Background: For many complex cardiovascular procedures the well-established link between volume and outcome has rested on the underlying assumption that experience leads to more reliable implementation of the processes of care which have been associated with better clinical outcomes. This study tested that assumption by examining the relationship between cardiovascular case volumes and the implementation of twelve basic evidence-based processes of cardiovascular care.
Method and results: Observational analysis of over 3000 US hospitals submitting cardiovascular performance indicator data to The Joint Commission on during 2005. Hospitals were grouped together based upon their annual case volumes and indicator rates were calculated for twelve standardized indicators of evidence-based processes of cardiovascular care (eight of which assessed evidenced-based processes for patients with acute myocardial infarction and four of which evaluated evidenced-based processes for heart failure patients). As case volume increased so did indicator rates, up to a statistical cut-point that was unique to each indicator (ranging from 12 to 287 annual cases). t-Test analyses and generalized linear mixed effects logistic regression were used to compare the performance of hospitals with case volumes above or below the statistical cut-point. Hospitals with case volumes that were above the cut-point had indicator rates that were, on an average, 10 percentage points higher than hospitals with case volumes below the cut-point (P < 0.05).
Conclusion: Hospitals treating fewer cardiovascular cases were significantly less likely to apply evidence-based processes of care than hospitals with larger case volumes, but only up to a statistically identifiable cut-point unique to each indicator.