Reevaluation of the Volume-Outcome Relationship for Pediatric Cardiac Surgery

Over the last 3 decades, a growing body of work has demonstrated a relationship between volume and outcome for a variety of complex surgical procedures and medical conditions. Two large-scale reviews have systemically evaluated the methodology and results of many of these studies across a broad range of conditions.1,2 In 2000, Dudley et al1 found that, among 128 studies examining 40 different procedures or conditions, 80% reported a statistically significant relationship between higher institutional case volume and better clinical outcomes; none of the published studies reported an association between higher volume and worse outcomes. In 2002, Halm et al2 evaluated 135 studies for 27 procedures or conditions, many of which were included in the previous review; a preliminary version of this report served as the focus of an Institute of Medicine workshop examining the volume-outcome relationship in the context of healthcare quality.3 The authors concluded that 70% of comparisons examining either institutional or physician case volume noted a statistically significant relationship between higher volume and better outcomes. Once again, none of the reports found the opposite to be true.Article p 2652 Pediatric cardiac surgery is the only surgical procedure performed in children for which a volume-outcome relationship has been documented. In 4 large studies conducted in the United States (2 studies4,5 included in the review by Dudley et al,1 3 studies4–6 in the Halm et al2 review, and 1 study7 published subsequent to these reviews), larger annual surgical case volumes were associated with substantial reductions in in-hospital mortality. These results were quite consistent despite the fact that the studies used different data sources, different patient selection, different risk adjustment methods, and different definitions of volume. Jenkins et al4 used aggregated hospital discharge data from California (1988) and Massachusetts (1989) …