Classifying Heterotaxy Syndrome

Abstract

Heterotaxy syndrome is a complex set of abnormalities related to abnormal left–right axis patterning. Although rare (occurring in just over 1 in 10 000 live births1), congenital heart defects associated with heterotaxy syndrome carry a disproportionate burden of morbidity and mortality.2,3 Despite numerous investigations on the genetic underpinning, epidemiology, anatomic pathology, diagnostic imaging, and management, agreement regarding the best method to classify patients with heterotaxy continues to elude our field.4 Specifically, a growing body of experience has noted that the 2 most common methods of classifying patients with heterotaxy—based on the status of the spleen or on the morphology of the atrial appendages—is frequently incongruent with the expected pattern of cardiac and noncardiac anomalies,5 is difficult to ascertain clinically, and may not be helpful in guiding clinical management.2–4 See Article by Yim et al In this issue of Circulation: Cardiovascular Imaging , Yim et al6 provide further evidence that the prevailing classification schemes used in heterotaxy syndrome are flawed. In a retrospective analysis of noninvasive imaging data from 114 patients with heterotaxy, they noted that the classic pattern of isomerism was breached in 1 of every 5 patients. Furthermore, they documented the limited clinical utility of relying on atrial appendage morphology or the status of the spleen and …