The term volume outcomes effect appeared in the literature in 1979 to describe the lower mortality rates experienced by hospitals performing a higher volume of specific surgical procedures [1Luft H.S. Bunker J.P. Einthoven A.C. Should operations be regionalized? The empiric relationship between surgical volume and mortality.N Engl J Med. 1979; 301: 1364-1369Crossref PubMed Scopus (1339) Google Scholar]. Numerous follow-up studies, including many involving cardiac surgical patients, seem to support these findings. Recently, a growing number of reports have found a breakdown in the volume outcomes effect. Few would argue that inexperienced clinicians caring for the occasional high-risk patient in an unstructured environment using insufficient resources should expect excellent outcomes. Yet there is a growing body of evidence that the relationship between volume and outcome is much more complex than originally described. This current study [2Pasquali S.K. Jacobs J.P. He X. et al.The complex relationship between center volume and outcome in patients undergoing the Norwood operation.Ann Thorac Surg. 2012; 93: 1556-1562Abstract Full Text Full Text PDF PubMed Scopus (66) Google Scholar] uses a large, multicenter registry to evaluate the association of the number of Norwood procedures performed at a center with mortality results. Annual Norwood volume and preoperative risk tertiles were analyzed for association with mortality, revealing a modest association of center volume with outcome. Despite much improvement in surgical technique and perioperative care over the last two decades and a number of outstanding reports of interval results, it is important to note that approximately 20% of all patients undergoing the Norwood procedure and one third of high-risk patients do not survive more than 30 days. Higher-volume centers, on average, had lower mortality rates but the results were not universal. Center volume explained approximately 14% of between center variation, leaving the remainder of the causation uncertain. The use of center volume alone to predict outcomes overlooks the improvements that can occur in concert with increasing case load: hospital structure and process measures, level of expertise and availability of vital caregivers, development of evidence-based best practice guidelines, and ongoing quality assurance and quality improvement initiatives. The current analysis also does not account for the frequent changes in key personnel (e.g., experienced surgeons, intensive care unit physicians) that occur frequently in academic medicine. The fact that center volume does not completely explain differences in survival may be related to our place on the collective learning curve for the procedure. For example, drawing on the evolution of the arterial switch procedure, no amount of expert perioperative care (likely to exist in a high-volume center) could atone for the misdeeds of an inexperienced surgeon, whereas an experienced surgeon could routinely achieve excellent results working in a lower volume center. Many surgeons are currently comfortable with the technical aspects of the Norwood operation, and intraoperative deaths have become infrequent; however, perioperative care paradigms vary greatly and mortality still remains higher than expected. It may be inferred that there is still much to learn about the physiology and perioperative as well as interstage care of these patients. It is likely that these lessons, similar to the discovery of the importance of removing mechanical and vascular afterload and countless other innovations, will be gleaned from work in high-volume, experienced centers that are able and willing to invest the resources necessary to adequately study these patients. This important article helps to focus our future researchers into procedural specific outcomes. The next steps are to deconstruct and investigate other potentially overlooked factors that may be related to mortality and expand these studies to significant morbidities as well. The public and our payers demand it. The Complex Relationship Between Center Volume and Outcome in Patients Undergoing the Norwood OperationThe Annals of Thoracic SurgeryVol. 93Issue 5PreviewNorwood outcomes vary across centers, and a relationship between center volume and outcome has been previously described. It is unclear whether this volume-outcome relationship exists across all levels of patient risk or holds true for all centers. We evaluated the impact of patient risk status on the relationship between center volume and outcome, and the extent to which differences in center volume account for between-center variation in outcome. Full-Text PDF