**3. Classification**

Congenital heart defects may be classified into acyanotic and cyanotic depending upon whether the patients clinically exhibit cyanosis. The acyanotic defects may further be subdivided into obstructive lesions and left-to-right shunt lesions. The cyanotic defects, by definition, have right-to-left shunt. The relative incidence of these groups of defects and most common defects in each group are listed in table I. The total percent is not 100 because some of the heart defects cannot be classified into the categories listed.
