Head-to-Head Comparison and Temporal Trends of Cardiac MRI Recommendations in ESC versus ACC/AHA Guidelines: A Systematic Review and Meta-Analysis

Abstract

Purpose

To provide a comprehensive head-to-head comparison and temporal analysis of cardiac MRI indications between the European Society of Cardiology (ESC) and American College of Cardiology/American Heart Association (ACC/AHA) guidelines to identify areas of consensus and divergence.

Materials and Methods

A systematic review and meta-analysis was conducted. ESC and ACC/AHA guidelines published until May 2023 were systematically screened for recommendations related to cardiac MRI. The class of recommendation (COR) and level of evidence (LOE) for cardiac MRI recommendations were compared between the two guidelines and between newer versus older versions of each guideline using χ² or Fisher exact tests.

Results

ESC guidelines included 109 recommendations regarding cardiac MRI, and ACC/AHA guidelines included 90 recommendations. The proportion of COR I and LOE B was higher in ACC/AHA versus ESC guidelines (60% [54 of 90] vs 46.8% [51 of 109]; P = .06 and 53% [48 of 90] vs 35.8% [39 of 109], respectively; P = .01). The increase in the number of cardiac MRI recommendations over time was significantly higher in ESC guidelines (from 63 to 109 for ESC vs from 65 to 90 for ACC/AHA; P = .03). The main areas of consensus were found in heart failure and hypertrophic cardiomyopathy, while the main divergences were in valvular heart disease, arrhythmias, and aortic disease.

Conclusion

ESC guidelines included more recommendations related to cardiac MRI use, whereas the ACC/AHA recommendations had higher COR and LOE. The number of cardiac MRI recommendations increased significantly over time in both guidelines, indicating the increasing role of cardiac MRI evaluation and management of cardiovascular disease.

Keywords: Cardiovascular Magnetic Resonance, Guideline, European Society of Cardiology, ESC, American College of Cardiology/American Heart Association, ACC/AHA

Supplemental material is available for this article.

© RSNA, 2024

Summary

European Society of Cardiology guidelines included more cardiac MRI recommendations, while American College of Cardiology/American Heart Association guidelines attributed higher class and level of evidence to their recommendations. For both guidelines, the number of recommendations increased over time.

Key Points

• ■ European Society of Cardiology (ESC) guidelines included more recommendations for the use of cardiac MRI compared with American College of Cardiology/American Heart Association (ACC/AHA) guidelines (109 vs 90).

• ■ ACC/AHA guidelines attributed a higher class of recommendations (class I: 60% [54 of 90] vs 46.8% [51 of 109]; P = .06) and level of evidence (level B: 53% [48 of 90] vs 35.8% [39 of 109]; P = .01) to their recommendations compared with ESC guidelines.

• ■ Both ESC and ACC/AHA guidelines increased their total number of cardiac MRI recommendations over time (+73% for ESC 2017–2023 and +38% for ACC/AHA 2016–2023).

Introduction

Cardiac MRI has emerged as a versatile, cost-effective, noninvasive imaging modality for the comprehensive assessment of various cardiovascular conditions. Its ability to provide high-resolution anatomic and functional information, along with tissue characterization, has contributed to its increasing use in clinical practice (1,2). Thus, cardiac MRI demonstrates a unique versatility allowing for investigation of a broad range of cardiac diseases, and standardized cardiac MRI protocols are available (3).

As the field of cardiac MRI continues to evolve, guidelines from professional societies play a crucial role in providing recommendations for its appropriate use and integration into clinical decision-making. The European Society of Cardiology (ESC) and the American College of Cardiology/American Heart Association (ACC/AHA) independently develop guidelines for the diagnosis and management of cardiovascular diseases, serving as invaluable resources for health care clinicians worldwide. However, they may differ in their recommendations due to variations in available evidence, appraisal of the current literature, expert opinions, and regional considerations.

