Precision in Norwood Shunt Sizing: Single Ventricle Reconstruction Trial Public Dataset Analysis

BACKGROUND Morbidity and mortality following the Norwood procedure remains high. Shunt size selection is not standardized and the impact of shunt size on outcomes is poorly understood. The Single Ventricle Reconstruction trial randomized infants to modified Blalock-Taussig-Thomas shunt (MBTTS) or right ventricle-to-pulmonary artery shunt (RVPAS) at the Norwood procedure. We assessed shunt size distribution and its association with postoperative outcomes. METHODS We included 544 patients, excluding 5 with ambiguous shunt crossover data. Normalized Shunt Diameter 1 and 2 were calculated as shunt diameter divided by patient’s weight and body surface area, respectively. The primary outcome was 30-day mortality after Norwood. Secondary outcomes were intensive care and total length of stay, and survival to Glenn. Logistic and ordinal regression models evaluated the association of normalized shunt diameter with outcomes. RESULTS 30-day mortality after Norwood was 11.4% (n=62), survival to Glenn was 72.6% (n=395), median lengths of stay were 14.0 days (9.0-27.7) and 24.0 days (16.0-41.0) in the intensive care and total, respectively. Both normalized shunt diameters exhibited variation in both shunt types but were not associated with 30-day mortality. RVPAS size was not associated with secondary outcomes. However, a MBTTS diameter ≥1.5mm/kg predicted longer Norwood (odds ratio=4.89 [1.41-16.90]) and intensive care (odds ratio=4.11 [1.25-13.49]) duration. CONCLUSIONS Shunt size selection was variable. RVPAS had a wider size range seen with favorable outcomes compared to MBTTS. A MBTTS either too large or too small is associated with worse post-operative outcomes. Refining shunt sizing practices can improve surgical outcomes after the Norwood procedure.