Isomerism of atrial appendages

This code represents a congenital heart anomaly where the atrial appendages, which are muscular pouches extending from the atria, are morphologically identical to each other, rather than exhibiting their typical distinct right and left forms. This condition, often associated with complex congenital heart disease, can manifest as either bilateral right atrial appendages (right isomerism or asplenia syndrome) or bilateral left atrial appendages (left isomerism or polysplenia syndrome).

Use this code when documentation explicitly states "isomerism of atrial appendages," "atrial isomerism," or specifies bilateral right or left atrial morphology. This diagnosis is typically made through echocardiography, cardiac MRI, or at the time of surgical repair for associated cardiac defects.

• Differentiate between right atrial isomerism (asplenia syndrome) and left atrial isomerism (polysplenia syndrome) if specified, as these have different clinical implications and associated anomalies.
• Always code any associated congenital heart defects, such as transposition of the great arteries, common atrium, or anomalous pulmonary venous return, in addition to this code.
• Review imaging reports and cardiology notes for definitive statements regarding atrial appendage morphology.