With a single ‘wave of the wand’: cardiovascular magnetic resonance transforms the diagnostics of acute coronary syndrome

This editorial refers to ‘CMR reclassifies the majority of patients with suspected MINOCA and non MINOCA’, by K. Liang et al., https://doi.org/10.1093/ehjci/jead182. The term acute coronary syndrome (ACS) refers to a multitude of diseases leading to signs and symptoms of myocardial ischaemia, including ST-elevation or non-ST-elevation myocardial infarction (STEMI/NSTEMI), as well as unstable angina.1 ACS accounts for a third of total deaths amongst those aged older than 35 years.2 Accordingly, it is responsible for considerable associated hospitalizations and healthcare costs.3 Currently, the diagnosis of ACS is based on the presenting symptoms of the patient, combined with electrocardiographic changes and elevated circulating high-sensitivity troponin levels. However, it is being increasingly recognized that conditions other than STEMI/NSTEMI and unstable angina may present as an ACS. Namely, aortic dissection, vasculitis, arrhythmias, myocarditis, cardiomyopathies, heart failure, and Takotsubo disease may have the same clinical and biochemical presentation.4 Having said that, Liang et al. attempted to answer the important question of making a definitive diagnosis in patients presenting with ACS, but without any abnormalities in epicardial coronary arteries (also known as myocardial infarction with non-obstructive coronary arteries-MINOCA). The authors retrospectively analysed a single-centre cohort of 888 patients with ACS presentations. All included participants had coronary lesions (if any) with <50% lumen obstruction on angiography and were referred for cardiovascular magnetic resonance (CMR) for the purpose of a diagnostic workup for MINOCA. The authors contrasted the working diagnosis at referral (myocardial infarction, myocarditis, Takotsubo syndrome, cardiomyopathy, or non-specific) with the final diagnosis based on the CMR findings of each patient. This permitted the calculation of the diagnostic reclassification rate afforded by CMR in this cohort. The authors reported that the majority of patients had a non-MINOCA diagnosis (73%) (myocarditis, Takotsubo's syndrome, cardiomyopathies, or normal CMR/non-specific findings), whilst only a minority had confirmed MINOCA (27%). Additionally, the authors identified an impressive 78% reclassification of patients, compared with the original working diagnosis. Most notably, the authors showed that a considerable proportion of patients with a final diagnosis of infarction would have been missed, had they not been evaluated with CMR.5 CMR is the gold standard for the non-invasive assessment of cardiac function as well as the characterization of myocardial tissues, notably without the use of ionizing radiation. Additionally, CMR can demonstrate even mild alterations of bi-ventricular function that can potentially be missed by other imaging modalities.6 Furthermore, abnormalities in CMR-derived tissue characterization have good agreement with histologically identified structural lesions.7 Consequently, the role of CMR in the evaluation of various disease states in the field of cardiology is well established.8–10 The authors included 888 patients in their cohort, out of a total of 14 296 patients that presented with ACS and underwent coronary angiography at their centre in the span of 10 years (2011–21). This corresponds to a percentage rate of 6.2% of patients that presented with an ACS and had a non-diagnostic coronary angiography. The findings of the study at hand clearly demonstrate that CMR can offer impressive incremental utility in such cases, by clarifying the underlying diagnosis and facilitating the initiation of appropriate treatment or subsequent diagnostics. Thus, the diagnostic approach to ACS should not stop at a non-diagnostic coronary angiogram, but should instead continue searching for an underlying aetiology using diagnostic tools like CMR. Despite these important findings, it should be noted that the median time from presentation to scan in this study amounted to 21 days. It could be argued that a combination of referral delay by the referring physician combined with limited scan time availability could have contributed to this average delay of 3 weeks. As the authors acknowledge, CMR also has an excellent diagnostic yield when performed in the acute setting (within 3 days of presentation). Although availability and scheduling issues can invariably be circumvented in daily practice, the bottleneck of a delayed CMR referral for such patients is a different matter that requires more in-depth analysis. Understandably, concerns regarding longer scanning times were warranted in previous years. Nevertheless, currently available short protocols, as proposed by the Society of Cardiovascular Magnetic Resonance (SCMR), render the use of CMR feasible even in cases of cardiac emergencies. Referring physicians should thus avoid delays in referrals, as these could lead to the loss of therapeutic ground, which can be avoided by the timely determination of a diagnosis using CMR. An additional point that merits discussion is the cost–benefit trade-off of a CMR-based diagnostic approach in patients with ACS. It has already been demonstrated that CMR can optimize resource utilization in the diagnosis of coronary artery disease.11,12 However, little is known specifically in the setting of ACS, which should be addressed in future studies in order to clarify the financial aspect of CMR use in patients with ACS and non-diagnostic coronary angiography. To conclude, advanced as the practice of cardiology may be, it is not and should never be set in stone. In striving to do better for subgroups of patients that may be underserved by current approaches, CMR transforms the practice of cardiology with a single ‘wave of the wand’, elevating it to the exacting standards of 21st-century personalized and patient-centred medicine. None declared.