelines which have emerged regarding low-risk (type B) patients in the mode of multifactorial inheritance include: a higher risk for offspring than for sibs of a patient with congenital heart disease; a higher risk if the lesion is common (e.g., ventricular septal defect) than if the lesion is uncommon (e.g., tricuspid atresia); a 2-fold to 3-fold increase in risk if there are 2 affected 1st-degree relatives rather than one. A risk comparable to or greater than Mendelian risks is found if there are 3 affected 1st-degree relatives (especially if there is an affected parent). This is the so-called type C family. Answers to patients'' questions regarding etiology and recurrence risks should be made in the context of carefully evaluated clinical and historical data looking specifically for Mendelian, chromosomal and multifactorial inheritance modes and environmental effects.