Volume-outcome relationships in cardiovascular operations: New York State,1990-1995

Background: It has been known for nearly 20 years that, in cardiovascular o perations, a significant inverse relationship exists between clinical outco mes and the volume of procedures performed. Interestingly, this relationshi p persists 2 decades after it was recognized. Objective: The purpose of thi s study was to examine the relationship between hospital volume and in-hosp ital deaths in 3 cardiovascular procedures: coronary artery bypass grafting , elective repair of abdominal aortic aneurysms, and repair of congenital c ardiac defects. Methods: The database includes all patients who were hospit alized in New York State during the Sears 1990 to 1995, Using standard logi stic regression techniques, we analyzed the relationship between hospital v olume and outcome. Results. No correlation exists between hospital volume a nd in-hospital deaths in coronary artery bypass grafting. Statewide, 31 hos pitals performed 97,137 operations over the 6-year period (overall mortalit y rate, 2.75%), By contrast, most of the hospitals statewide (195 of 230 ho spitals) performed 9847 elective abdominal aortic aneurysm repairs with an overall mortality rate of 5.5%, In abdominal aortic aneurysm operations, a significant inverse relationship between hospital volume and in-hospital de aths was determined. Sixteen hospitals performed 7199 repairs for congenita l cardiac defects. A significant inverse relationship (which was most prono unced for neonates) was found between volume and death. Conclusions: The im portance of these findings lies in the rather striking difference between t he volume-outcome relationship found for operations for abdominal aortic an eurysms and congenital cardiac defects and the lack of such a relationship for coronary artery bypass grafting. This observation may be largely explai ned by the quality improvement program in New York State for bypass operati ons since 1989. If so, these results have important implications for expand ing the scope of quality improvement efforts in New York State.