Background: Conotruncal heart defects compose 25% to 30% of nonsyndromic congenital heart defects. This study describes the frequency of chromosome abnormalities and microdeletion of 22q11 associated among infants and fetuses delivered with conotruncal heart malformations.
Methods: From a population base of 974,579 infants/fetuses delivered, 622 California infants/fetuses were ascertained with a defect of aortopulmonary septation. Infants whose primary cardiac defect was tetralogy of Fallot (n = 296) or d-transposition of the great arteries (n = 189) were screened for microdeletion of 22q11.
Results: Of the infants who had routine karyotypes, 5% had chromosomal abnormalities, including four with extra sex chromosomes. Thirty infants had chromosome 22q11 microdeletions, providing a cause for 10% of infants whose primary defect was tetralogy of Fallot. Right aortic arch, abnormal branching patterns of the major arteries arising from the thoracic aorta, and pulmonary artery abnormalities were observed more frequently among infants with tetralogy of Fallot caused by 22q11 microdeletion.
Conclusions: We found an unusual number of infants with an extra sex chromosome and a conotruncal defect. Infants with tetralogy of Fallot owing to 22q11 microdeletion showed more associated vascular anomalies than infants with tetralogy without a 22q11 microdeletion. Although these associated vascular anomalies provide clues as to which infants with tetralogy of Fallot are more likely to carry the microdeletion, the overall risk of 10% among infants with tetralogy of Fallot warrants chromosome analysis and fluorescent in situ hybridization (FISH) testing routinely, which may be supplanted by genome-wide copy number testing as it becomes more widely utilized.