James S. Tweddell Memorial Paper for Congenital Heart Surgery: Volume-Outcome Relationship of Norwood Procedures: Insights from the National Pediatric Cardiology Quality Improvement Collaborative Database

M. Schäfer¹, C. MacFarland², A. Venugopal³, D. Truong³, L. Lambert³, E. Griffiths⁴, A. Eckhauser⁵, S. Husain⁶, R. Hobbs^4
1University of Utah, Salt Lake City, Utah ²Seattle Childrens, Seattle, Washington ³Primary Children's Hospital, Salt Lake City, Utah ⁴University of Utah/Primary Children's Medical Center, Salt Lake City, Utah ⁵University of Utah and Primary Children's Hospital, Salt Lake City, Utah ⁶University of Utah School of Medicine, Salt Lake City, Utah

Purpose: Multiple investigations of the effect of center-specific case volume on outcomes using data from The Society of Thoracic Surgeons Congenital Heart Surgery have generated mostly conflicting results. The purpose of this study was to investigate the center volume-outcome relationship in patients following the Norwood procedure, considering baseline high-risk features.

Methods: The National Pediatric Cardiology Quality Improvement Collaborative (NPC-QIC) samples the wide array of data on participants undergoing single ventricle palliation through one year of age. The participating centers were categorized based on Norwood procedures into low (≤ 5 cases/year), medium (5 to 10 cases/year), and high volume centers (≥ 10 cases/year) as defined by the tertile distribution. We performed a focused comparative analysis comparing pre-operative high-risk features between the center volume categories. We further compared short-term perioperative morbidity outcomes, including the need for ECMO, catheterization, and reoperation. Lastly, we assessed survival outcomes among the volume categories focusing on transplant-free survival beyond stage II palliation and any form of early exit (1-year mortality, referral for a heart transplant, switch to two ventricle repair, and others).

Results: We analyzed 3578 participants from 69 institutions participating in NPC-QIC (Figure 1A). 29 centers were classified as a low (LVC), 20 as medium (MVC), and 20 as high-volume centers (HVC). There was no difference in frequency of preoperative high risk features among the center categories in the majority of considered variables (Table 1). Post-operative comorbidities were more frequent in MVCs and LVCs (Figure 1B) including need for ECMO (P = 0.048), catheterization (diagnostic) (P < 0.001), catheterization with intervention (P < 0.001), and need for reoperation (P = 0.019). Transplant-free survival beyond stage II (Figure 1C) was highest in HVCs (72.4%) and lowest in LVCs (65.2%) (P < 0.001), and conversely, mortality was highest in LVCs and lowest in HVCs (P < 0.001). For patients with 1 or more high-risk features (Figure 1D), transplantation-free survival beyond stage II was highest in HVCs (71.0%) and lowest in LVCs (55.9%) (P < 0.001) and conversely, mortality was highest in LVCs (26.5%) and lowest in HVCs (17.4%) (P = 0.031).

Conclusion: Patients undergoing Norwood procedure in LVCs have worse transplant-free survival and overall outcomes when compared to HVCs despite similar baseline risk profile characteristics. The outcome characteristics are potentiated when adjusted for the presence of high-risk features with significantly higher survival and lower mortality in patients treated with HVCs.

Identify the source of the funding for this research project: NA