Abstract 3898: Contemporary Analysis of the Association between Hospital Volume and In-Hospital Death in Patients Undergoing Percutaneous Coronary Intervention: Results from the National Cardiovascular Data Registry
Background: Prior studies inconsistently demonstrate a hospital ‘volume-outcome’ relationship in patients undergoing PCI. This may be due in part to study populations with different baseline patient risks for in-hospital death. Thus we analyzed the ‘volume-outcome’ relationship in PCI for in-hospital death using contemporary data from the American College of Cardiology-National Cardiovascular Data Registry (ACC-NCDR), specifically evaluating its interaction with patient risk.
Methods: We used abstracted data on patients undergoing PCI in 2005 from ACC-NCDR, a large PCI registry. We excluded hospitals that reported <5 PCIs and transferred out >5% of patients. Hospitals were divided into quartiles of hospital volume (<400, 400 to 700, 700 to 1000, >1000); patients were categorized into risk quartiles based on the established ACC-NCDR risk score. We analyzed the relationship between hospital volume and in-hospital death using hierarchical regression models before and after accounting for patient risk.
Results: Our final study population included 289,059 patients at 410 hospitals. Overall mean age was 64.1 years (± 12.2); 33.6% were women, 31.8% had diabetes mellitus, 10.4% had heart failure, 10.3% underwent primary PCI for STEMI and 15.9% had PCI after an ACS. Patients in the lowest quartile of hospital volume had fewer co-morbidities (diabetes mellitus, heart failure, renal insufficiency), but more acute presentations with a higher percentage of primary PCI for STEMI (17.0% vs. 12.4% in highest quartile), PCI after ACS (17.7% vs. 14.1%) and cardiogenic shock (2.6% vs. 1.9%). In crude analysis, greater hospital volume was associated with a lower risk of in-hospital death (OR for each increasing quartile, 0.94; 95% CI, 0.90–0.98; P=006). After adjusting for patient risk, this relationship became non-significant (OR, 0.97; 95% CI, 0.93–1.1; P=0.11) and additional models demonstrated no significant interaction between volume and patient risk (P=0.90).
Conclusion: Contemporary data suggest the volume-outcome relationship in PCI is primarily driven by differences in patient risk across hospitals. This finding appears consistent across different categories of patient risk with no evidence of a significant interaction.