A mounting body of literature supports the diagnostic and prognostic values of cardiac MRI in various cardiovascular conditions. The growing evidence on the clinical utility of cardiac MRI calls for a careful evaluation of how this evolving knowledge is incorporated into the ESC and ACC/AHA guidelines. Identifying and analyzing discrepancies in cardiac MRI indications are essential steps toward harmonizing guidelines and ensuring consistency in cardiac MRI use to ensure appropriate clinical decision-making and patient care.

This systematic review and meta-analysis aims to provide a comprehensive head-to-head comparison and temporal analysis of cardiac MRI indications within the ESC and ACC/AHA guidelines, focusing specifically on cardiovascular diseases and conditions for which cardiac MRI is recommended. By conducting an evaluation of the similarities, differences, and emerging trends, we aim to elucidate the current landscape of cardiac MRI use, identify areas of consensus and divergence, explore the underlying rationale, and assess the level of supporting evidence for the recommendations across both societies.

Materials and Methods

This systematic review follows a prespecified study protocol that was registered on the PROSPERO International Prospective Register of Systematic Reviews (Comparison and Trends of Cardiovascular Magnetic Resonance Recommendations in ESC versus ACC/AHA Guidelines; CRD42023443515). Results were reported according to the Preferred Reporting Items for Systematic Reviews 2020 statement (4) (Table S1). The nature of this meta-analysis, which involved the synthesis of secondary data from previously published studies without direct involvement of human participants, did not necessitate ethical approval, and thus, the requirement for an institutional review board assessment was waived.

Literature Search and Selection Criteria

All the guidelines available on the ESC (5) and ACC websites (6) up to May 2023 were collected for analysis. The primary databases searched included MEDLINE/PubMed, Embase, and the Cochrane Library for systematic reviews and clinical trials. Guidelines addressing conditions unrelated to the use of cardiac MRI (such as peripheral arterial disease, carotid and vertebral artery disease, pharmacology), and those that did not provide recommendations, were excluded. When a more recent article for the same topic was published, we ensured that all recommendations of the previous article were incorporated into the new one. In case of overlap or replacement, the newer article was retained. The guidelines included in the study are summarized in Table S1.

To identify recommendations related to cardiac MRI, the guidelines were systematically screened using the “ctrl+F” search function with the following terms: “CMR,” “MR,” “MRI,” “magnetic,” “resonance,” “non-invasive,” “functional,” “stress,” “perfusion,” or “imaging,” and if present, the relation to cardiac MRI was evaluated.

Data Extraction

Data extraction was performed using a standardized form that included predefined variables (class of recommendation [COR], level of evidence [LOE], text of recommendation) to ensure consistency in data extraction. After consulting with a librarian, the screening, eligibility, and extraction of recommendations was independently conducted by two authors (N.C., P.A.), and any discrepancy was resolved with the help of a third author (Y.G.). These authors have more than 20 years of cumulative academic experience in cardiology and have previously published systematic reviews and meta-analyses in leading, peer-reviewed cardiology journals.

Statistical Analysis

Regarding cross-sectional comparisons, data were grouped into specific diagnostic subgroups (acute coronary syndrome [ACS], chronic coronary syndrome [CCS], valvular heart disease, heart failure, arrhythmias, congenital heart disease [CHD], hypertrophic cardiomyopathy) for direct comparisons between the latest versions of guidelines. To facilitate temporal comparisons, data were further organized in a manner consistent with earlier publications by von Knobelsdorff-Brenkenhoff et al (7,8): Results from the previous studies were compared with this study to carry a direct temporal comparison. COR and LOE were standardized across the ESC and ACC/AHA guidelines, as previously described (9) (Table). Finally, recommendations that were presented in several guidelines were considered once in the latest guideline document available.

