Introduction

Since the development of echocardiography by Swedish cardiologist Dr. Inge Edler in the 1950s, there has been tremendous growth in the use of cardiac imaging in the clinical management of cardiac diseases, permitted by substantial advances in imaging technology.¹ Cardiac imaging may be used for diagnosis, surveillance for progression of disease, therapeutic management decision-making, or, increasingly, for procedural guidance. The multitude of imaging options now available permits detailed clinical phenotyping across a range of diseases but may be confusing and overwhelming to physicians selecting the appropriate test for a given patient. Furthermore, there has been increasing national attention on costs of medical imaging and the avoidance of unnecessary testing.

It is in this context that the American College of Cardiology (ACC) and other cardiac professional societies published the 2017 Appropriate Use Criteria (AUC) for multimodality imaging in the assessment of valvular heart disease in the Journal of the American College of Cardiology (JACC), standardizing and summarizing recommendations about the appropriate use of imaging to promote optimal rational care delivery.² Based on the success of this initial document, the ACC, along with partner organizations, recently published 2019 AUC for multimodality imaging in the assessment of cardiac structure and function in nonvalvular heart disease in JACC. The stated goal of the companion AUC document is "to provide a comprehensive resource for multimodality imaging in the context of structural and valvular heart disease."³

AUC for Imaging in Nonvalvular Heart Disease: Scope, Structure, and Methods

Scope

The 2019 AUC document is broad in scope, encompassing cardiac conditions including cardiomyopathy, hypertension, diseases of the aorta, pulmonary arterial hypertension, pericardial disease, supraventricular arrhythmias, and ventricular arrhythmias.

Structure

The document is divided into four sections with a total of eight tables, as outlined in Table 1.

Table 1: Structure of the 2019 AUC for Imaging in Nonvalvular Heart Disease Document³

Section	Topic	Tables
Section 4	Key concepts in structural heart disease	Table A: Definition of stages of valvular heart disease Table B: Definition of stages of heart failure
Section 6.1	Initial evaluation with no prior imaging	Table 1: Asymptomatic patient scenarios Table 2: Symptomatic patient scenarios
Section 6.2	Prior imaging has been performed, and sequential evaluation is required	Table 3: Additional testing to clarify initial diagnosis Table 4: Follow-up testing after diagnosis in asymptomatic patients Table 5: Follow-up testing in symptomatic patients
Section 6.3	Transcatheter interventions for structural heart disease	Tables 6 and 7: Imaging for transient ischemic cerebral attacks and patent foramen ovale Table 8: Pre-, intra-, and post-procedural imaging for left atrial appendage occlusion

Methods

• Development of Clinical Scenarios. The AUC document summarizes recommendations for 102 different clinical scenarios. When possible, clinical scenarios/indications were developed according to the most current ACC/AHA Clinical Practice Guidelines. Once these indications were formed, they were reviewed and critiqued by the parent AUC Task Force and numerous external reviewers across a broad range of specialties. After incorporating this initial feedback, indications were sent to an independent rating panel consisting of experts in structural heart disease and sent back to the writing group for vetting.
• Determination of Appropriateness. As with other AUC documents, the modified Delphi exercise was used to achieve consensus about appropriateness ratings. A rating panel first evaluated all indications independently. Subsequently, members convened for a face-to-face meeting at which each were given their own scores and blinded to a summary of their peers' scores. After this meeting, panel members were asked to provide final scores for each indication independently. Appropriate imaging was defined as "one in which the expected incremental information, combined with clinical judgement, exceeds the expected negative consequences by a sufficiently wide margin for a specific indication that the procedure is generally considered acceptable care and a reasonable approach for the indication."³
• Scoring of Appropriateness. The AUC document rates appropriateness for each indication on a numerical scale from 1 to 9, where a median score of 7-9 indicates that a test for a given indication is "Appropriate (A)," 4-6 indicates it "May Be Appropriate (M)," and 1-3 indicates it is "Rarely Appropriate (R)." The authors emphasize that these categories are somewhat arbitrary and that the numeric designations be viewed as a continuum. Furthermore, many different tests may be appropriate for a given condition, but this does not imply that all need to be obtained.
• Assessment of Agreement. Level of agreement among panelists was defined by RAND and analyzed on the basis of the BIOMED rule for a panel of 14-16 members. As such, disagreement was defined as when at least 5 panelists' ratings fell into both the Appropriate and Rarely Appropriate categories.

