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32-channel 3.0-T MRI and 64-slice CT detect CAD equally well

Reuters Health • The Doctor's Channel Daily Newscast

NEW YORK (Reuters Health) – In a prospective comparative study, 32-channel 3.0 Tesla magnetic resonance imaging (MRI) and 64-slice computed tomography (CT) angiography similarly identified significant coronary stenosis and similarly predicted revascularization in patients with suspected or known coronary artery disease (CAD).

However, CT angiography showed a favorable trend toward higher diagnostic performance and better prediction of subsequent revascularization, Dr. Ashraf Hamdan, of the German Heart Institute of Berlin and colleagues report in the January issue of JACC: Cardiovascular Imaging.

In an e-mail to Reuters Health, Dr. Hamdan noted that “the use of 3.0 Tesla MRI and 32-element coils has allowed improvements of the spatial and temporal resolution of MRI coronary angiography. However, this technology had never been compared with 64-slice CT, which has higher spatial and temporal resolution than the older CT generations and therefore had a wide spectrum for clinical use.”

In addition, until now, there has been no direct comparison of the ability of MRI and CT angiography to predict the need for revascularization.

In their paper, Dr. Hamdan and colleagues report results of 110 patients with stable or suspected CAD who underwent 32-channel 3.0-T MRI and 64-slice CT before elective X-ray angiography.

They compared the diagnostic accuracy of the two noninvasive modalities for detecting luminal stenosis of 50% or greater in diameter in segments 1.5 millimeters in diameter, using quantitative invasive coronary angiography as the reference standard.

The clinicians report that all cases of left main or 3-vessel disease (2 and 11 patients, respectively) were correctly identified by MRI and CT angiography. The diagnostic accuracy of MRI and CT was 83% and 87%, respectively; sensitivity was 87% and 90%; and specificity 77% and 83%, respectively.

The diagnostic accuracy of MRI and CT angiography was also similar on a per-vessel basis, with no significant differences among the right and left-main left anterior descending arteries. CT, however, had significantly higher diagnostic accuracy for the intermediate branch left circumflex coronary artery, the clinicians say.

Both techniques were similarly able to identify patients who subsequently underwent revascularization; the area under the receiver-operator characteristic curve was 0.78 for MRI and 0.82 for CT angiography. However, invasive angiography predicted coronary revascularization significantly better than MRI and CT, the authors point out.

Dr. Hamdan noted that the results of this study cannot be extrapolated to the relatively older MRI generations and coils.

For now, the clinician offered the following guidance. In centers that have the ability to perform 32-channel 3.0-T MRI and 64-slice CT coronary angiography, “MRI should be performed in patients with renal failure (absence of iodinated contrast agent); patients who need additional functional information (stress testing, left or right ventricular volumes and functions); or repeated coronary angiography (absence of radiation exposure).”

CT coronary angiography, Dr. Hamdan added, “should be used in patients with claustrophobia and in patients with bimetallic implants. In addition, patients after coronary artery stenting with a stent diameter of greater than 3 millimeters might be evaluated using CT but not using MRI.”

The authors of an accompanying editorial look forward to future prospective studies that will assess the value of these modalities in a more comprehensive fashion against clinical outcomes.

“Such clinical trials are currently enrolling patients,” Drs. Paul Schoenhagen of the Imaging Institute and Heart and Vascular Institute at the Cleveland Clinic, Ohio and Dr. Eike Nagel of King’s College, London, UK, note in the article. “Over the next several years, such data will define the role of these modalities in the context of existing invasive and noninvasive modalities,” they conclude.

J Am Coll Cardiol Img 2011;4:50-61.