The search for borderline hearts within biventricular repairs of complete atrioventricular septal defects

To discover distinct clusters of morphologic features within the spectrum of complete atrioventricular septal defect among children who underwent biventricular repair and determine their association with postrepair mortality and left atrioventricular valve reintervention.

From January 1, 2012, to July 1, 2024, 685 children with complete atrioventricular septal defect enrolled across 34 Congenital Heart Surgeons' Society hospitals underwent biventricular repair 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 left atrioventricular valve reintervention was 4.1 and 3.3 years, respectively, with 10% of each followed >8.4 and >7.7 years, respectively.

Four clusters-B, D, C, and A-were identified: median common atrioventricular valve diameter closed at end-diastole was 8.6 cm/m² in B (n = 136), 10 cm/m² in D (n = 224), 11 cm/m² in C (n = 156), and 12 cm/m² in A (n = 169). Hearts in B had lower indices of left ventricular constituents: length from atrioventricular valve to apex 11 cm/m² versus 12 in D, 13 cm/m² in C, and 14 cm/m² in A. Mortality at 1 and 8 years, respectively, 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. Left atrioventricular valve reintervention at 1 and 8 years, respectively, 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.

Preintervention echocardiographic features identify 4 morphologic clusters of complete atrioventricular septal defect. Associations with survival and left atrioventricular valve reintervention after biventricular repair provide knowledge that may guide decision making in surgical management of so-called borderline hearts.