Definitions of Categories for Class of Recommendation and Level of Evidence

Data are summarized using descriptive statistics, with medians (IQRs) or means ± SDs for continuous variables and frequencies with percentages for dichotomous variables. Comparison of categorical variables was assessed using the χ² test, and if more than 20% of the expected cell counts were less than five, the Fisher exact test was used instead. When comparing diagnostic subgroups, the Benjamini-Hochberg procedure was used to reduce the false discovery rate (10).

All P values were two-sided, and a value < .05 was considered statistically significant. The analyses were performed using Stata, release 17.0 (Stata).

Results

Cross-sectional Comparison of Cardiac MRI Recommendations in the Latest ESC versus ACC/AHA Guidelines

Overall.— Figure 1 shows the number of cardiac MRI recommendations in ESC versus ACC/AHA guidelines in 2023, categorized by COR and LOE. The ESC guidelines included 109 recommendations related to cardiac MRI: 51 (46.8%) COR I, 33 (30.3%) COR IIa, 22 (20.2%) COR IIb, and three (2.8%) COR III. With regard to LOE, five (4.6%) recommendations were supported by level A, 39 (35.8%) by level B, and 65 (59.6%) by level C. Six guidelines mentioned cardiac MRI use in free text without giving a COR.

Figure 1:

Graph of cardiac MRI recommendations in European Society of Cardiology versus American College of Cardiology/American Heart Association guidelines in 2023. COR = class of recommendation, LOE = level of evidence.

The ACC/AHA guidelines encompassed 90 recommendations related to cardiac MRI, with 54 (60%) falling under COR I, 28 (31%) under COR IIa, six (7%) under COR IIb, and two (2%) under COR III. Notably, there were no LOE A recommendations, 48 (53%) were classified as level B, and 42 (47%) were classified as level C. Three guidelines mentioned cardiac MRI in free text without a COR.

Overall, the distribution of COR was statistically different between the guidelines (P = .04). Specifically, the ACC/AHA guidelines had a higher proportion of COR I recommendations compared with the ESC guidelines, though not reaching statistical significance (60.0% vs 46.8%; P = .06). Both guidelines showed a similar proportion of COR IIa recommendations (30.3% vs 31.1%; P > .99). However, the ESC guidelines had a significantly higher proportion of COR IIb recommendations (20.2% vs 6.7%; P = .006).

The distribution of the LOE was also found to be statistically different between the ESC and ACC/AHA guidelines (P = .01). The ACC/AHA guidelines had a higher proportion of LOE B recommendations compared with the ESC guidelines (53.3% vs 35.8%; P = .01). There was no LOE A recommendation in the ACC/AHA guidelines and five in the ESC guidelines.

Comparison of cardiac MRI recommendations by diagnostic subgroups.— Figure 2 shows the number of recommendations issued by the ESC and the ACC/AHA, broken down by diagnostic subgroups.

Figure 2:

Graph of cardiac MRI recommendations in European Society of Cardiology (ESC) versus American College of Cardiology/American Heart Association (ACC/AHA) guidelines by diagnosis group. ACS/CCS = acute coronary syndrome and chronic coronary syndrome, COR = class of recommendation, HCM = hypertrophic cardiomyopathy.

For ACS and CCS, the ESC (11,12) and ACC/AHA guidelines (13) included 24 and 14 recommendations, respectively (Tables S2, S3). There was a higher proportion of recommendations for cardiac MRI in ACS and CCS in ESC guidelines, which did not reach statistical significance (24 of 109 [22.0%] vs 14 of 90 [16%]; P = .25). Among the total ACS and CCS recommendations, COR I recommendations accounted for 12 of 24 (50%) in the ESC guidelines versus five of 14 (36%) in the ACC/AHA guidelines (P = .39), COR IIa accounted for four of 24 (17%) versus nine of 14 (64%) (P = .003), COR IIb accounted for seven of 24 (29%) versus none (P = .03), and COR III accounted for one of 24 (4%) versus none (P = .44).

