Which is worse right sides ventricular dilation or left sided dilation. does asd tend to run in families?

Depends: Like sticks and stones both of which can break your bones, heart failure whether right or left can be serious or mild depending on the cause and how severe it is. Your doctor can best tell you what's going on. The cause of ASD (atrio-septal defect) and many other congenital heart defects is unknown. See http://www.cdc.gov/ncbddd/heartdefects/atrialseptaldefect.html