The American College of Cardiology, together with other specialty and subspecialty societies, has recently published Appropriate Use Criteria (AUC) for the Detection and Risk Assessment of Chronic Coronary Disease (CCD) [
1]. The document updates the 2013 AUC for the management of Stable Ischemic Heart Disease (SIHD) [
2] and covers the use of radionuclide imaging, stress echocardiography (echo), coronary computed tomography angiography (CCTA) and calcium scoring, stress cardiovascular magnetic resonance (CMR), and invasive coronary angiography. The document aims to complement clinical practice guidelines and aid clinicians in decision-making for common clinical scenarios in CCD and implement best practices in patient care. Recommendations are given for symptomatic and asymptomatic patients with a spectrum of scenarios in each of the two categories.
The Society for Cardiovascular Magnetic Resonance (SCMR) was represented on the writing and rating panels of this document and approved its final version. Here we discuss the recommendations in the AUC from the perspective of the CMR practitioner and in the context of other relevant guidance.
Changes from the 2013 AUC for multimodality imaging in SIHD
In the last decade, numerous studies, trials, and meta-analyses have established the diagnostic accuracy, cost-effectiveness, and predictive value of stress perfusion CMR in patients with CCD. In recognition of this increasing evidence for CMR, the ratings for stress CMR in the 2023 AUC for Multimodality Imaging in CCD have generally increased compared with the 2013 AUC for Multimodality Imaging in SIHD. The AUC classes of stress CMR are now equivalent to nuclear imaging and stress echocardiography across almost all clinical scenarios. The document recommends that where more than one test is rated as ‘appropriate’ in a clinical scenario, clinician judgment, test advantages and disadvantages, and local expertise should govern the choice of test for an individual patient. This recommendation now allows practitioners to choose stress CMR as the first line non-invasive functional imaging modality across a range of presentations of CCD.
The most recent AUC also includes a new category of ‘No Test’, and indeed is the first document that provided this AUC rating option across all the described clinical scenarios in CCD. This is an important addition because most patients presenting with stable chest pain are at low risk of adverse cardiac events. This addition provides useful guidance to clinicians when it may be in the best interest of the patient not to undergo further assessment.
Also of note, in addition to clinical pre-test probability assessment, the 2023 AUC document incorporates targeted patient clinical symptoms, scenarios, atherosclerotic cardiovascular disease risk assessment, and other factors that were not previously emphasized.
The 2023 AUC for multimodality imaging in CCD in the context of other guidelines
The 2023 update brings the recommendations for the appropriate use of stress CMR more in line with other international practice guidelines. Both the 2021 AHA/ACC/ASE/CHEST/SAEM/SCCT/SCMR Guideline for the Evaluation and Diagnosis of Chest Pain [
3] and the 2019 ESC Guidelines for the Diagnosis and Management of Chronic Coronary Syndromes [
4] generally rate stress CMR, nuclear imaging and stress echocardiography with the same level of indication, including Class 1 indications in many clinical scenarios.
However, some differences with these practice guidelines remain. In the 2021 US chest pain guidelines [
3], CMR and positron emission tomography (PET) have an additional Class 2a indication for the quantification of myocardial blood flow reserve (MBFR) to improve diagnostic accuracy and enhance risk stratification and to detect coronary microvascular disease. Similarly, the 2019 ESC guidelines assign transthoracic Doppler of the left anterior descending artery, stress CMR, and PET a Class 2b recommendation for assessing patients with suspected microvascular disease [
4]. The 2023 AUC document does not specifically cover coronary microvascular disease and includes only a ‘may be appropriate’ rating for PET and CMR in patients with normal anatomical coronary imaging, which may be applicable to patients with suspected coronary microvascular disease.
Importantly, the 2023 AUC guidelines also do not specifically address sex as a biological variable, while the 2021 US chest pain guidelines mention “the uniqueness of chest pain in women”. CMR may be particularly suited for the assessment of women with CCD as it does not expose patients to ionizing radiation, has a higher spatial resolution for smaller-sized hearts than nuclear imaging, and can quantify myocardial blood flow in women with chest pain but no obstructive coronary disease.
