Editor's Note: Based on Ko DT, Guio H, Wijeysundera HC et al. Assessing the Association of Appropriateness of Coronary Revascularization and Clinical Outcomes for Patients with Stable Coronary Artery Disease. J Am Coll Cardiol 2012; 60:1876-84.

Summary

In the current environment of increasing cardiac morbidity and health care costs, appropriate use criteria have been developed to enhance the rational use of coronary revascularization. This retrospective study conducted in Ontario, Canada, addresses the validation of these criteria against long term outcomes in a real world setting. Appropriate use criteria were applied to a random sample of patients undergoing cardiac catheterization for non-acute indications at all Ontario cardiac invasive centers. Outcomes were compared across cardiac catheterizations stratified by appropriate, uncertain and inappropriate indications for revascularization.

Methods

A total of 1628 patients were selected from a random sample of 8972 patients who underwent cardiac catheterization in the Cardiac Care Network, between April 1, 2006 and March 31, 2007. Patients with a prior history of PCI, CABG and stenosis ≤ 50% were excluded to allow inception of a cohort reflected in the guidelines. Data variables reporting on appropriate use criteria were abstracted from hospital charts retrospectively and each cardiac catheterization was assigned an appropriateness score from 1 to 9. Investigators examined the downstream use of coronary revascularization or lack thereof (medical treatment only) in different appropriateness categories. Outcomes of revascularization versus no revascularization were compared in patients with appropriate, uncertain and inappropriate indications in stratified analyses. Statistical modeling was done to adjust for the potential influence of confounding factors and survivor bias.

Results

Out of 1628 patients undergoing diagnostic cardiac catheterization, 991 patients (61%) had appropriate indications for revascularization and 311 (19%) did not meet appropriate indications; for the remaining 326 patients (20%), the appropriateness of revascularization was uncertain. Among the 997 patients who ended up receiving revascularization, 68% were considered appropriate, 14% were inappropriate, and the remaining 18% were unclear. Of the 991 patients who were considered appropriate candidates for revascularization by AUC, only 69% received revascularization. Across the appropriateness categories, patients who received revascularization were younger with less comorbidity compared to those who were medical managed. Among those with uncertain or appropriate indications, revascularization was performed more often when an interventional cardiologist performed the catheterization.

Amongst patients with appropriate indications, after adjusting for confounding factors, revascularization was associated with a lower hazard for death or repeat ACS (hazard ratio [HR]: 0.61; 95% confidence interval [CI]: 0.42, 0.88). When indications were uncertain (HR 0.57; 95%CI 0.28, 1.16) or inappropriate (HR 0.99, 95% CI 0.48, 2.02), revascularization was not associated with benefit.

Conclusions

Both over and underutilization of revascularization was found using the appropriate use criteria. The authors concluded, "Underutilization of coronary revascularization is associated with significantly increased risks of adverse outcomes in patients with appropriate indications."

Perspective

Optimal care for patients can be defined from the perspective of an individual patient as well as society and health care cost/resource utilization. Broadly speaking, the development of appropriate use criteria (AUC) was an attempt to inter-relate these domains in clinical decision-making with the goals of 1) providing standards for the practicing community 2) promoting consistent quality and access across a variety of health care settings and 3) improving health outcomes.

Coronary revascularization in patients with coronary heart disease remains a subject of scrutiny and debate and often poses a challenging management decision for both physicians and patients. The AUC document for coronary revascularization outlines clinical scenarios using key variables including patient symptoms status, ischemic burden projected by noninvasive tests, intensity of anti-ischemic medical therapy and the extent of coronary disease on cardiac catheterization.¹ These scenarios are given an appropriateness score of 1-9 to delineate inappropriate (score 1-3), uncertain (score 4-6), and appropriate (score 7-9) indications for revascularization. While these criteria provided guidance for revascularization decisions in various clinical scenarios, data regarding their validity in terms of long-term clinical outcomes was lacking.

This retrospective real world setting validation of the AUC for coronary revascularization by Ko et al.,² is a necessary step in assessing the utility of AUC in understanding current practice patterns and their association with long term clinical outcomes.

Ko et al. found that only 69% of patients with an appropriate indication for coronary revascularization underwent revascularization (57% with PCI and 43% with CABG), and the patients who underwent revascularization had a significantly lower risk of death or repeat ACS at three years (HR 0.61; 95% CI 0.42, 0.88) when compared to similarly categorized patients who were treated only with medical therapy, even after multivariate adjustment. Although these findings contradict revascularization vs. medical therapy trial comparisons from COURAGE and BARI-2D, a significant portion of this cohort likely would have been excluded from that trial based on high-risk features.^{3, 4} While these data are encouraging for the use of revascularization in appropriate candidates, it is important to note that the adequacy of cardiovascular medical therapy, other than anti-anginal medications, was not evaluated or described in this non-randomized, retrospective study and likely did not reach levels of adherence observed in the trials.

