Chapter 13: The Appropriate Use of Nuclear Cardiology Techniques

The past several decades have witnessed remarkable advances in medical care, including cardiac imaging. This rapid pace of technological development has provided a wealth of diagnostic and therapeutic tools that have impacted both quality and longevity of an individual's life.^1,2 Particularly notable are the advances in cardiac imaging, which have revolutionized how patients are diagnosed and treated, enhancing the sensitivity and specificity for the detection of ischemic heart disease and related these results to patient outcomes, thereby resulting in an impact on survival and quality of life.

However, the exuberance for nuclear cardiology, including single-photon emission tomography myocardial perfusion imaging (SPECT MPI) and positron emission tomography (PET), has resulted in a dramatic increase in its use and has contributed to the spiraling costs of health care cost.^3,4 Furthermore, unnecessary testing may result in additional diagnostic tests and potentially unjustified therapeutic intervention, further escalating costs but also potentially impacting on patient health. Furthermore, the use of nuclear cardiology procedures exposes patients who do not need the testing to avoidable risks, as related to ionizing radiation and stress testing.

The Medicare Payment Advisory Commission (Med-PAC) found that the rate of medical imaging between 1999 and 2002 far exceeded other medical services, with an annual increase by 10.1% during this time period (Fig. 13-1).^2,4 Although it was concluded that no determination of inappropriateness was possible to be made due to lack of credible data,⁴ concern was raised as to the possible performance of unnecessary testing, which may have included financial motivation on the part of the providers. In addition to the excessive growth rate, SPECT/PET utilization demonstrated wide geographic variability across the United States, suggesting that differences in the volume of stress imaging procedures were unlikely a consequence of demographics or the prevalence of comorbid conditions alone,^2,7 as these data were corrected for disease severity. Possible contributing factors included the nonuniform distribution of specialized imaging centers, self-referral practice at specific centers, and variances in the understanding of the medical literature.²

Based on the concerns of overuse and misuse noted above, providers, regulators, and payers raised concern about overuse and misuse of radionuclide imaging, especially with regard to the negative economic consequences.^2,5 In response to this and in an effort to reduce spending, health plans began to use radiology benefits management (RBM) companies to act as procedural governors by developing mechanisms to constrain the exponential growth of imaging and limit associated costs.^2,3 The most common used programs included provider exclusion from imaging network and prior notification and precertification.^1,2 These RBM programs reflected a contract with payers and usually functioned with a model based on incentives to reduce volume and costs even though there was little evidence for the improvement of quality of care. The rules that governed the RBM were not necessarily literature based and often lacked transparency in informing providers of why a test was denied. This process varied from one RBM/health plan to another and caused delays in patient care, increased provider and staff work, and led to increased inefficiency. The mere presence of these onerous programs underscored the need for improved guidance regarding optimal patient selection for specific procedures.^6,7

Appropriate Use Criteria

In response to fiscal pressures and with the goal of optimizing test/patient selection to improve the utilization of cardiovascular procedures in an efficient and contemporary fashion,^1,3 appropriate use criteria (AUC) were developed by several organizations, including the American College of Cardiology Foundation (ACCF) and the American Society of Nuclear Cardiology (ASNC).^8–10 The first set of AUC was released in 2005, focused in the indications of cardiac radionuclide imaging¹¹ with an emphasis on the performance of the right test for the right patient at the right time. The appropriateness of a cardiovascular procedure or test is based on the definition showed in Table 13-1. A revised and expanded version of the AUC for radionuclide imaging was published in 2009.¹² However, the latest criteria were in the form of a multimodality testing document for use with stable ischemic heart disease published in 2013. The indications and ranking for SPECT and PET imaging were intended to replace the prior AUC documents for stable ischemic heart disease scenarios.¹⁶ The goal of these 2013 multimodality AUC was to determine which testing modalities, if any, are reasonable for a specific indication. Importantly the new AUC introduced new definitions for categories of appropriate use, which include "may be appropriate" and "rarely appropriate" replacing the prior terminology of "uncertain" and "inappropriate" (Table 13-2).¹ However, original and revised definitions of appropriate use should not be used interchangeably as each set of documents was created independently and the raters of the scenarios were asked to utilize the specific definitions for these terms.

