Contemporary Relationship Between Volume And Mortality After Congenital Cardiac Surgery
Karl F. Welke1, Tara Karamlou2, Sean M. O'Brien3, Joseph A. Dearani4, James S. Tweddell5, S. Ram Kumar6, Jennifer C. Romano7, Carl L. Backer8, Sara K. Pasquali9.
1Atrium Health Levine Children's Hospital, Charlotte, NC, USA, 2Cleveland Clinic Children's Hospital, Cleveland, OH, USA, 3Duke Clinical Research Institute, Durham, NC, USA, 4Mayo Clinic, Rochester, MN, USA, 5Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA, 6Children's Hospital Los Angeles, Los Angeles, CA, USA, 7University of Michigan, C.S. Mott Children's Hospital, C.S. Mott Children's Hospital, Ann Arbor, MI, USA, 8UK HealthCare Kentucky Children's Hospital, Lexington, KY, USA, 9University of Michigan, C.S. Mott Children's Hospital, Ann Arbor, MI, USA.
Objectives: Most studies examining the volume-outcome relationship in congenital heart surgery were conducted over a decade ago. Since then mortality has declined, case-mix adjustment has evolved, and there have been a variety of changes across centers. Whether there is a current relationship between surgical volume and mortality is unclear.
Methods: Patients ≤18 years undergoing index operations in the STS Congenital Database (2017-2020) were included. The association between annual volume and case-mix adjusted operative mortality was assessed using Bayesian hierarchical models, overall and by STAT category.
Results: Across 101 centers (n=76,714), median annual volume was 144 cases/year (range 27 - 863) (Figure 1A), and overall operative mortality 2.7%. Lower volume centers had higher mortality, with a transition zone for volume below which there was a sustained uptick in the odds of mortality at approximately 189 cases/year (95% CrI 115-450) (Figure 1B). Odds of mortality at various points on the curve compared to a 450 case/year reference point were: 50 cases/year (1.84, 95% CrI 1.41-2.37), 100 cases/year (OR 1.37, 95% CrI 1.08-1.71), 200 cases/year (OR 0.92, 95% CrI 0.1-1.18), 300 cases/year (OR 0.89, 95% CrI 0.76-1.04). The volume-outcome effect was most apparent for STAT 4-5 cases.
Conclusions: There remains an association between volume and mortality after congenital heart surgery, most notable for STAT 4-5 cases. Ongoing efforts aim to understand the association between volume and other outcomes.
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