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.