How Appropriate for Assessing Quality Are the 2009 Appropriateness Criteria for Coronary Revascularization?

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Lloyd W. Klein, MD

From Advocate Illinois Masonic Medical Center, Chicago, Illinois.
The author reports no conflicts of interest regarding the content herein.
Address for correspondence: Lloyd W. Klein MD, Advocate Illinois Masonic Medical Center, Professional Office Building Suite #625, 3000 North Halsted Avenue, Chicago, IL 60614. E-mail: [email protected]

“Science is the father of knowledge, but opinion breeds ignorance.” — HIPPOCRATES

Whether it is most appropriate to treat coronary artery disease (CAD) patients with medical therapy alone, or to prescribe medical therapy and also perform revascularization — either by percutaneous coronary intervention (PCI) or bypass surgery (CABG) — depends on a myriad of clinical, angiographic and physiologic factors that vary widely from patient to patient. In some cases the best decision is readily apparent based on objective evidence from clinical trials; but often, the best course to take is more nuanced and dependent on one’s interpretation of that individual’s clinical and angiographic findings, then placed in the context of existing clinical trial data.

Concept of appropriateness. It seems intuitive that if one could create a matrix of a large number of relevant factors and submit each scenario to a panel of thoughtful, impartial practitioners from the various fields of cardiology, that their dispassionate consensus opinion would provide a practical tool for weighing each of those factors to arrive at the principles leading to the right treatment decision. This is the concept behind the development of the ACCF/SCAI/STS/AATS/AHA/ASNC 2009 Appropriateness Criteria for Coronary Revascularization.1

Appropriateness Criteria for Coronary Revascularization.1 A technical panel consisting of cardiologists, surgeons, and numerous other stakeholders developed a ranked score of 1–9 for each of 180 clinical scenarios, scoring each according to whether revascularization was appropriate, inappropriate or uncertain. These Appropriateness Criteria were not intended to diminish the importance of clinical judgment in evaluating individual patients, nor was it possible to include every possible variable or influential fact which might correctly sway a clinical decision. The reasons for the development of these criteria include an initial attempt at objective measurement of what constitutes quality practice, to provide a framework for evaluating patterns of care and to help reduce the large variation in rates of revascularization that has been observed.

Appropriateness criteria differ from clinical guidelines both in their purpose and their format. Clinical guidelines provide a summary and discussion of evidence from trials; appropriateness criteria focus on the presenting features and clinical status of patients of the type seen in contemporary daily practice. Clinical trials and published studies frequently exclude high-risk patient subgroups and, therefore, existing scientific evidence may not be directly applicable to therapeutic decisions. The Appropriateness Criteria begin by characterizing patients according to four critical features: 1) the severity and nature of symptoms; 2) the angiographic severity and location of coronary stenoses; 3) how much of the myocardium, according to noninvasive testing, is ischemic; and 4) whether the patient is receiving an optimal medication regimen at optimal dosages. Revascularization is considered appropriate if the expected improvement in survival, symptoms, functional status and/or quality of life outweigh the risks as compared to medical therapy. The panel considered revascularization by either CABG or PCI for most of the scenarios presented, without specific consideration of the method. The relative merit of CABG versus PCI was considered only in a subset. The “rules” that were mandated at the onset include: acceptance of the size of a thallium defect as the accurate means to assess the degree of myocardium at risk; presumption that the designation of the number of vessels diseased accurately depicted large branches of that vessel; supposition that there were no relevant medical problems or patient preferences that might influence such decisions; and allowance that the clinical evaluation of symptom severity was precise.

Surprisingly to many interventionists, CABG was considered the more appropriate revascularization method for patients with 13 of 14 conditions and anatomic descriptors, including two-vessel disease with proximal left anterior descending (LAD) stenosis. CABG was also favored for patients with three-vessel coronary disease regardless of left ventricular (LV) function or presence of diabetes. In only one scenario — patients with native three-vessel disease with failure of multiple bypass grafts, left interior mammary artery patent to a native coronary artery, and depressed LV ejection fraction (LVEF) — was stenting considered appropriate and bypass surgery inappropriate. Given the actual utilization of these procedures in practice, the question arises whether the apparent “disconnect” between modern interventional practice and the “objective” analysis of the technical panel accurately depicts an overperformance of PCI. Conversely, it is possible that the mandated rules guiding interpretation resulted in a skewed outcome.

