For decades the use of cardiac magnetic resonance (CMR) imaging has served as one of the most effective procedures for physicians to glimpse into the inner workings of the human body. Offering incredibly high spatial and temporal resolution of internal structures and masses, the procedure has had irreplaceable diagnostic value in the field of cardiology. However, for all its diagnostic ability, using CMR imaging as a prognostic tool still has its level of unknowns.

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A study published Jan. 29 in the Journal of the American College of Cardiology sought to find the best predictive figures for patients undergoing CMR imaging, and found that independent predictors of future cardiovascular events were left ventricular ejection fraction (LVEF) for patients who have undergone a recent myocardial infarction (MI), and wall motion abnormality, inducible perfusion defects, LVEF and presence of infarction for patients with suspected or known coronary artery disease (CAD).

The researchers, led by Hamza El Aidi MD, Department of Cardiology, University Medical Center Utrecht, conducted a systematic review of data from patients undergoing CMR imaging, and performed a comprehensive search in the MEDLINE and EMBASE electronic databases in February of 2013. They reviewed data on LVEF, inducible wall motion abnormalities, abnormal myocardial perfusion, microvascular obstruction, late gadolinium enhancement, edema, intramyocardial haemorrhage, as well as hard events such as all-cause mortality, cardiac death, cardiac transplantation, MI and major adverse cardiovascular events.

Evaluating 56 studies comprised of 25,497 patients, El Aidi and this team concluded CMR "is capable of providing independent prognostic information that allows for risk stratification" cardiovascular events in patients with recent MI as well as patients with suspected or known CAD. While independent association could not be found between any of the investigated CMR findings and hard events since none of the findings were studied in more than 1,000 patients, LVEF was found to be an independent predictor associated with major adverse cardiovascular events. The investigation also found that patients with suspected or known CAD wall motion abnormality, inducible perfusion defects, LVEF, and infarction were independently associated with hard events, and that the presence of inducible perfusion defects was associated with major adverse cardiac events.

"Few imaging modalities offer a more comprehensive phenotyping of the heart than CMR," writes Ilan Gottlieb MD, PhD, National Institute of Cardiology, Rio de Janeiro in an editorial comment. "It is currently the non-invasive gold standard for quantification of cardiac volumes and function, provides excellent anatomic depiction of cardiac structures and masses — benefiting from its unique ability to differentiate and characterize tissues — and has been shown to be at least as accurate as single photon emission tomography for myocardial ischemia detection. CMR has also been shown to detect myocardial fibrosis and necrosis, microvascular obstruction and hemorrhage, and myocardial edema."

However, Gottlieb argues that "the reason for the authors’ findings is the somewhat arbitrary determination that any variable that has less than 1,000 patients studied did not present enough evidence for conclusion," nonetheless, he believes that their conclusions "bring into light the urgent need of CMR studies in the acute MI setting."

Keywords: Coronary Artery Disease, Myocardial Infarction, Tomography, Emission-Computed, Single-Photon, Stroke Volume, Magnetic Resonance Imaging

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