The Misapplication of the 2009 AUC
Application of AUC in the setting of coronary revascularization comes in a time of a more than 40-year trend of improved outcomes in coronary heart disease, undoubtedly based on both prevention and treatment measures. Moreover, there has been a marked decrease in use of PCI, especially after the publication of the Clinical Outcomes Utilizing Revascularization and Aggressive Drug Evaluation (COURAGE) trial. This study, published in 2007, intended to compare a strategy of medical therapy plus PCI versus medical therapy alone in patients with stable ischemic heart disease (SIHD), showed that PCI did not improve survival or prevent myocardial infarction compared with medical therapy alone. However, in COURAGE, patients with significant ischemia on myocardial perfusion study (MPS) had a trend toward mortality benefit from revascularization. Despite this, there has been widespread application of COURAGE as support against the use of PCI, and subsequent decline in the use of and geographic variation in PCI for SIHD. Because of this perceived lack of benefit for PCI, and the perception of financial incentives driving the decision to revascularize, there has been emphasis placed on identifying perceived overuse of revascularization as opposed to underuse, despite the strong evidence arguing for emphasis on the latter.
In this tenor, Chan et al. studied the appropriateness of PCI in a multicenter, prospective study of over 500,000 patients in the NCDR undergoing PCI for acute and nonacute indications. For acute indications, 98.6% of PCIs were classified as appropriate. For nonacute indications, 50.4% of PCIs were classified as appropriate; moreover, 11.6% of these PCIs were classified as inappropriate. With just a superficial understanding of what constitutes these figures, many would presume that there is a significant overuse of PCI. However, in examining the numbers treated within the acute and nonacute indications, 82.7% of the patients in this study had PCI for acute indications. Thus, only 4.1% of the study population had PCI that was defined as 'inappropriate.' Nearly 40% of defined inappropriate PCI was based on AUC scenario 12B, which was defined by one- or two-vessel CAD with no proximal LAD involvement, CCS Class I or II symptoms, a low risk stress test and none/minimal anti-ischemic therapy. The evidence base that would justify this particular scenario as inappropriate for PCI is absent. To the contrary, PCI has been shown to provide significantly superior symptom benefit versus medical therapy alone, in several studies enrolling a substantial number of patients with sub-CCS Class III symptoms. Regardless, the intent of this study was to identify PCI overuse.
Chan et al. studied over 200,000 nonacute PCIs in the NCDR with 12.2% classified as inappropriate. With societal and cultural implications, Chan et al. argued that higher rates of PCIs in men, whites and those who had private insurance, may, in part, be due to procedural overuse. Ironically, these are the very groups that are generally considered more likely to make informed choices.
A more recent study assessed over 8000 patients undergoing CABG and approximately 34,000 patients undergoing PCI for nonacute indications in New York and classified appropriateness based on AUC. Out of the PCIs able to be rated by AUC (28% lacked sufficient information), 36.1% were appropriate, 14.3% were inappropriate and 49.6% were uncertain by AUC. Of note, 91% of PCIs that were classified as inappropriate had one- or two-vessel CAD with no proximal LAD involvement, and sub-CCS III symptoms. Comparatively, only 1.1% of CABGs were deemed inappropriate by AUC.
Indeed, a more impactful and meaningful study in terms of outcomes would assess and underscore the number of patients that do not receive appropriate PCI per AUC criteria – a percentage likely significantly larger than 4.1%, or even 14.3%. A study by Hemingway et al. in 2008 followed over 9000 patients with suspected stable angina and found that up to 57% of patients deemed appropriate for angiography did not undergo the procedure, which translated into a difference in a combined endpoint of death or acute coronary syndrome on 3-year follow-up (HR 2.67; 95% CI: 1.77–4.01). Ko et al. retrospectively studied 1625 patients with stable coronary artery disease, of which only 69% with appropriate indication for coronary revascularization underwent treatment. Though possibly confounded by underlying comorbidities, this comparison retains validity in that all patients in the study were well enough to undergo coronary angiography. Compared those that did not get revascularized, patients receiving revascularization with an appropriate indication had a lower adjusted hazard of death or acute coronary syndrome (HR 0.61; 95% CI: 0.42–0.88). The depiction in the public and lay media has been slanted in the direction of perceived overuse of PCI, largely due to a rather myopic interpretation of the data. The true health hazard is in lack of access to PCI and underuse.
The translation of AUC to clinical practice has been unfortunate. A study by Khawaja et al. studied the clinical implications of abnormal MPS based on AUC. Out of the patients receiving appropriate MPS, 21.0% had studies noting high-risk summed stress scores. Out of these, only 32.4% underwent subsequent angiography, with 50% of these patients proceeding to revascularization. The actual clinical outcomes related to implementation of AUC were questionable in a retrospective study by Barbash et al., which followed 3817 patients undergoing elective PCI. There was no significant difference in major adverse cardiac event rates after PCI at 30 days or 1 year in patients with appropriate, uncertain or inappropriate AUC indications. Similarly, in a study performed assessing over 200,000 patients having undergone nonacute PCI in the NCDR, a hospital's proportion of inappropriate PCIs was not associated with in-hospital mortality, bleeding or medical therapy at discharge. Yet, there has been growing importance placed on AUC that has even translated to a palpable economic impact. For example, New York state Medicaid payments are linked to AUC-based adjudication of PCI appropriateness.