Although the 2009 and 2013 multimodality AUC ratings were similar for most indications, Table 13-3 shows the differences of appropriateness categorization between the 2009 radionuclide imaging AUC and the 2013 multimodality AUC.

AUC Methodology

How the ratings for appropriate use were developed is important, in order to understand that there is a rigorous methodology behind these criteria. The methods for AUC have evolved since the first publication in 2005, but the process remains based in the application of the validated, prospectively based modified Delphi approach and previously published UCLA/RAND Appropriateness Method (Fig. 13-2).^13,14 Following the selection of a topic, and determination of definitions and assumptions, a writing group is created, clinical scenarios, definitions, and assumptions are created, which then undergo an external review. Subsequently, a literature review and guideline mapping is performed, a review panel of more than 30 members then provide feedback, and the writing group revises each of the indications and summary tables that are prepared for the indications raters. The rating panel composed of a variety of individuals with specific backgrounds rate each indication. A second rating is performed after the rating panel has a face-to-face meeting to scores the different scenarios. The final rating is then compiled with the appropriate use score of 7 to 9 as appropriate, 4 to 6 as may be appropriate, and 1 to 3 as rarely appropriate.¹⁵ However, only the category of appropriate use is presented as the final rating, so as to avoid artificial comparisons among the testing modalities.

The indications are grouped under common headings in a structured approach, with the implementation of tables for diagnosis and risk assessment, symptomatology, prior testing, previous revascularization, evaluation for a change in clinical status, and consideration for special circumstances. A hierarchic approach of the indications is used to stratify a clinical situation to one of the indications.^3,16 This flowchart is designed to place clinical conditions into a hierarchy to help assess the appropriateness of a test (Fig. 13-3). The indications are not entirely comprehensive and are not intended to be, are meant to identify common clinical scenarios in the evaluation and follow-up of stable ischemic heart disease (SIHD) that could embrace the majority of contemporary practice, attempting to determine which testing modalities, may or may not be reasonable for a specific indication.¹⁶

The new multimodality AUC emphasizes not on which test is best for each indication but rather on whether a specific testing modality is reasonable for a specific indication. Seven different diagnostic procedures are presented including radionuclide imaging, in order to offer aid to clinical decision making for the detection and risk assessment of stable ischemic heart disease. Eighty indications were included in the most recent publication.¹

AUC for Radionuclide Imaging

Indications are often constructed based on pretest probability of CAD or global coronary heart disease (CHD) risk, exercise ability and electrocardiogram (ECG) interpretability (Appendix 13-1). The first subsection focuses on symptomatic patients where the clinicians should estimate the likelihood of coronary artery disease (CAD) before selecting testing based on age, sex and typical or atypical presentation based on the Diamond and Forrester pretest probability of CAD.³⁶ The next subsection is for asymptomatic patients and takes into account the global CHD risk estimating the probability of experience a cardiovascular event over a given period of time. The third subsection is related to newly diagnosed heart failure, evaluation of arrhythmias without ischemic equivalent or prior cardiac evaluation, and syncope without ischemic equivalent.

The next part of the AUC is designed for patients with prior testing, with subsections for patients without previous intervening revascularization, as sequential testing, as follow-up testing in stable patients or with new or worsening symptoms, also includes another section for postrevascularized patients with percutaneous coronary intervention (PCI) or coronary artery bypass grafts (CABG), that are symptomatic or asymptomatic (Appendix 13-2). The third section is for preoperative evaluation of noncardiac surgery in view of the type of surgery, functional capacity, previous cardiac imaging, active cardiac conditions, and clinical risk factors.¹⁶ This mimics the clinical practice guidelines and is discussed in detail in Chapter 16. The final section focuses on the value of testing to determine the exercise level prior to initiation of exercise prescription or cardiac rehabilitation in patients with and without revascularization, or heart failure.

The multimodality AUC provides several key conclusions:

• Guided by pretest probability, exercise ability and ECG interpretability stress radionuclide and echo imaging are appropriate for most categories.

• For asymptomatic patients, only exercise ECG is appropriate for high-risk patients who can exercise and had an interpretable ECG.

• Follow-up testing is largely inappropriate in asymptomatic patients or those with stable symptoms.

• Stress testing is appropriate for patients with syncope who have at least an intermediate likelihood of CAD.

• Among asymptomatic patients who have undergone revascularization, RNI is appropriate only for those with incomplete revascularization or when a substantial period of time has elapsed after coronary revascularization.