In the free text of the recommendations, the main points of consensus were in (a) the role of cardiac MRI in patients with myocardial infarction with nonobstructive coronary arteries (11,13), and (b) its role in patients with chest pain and negative troponin levels (angina with nonobstructive coronary arteries) (11,13). The main divergences found related to the emphasis in the ESC guidelines on the use of cardiac MRI to determine myocardial viability before revascularization (12), whereas ACC/AHA guidelines emphasized the predictive value of cardiac MRI in estimating the risk of major adverse cardiovascular events (13).

Regarding valvular heart disease, ESC (14) and ACC/AHA guidelines (15) included one and six recommendations, respectively (COR I: none versus five [83%], COR IIa: one [100%] versus one [17%]). There was a significantly higher proportion of recommendations for valvular heart disease in the ACC/AHA guidelines (0.9% vs 6.7%; P = .03), but there was no evidence of a difference in the distribution in COR between the two guidelines (P = .29). Despite the limited number of recommendations in the ESC guidelines, there were several mentions of cardiac MRI use as free text that aligned with ACC/AHA recommendations (Table S4). The ESC’s choice to mention cardiac MRI as free text in the guidelines without formally stating recommendations with COR and LOE indication partially explains the discrepancy observed.

Regarding heart failure, the ESC guidelines (16) outlined four recommendations: two (50%) fell under COR I, one (25%) under COR IIa, and one (25%) under COR IIb. The ACC/AHA guidelines (17) presented three recommendations: one (33%) classified as COR I, one (33%) as COR IIa, and one (33%) as COR IIb. There was no evidence of a difference in COR and the proportion of recommendations related to cardiac MRI between the two sets of guidelines (P = .90 and .87, respectively). The free text of the recommendations overlapped almost completely, reflecting a general consensus. As mentioned in previous studies (9), cardiac MRI indications were more detailed in ESC guidelines, especially with regard to myocardial tissue characterization and the distinction between ischemic and nonischemic myocardial damage (Table S5), but without specifying specific cardiac MRI sequences to implement.

Regarding arrhythmias, the ESC guidelines (18) included 20 recommendations: six (30%) fell under COR I, 11 (55%) under COR IIa, and three (15%) under COR IIb. The ACC/AHA guidelines (19) gave nine recommendations: two (22%) classified as COR I, five (56%) as COR IIa, and two (22%) as COR IIb. There was a higher proportion of recommendations in ESC guidelines, which did not reach statistical significance (19.2% vs 10.2%; P = .10). There was no evidence of a difference in the proportion of COR between the two groups (P = .85). In the free text of the recommendations, the ESC emphasized the role of cardiac MRI and included specific recommendations in survivors of sudden cardiac death, patients with neuromuscular disorders, and athletes and in the choice of implantation of an implantable cardioverter defibrillator in patients with a dilated cardiomyopathy. Both sets of guidelines agree on cardiac MRI use in patients with ventricular arrhythmias to investigate the presence of structural heart disease and estimate the risk of sudden cardiac death. Details are presented in Table S6.

Regarding CHD, the ESC guidelines (20) gave four recommendations: two (50%) fell under COR I and two (50%) under COR IIa. The ACC/AHA guidelines (21) presented 19 recommendations: 16 (84%) classified as COR I and three (16%) as COR IIa. The proportion of CHD recommendations was statistically higher in ACC/AHA guidelines (3.7% vs 21.1%; P < .001), while there was no evidence of a difference in the proportion of COR between the two guidelines (P = .19). In reviewing the free text of the guidelines, the ESC refers to “indications for the use of CMR [cardiac MRI]” but does not provide any formal recommendations. Moreover, in ESC guidelines for CHD, the authors recommended the use of late gadolinium enhancement imaging and T1 mapping for detection and quantification of myocardial fibrosis and scar (see Table S7), while in the corresponding ACC/AHA guidelines, there was no such mention. Details are presented in Table S7.