Comparison of imaging modalities
Consistent with the process of previous AUC development, only the median score from the rating panel was used in formulating the AUC class as “appropriate” (A), “may be appropriate” (M), or “rarely appropriate” (R) in each of the 64 described clinical scenarios. The AUC process aims to collect inputs from a broad array of stakeholders with variable experience in the different diagnostic tests. These rating panel members were presented with a description of the current literature relevant to each of the clinical scenarios and were asked to score the appropriateness of each modality based on clinical impact, safety, and cost. Stress CMR remains a modality less familiar in practice to some of the rating panel members, compared to the other modalities, and this likely prohibited CMR in achieving higher rating scores in some of the scenarios.
Notably, the AUC specifically refrained from competitive ranking of imaging modalities, citing 'the limited availability of comparative evidence, patient variability, and the range of capabilities available in any given local setting’. This approach aims to provide general evidence of each modality toward clinical use, but it neglects the growing body of evidence that shows higher diagnostic accuracy and effectiveness of management of PET and CMR over SPECT and stress echocardiography to detect significant coronary artery stenosis. Stress CMR has been compared with SPECT in single-center and multi-center studies, which have consistently shown higher diagnostic accuracy over SPECT [
5,
6] and comparable diagnostic performance of CMR against PET [
7,
8]. While less evidence exists for their direct comparison, meta-analyses have indicated higher performance of CMR against stress echocardiography [
7,
8].
The AUC also has not provided specific guidance on the cost-effectiveness of the different imaging modalities—an important factor in clinical practice, particularly when multiple tests are available. Within a group of stable chest pain patients in the US, stress CMR was a cost-effective gatekeeping tool, and its use avoids unnecessary invasive coronary angiography [
9]. Similarly, within the UK, the CE-MARC study performed a cost-analysis of different strategies that included different combinations of exercise stress testing, SPECT, CMR, and coronary angiography, and found that the two most cost-effective strategies were ones that utilized CMR [
10].
Instead of competitive rankings, the AUC encourage physicians to consider patient-specific and local factors in choosing an appropriate test. To aid this decision-making process, the document includes sections listing the ‘advantages’ and ‘limitations’ of the different tests. For CMR, the advantages are listed as: “Can assess wall motion, ischemia, and infarction in one study. Can quantify myocardial blood flow to improve test accuracy and assess myocardial and pericardial diseases. Can perform viability testing.” A key advantage of stress CMR that may have also warranted a mention is its unique ability to provide a co-registered assessment of cardiac structure/function, ischemia, and tissue characterization, which accurately quantifies ischemia and infarct burden at both global and segmental levels. In addition to characterizing ischemia/viability from coronary disease, this multi-parametric capability of CMR can help simultaneously diagnose other causes of chest pain and cardiac symptoms. In particular, myocarditis and pericarditis may not be detectable using some of the other imaging modalities but are readily identifiable on CMR and their inflammatory states can be quantified to monitor disease progression. Hypertrophic cardiomyopathy and other cardiomyopathies, such as arrhythmogenic cardiomyopathy (ACM) which may require clear visualization of subtle abnormal anatomy, are better assessed using CMR, which has high spatial resolution and is not limited by imaging windows. During a standard CMR, at least a qualitative assessment of valvular heart disease is also routinely made, allowing, for example, the detection of significant aortic stenosis as a potential cause of chest pain.
The ‘limitations’ of CMR are listed in Table A of the AUC document as ‘Claustrophobia, artifacts, and safety precautions with metallic medical devices’. However, in clinical routine, claustrophobia can usually be overcome with sedation or the use of wide bore MRI systems, and artifacts do not affect CMR more than other imaging modalities. Additionally, technical development of CMR has progressed to the extent of being able to mitigate a majority of common artifacts related to irregular heart rhythms and breathing. And lastly, specific processes exist for CMR to enable diagnostic quality imaging in patients with metallic devices, and the vast majority of pacemakers, implantable cardioverter defibrillators, and other implantable cardiac monitors (e.g. loop recorder) as well as metallic heart valves are no longer contraindicated for CMR [
11,
12].
Table B of the AUC lists “Examples of Inconclusive Stress Imaging” and for CMR, “artifacts and arrhythmia”. In reality, with the current technology available and appropriate operator training, inconclusive stress CMR related to artifacts and arrhythmias is rare; inadequate vasodilator response is more common but can often be identified by assessment of splenic switch-off for adenosine stress or quantitative perfusion and is a limitation of all pharmacologic stress testing modalities.
Overall, CMR will be an excellent, and often the preferred choice for the assessment of CCD, when multiple tests are available locally. CMR offers the most comprehensive assessment of both coronary disease and other causes of chest pain in a single examination and is a test that is free of ionizing radiation and with high diagnostic accuracy.