CE-MARC: CV magnetic resonance bested standard imaging technique for diagnosing CHD

Multiparametric CV magnetic resonance demonstrated high diagnostic accuracy and appeared superior to standard single-photon emission CT for identifying coronary heart disease, according to data from the CE-MARC trial.

Although widely used, SPECT has limitations, such as patient and staff exposure to ionizing radiation, as well as limited spatial resolution of images, researchers wrote in The Lancet. However, CV magnetic resonance (CMR) is considered safe, but testing is time-consuming.

Comparing CMR and SPECT

From March 2006 to August 2009, researchers enrolled patients with suspected angina pectoris and at least one CV risk factor in the CE-MARC trial. Patients were scheduled for invasive X-ray coronary angiography, CMR and SPECT.

Results showed that 39% of the 752 patients included in the study had significant CHD as identified by X-ray angiography. Compared with SPECT, CMR demonstrated significantly better sensitivity (86.5% vs. 66.5%; P<.0001) and negative predictive value (90.5% vs. 79.1%; P<.0001) for diagnosing CHD. However, the differences in specificity (83.4% vs. 82.6%; P=.916) and positive predictive value (77.2% vs. 71.4% P=.061) did not reach statistical significance.

"We have shown convincingly that of the options available to doctors in diagnosing coronary heart disease, MRI is better than the more commonly used SPECT imaging test. As well as being more accurate, it has the advantage of not using any ionizing radiation, sparing patients and health professionals from unnecessary exposure," John P. Greenwood, PhD, senior lecturer and consultant cardiologist at University of Leeds, stated in a news release.

"The MRI technique could be used widely and not just in the United Kingdom," Greenwood added. "The scans were all carried out on a standard 1.5 Tesla scanner - exactly the type of MRI scanner that you would find in most hospitals today."

Appropriate use of imaging

In an accompanying editorial, Robert O. Bonow, MD, of the Center for CV Innovation at Northwestern University Feinberg School of Medicine, wrote that, although there has been a correlation between the growth of CV technology and the decrease in coronary mortality, the role that diagnostic imaging has played in improving these outcomes is unclear.

“What is clear is that imaging has increased, in terms of the number of procedures and expenditure, more rapidly than any other component of medical care,” Bonow wrote. “Research is now sorely needed to show that the appropriate use of these resources can further improve patient outcomes.”

Disclosure: The researchers report no relevant financial disclosures.

For more information:

• Burrow RO. Lancet. 2011;doi:10.1016/S0140-6736(11)61671-1.
• Greenwood JP. Lancet. 2011;doi:10.1016/S0140-6736(11)61335-4.

Nathaniel Reichek

This is the first paper on the topic of CMR stress perfusion imaging in a major general-interest medical journal. Its greatest significance is the impact it will have to increase awareness among a broader medical public of the power of the CMR stress perfusion imaging for diagnosis of CAD. The specific results largely confirm and extend those of many earlier and smaller studies, rather than break new ground. I have one major concern about the study: the sensitivity of SPECT imaging was significantly worse in this study than that found in many other studies, especially in view of the use of a 70% stenosis threshold. Nonetheless, in light of the fact that CMR stress perfusion requires no ionizing radiation and is actually cheaper than adenosine SPECT imaging (at least based on relative reimbursement for the procedures) it is important that the word get out.

– - Nathaniel Reichek MD, FACC, FAHA
Cardiology Today Editorial Board member

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