Abnormal position of the heart, with location of left atrium on right side and vice versa (i.e. situs inversus), is classified according to the position of the left atrium, the main bronchi, and the abdominal organs. Inversion of viscera (abdominal situs inversus) is always associated with atrial inver-sion. Major malformations of heart structures are usually found in either of the following:
· Dextrocardia + normal position of abdominal organs.
· Normal position of heart (laevocardia) + abdominal situs inversus.
Characteristic heart malformations include—pulmonary stenosis; tricuspid atresia; transposition of the great arteries; anomalous pulmonary venous drainage; atrioventricular septal defects; single ventricle.
No malformations of the heart structures are found when dextrocardia and abdominal situs inversus (i.e. mirror-image dextrocardia) are present in combination.