A child presenting to the clinic is showing features of Down's syndrome. Which is the MOST common cardiac lesion in a child with Down's syndrome?

The most common cardiac abnormality in children with Down's syndrome is atrioventricular septal defect which occur in 45% of cases. Isolated VSD occur in 35% cases, isolated secundum ASD is seen in 8% of cases and TOF is seen in 5% cases. Clinical manifestations of Down's syndrome are: Congenital anomalies of hea and GIT Epicanthal folds Flattened facial profile Small rounded ears Upslanted palpabral fissures Excess nuchal skin Brachycephaly Increased risk of leukemia Immune system defects Alzheimer like dementia Ref: Hurst's The Hea, 13e chapter 82.