Geometry of the Aortic Arch After Initial Hybrid or Norwood Palliation

Aortic arch reconstruction is a challenging technical step in the Norwood operation or the comprehensive stage II operation. This study sought to analyze differences in aortic arch geometry and dimensions in patients undergoing Norwood or hybrid palliation.

Retrospective data collection included all patients who underwent Norwood or hybrid palliation at the Hospital for Sick Children in Toronto between 2007 and 2014; 139 patients were analyzed. Lateral angiograms obtained before stage II or comprehensive stage II and Fontan completion were measured at the level of the ascending aorta, transverse arch, isthmus, and descending aorta. Reintervention rate and type were assessed.

Before stage II or comprehensive stage II hybrid procedures, patients had significantly larger descending aorta z-scores. Patients undergoing Norwood operations showed a significant increase in descending aorta z-scores before Fontan completion. Comparable dimensions (absolute and z-scores) were found at all points of measurements before Fontan completion. Geometry was similar in both groups but significantly different compared with normal dimensions. Reduction in aortic arch diameter happened almost solely in the segment between the transverse arch and the isthmus. Stent inclusion in patients undergoing hybrid procedures led to similar dimensions. Reintervention rates were very low (Norwood 9.6% vs hybrid 7.6%). Reintervention for excessive dimensions was as common as for recoarctation.

Aortic arch geometry and growth is not altered by palliation type. The increase in descending aorta diameter seen in patients undergoing Norwood operations is in accord with physiologic changes and may reflect catch-up growth. Reintervention rates are low and are not related to recoarctation alone.