For hypertrophic cardiomyopathy, the ESC guidelines (22) included 10 recommendations: three (30%) fell under COR I, four (40%) under COR IIa, and three (30%) under COR IIb. The ACC/AHA guidelines (23) presented eight recommendations: five (62%) classified as COR I and three (38%) as COR IIb. There was no evidence of a difference in the proportion of recommendations and COR between the two guidelines (P = .94 and P = .11, respectively). The free text of the recommendations overlapped almost completely, reflecting a general consensus. In terms of specific imaging sequences, both guidelines suggest the use of late gadolinium enhancement sequences as the cornerstone for evaluating the extent of cardiac fibrosis and the risk of sudden cardiac death (details presented in Table S8).

For aortic diseases, the ESC guidelines (24) included 11 recommendations: eight (73%) fell under COR I, two (18%) under COR IIa, and one (9%) under COR IIb. The ACC/AHA guidelines (25) presented 26 recommendations: 18 (69%) classified as COR I and eight (31%) as COR IIa. The proportion of aortic disease recommendations was statistically higher in ACC/AHA guidelines (26 of 90 [29%] vs 11 of 109 [10.1%]; P < .001). In the free text of the recommendations, the main consensus found was in the role of cardiac MRI for acute aortic syndrome and coarctation of aorta. The main divergences related to the ACC/AHA, including specific recommendations in patients with Marfan, Loey-Dietz, and Turner syndromes as well as in pregnancy, postpartum, and cases of inflammatory aortitis (25).

For peripheral artery diseases, the ESC guidelines (26) included five of five (100%) recommendations of COR I. The ACC/AHA presented (27) two recommendations: one (50%) classified as COR I and one (50%) as COR III. In the free text of the recommendations, both societies agreed on the role of imaging before invasive revascularization, especially in asymptomatic patients with peripheral artery disease. On the other hand, the ESC mentioned specific indications for cardiac MRI in cases of carotid or renal stenosis.

Temporal Evolution of Cardiac MRI Recommendations in ESC versus ACC/AHA Guidelines

Overall.— The overall number of recommendations for cardiac MRI in both the ESC and ACC/AHA guidelines significantly rose over time. In the case of the ESC, the number increased from 63 in 2017 (7) to 109 in 2023 (+73%). For the ACC/AHA, the number increased from 65 in 2016 (8) to 90 in 2023 (+38%) (Fig 3). The magnitude of increase was higher in ESC guidelines (P = .03).

Figure 3:

Graph of temporal evolution of the number of cardiac MRI recommendations in European Society of Cardiology (ESC) and American College of Cardiology/American Heart Association (ACC/AHA) guidelines. COR = class of recommendation, LOE = level of evidence.

There were increases across all COR categories in the ESC guidelines: +31% for COR I, +175% for COR IIa, and +120% for COR IIb. For the ACC/AHA guidelines, the increases in the corresponding categories were +74%, +22%, and +0%, respectively.

LOE also saw significant changes over time in the ESC guidelines (-17% for LOE A, +144% for LOE B, and +59% for LOE C). In the ACC/AHA guidelines, there was a considerable increase in LOE B recommendations (+129%), a slight decrease in LOE C (-4.5%), and no increase in LOE A.

Comparison by diagnostic subgroups.— In the ESC guidelines for ACS and CCS (11,12), there was a decrease in the number of recommendations between 2017 (7) and 2023 (29 vs 24) (Fig 4) and a statistically significant decrease in the proportion of recommendations for ACS and CCS (29 of 63 [46.0%] vs 24 of 109 [22.0%]; P = .001). This decrease is attributable to substantial reorganization and regrouping of individual recommendations between the two versions of the guidelines. Therefore, the number of COR I among ACS and CCS recommendations decreased (the proportion fell from 20 of 29 [69%] to 12 of 24 [50%]; P = .16). COR IIa recommendations remained stable (four of 29 [14%] to four of 24 [17%]; P = .40), and COR IIb increased (five of 29 [17%] to seven of 24 [29%]; P = .30). The overall distribution of COR I, IIa, and IIb between 2017 and 2023 did not change (P = .43). In the ACC/AHA guidelines for ACS and CCS (13), there was an increase in the number of recommendations between 2016 (8) and 2023 (nine of 65 [14%] to 14 of 90 [16%]; P = .78) (Fig 5). The number of COR I increased (two of nine [22%] to five of 14 [36%]; P = .66). From the free text of the guidelines, it was observed that the decrease in ESC recommendations over time was explained by a consolidation of individual recommendations in the field of CCS, while both societies emphasized the major role of cardiac MRI in myocardial infarction with nonobstructive coronary arteries in their latest versions.

