Geometry of the Aortic Arch After Initial Hybrid or Norwood Palliation

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.

Principal component analysis identified neo-aortic diameter variations post Norwood surgery associated with the single ventricle performance and flow quality

The purpose of this study was to investigate neo-aortic curvature and diameter variation using the principal component analysis in patients who underwent a Norwood procedure for hypoplastic left heart syndrome. We further assessed whether neo-aortic curvature and diameter features are associated with clinical outcomes, single right ventricle function and flow hemodynamic patterns derived by 4D-Flow MRI. 55 patients with Fontan circulation who underwent a Norwood procedure in infancy underwent cardiac MRI as part of surveillance of their Fontan circulation. Neo-aortic models segmented from the MRI angiography were subjected to principal component analysis. Principal component (PC) score values representing curvature and diameter variability were compared between patients with and without composite clinical event and correlated with standard cardiac hemodynamics. Fourteen patients experienced composite adverse clinical events. The PCs describing the variations in aortic curvature were not associated with cardiac MRI hemodynamics or clinical events. The diameter-based 2nd PC describing the degree of aortic tapering was significantly associated with the end-systolic volume index (R = 0.34, P = 0.011), ejection fraction (R = -0.44, P = 0.001), and viscous energy loss measured in the ascending aorta (R = 0.45, P = 0.009). High 2nd PC score values describing abrupt diameter changes were also associated with worse freedom from clinical events (P = 0.042). Neo-aortic shape variation described by gradual diameter tapering is strongly linked to better clinical and hemodynamic outcomes. Neo-aortic curvature and luminal trajectory seems to have less impact on the overall hemodynamics and long-term outcomes.

Incidence of and Risk Factors for Aortic Arch Interventions After the Comprehensive Stage II Procedure for Hypoplastic Left Heart Syndrome

Minimal data exist about the incidence and risk factors for arch intervention after comprehensive stage II (CSII). Goal of this study was to document incidence of arch interventions after CSII and determine if any differences existed between those who underwent an arch intervention (aiCSII) versus those did not have an intervention. Single-center retrospective chart review of all hypoplastic left heart syndrome patients who underwent a CSII between 6/1/2005 and 2/1/2020 was performed. Univariate analysis was conducted in addition to principal components analysis (PCA). One hundred patients were evaluated. Sixteen patients underwent 24 arch interventions. Age at initial arch reintervention was 1.3 ± 1.2 years (median 1.0 years, range 0.5-2.2 years). Univariate analysis showed that the aiCSII group were more likely to be female, to have had a retrograde arch intervention post-hybrid procedure, and to be younger at time of CSII. On echocardiograms, aiCSII group had significantly higher pre-CSII patent ductus arteriosus velocities, arch velocities on their 1st post-operative and discharge study post-CSII, and arch velocities pre-Fontan. Gradients were higher in the aiCSII via pre-Fontan catheterization. With PCA, echocardiographic and catheterization data remained significantly associated with aiCSII versus those who did not undergo an arch intervention (OR = 4.5 (1.9, 19.8), p = 0.008). Incidence of arch intervention post-CSII was 16%. Echocardiographic arch velocities during the CSII hospitalization were the strongest predictors for subsequent aortic arch interventions. Further studies are needed to determine any modifiable variables that may reduce the incidence of arch interventions.