Shirley's heart is very different from the normal heart. Shirley has type-1 truncus arteriosus. This very rare CHD is only seen in about 300 children per year, making it one of the least common forms of CHD. Thankfully, although truncus is life threatening and nothing is certain, the surgery for type-1 truncus is very effective and the mortality rate is relatively low. This page will help provide more information specifically about truncus arteriosus.