Figure 4:

Graph of temporal evolution of cardiac MRI recommendations in European Society of Cardiology (ESC) guidelines by diagnostic subgroups (2017–2023). ACS/CCS = acute coronary syndrome and chronic coronary syndrome, COR = class of recommendation.

Figure 5:

Graph of temporal evolution of cardiac MRI recommendations in American College of Cardiology/American Heart Association (ACC/AHA) guidelines by diagnostic subgroups (2016–2023). COR = class of recommendation.

Regarding valvular heart disease, cardiac MRI was not included in the 2017 ESC guidelines, while only one recommendation (COR IIa) was retrieved in 2023 (14) (Fig 4). In the ACC/AHA guidelines (15), there were six recommendations for cardiac MRI use in 2016 and in 2023, with a high proportion of COR I (83.3% COR I in both groups) (Fig 5).

For heart failure, ESC recommendations (16) for cardiac MRI increased from two to four, while the proportion of COR I remained the same (one of two and two of four [50%]) (Fig 4). ACC/AHA recommendations (9) for cardiac MRI slightly decreased from four to three. In 2016 all recommendations were classified as COR IIa; however, in the 2023 guidelines, the distribution of recommendations changed, with 33% classified as COR I, 33% as COR IIa, and 33% as COR IIb (Fig 5).

Regarding arrhythmias, ESC recommendations (18) for cardiac MRI significantly increased in the latest guidelines from four of 63 (6%) to 20 of 109 (18.3%) (P = .04), without evidence of increase in the proportion of COR I (two of four [50%] to six of 20 [30%]; P = .58) and COR IIa (one of four [25%] to 11 of 20 [55%]; P = .59) categories (Fig 4). ACC/AHA recommendations (19) for cardiac MRI also increased but to a lesser degree (from three of 65 [5%] to nine of 90 [10%]; P = .36) (Fig 5). Upon examination of the free text of the ESC guidelines, the increase in recommendations in this area was mainly due to implementation of the role of cardiac MRI in patients with ventricular arrhythmias of unclear etiology; assessment of the risk of sudden cardiac death; decision to implant an implantable cardioverter defibrillator; and development of specific rhythm-related recommendations in dilated cardiomyopathy, sarcoidosis, and neuromuscular diseases.

In CHD guidelines, four new recommendations regarding cardiac MRI were found in the 2023 ESC guidelines (20), while none existed in 2017 (Fig 4). ACC/AHA guidelines (21) already included a notable number of recommendations for cardiac MRI in 2016, with a slight increase in 2023 (17 vs 19; P = .44) (Fig 5). The proportion of COR I recommendations was already high for ACC/AHA in 2016 and remained stable (82.4% and 84.2%, respectively).

Finally, the number of ESC recommendations (22) regarding cardiac MRI use in hypertrophic cardiomyopathy did not change between 2017 and 2023 (remained at 10 recommendations) (Fig 4). On the other hand, ACC/AHA recommendations (23) for cardiac MRI increased from four to eight (P = .76), with an increase in the proportion of COR I (0% vs 62.5%; P = .08) (Fig 5). This increase allowed for a broad consensus to be achieved for hypertrophic cardiomyopathy among the societies, as expressed in the Comparison of cardiac MRI recommendations by diagnostic subgroups section.

