Neo-Aortic Valve Insufficiency and Root Dilatation During and After the Staged Palliation for Hypoplastic Left Heart Syndrome and Variants.

In hypoplastic left heart syndrome (HLHS) and variants, the pulmonary valve functions as the neo-aortic valve after the Norwood procedure. Neo-aortic valve insufficiency (Neo-AI) represents an emerging complication with implications for long-term survival. This study investigated the clinical impact and patterns of Neo-AI development following staged palliation. Neonates undergoing the Norwood procedure (2001–2023) were retrospectively reviewed. Neo-AI was evaluated using serial echocardiograms, with patients classified into two groups: early onset (during the Norwood hospitalization) and late onset (after the Norwood discharge). Neo-aortic root dimensions were measured at four time points during staged palliation, with Z-scores calculated for patient growth. Among 378 patients, significant Neo-AI developed in 30 (7.9%) during median follow-up of 4.3 years. Early onset neo-AI occurred in 13 patients (43.3%) and late onset neo-AI in 17 (56.7%). Cox regression revealed 7.9-fold increased mortality risk in early onset patients (hazard ratios 7.87, p = 0.009), with 5-year survival of 38.5% versus 87.8% in late onset patients. All early onset deaths occurred within the first year. Late onset neo-AI patients demonstrated progressive sinus of Valsalva dilatation (annual progression 0.33 Z-score units). At Fontan completion, late onset neo-AI patients had larger Z-scores than early onset patients [5.14 vs. 2.18, p = 0.006], while surviving early onset patients demonstrated Neo-AI improvement after bidirectional cavopulmonary shunt with subsequent stable root dimensions. Early onset neo-AI associates with acute hemodynamic compromise and higher perioperative mortality. Late onset neo-AI demonstrates progressive root dilatation with superior survival, raising concerns for future valve intervention.