• For preoperative assessment, testing is indicated only for high-risk surgery in patients with poor or unknown functional capacity who also have ≥1 risk factor.

• In asymptomatic patients those with low and moderate global CHD risk but with an interpretable ECG and have ability to exercise testing is rarely appropriate.

• Those patients with prior testing less than 2 years ago and those with PCI or CABG less than 5 years ago, follow-up testing is rarely appropriate.

• As part of preoperatory evaluation before noncardiac surgery, testing is rarely appropriate prior to low-risk surgery, in asymptomatic patients with normal prior testing less than 1 year ago and in patients with moderate to good functional capacity or no clinical risk factors.

• Testing is rarely appropriate as part of evaluation prior to exercise prescription or cardiac rehabilitation, except in patients with heart failure.

AUC Implementation and Evaluation

The development of AUC is not likely sufficient alone to impact on changes in utilization. Appropriate utilization must be monitored, and this information used to impact on changes in practice. Numerous abstracts and papers focusing on the evaluation of appropriate use of radionuclide imaging have been published, clearly demonstrating that appropriateness is a metric that can be assessed. For radionuclide imaging, it appears that approximately 10% to 20% of the studies are performed for inappropriate indications (or rarely appropriate) (Table 13-4) and the most common reasons for inappropriate use of SPECT imaging are readily identifiable. In the largest multicenter study published with 6351 patients enrolled, the inappropriate use of MPI was noted in 14.4% of the patients, with a range of 4% to 22% at different sites. Importantly, this trial defined key categories of inappropriate SPECT use, as women and younger asymptomatic patients were more likely to undergo inappropriate testing. The most common indications of inappropriate SPECT use was in low-risk patients who had an interpretable ECG and were able to exercise, accounting for 44.5% of the inappropriate indications (Table 13-5).²⁰ In addition to the many studies examining the appropriateness of SPECT MPI, Winchester et al.¹⁷ evaluated the appropriateness used criteria for MPI clinical utility use for PET and found that appropriate or uncertain indications for PET were present in 79.5% and 10.4%, respectively, with an inappropriate rate of 10.2%, demonstrating that the categorizations for PET appropriate use are similar to those for SPECT.^18–33

A recent meta-analysis systematically review the literature on appropriate use criteria, with a total of 22,443 patients from 22 studies, showed that inappropriate studies are consistently less likely to be abnormal and lack ischemia than appropriate MPI, 15.6% versus 42%, respectively. However, multiple trials have described that even when SPECT MPI is performed for inappropriate or rarely appropriate indications, there remain a number of patients who have abnormal results (Table 13-6). These data raise the concern that the AUC may discourage performing a radionuclide examination and therefore miss important information. However, when the association of outcomes of patients with appropriateness categorization is compared, inappropriate studies carried far less associated risk even when abnormal.⁴¹ In a large prospective study, Doukky et al.²⁸ evaluated the appropriateness of SPECT MPI related to its prognostic value and demonstrated that when SPECT MPI was performed for inappropriate indications, an abnormal perfusion imaging failed to predict major adverse cardiac events, in stark comparison to the excellent risk assessment provided by SPECT imaging when performed for appropriate indications. Inappropriate testing was associated with a higher revascularization rate but lacked effectiveness for risk stratification and had high societal costs and unnecessary radiation exposure. Conversely, when MPI was used for the appropriate indications, it demonstrated a high prognostic value with patients with higher rates of all-cause mortality and cardiac death. Another finding from the aforementioned meta-analysis is a trend from noncardiology physicians compared to cardiologist to order more inappropriate studies, consistent with similar findings in other studies.^30,49

The development and publication of AUC is changing the practice patterns, supported by the development of tools for quality improvement. Many educational initiatives have been implemented. One of these strategies is the Choosing Wisely Campaign, a national program created with the goal to reduce waste in the health care system and avoid risks associated with unnecessary treatment, with a list of recommendations created by the ACC standing clinical councils, recommend procedures that should not be performed or rarely performed in specific circumstances. Four of the five items are based on AUC³⁷ and are shown in Table 13-7.