Assumptions

The report states some important assumptions:

1. All AUC recommendations apply only to nonurgent clinical circumstances.
2. It is assumed that asymptomatic patients are indeed asymptomatic after extensive questioning, that patients are otherwise receiving optimal standardized care, and that individuals are considered appropriate candidates for all the tests rated.
3. Tests are performed and interpreted by qualified individuals and facilities according to national standards.
4. Appropriateness ratings define the range of modalities that may be reasonable for a specific indication rather than specifying one modality as the best choice and thus require physician judgement in test ordering.
5. Cost is considered as a secondary relationship to clinical benefit when determining net value for a test.

AUC for Imaging in Nonvalvular Heart Disease: Content

The following represents a sample of the overall recommendations and is not meant to be exhaustive. For a more comprehensive summary of recommendations, the original source document should be reviewed.

The initial imaging modality suggested for almost all conditions assessed was transthoracic echocardiography (TTE) because it is typically high yield, low cost, and lacks radiation and other safety concerns. The document scored certain nonvalvular conditions below a 7 for TTE, including assessment of new right bundle branch block, otherwise uncomplicated paroxysmal supraventricular tachycardia, routine evaluation of uncomplicated hypertension, and palpitations with low suspicion of a cardiac etiology. Screening TTE prior to athletic participation was deemed appropriate when either physical exam or electrocardiogram was abnormal, or a family history was deemed concerning.

Cardiac computed tomography (CT) and cardiac magnetic resonance imaging (CMR) were often both suggested for follow-up testing after an initial TTE, such as with suspected ischemic heart disease and aortopathy, and CT, CMR, and transesophageal echocardiography (TEE) are all considered appropriate tests for cardiac mass evaluation. Notable conditions with a stronger recommendation for CMR over CT include evaluation of undefined cardiomyopathy, infiltrative diseases such as amyloidosis/sarcoidosis, hypertrophic cardiomyopathy, and interval assessment of pericardial constriction. Radionucleotide ventriculography was recommended over CT or CMR for interval assessment of cardiac function in patients receiving cardiotoxic chemotherapeutic agents.

TTE, TEE, and carotid Doppler ultrasound were considered appropriate tests for evaluating the etiology of cerebrovascular events including stroke and transient ischemic attack, and magnetic resonance and CT angiography were deemed appropriate to image intracranial and extracranial vessels. For pre-procedural assessment of patent foramen ovale or atrial septal defect, TTE, TEE, CMR, or CT were considered appropriate, and TEE or intra-cardiac echocardiography were recommended as more appropriate intra-procedurally for guidance during septal closure. For pre-procedural assessment of left atrial appendage occlusion candidacy, TEE is most appropriate. Post-procedure, TEE is recommended at 45 days post device implantation.

AUC for Imaging in Nonvalvular Heart Disease: Interpretation/Application

Rather than focusing on one particular imaging modality, the 2019 AUC document refers to specific clinical scenarios or indications, allowing for multiple possible appropriate imaging tests for a given scenario. In doing so, the document reflects how these guidelines are applied in clinical practice, allowing for clinical judgement to discern which modality is most appropriate for a given patient and circumstance.^4-8 For most indications, there are multiple appropriate possible imaging tests, many of which vary in availability, cost, radiation exposure, and quality based on specific patient characteristics. For example, atrial septal anatomy can be appropriately assessed with TTE, TEE, CMR, or CT. Choosing the most appropriate modality/modalities for a given patient in this circumstance depends on integrating multiple patient characteristics, including body habitus, heart rate, age, potential location of septal defect, and need for quantification of left to right shunting.

However, for several clinical scenarios, there may be only one test (Table 2) or no test (Table 3) deemed appropriate. For example, TTE is the only modality considered appropriate for initial evaluation of a patient with "presyncope without other symptoms or signs of cardiovascular disease." In other circumstances, no testing is considered appropriate, as is the case with "preparticipation athlete assessment in a patient with no symptoms, normal examination, and no family history of inheritable heart disease."

Table 2: Scenarios for Which Only One Imaging Modality Is Considered Appropriate or Maybe Appropriate

