The Search for Borderline Hearts within Biventricular Repairs of Complete Atrioventricular Septal Defects.

OBJECTIVES: To discover distinct clusters of morphologic features within the spectrum of complete atrioventricular septal defect (cAVSD) among children who underwent biventricular repair (BVR), and determine their association with post-repair mortality and left atrioventricular valve (LAVV) reintervention. METHODS: From 1/1/2012 to 7/1/2024, 685 children with cAVSD enrolled across 34 Congenital Heart Surgeons' Society hospitals underwent BVR and had core laboratory analysis of a preintervention echocardiogram. Morphologic clusters were identified by unsupervised staggered interaction distance clustering. Median follow-up for mortality and LAVV reintervention was 4.1 and 3.3 years, with 10% of each followed >8.4 and >7.7 years, respectively. RESULTS: Four clusters-B, D, C, A-were identified: Median common atrioventricular valve (AVV) diameter closed at end-diastole was 8.6 cm/m2 in B (n=136), 10 in D (n=224), 11 in C (n=156), and 12 in A (n=169). Hearts in B had lower indices of left ventricular constituents: length from AVV to apex 11 cm/m2 versus 12 in D, 13 in C, and 14 in A. Mortality at 1 and 8 years was 5.5% and 9.1% in B, 5.4% and 6.9% in D, 4.6% and 9.7% in C, and 4.5% and 11% in A. LAVV reintervention at 1 and 8 years was 8.4% and 14% in B, 7.4% and 15% in D, 9.3% and 14% in C, and 6.7 and 15% in A. CONCLUSIONS: Preintervention echocardiographic features identify 4 morphologic clusters of cAVSD. Associations with survival and LAVV reintervention after BVR provide knowledge that may guide decision-making in surgical management of "borderline" hearts.