[Genetic aspects of cardiac conduction defects]

Degenerative conduction defects are usually considered to be exaggerated ageing affecting the conduction pathways. For several years familial forms have been described, and a first locus on chromosome 19 and then a first gene, SCN5A on chromosome 3 (coding for the sodium channel alpha subunit), have been identified. Mutations of this gene can lead not only to congenital conduction defects but also to progressive forms of conduction defects similar to Lenègre disease. A third locus on chromosome 16 at 16q23-24 has been identified, as have other families not linked to the loci described previously. Although it now seems clear that conduction defects can have a genetic component, the frequency of the familial forms remains to be determined. Important progress could be made in the understanding of this disease if other implicated genes were identified. It would then become possible to elucidate the different pathophysiological mechanisms responsible for conduction defects.