Indication/Scenario	Imaging Modality	Appropriateness Category (Rating)
Initial evaluation of newly diagnosed right bundle branch block	TTE	May Be Appropriate (5)
Evaluation of episodes of supraventricular tachycardia without other evidence of heart disease	TTE	May Be Appropriate (6)
Palpitations without other signs/symptoms of cardiovascular disease	TTE	May Be Appropriate (6)
Presyncope without other signs/symptoms of cardiovascular disease	TTE	Appropriate (7)
Assessment of volume status in a critically ill patient	TTE	Appropriate (7)
Initial evaluation of suspected hypertensive heart disease	TTE	Appropriate (8)
Routine evaluation of systemic hypertension without signs/symptoms of hypertensive heart disease	TTE	May Be Appropriate (5)
Exertional dyspnea or hypoxemia when a noncardiac etiology of dyspnea has been established	TTE	May Be Appropriate (4)
Initial evaluation for cardiac resynchronization therapy device optimization after implantation	TTE	Appropriate (7)
Re-evaluation (<1 year) of known moderate or greater pulmonary hypertension without change in clinical status or cardiac examination	TTE	May Be Appropriate (4)
Re-evaluation (≥1 year) of known moderate or greater pulmonary hypertension without a change in clinical status or cardiac examination	TTE	Appropriate (7)
Re-evaluation of known heart failure (systolic or diastolic) with a change in clinical status or cardiac examination with a clear precipitating change in medication or diet	TTE	May Be Appropriate (4)
Assessment following left atrial appendage occlusion prior to discharge	TTE	May Be Appropriate (6)
Assessment following left atrial appendage occlusion—long-term follow-up	TTE	May Be Appropriate (5)

Table 3: Scenarios for Which No Imaging is Considered Appropriate

Indication/Scenario

Preparticipation athlete assessment in a patient with no symptoms, normal examination, and no family history of inheritable heart disease

Further characterization of a known or suspected, incidentally noted, small, cardiovascular implantable electronic device-related thrombus identified by TTE in an asymptomatic patient

Re-evaluation (<1 year) in a patient at risk for heart failure without structural heart disease on prior TTE and no change in clinical status or cardiac examination (stage A)

Re-evaluation (<1 year) of known hypertensive heart disease without a change in clinical status or cardiac examination (stage A)

Re-evaluation (<1 year) of heart failure (systolic or diastolic) or cardiomyopathy without a change in clinical status or cardiac examination

Re-evaluation (<1 year) of known aortic dilatation in a patient without bicuspid aortic valve

Re-evaluation (<1 year) of the size and morphology of aortic sinuses and ascending aorta in patients with a bicuspid aortic valve and an aortic diameter >4 cm without one of the following characteristics: aortic dilation >4.5 cm, rapid rate of change in aortic diameter, family history of aortic dissection

Re-evaluation of prior TEE findings for interval change (e.g., resolution of atrial thrombus after anticoagulation) when no change in therapy is anticipated

In most circumstances, however, multiple imaging modalities are considered appropriate or maybe appropriate, and it is up to the judgment of the clinician to decide which is most appropriate for a given patient. Cases with multiple appropriate imaging modalities underscore the value of cardiac imaging specialists beyond interpretation of a study. Indeed, in the current cost-conscious medical environment, one could consider consultation with a cardiac imager as the most "appropriate" next step.

Teaching Points

1. The ACC recently published the 2019 AUC for multimodality imaging in the assessment of cardiac structure and function in nonvalvular heart disease, which follows the 2017 publication of the AUC for multimodality imaging in the assessment of valvular heart disease.
2. A total of 102 nonurgent clinical scenarios was evaluated on the basis of ACC/AHA Clinical Practice Guidelines, rated independently, and subsequently scored from 1 to 9: 1-3 = "Rarely Appropriate (R)"; 4-6 = "May Be Appropriate (M)"; and 7-9 = "Appropriate (A)."
3. TTE is typically an appropriate initial imaging modality for nonvalvular heart disease. However, TTE may be less appropriate for the initial assessment of new right bundle branch block, otherwise uncomplicated paroxysmal supraventricular tachycardia, routine evaluation of uncomplicated hypertension, and development of palpitations with low suspicion of cardiac etiology.
4. Cardiac CT and CMR are often both suggested for follow-up testing after an initial TTE, though notable conditions with a stronger recommendation for CMR over CT include evaluation of undefined cardiomyopathy, infiltrative diseases such as amyloidosis/sarcoidosis, hypertrophic cardiomyopathy, and interval assessment of pericardial constriction.

