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Magnetic resonance imaging in ischaemic heart disease

Non-Invasive Imaging


In the last few years the evidence on the use of cardiovascular magnetic resonance (CMR) has rapidly accumulated, and there are increasing applications of this technique in ischemic heart disease.
Oliver Bruder described the impact of CMR in daily clinical practice in guiding patient management. In particular, he referred to the increasing role of stress perfusion CMR in patients with angina as a gatekeeper for invasive coronary angiography and unnecessary coronary interventions. He also highlighted that a normal stress CMR perfusion has a high negative predictive value.
He emphasized that CMR has also an important role in patients with heart failure, as it can inform on whether the etiology is ischemic vs non-ischemic. Interestingly in non-ischemic cardiomyopathy, CMR can in most cases inform differential diagnosis (myocarditis, sarcoidosis, amyloidosis and others) based on the different patterns of gadolinium contrast enhancement distribution.
CMR is also increasingly used before ICD implantation to inform about myocardial scar location (which has implication for pacing lead placement), and aid patient selection, in addition to ejection fraction, and identification of non-responders.
Finally he reported on the EuroCMR Registry, an initiative of the Working Group for Cardiovascular MRI of the ESC that has collected to date > 30,000 patients from 59 centres in 15 countries. The registry is collecting data on safety, clinical utility and use in daily routine of CMR.
Jan Bogaert illustrated the unique capability of CMR over echocardiography and nuclear medicine in assessing in details the anatomy of the acutely injured myocardium. In particular, he highlighted that a CMR carried out within a week of an acute myocardial infarction can visualise not only the size and location of the myocardial infarction but also its associated features such as microvascular obstruction, intramyocardial haemorrhage, and myocardial salvage. T2-weighted CMR techniques are able to visualise tissues with increased water content- which, in the case of acute myocardial infarction, is myocardial oedema.
This has been validated histologically and found to correlate significantly with the myocardial area at risk. Myocardial salvage is then easily calculated by subtracting the “area of myocardial infarction” from the “area at risk”. The retrospective assessment of myocardial salvage by CMR seems particularly attractive given that, compared to the nuclear techniques, it obviates the injection of radiotracer before urgent revascularisation.
Both microvascular obstruction and intramyocardial haemorrhage are strong predictors of left ventricular remodelling  and cardiovascular events. Myocardial salvage, microvascular obstruction and intramyocardial haemorrhage represent valuable surrogate endpoints for clinical trials, especially for assessing new myocardial reperfusion strategies.
Karine Moschetti illustrated the role of stress CMR in the evaluation of coronary artery disease. She initially described that both adenosine and dobutamine can be used as stressors in CMR with similar protocols used in echocardiography and SPECT. She then presented the evidence on the diagnostic accuracy of the technique in detecting coronary artery disease, starting from MR-IMPACT 1 (Schwitter et, EHJ 2008;4:480-9) and MR-IMPACT 2 (Schwitter et al, EHJ 2013;10:775-81).
She presented the results of the CE-MARC  (Greenwood et al, Lancet 2012;379:453-60), the largest (752 patients) prospective study on the topic demonstrating that stress CMR has a high diagnostic accuracy (sensitivity 86%, specificity 83%), which is superior compared to SPECT (sensitivity 66%, specificity 83%).
She also addressed the issue of cost-effectiveness of CMR in this setting by presenting the results of a sub-analysis from EuroCMR registry (Moschetti et al, JCMR 2012;14:35) and concluding that CMR is a cost-effective test when used as a gatekeeper for invasive coronary angiography. These results were consistent across different European health systems (Switzerland, Germany, and the UK). Another recent cost-effective sub-analysis of the CE-MARC study confirmed that CMR is a cost-effective strategy supporting the wider adoption of this modality (Walker et al, Heart 2013;99:873-81).
Andrew Arai presented a series of studies that investigated the role of CMR in the emergency department. A few years ago, a study (Ingkanisorn et al, JACC 2006;47:1427-32) showed that in patients with chest pain, troponin negative and with non-diagnostic electrocardiograms, adenosine CMR predicted with high sensitivity and specificity which patients had significant CAD during one-year follow-up, with a high negative predictive value.
More recently, it was demonstrated that in patients with intermediate or high probability for acute coronary syndrome without electrocardiographic or biomarker evidence of a myocardial infarction, an observation unit strategy involving stress CMR, compared to inpatient care reduced cost without missing any cases of acute coronary syndrome (Miller et al, Ann Emerg Med 2010;56:209-219)(Miller et al, JACC Imaging 2011;8:862-70). However, the ability of a physician to select a cardiac stress imaging modality (including echocardiography, CMR, or radionuclide testing) was more cost-effective than a pathway that mandates a CMR stress test (Miller et al, Circ Imaging 2012;5:111-8). Finally, he illustrated that for patients with intermediate risk, the observation unit strategy involving stress CMR also reduced revascularisation, hospital readmission and recurrent cardiac testing (Miller et al, JACC Imaging 2013;6:785-94).

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Magnetic resonance imaging in ischaemic heart disease

The content of this article reflects the personal opinion of the author/s and is not necessarily the official position of the European Society of Cardiology.