A substantial subset of patients, 31%, with appropriate indications did not undergo revascularization. This group of patients had a considerably higher unadjusted event rate: 16% compared to 12% in the revascularized group. Hemingway et al. found a similar pattern of underutilization of revascularization (PTCA and CABG) in the UK in the late 1990s.⁵ In their prospective study, 34% patients who were considered appropriate candidates for PTCA were treated medically instead. These medically treated patients were more likely to have angina at follow-up compared to those who underwent angioplasty (odds ratio 1.97; 95% CI, 1.29, 3.00). In addition, 26% patients deemed to be appropriate candidates for CABG were treated medically. Patients who were classified as appropriate candidates for CABG but who ended up receiving medical therapy alone were more likely to have angina (odds ratio, 3.03; 95 % CI, 2.08, 4.42) and death or nonfatal myocardial infarction during the follow-up period (HR: 4.08; 95 % CI, 2.82, 5.93) when compared to patient receiving CABG.

Because this was a retrospective chart review, the reasoning behind decision-making to pursue medical therapy alone in appropriate candidates for revascularization is somewhat elusive. On an examination of the baseline characteristics, a higher risk profile and more co-morbidities are evident amongst the medically treated group suggesting "treatment-risk paradox"⁶ played a role. Certainly, there may have been other unmeasurable factors that prompted the treating physician to prefer one therapy to another and which may have ultimately influenced results.

Another important finding by Ko et al. was that a reduction in events was not seen in patients with a revascularization classification of uncertain (HR: 0.57; 95% CI, 0.28, 1.16) or inappropriate indication (HR: 0.99; 95% CI, 0.48, 2.02). Importantly, a clear signal of harm was also not demonstrated for uncertain or inappropriate indications. The AUC do not take in to detailed account the presence of comorbidities or cardiac risk factors, characteristics that often, in the real world, push clinical decision making one way or another, and, which may have influenced decisions in the "uncertain" or "inappropriate" categories. Of note, a functional assessment of coronary stenosis such as fractional flow reserve (FFR) is not considered substantially in the current AUC document. This is another unmeasured factor, which may have influenced decision-making in these categories. There are several randomized trials with long term follow up that have rigorously validated the use of FFR and this measure could re-categorize patients in the "uncertain" AUC strata.^{7, 8}

Ko et al. did not assess other clinically relevant end points such as freedom from angina and quality of life in the different AUC groups who underwent revascularization versus medical therapy. Hence beneficial effects of revascularization with regards to these end points could not be excluded across the AUC strata.

While these data provide rationale for the use of AUC in clinical decision-making, they also allude to gaps in the current AUC document. The under utilization of revascularization in appropriate candidates is an area of concern and needs to be evaluated further in a prospective fashion. Incorporating AUC into an electronic health record decision support tool⁹ may offer a means to not only study the criteria and their effect on long-term health outcomes, but also potentially change guideline adherence patterns while reducing the number of inappropriate procedures.

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References

1. Patel MR, Dehmer GJ, Hirshfeld JW, Smith PK, Spertus JA. ACCF/SCAI/STS/AATS/AHA/ASNC/HFSA/SCCT 2012 appropriate use criteria for coronary revascularization focused update. J Am Coll Cardiol 2012;59:857-881.
2. Ko DT, Guo H, Wijeysundera HC, et al. Assessing the association of appropriateness of coronary revascularization and clinical outcomes for patients with stable coronary artery disease. Journal of the American College of Cardiology. 2012;60:1876-1884.
3. Boden WE, O'Rourke RA, Teo KK, et al. Optimal medical therapy with or without pci for stable coronary disease. N Engl J Med 2007;356:1503-1516.
4. Group BDS, Frye RL, August P, et al. A randomized trial of therapies for type 2 diabetes and coronary artery disease. N Engl J Med 2009;360:2503-2515.
5. Hemingway H, Crook AM, Feder G, et al. Underuse of coronary revascularization procedures in patients considered appropriate candidates for revascularization. N Engl J Med 2001;344:645-654.
6. Spertus JA, Furman MI. Translating evidence into practice: Are we neglecting the neediest? Arch Intern Med 2007;167:987-988.
7. De Bruyne B, Pijls NH, Kalesan B, et al. Fractional flow reserve-guided pci versus medical therapy in stable coronary disease. N Engl J Med 2012;367:991-1001.
8. Tonino PA, De Bruyne B, Pijls NH, et al. Fractional flow reserve versus angiography for guiding percutaneous coronary intervention. N Engl J Med 2009;360:213-224.
9. Patel MR. Appropriate use criteria to reduce underuse and overuse: Striking the right balance. J Am Coll Cardiol 2012;60:1885-1887.

Keywords: Cardiac Catheterization, Health Care Costs, Morbidity, Ontario

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