Classifying Cardiac Anomalies in Right and Left Isomerism: Concordant and Discordant Patterns

Aims: Evidence is emerging that, in the setting of isomerism, the atrial and bronchial arrangement are not always concordant, nor are these patterns always harmonious with the arrangement of the abdominal organs. We aimed to evaluate the concordance between these features in a cohort of patients with cardiac malformations in the setting of known isomerism, seeking to determine whether it was feasible to assess complexity on this basis, in this regard taking note of the potential value of bronchial as opposed to appendage morphology. Methods and Results: We studied 78 patients known to have isomerism of the bronchuses, 43 with right and 35 with left isomerism. Appendage anatomy could be determined in 49 cases (63%), all but one of these being concordant with bronchial anatomy. When assessing abdominal features, in only 59 cases (76%) was splenic morphology in keeping with the thoracic findings. As expected, right isomerism was associated with greater complexity of cardiac malformations, with an odds ratio of 6.53, with confidence intervals from 2.2-19.3 (p < 0.001). The odds were slightly decreased with thoraco-abdominal disharmony, when lesions shown to carry higher risk were then found in the setting of left isomerism. Conclusion: Harmony is excellent between bronchial and appendage isomerism, but less so with the arrangement of the abdominal organs. Right isomerism in our cohort, was indicative of a sixfold increase in intracardiac complexity. When discordance was found between the systems, however, the cardiac anomalies were less typical of the anticipated findings for right vs. left isomerism of the appendages.