References

1. Singh S, Goyal A. The origin of echocardiography: a tribute to Inge Edler. Tex Heart Inst J 2007;34:431-8.
2. Doherty JU, Kort S, Mehran R, Schoenhagen P, Soman P; Rating Panel Members; Appropriate Use Criteria Task Force. ACC/AATS/AHA/ASE/ASNC/HRS/SCAI/SCCT/SCMR/STS 2017 Appropriate Use Criteria for Multimodality Imaging in Valvular Heart Disease : A Report of the American College of Cardiology Appropriate Use Criteria Task Force, American Association for Thoracic Surgery, American Heart Association, American Society of Echocardiography, American Society of Nuclear Cardiology, Heart Rhythm Society, Society for Cardiovascular Angiography and Interventions, Society of Cardiovascular Computed Tomography, Society for Cardiovascular Magnetic Resonance, and Society of Thoracic Surgeons. J Nucl Cardiol 2017;24:2043-63.
3. Writing Group Members, Doherty JU, Kort S, et al. ACC/AATS/AHA/ASE/ASNC/HRS/SCAI/SCCT/SCMR/STS 2019 Appropriate Use Criteria for Multimodality Imaging in the Assessment of Cardiac Structure and Function in Nonvalvular Heart Disease: A Report of the American College of Cardiology Appropriate Use Criteria Task Force, American Association for Thoracic Surgery, American Heart Association, American Society of Echocardiography, American Society of Nuclear Cardiology, Heart Rhythm Society, Society for Cardiovascular Angiography and Interventions, Society of Cardiovascular Computed Tomography, Society for Cardiovascular Magnetic Resonance, and the Society of Thoracic Surgeons. J Am Soc Echocardiogr 2019;32:553-79.
4. Hendel RC, Lindsay BD, Allen JM, et al. ACC Appropriate Use Criteria Methodology: 2018 Update: A Report of the American College of Cardiology Appropriate Use Criteria Task Force. J Am Coll Cardiol 2018;71:935-48.
5. Hendel RC, Patel MR, Kramer CM, et al. ACCF/ACR/SCCT/SCMR/ASNC/NASCI/SCAI/SIR 2006 appropriateness criteria for cardiac computed tomography and cardiac magnetic resonance imaging: a report of the American College of Cardiology Foundation Quality Strategic Directions Committee Appropriateness Criteria Working Group, American College of Radiology, Society of Cardiovascular Computed Tomography, Society for Cardiovascular Magnetic Resonance, American Society of Nuclear Cardiology, North American Society for Cardiac Imaging, Society for Cardiovascular Angiography and Interventions, and Society of Interventional Radiology. J Am Coll Cardiol 2006;48:1475-97.
6. Taylor AJ, Cerqueira M, Hodgson JM, et al. ACCF/SCCT/ACR/AHA/ASE/ASNC/NASCI/SCAI/SCMR 2010 Appropriate Use Criteria for Cardiac Computed Tomography. A Report of the American College of Cardiology Foundation Appropriate Use Criteria Task Force, the Society of Cardiovascular Computed Tomography, the American College of Radiology, the American Heart Association, the American Society of Echocardiography, the American Society of Nuclear Cardiology, the North American Society for Cardiovascular Imaging, the Society for Cardiovascular Angiography and Interventions, and the Society for Cardiovascular Magnetic Resonance. J Cardiovasc Comput Tomogr 2010;4:407.e1-33.
7. Hendel RC, Berman DS, Di Carli MF, et al. ACCF/ASNC/ACR/AHA/ASE/SCCT/SCMR/SNM 2009 Appropriate Use Criteria for Cardiac Radionuclide Imaging: A Report of the American College of Cardiology Foundation Appropriate Use Criteria Task Force, the American Society of Nuclear Cardiology, the American College of Radiology, the American Heart Association, the American Society of Echocardiography, the Society of Cardiovascular Computed Tomography, the Society for Cardiovascular Magnetic Resonance, and the Society of Nuclear Medicine. J Am Coll Cardiol 2009;53:2201-29.
8. American College of Cardiology Foundation Appropriate Use Criteria Task Force; American Society of Echocardiography; American Heart Association; et al. ACCF/ASE/AHA/ASNC/HFSA/HRS/SCAI/SCCM/SCCT/SCMR 2011 Appropriate Use Criteria for Echocardiography. A Report of the American College of Cardiology Foundation Appropriate Use Criteria Task Force, American Society of Echocardiography, American Heart Association, American Society of Nuclear Cardiology, Heart Failure Society of America, Heart Rhythm Society, Society for Cardiovascular Angiography and Interventions, Society of Critical Care Medicine, Society of Cardiovascular Computed Tomography, and Society for Cardiovascular Magnetic Resonance Endorsed by the American College of Chest Physicians. J Am Coll Cardiol 2011;57:1126-66.

Keywords: Cardiac Imaging Techniques, Echocardiography, Tomography, X-Ray Computed, Magnetic Resonance Imaging, Follow-Up Studies, Quality of Health Care, Diagnostic Imaging, Tachycardia, Supraventricular, Hypertension, Multimodal Imaging, Heart Valve Diseases, Cardiomyopathy, Hypertrophic, Bundle-Branch Block

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