In recent years it has become clear that treatment of coronary artery disease – and in particular percutaneous coronary intervention (PCI) – must be guided by imaging techniques that give some information on the extent of myocardial ischaemia. While nuclear medicine techniques such as SPECT (single-photon emission computed tomography) have become widespread, and have a high negative predictive value, they still expose patients to ionising radiation. Furthermore, the sensitivity of SPECT has been noted to vary. Cardiac Magnetic Resonance Imaging (MRI), is a potential alternative that uses no ionising radiation, provides high-resolution images, and is capable of assessing various cardiac parameters in one comprehensive examination.
The CE-MARC study (Clinical Evaluation of MAgnetic Resonance imaging in Coronary heart disease) was designed to provide a real-world comparison of stress perfusion MRI and SPECT, using coronary angiography as the gold standard. 752 patients with stable angina (not including those who had had previous bypass surgery) were recruited over a three year period. Of these, 378 were assigned to CMR then SPECT, while 374 were assigned to SPECT then CMR. Overall 39% of patients had significant coronary disease as detected by X-ray angiography. For multiparametric CMR the sensitivity was 86·5% (95% CI 81·8—90·1), and specificity 83·4% (79·5—86·7), compared to the sensitivity of SPECT which was 66·5% (95% CI 60·4—72·1), and specificity 82·6% (78·5—86·1). The sensitivity and negative predictive value of CMR and SPECT differed significantly (p<0·0001 for both) but specificity and positive predictive value did not (p=0·916 and p=0·061, respectively).
This large, prospective trial of stress perfusion MRI shows its high diagnostic accuracy and superiority over SPECT imaging. As such CE-MARC is a landmark trial that is likely to challenge the current dominance of nuclear imaging for the assessment of myocardial perfusion.
- Greenwood JP, Maredia N, Younger JF et al. Cardiovascular magnetic resonance and single-photon emission computed tomography for diagnosis of coronary heart disease (CE-MARC): a prospective trial. Lancet 2011;379:453-460