[Left heart defects and genetics].

The obstructive cardiac defects of the left heart are an heterogeneous group of malformations. These past years their molecular bases have been partially understood. The associated chromosomal anomalies are mainly represented by the Turner syndrome, the microdeletion of the chromosome 11q and the 7q23 deletion in Williams syndrome. In isolated obstructive left heart diseases, new insights into their genetic bases have been made because the dominant inheritance has been demonstrated and the notion of a phenotypic continuum between bicuspid aortic valve and the complete form of hypoplastic left heart has been proposed. Finally, mutations in genes involved in heart development, namely NKX2.5 and NOTCH1, have been identified in these defects and support the former hypotheses. The low penetrance and the variable expression of these known mutations did not completely solved prenatal genetic counselling.