Appropriateness Criteria for Coronary Revascularization in Stable-Angina Patients

Coronary artery revascularization is performed to relieve symptoms, improve quality of life, and prevent cardiovascular death. In most patients with unstable angina who undergo coronary revascularization, these benefits are achieved. However, determining when coronary artery revascularization is appropriate for patients with stable angina remains a contentious issue. There seems to be an indication that stable-angina patients who are at increased risk for cardiac death and ischemic events experience a higher rate of event-free survival after revascularization by coronary artery bypass grafting or percutaneous coronary intervention (PCI) than with medical therapy alone.

The results of the widely publicized COURAGE (Clinical Outcomes Utilizing Revascularization and AGgressive drug Evaluation) trial¹ have generated discussion about the efficacy of PCI with medical therapy in comparison with medical therapy alone in patients with stable coronary artery disease (CAD). The COURAGE researchers concluded that revascularization as part of an initial management strategy does not reduce the risk of death, myocardial infarction (MI), or major cardiovascular events in this patient group. However, several factors should be considered when evaluating these results. In a review of 6 randomized, controlled coronary revascularization trials,² the COURAGE trial had the lowest mortality rate per year, at 1.7%. More than 35,000 patients were considered, but only 3,071 met the stringent eligibility criteria of the trial. Most of the enrolled patients were white men, and only 5% had congestive heart failure. In addition, many risk factors were well controlled, and patients with left ventricular ejection fractions (LVEFs) <0.30 were excluded. Consequently, the COURAGE trial showed that PCI reduces anginal symptoms but does not provide survival or recurrent-ischemic-event benefits in white male patients who have stable angina, preserved LVEF, few-to-no congestive heart failure symptoms, controlled diabetes mellitus, controlled blood pressure, and controlled levels of low-density-lipoprotein-cholesterol (≤70 mg/dL).

Although PCI can improve symptoms without offering survival benefits in low-to-moderate-risk patients with stable angina, what about high-risk patients with stable angina? The TIME (Trial of Invasive vs Medical therapy in the Elderly) study³ provides valuable information on this issue. In this study, elderly patients with chronic stable angina despite antianginal therapy were randomly assigned to medical therapy (with an increase in drugs or dosage) or to revascularization. The mortality rate for TIME's medical therapy group (5.8%) was one of the highest in contemporary revascularization trials. At 1 year, event-free survival was higher for patients who underwent revascularization, and this trend was maintained at 4 years.⁴

The finding that the benefits of revascularization can differ slightly in low-risk versus high-risk patients with stable angina raises the important question of how to evaluate cardiac risk in the stable-angina group. Coronary anatomy, LVEF, and symptoms are important factors in considering PCI in a patient with stable angina. Which coronary artery is involved in CAD affects survival. Survival rates are lower for those with left main CAD. The involvement of multiple coronary arteries also decreases survival rate. Patients with preserved LVEF are probably considered to be at lower risk, whereas patients with LVEFs <0.35 might have poor outcomes without revascularization. Symptoms play an important role in the decision as well. Revascularization should probably not be chosen for a patient whose mild angina does not reduce the quality of his or her life, provided that functional studies support that decision.

One of the most valuable risk-assessment tools is single-photon emission computed tomography (SPECT), which provides information about the percentage of the left ventricle at risk. Using SPECT to measure perfusion, physicians are able to identify the location and extent of ischemia. The use of SPECT as a tool for predicting therapeutic benefit from revascularization procedures has been elegantly studied by Hachamovitch and colleagues.⁵

Those investigators, in a large retrospective study of 5,366 patients without previous revascularization who underwent SPECT, showed that patients with minimal myocardial ischemia were more likely to survive with medical therapy without early revascularization, whereas revascularization resulted in progressive improvements in survival in patients with increasing myocardial ischemia. Moreover, in patients with little or no ischemia, early revascularization carried a greater risk (∼50%) than did medical therapy alone. Survival benefits were seen with revascularization if patients had extensive myocardial ischemia (≥20%).⁵ Therefore, revascularization benefits patients with significant ischemia, but may harm those with none.

To aid in assimilating this information into clinical practice, the American College of Cardiology Foundation Appropriateness Criteria Task Force⁶ reviewed clinical scenarios in which revascularization is considered, ranking each scenario as appropriate or inappropriate for revascularization or as “uncertain,” indicating that revascularization might be beneficial but that more research or patient information is necessary. In evaluating each situation, the experts considered results from noninvasive tests (for example, SPECT), the patient's functional class and success on medical therapy, and his or her coronary anatomy. Revascularization was considered inappropriate for patients who were deemed low-risk on SPECT and were asymptomatic or had mild symptoms in the absence of optimal medical therapy—and also for patients who lacked multivessel or proximal left anterior descending coronary artery involvement. Revascularization is favored in most intermediate-risk patients. High-risk patients (those with 15%–20% of myocardium at risk) benefit from revascularization (with the exception, possibly, of asymptomatic patients).

In summary, stable-angina patients who are low-risk on the basis of these criteria should not undergo revascularization procedures unless they experience significant angina, in which case revascularization can improve quality of life. Revascularization can offer survival benefits in high-risk, stable-angina patients, who are formally defined as those with multivessel coronary artery involvement or left main CAD, LVEFs <0.35, and myocardial ischemia affecting ≤15% to 20% of the left ventricular myocardium. In the clinical setting, however, physicians can gain valuable knowledge regarding the decision to recommend revascularization by considering a patient's symptoms and evaluating the results of noninvasive studies.