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Appropriate Use Criteria for Cardiac Radionuclide Imaging: Part I
Assessment of myocardial perfusion can be used to diagnose coronary artery disease (CAD) and, in patients with known or suspected CAD, provide important information about risk that can guide patient management decisions. Stress imaging modalities include stress echocardiography, cardiac magnetic resonance imaging, cardiac computed tomography, and radionuclide imaging. Radionuclide myocardial perfusion imaging (MPI) is commonly used to assess CAD. In fact, nearly 8 million MPI scans are performed each year in the United States.1
The appropriate use of radionuclide MPI may benefit patients; however, inappropriate use of MPI may be potentially harmful to patients and generate unwarranted costs to the healthcare system. Therefore, it is essential that the healthcare community knows how to effectively integrate and utilize MPI in daily clinical care and takes a proactive role in ensuring best practices.
The Appropriate Use Criteria (AUC) for Cardiac Radionuclide Imaging (the term “radionuclide imaging” in the AUC is synonymous with radionuclide MPI) were developed by the American College of Cardiology Foundation (ACCF), along with key cardiology societies, to serve as a guide for the responsible use of radionuclide MPI in single-photon emission computed tomography (SPECT) and positron emission tomography (PET).2 The AUC were updated in 2009 to reflect changes in test utilization and new clinical data based upon a broad range of clinical experiences and available evidence-based information. The indications were drawn from common applications, anticipated uses, and current clinical practice guidelines. Sixty-seven clinical scenarios were developed by a writing group and scored by a separate technical panel to designate various clinical indications for which radionuclide MPI is appropriate, inappropriate, or uncertain. Together with sound clinical judgment, the AUC can help practitioners determine whether radionuclide MPI is appropriate in individual patient cases.
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The indications included in the AUC represent the majority of cardiovascular nuclear testing scenarios and fall into 8 general categories, which will be covered in a 2-part series of the CardioWatch e-newsletter. Part I will review 4 types of indications, including CAD in symptomatic and asymptomatic patients, risk assessment for patients with a prior stress imaging test and/or chronic CAD, and preoperative risk assessment prior to noncardiac surgery.
MPI FOR THE DETECTION OF CAD IN SYMPTOMATIC PATIENTS2
To assess the appropriateness of radionuclide MPI for the detection of CAD, patients with ischemic equivalent, defined as symptoms associated with CAD or abnormal electrocardiogram (ECG) findings, were divided based on the likelihood of CAD by the AUC panel. According to the AUC, patients with an intermediate or high likelihood of CAD are considered appropriate for MPI, as shown in Figure 1. MPI is also appropriate for patients with a low likelihood of CAD if they are unable to exercise or have an uninterpretable ECG. For patients with possible acute coronary syndrome (ACS), radionuclide imaging is considered appropriate regardless of the thrombolysis in myocardial infarction (TIMI) score (a risk scoring system used to measure coronary blood flow during percutaneous coronary angioplasty) or whether troponin levels are elevated.
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MPI FOR THE DETECTION OF CAD IN ASYMPTOMATIC PATIENTS2
As shown in Figure 2, radionuclide MPI is only considered appropriate for asymptomatic patients with a high risk for coronary heart disease (CHD) according to NCEP/ATP III risk criteria. The presence of newly diagnosed heart failure, ventricular tachycardia, or unexplained troponin elevations are appropriate indications for MPI. The appropriateness of MPI is “uncertain” for asymptomatic patients with an intermediate risk of CHD and nondiagnostic ECG, and for patients with atrial fibrillation. The appropriate use of MPI for syncope is based on intermediate or high CHD risk.
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MPI FOR PATIENTS WITH PRIOR TEST RESULTS2
As shown in Figure 3, radionuclide MPI is not appropriate for patients with normal imaging test results performed within the past 2 years. If prior results were abnormal or the patient currently has an intermediate or high risk of CHD, the appropriateness of MPI is uncertain. When new or worsening symptoms are present, MPI is appropriate with prior abnormal results. However, the appropriateness of MPI is uncertain if the prior results were normal.
For patients with a prior coronary artery calcium (CAC) score of less than 100, MPI is not appropriate. MPI is appropriate when the patient’s CAC score is greater than 400 or when the patient has a CAC score between 100 and 400 plus an intermediate risk of CHD. However, the appropriateness of MPI is uncertain for patients with a CAC score between 100 and 400 plus low to intermediate risk of CHD. For patients with an intermediate- to high-risk Duke treadmill score, MPI is appropriate for assessing the risk of CAD.
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MPI FOR PREOPERATIVE RISK ASSESSMENT2
The appropriateness of preoperative MPI prior to noncardiac surgery is shown in Figure 4. In general, MPI is considered inappropriate for preoperative risk assessment except for intermediate-risk surgery or vascular surgery when at least 1 risk factor is present and the patient has limited functional capacity.
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SUMMARY
The objective of the AUC is to improve patient care and health outcomes in a cost-effective manner but is not intended to ignore ambiguity and nuance intrinsic to clinical decision-making. The recommendations are intended as a practical guide for practitioners who order radionuclide MPI and should be considered in conjunction with clinical experience and judgment.
In general, the use of MPI is appropriate for the diagnosis and risk assessment of intermediate- and high-risk CAD patients, according to the AUC. MPI testing for low-risk patients, routine repeat testing, and general screening in certain clinical scenarios are considered less appropriate.
Be sure to look for the next issue of CardioWatch, which will cover the remaining 4 types of indications, including the use of radionuclide MPI for risk assessment within 3 months of ACS, risk assessment postrevascularization, assessment of viability, and the evaluation of ventricular function.
REFERENCES
| 1. |
AMR Data on File. 2009. |
| 2. |
Hendel RC, Berman DS, DiCarli MF, et al. ACCF/ASNC/ACR/AHA/ASE/SCCT/SCMR/SNM 2009 appropriate use criteria for cardiac radionuclide imaging. J Am Coll Cardiol. 2009;53:2201-2229. |
CONSULTANT DISCLOSURE
Len Fromer, MD from the University of California, Los Angeles and the David Geffen School of Medicine at UCLA is the consultant for this CardioWatch series. Dr Fromer is a speaker and consultant for Astellas Pharma US, Inc.
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| ©2011 Astellas Pharma US, Inc. All rights reserved. 011F-012-3679-1 8/11
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