Discussion

The main findings of this systematic review can be summarized as follows: (a) the ESC guidelines included more recommendations than the ACC/AHA guidelines regarding the use of cardiac MRI; (b) the ACC/AHA guidelines attributed higher COR to their recommendations for cardiac MRI use compared with the ESC guidelines; (c) the ACC/AHA guidelines assigned higher LOE to their recommendations for cardiac MRI; (d) both ESC and ACC/AHA guidelines increased the total number of their recommendations related to cardiac MRI over time; and (e) the main areas of consensus in the guidelines were found in the fields of heart failure and hypertrophic cardiomyopathy, while the main divergences were in valvular heart disease, arrhythmias, and aortic disease (Fig 6).

Figure 6:

Central figure summarizes the main points of the article. ACC/AHA = American College of Cardiology/American Heart Association, ACHD = adult congenital heart disease, COR = class of recommendation, CMR = cardiac MRI, ESC = European Society of Cardiology, ICD = implantable cardioverter defibrillator, LGE = late gadolinium enhancement, LOE = level of evidence, VHD = valvular heart disease.

Our study’s first finding was that the ESC guidelines included more recommendations regarding cardiac MRI use compared with the ACC/AHA guidelines. Further analysis of the diagnostic subgroups provides a more detailed understanding of the distribution of recommendations within each society. The increased number of recommendations in the ESC guidelines can be attributed to a greater number of recommendations in the fields of coronary syndrome (24 vs 14) and rhythm disorders (20 vs nine). For the former, analysis of the ESC recommendations revealed a widespread consensus in considering the clinical use of stress perfusion cardiac MRI, while for the latter, the ESC emphasized the role of cardiac MRI to a significantly greater extent and included specific recommendations on various clinical conditions. The fact that there were no new recommendations regarding rhythm disorders published by the ACC/AHA since 2017 may also contribute to the differences with the ESC. The ACC/AHA guidelines featured a higher number of recommendations in the CHD subgroup, while in the ESC guidelines, we found a lack of recommendations regarding the use of cardiac MRI in valvular heart disease. Interestingly, most of the recommendations issued by the ACC/AHA were found as free text in the ESC guidelines, especially in the field of mitral and aortic regurgitation, where the role of cardiac MRI in accurately and reproducibly measuring regurgitant volume and fraction is well recognized. Both societies include recent, high-quality, and overlapping studies (28,29), and timing of publication of the guidelines is not a confounding factor, as the ESC guidelines are more recent (2021 vs 2020). These differences probably reflect variations in expert opinions regarding the use of cardiac MRI in different clinical contexts and a different stylistic choice in conveying key messages by the authors, and the publication of new studies in this domain since the release of the guidelines (30) shows that assessment of valvular regurgitation by cardiac MRI is a rapidly evolving field that already has high-quality evidence. In terms of specific advanced imaging sequences, we found little information available across the guidelines with no evidence of differences between the two societies.

Our second notable observation pertains to the COR assigned to cardiac MRI recommendations in the ESC and ACC/AHA guidelines. The ACC/AHA guidelines included a greater proportion of COR I recommendations, reflecting a robust endorsement from experts who deem cardiac MRI not only beneficial but also a crucial component in patient care. This endorsement starkly contrasts with the actual use of cardiac MRI, which remains markedly underused, representing less than 0.1% of all diagnostic procedures in the United States as of 2018. Meanwhile, cardiac MRI is more extensively used in the European Union, which implies a disconnect between the recommendations outlined in the guidelines and the real-world implementation of cardiac MRI in clinical practice patterns (2).

Our third finding relates to the LOE attributed to cardiac MRI recommendations in the different guidelines. We found that the ACC/AHA guidelines assigned a higher LOE to their cardiac MRI recommendations. Specifically, the ACC/AHA guidelines included a larger number of recommendations with LOE B, indicating moderate-quality evidence. In contrast, the ESC guidelines had a higher proportion of recommendations with LOE C, suggesting a lower quality of evidence supporting cardiac MRI. An interesting observation relates to the low number of LOE A recommendations in both guidelines (five in the ESC and none in the ACC/AHA) despite the publication of high-level evidence in the literature (randomized control trials, meta-analysis of high-quality studies) for cardiac MRI (1).

