Long-term enlargement of the neo-aortic root and aortic arch following arch reconstruction in hypoplastic left heart syndrome

Background: Long-term enlargement of the aortic arch after aortic arch reconstruction in hypoplastic left heart syndrome is not well described.

Methods: Aortic arch measurements for 50 patients with hypoplastic left heart syndrome who achieved Fontan completion were converted to Pediatric Heart Network z-scores. Dimensions were assessed using linear mixed models, and differences among time points were evaluated with F-tests. Sub-analysis was conducted comparing Norwood (n = 36) with hybrid (n = 14) strategies.

Results: Median time to last imaging was 6.4 (interquartile range, 3.5-11.3) years. Before intervention, the main pulmonary artery was dilated, whereas the ascending aorta, transverse arch, and isthmus were hypoplastic. With aortic arch reconstruction, there were expected increases in all arch z-scores. The aortic arch continued to dilate after aortic arch reconstruction, reaching peak values at 7 months (neo-aortic complex: z = 6.9 [5.6-8.0]) or 12 months after stage I (ascending aorta: z = 6.1 [2.9-8.3]; transverse arch: z = 4.7 [3.0-5.9]). After peak values, there was a gradual decline in z-scores with most components still at least mildly dilated at 16 years (neo-aortic complex: z = 3.2 [3.1-3.9], ascending aorta: z = 3.9 [3.3-4.2]; transverse arch: z = 3.1 [2.5-3.7]) with abrupt caliber change at the isthmus: z = -0.8 (-1.1 to -0.3). Norwood and hybrid strategies showed similar enlargement profiles after 7 months of age.

Conclusions: Neo-aortic root and aortic arch in hypoplastic left heart syndrome are enlarged early after aortic arch reconstruction and continue to enlarge out of proportion to normal controls until 12 months of age, with gradual decline in enlargement up to adolescence. Further work should focus on modifiable surgical factors that may prove important to optimize arch growth and geometry.