Left atrial isomerism, also called Polysplenia syndrome, is one of the heterotaxy syndromes. It is a failure to differentiate into the right/left sidedness of the body, involving all internal organs. The cardiac anatomy can be highly variable, with conduction tissue abnormalities, septal defects, either atrial or ventricular, problems with valves, abnormal venous return, either systemic (vena cavae) or pulmonary, abnormal ventricular outflow and arteries, such as transposition of the great arteries or double outlet ventricles. Anaesthetic management depends on the details of the lesion.