Last, our analysis demonstrated an overall significant and harmonious increase in the total number of cardiac MRI recommendations in both the ESC and ACC/AHA guidelines over the years. It is of particular interest that the minor decrease observed in the number of ESC recommendations for coronary syndrome over the years was common across all functional imaging modalities—and thus, is not limited to the use of stress perfusion cardiac MRI and is attributable to a restructuring of previously individual recommendations in the ESC guidelines. Cardiac MRI is progressively gaining importance in the management of an array of cardiovascular conditions. Recent analyses revealed the widespread adoption of cardiac MRI globally, highlighting both convergences and divergences in its application, indications, educational prerequisites, training modalities, and encountered challenges (31). Notably, regions like the United Kingdom exhibit remarkable success in the increased application of cardiac MRI (32), possibly influenced by their early and expansive integration of cardiac MRI into clinical guidelines, especially in areas like chest pain assessment and acute myocardial infarction, leading to discernible regional use variations when juxtaposed with the United States (33). As global initiatives work toward the comprehensive incorporation of cardiac MRI in clinical protocols, our findings may provide pivotal insights for the development of strategies to boost its integration and uptake.

This study had limitations. First, it focused solely on the guidelines of the ESC and ACC/AHA, and thus, our findings may not reflect the global landscape of cardiac MRI use. It is possible that other regional or specialty-specific guidelines may have different perspectives and recommendations regarding the use of cardiac MRI. Second, the guideline documents themselves are subject to periodic updates, and our analysis was based on the most recent versions available at the time of our study. Future revisions of the guidelines may alter the number and content of cardiac MRI recommendations. Last, although we compared the number, COR, and LOE of cardiac MRI recommendations, our study did not delve into the specific clinical contexts and indications for cardiac MRI use in each guideline, and a greater or lesser number of recommendations does not in itself determine guideline quality. Further research is warranted to explore the clinical implications and context-specific considerations associated with the recommendations.

In conclusion, our systematic review and meta-analysis revealed several notable differences between the ESC and ACC/AHA guidelines regarding the use of cardiac MRI in various cardiovascular diseases and conditions. The ESC guidelines encompassed a greater number of recommendations for cardiac MRI use, while the ACC/AHA guidelines attributed a higher COR and better LOE to their cardiac MRI recommendations. The main areas of consensus in the guidelines were found in the field of heart failure and hypertrophic cardiomyopathy, while the main divergences were in valvular heart disease, arrhythmias, and aortic disease. The increasing number of recommendations over time in both sets of guidelines signified the expanding recognition of cardiac MRI as a valuable imaging modality in cardiovascular medicine. These findings and the differences found in the analysis of diagnostic subgroups emphasize the need for continued research and consensus-building efforts to establish standardized approaches and evidence-based recommendations for cardiac MRI use in clinical practice. Future guideline updates should consider incorporating emerging evidence and refining the clinical guidance for cardiac MRI, taking into account the variations in available evidence and regional perspectives.

Competency in Medical Knowledge

By enhancing our understanding of discrepancies between the two guidelines, this comparative analysis serves as a valuable resource for health care clinicians, policymakers, and researchers, enabling them to make evidence-based decisions and optimize the use of cardiac MRI in clinical practice.

Translational Outlook

The identification of any discrepancies or gaps in the guidelines underscores the importance of incorporating emerging evidence into future iterations, so that the recommendations best align with the most current understanding of cardiac MRI’s diagnostic and prognostic capabilities. Simultaneously, by critically evaluating the scientific basis and LOE for cardiac MRI recommendations, we aim to identify potential areas for further research.