Cardiac Malposition and Heterotaxy

One of the more challenging areas in the echocardiographic evaluation of congenital heart disease (CHD) is the analysis of cardiac malpositions and heterotaxy. This is in large measure due to the fact that cardiac malpositions can occur with many different types of CHD. While abnormalities of cardiac position do tend to be seen more frequently with certain forms of CHD, the possibilities are numerous and varied, and one cannot draw any preliminary conclusions of the underlying cardiac anatomy/physiology based upon the position and orientation of the heart in the thorax. Instead, one must maintain an open mind to the various possibilities, guided by the segmental approach to CHD. This chapter provides an overview to the transesophageal echocardiographic evaluation of cardiac malpositions, including dextrocardia. In addition, the topic of heterotaxy (isomerism) will be discussed. Heterotaxy is a disorder of laterality that results in structural abnormalities affecting many organs in the body including the lungs, abdominal viscera, and heart. Patients with heterotaxy frequently have prominent cardiac abnormalities involving many levels of the heart. A significant proportion of these patients will also have a cardiac malposition, but even if they do not, most will still have multiple congenital cardiac defects that require a careful and systematic approach to evaluation. Therefore, the same fundamental diagnostic echocardiographic approach should be utilized to evaluate both cardiac malpositions and heterotaxy.