Current study. In this context, the study in this issue of the Journal of Invasive Cardiology by Brener and colleagues2 is important because it addresses the question of whether the appropriateness class for those patients who received PCI predicted 3-year outcomes. In their practice of over 2,000 PCIs performed in the years 2005–2007, 80% were classified as appropriate, 19.4% were uncertain and just 0.6% were inappropriate. The 900-day survival rate was 92.6% in the appropriate category, 91.3% in the uncertain group and 66.9% in the inappropriate group. Multivariate analysis showed that appropriateness class did not predict outcomes; only age and comorbidities were predictive. They conclude that, at least in those years “at a large-volume, academic and private practice,” there were very few inappropriate PCI procedures and those with “uncertain” appropriateness had similar outcomes to those with appropriate indications. The authors interpret these results, I think correctly, to mean that perhaps there are other important considerations in proper case selection than the anatomic extent of disease, particularly as technical proficiency and interventional tools improve in complex subsets.

However, it must be stated that there are several very significant deficiencies in this study, a statement which is not intended as a negative appraisal of how the authors conducted the study, but rather a critical evaluation of how difficult it is to retrospectively evaluate this problem. The authors appear to have included only unprotected left main stenosis PCI as inappropriate, and classified all three-vessel CAD as uncertain; this is not how the Appropriateness Criteria were constructed: ACS, anginal class, diabetes status and LVEF are critical considerations. Only patients without prior CABG and with stable angina were included, and completeness of follow up was not given for the study cohort (but was 98% for the entire group). The only endpoint studied was survival, when obviously improvement in anginal status, freedom from repeat procedures and other events may be important as well.

Further, these results are in conflict with those of Anderson and colleagues.3,4 Using the National Cardiovascular Data Registry (NCDR), the authors showed in a large survey of contemporary PCI practice, as do Brener et al, that most procedures were performed for Class I indications. However, they found a significant relationship between evidence-based indications and in-hospital outcomes. Their conclusion, that “closer adherence to guidelines can reduce variations in care, can improve quality, and may ultimately result in better outcomes,”3 is one of the critical underpinnings of the Appropriateness concept. A follow-up study demonstrated that the ACC-NCDR risk-adjusted mortality model, combined with the PCI guideline5 indication scheme, produces mortality risk estimates by indications classes that are close to actual observed values.4 Hence, the current study runs counter to an established relationship and further raises suspicions regarding the classification of their cases.

For these reasons, the authors’ conclusions should be regarded as interesting and provocative, but require much more detailed study and far more sophisticated analyses with a larger, multicenter database. It may be that the authors have identified some important problems with the criteria, but it is also possible that their case selection and/or categorization do not reflect current practice everywhere. A 7.4% mortality rate in PCI cases deemed “appropriate” over a 3-year follow-up period seems exceedingly high, and may represent a more aggressive case selection than the appropriateness ratings suggest.

Are anatomic-based criteria the best structure for making clinical decisions? Despite the clear limitations of the study, the issue raised by the authors of whether subsequent versions of the Appropriateness Criteria should be anatomic-based, however, is a serious question that should be considered. The antiquated view that single-vessel involvement is not “surgical” disease, but that most three-vessel disease is preferentially a surgical problem, is simply obsolete. Yet, existing guidelines5,6 sustain this approach regarding which revascularization method is best employed. The reason is simple: all of the surgical and medical literature up to now has been based on this simplified version of coronary disease extent.

In theory, the severity and location of a coronary stenosis and the amount of myocardium at jeopardy should correlate closely with symptoms and angiographic and functional testing; unfortunately, in practice, these relationships are not infallible. The problem of course is that in the “real world,” no one knows which test result to rely upon when there are disparate results, clinical manifestations are often difficult to characterize and angiographic interpretation is a subjective art. Although the “rules” of the Appropriateness Committee were set so that such technical issues could not derail the process, the fact is that at least three factors are almost always open to interpretation in making a clinical judgment: 1) the limitations of evaluating an angiogram in determining a “significant” stenosis, including the difficulties of defining the reference-vessel size and the presence of diffuse disease; 2) the definitions of medically refractory angina and optimal medical therapy; and 3) the role of functional tests in demonstrating the extent and severity of ischemia among patients with minimal or difficult-to-interpret symptoms.

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