Is a Shorter Atrioventricular Septal Length an Intermediate Phenotype in the Spectrum of Nonsyndromic Atrioventricular Septal Defects?

Evidence for two-component distributions from the analysis of AVSL standardized for age and body surface area for case parents and case siblings suggests the presence of an intermediate phenotype for nonsyndromic AVSD. The high heritability in the control families suggests that there may be polygenic involvement in the determination of AVSL. Broadening the definition of AVSD to include those with shortened AVSL may increase the power of genetic association and mapping studies to identify susceptibility genes for AVSD.