Also a variety of tools have been created that include web-based and portable device applications to foster the appropriate use of cardiovascular technology. There is an increasing trend of physicians that incorporate smartphones and tablets into their daily practice,³⁸ with the rate of smartphone usage among physicians has been reported as high as 75% and 81%.^39,40 An AUC smartphone app can be used to determine the level of appropriateness in less than a minute, demonstrating decision support in a time-effective manner, is free, convenient and easy to use, with the potential to promote the usage of AUC and possibly aid reduction of cost and radiation burden. (Fig. 13-4).³⁸ Internet-based instruments have also been created to reduce inappropriate imaging such as the FOCUS PMI (FOCUS: Formation of Optimal Cardiovascular Utilization Strategies, PMI: Imaging Performance Improvement Module), which is a national web-based community and quality improvement instrument created to increase use of the AUC and improve practice patterns. FOCUS has showed that the use of a self-directed quality improvement software and interactive community, makes possible for clinicians to decrease their proportion of test not meeting appropriateness of use.³⁴ Initial data from this program reveal that this tool resulted in a 50% reduction in the rate of inappropriate tests, from 10% to 5%, which was sustained during the follow-up period.³⁴

Other interventions to reduce inappropriate testing include educational initiatives, peer review with feedback, and point-of-care decision support systems.^19,28,42,43 Overall, it appears that education alone seems insufficient to reduce inappropriate MPI, and that provider feedback and/or decision support systems are key in reducing unnecessary imaging.^44–46 A meta-analysis by Chaudhuri et al. designed to evaluate the quality improvement initiatives and its impact in appropriate testing showed that the presence of a physician audit and feedback mechanism is associated with lower odds of inappropriate testing (OR, 0.36 [95% CI, 0.31–0.41]; p < 0.001), while studies without this interventions had no significant impact on inappropriate testing (OR, 0.89 [95% CI, 0.61–1.29]; p = 0.51). This positions quality interventions with physician audit and feedback as an important process impacting the effectiveness of cardiovascular testing.⁴⁷ A prospective multicenter study by Lin et al. studied the use of a multimodality decision support tool and demonstrated that appropriate testing increased from 49% to 61%, and inappropriate testing was reduced from 22% to 6%, and required an average of 2 minutes to perform this consultation.⁵⁰ In contrast, a study which analyzed the alternative approach of prior authorization as frequently done by health insurance carriers, showed a lack of effect of this strategy on the rate of inappropriate MPI and physicians adherence to AUC.⁴⁸

The AUC and various implementation strategies allow clinicians to optimize their use of cardiac imaging, by maximizing the clinical impact of cardiovascular technology and permitting cost reductions through the elimination of unnecessary tests and procedures.^1,3 Although adoption by private payers has been slow, the United States Congress passed legislation (Protecting Access to Medicare Act [PAMA]) in 2015 that mandates the use of the AUC for advance cardiac imaging, including nuclear cardiology, for all Medicare beneficiaries.³⁵ Following a 3-year period of data collection and self-evaluation of appropriateness patterns, physicians who demonstrate low adherence to the AUC may be required to obtain prior authorization before the performance of advanced cardiac imaging. The AUC developed by the American Colleague of Cardiology (ACC) will be included in this programs, as well several other provider lead entities, including the American College of Radiology (ACR).^52,53

A recent study by Winchester et al.⁵³ examined differences between the ACC AUC and the ACR appropriateness criteria for radionuclide MPI. Notably, 52.2% of the indications of the ACC AUC could not be matched to an ACR rating, and 20.9% were in disagreement related to appropriateness. Further support for the use of the ACCF AUC is that the detection of myocardial ischemia was infrequent among patients rated as "inappropriate" by the ACC AUC (2.6%), whereas patients rated as "usually not appropriate" by the ACR AUC had ischemia noted in 17.5% of the patients. Thus, clear differences between criteria for appropriateness exist, which likely impact on the utility of these documents for clinical practice.

The appropriate use of radionuclide cardiac imaging, along with other applications of cardiovascular technologies, is of critical importance in the current era in order to maximize the value of such testing and to potentially reduce the costs and risks associated with unnecessary examinations. AUC were developed to promote change in utilization patterns and increase the value of cardiac imaging, including SPECT and PET. However, these documents must be incorporated into clinical practice in order to have an impact. The evaluation of clinician performance regarding technology utilization is paramount for the optimization of care and includes clinical decision support and audit/feedback mechanisms to allow for providers to continuously improve their practice.⁵¹