Much Ado About Nothing?
The Relationship of Institutional Percutaneous Coronary Intervention Volume to Mortality
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In a seminal narrative, Donabedian1 defined 3 domains in quality of care: structure, process, and outcomes. Structure refers to the attributes of healthcare systems that are organized to deliver quality care, process describes what we do for patients, and outcome describes the changes in patients’ health status. Over the past 3 decades, hospital volume has evolved into an important structural metric. In the field of cardiovascular quality of care, it was initially described for cardiac surgery.2 Subsequently, Phillips et al3 assessed patients undergoing balloon angioplasty in the California inpatient database. Hospitals that performed <200 balloon angioplasties did worse than those who did 400, which, in turn, did worse than those who did >400. These thresholds were chosen based on coronary artery bypass graft outcomes from the same database.2 Other studies reported a similar volume–outcomes relationship for patients undergoing balloon angioplasty and bare-metal stents, mostly for hospitals performing <200 angioplasties a year.4
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Conflating this association between volume and outcomes as causal, policy makers, and third-party payers started endorsing percutaneous coronary intervention (PCI) volume minimums as a surrogate for quality of care. The American College of Cardiology’s clinical competence statement on PCI from 1998 was one of the first to recommend a minimum annual hospital PCI volume of 400.5 Initiatives such as the Leapfrog Group made 400 PCIs the minimum requirement as part of their evidence-based volume referral standard.6 In fact, so entrenched is the 400 PCI benchmark as a measure of quality that the Center for Medicare and Medicaid Services recently mandated that for hospitals to get reimbursed for procedures such as transcatheter aortic valve replacement and MitraClip, they should maintain an annual minimum volume of 400 PCIs, despite there being minimal correlation between the performance of PCI …