MRI (left) and CT (right) coronary angiography. Image Source: J Am Coll Cardiol Img, 2011; 4:50-61.

CT and MRI angiography yield similar accuracy in the diagnosis of coronary artery stenosis, with CT demonstrating a nonsignificant advantage and conventional angiography outperforming both, according to a study published in the January issue of the Journal of the American College of Cardiology.

Several studies have compared CT angiography (CTA) and MR angiography's (MRA) diagnosis of coronary artery disease (CAD), but as the technologies have improved, so have their accuracies. Moreover, with CAD continuing to be the leading cause of death in the West, "noninvasive, low-risk, and cost-effective coronary angiography would represent important progress in the diagnosis of obstructive CAD," wrote Ashraf Hamdan, MD, of the department of internal medicine/cardiology at the Deutsches Herzzentrum Berlin, in Berlin.

Researchers at two facilities scanned 110 consecutive patients with known or suspected CAD for coronary artery stenosis. All patients underwent CTA and MRA, in random order, prior to undergoing conventional coronary angiography, which was taken as the gold standard. Two blinded reviewers read all images and determined diagnoses by consensus, while also rating image quality on a four-point scale (one: "poor, nondiagnostic"; four: "excellent visibility and differentiation of the anatomic details of the coronary arteries").

Patient-based diagnostic accuracy measured 87 percent for CT and 83 percent for MRI, while vessel-based accuracy was 86 and 83 percent, respectively. The specificity and sensitivity of CT for the patient-based analyses were 83 percent and 90 percent, compared with a specificity of 77 percent and a sensitivity of 87 percent for MRI.

CT and MRI also yielded value in predicting revascularization, with areas under the receiver-operator characteristic curves of 0.82 for CT and 0.78 for MRI. Moreover, all 13 cases of left main or three-vessel disease were correctly diagnosed by both modalities.

The image quality of CT and MRI was likewise comparable, with CT earning a 3.6 versus a 3.5 for MRI on the left anterior descending artery. MRI slightly outperformed CT in visualizing the right coronary artery, 3.6 versus 3.3; and CT outscored MRI, 3.6 to 3.0, in visualizing the left circumflex coronary artery. Moreover, MRI could not assess significantly more coronary artery segments than CT. Overall diagnostic accuracy on a per-vessel level did not vary significantly between CT and MRI.

The authors found that the "advantage of using 32-channel 3T MRA was translated in the present study into high image quality of the coronary arteries as shown by visual assessment and high diagnostic performance, which was comparable to that of CT angiography."

Although acknowledging Hamdan et al's findings that "both MRA and CT can assess the anatomy of coronary artery stenoses, with high negative predictive value," an accompanying editorial questioned the research's extrapolatory power. "[T]o fully understand the value of these noninvasive modalities in the assessment of coronary artery disease, their additional prognostic value needs to be considered," argued Paul Schoenhagen, MD, of the Cleveland Clinic in Cleveland, Ohio, and Eike Nagel, MD, PhD, of King's College in London. "Future prospective studies will assess the value of these modalities in a more comprehensive fashion against clinical outcome," Schoenhagen and Nagel continued.

"In this study we have demonstrated that 32-channel 3T MRI and 64-slice CT angiography similarly identify clinically relevant coronary stenosis and similarly predict subsequent revascularization in patients with suspected or known CAD scheduled for elective coronary angiography," Hamdan and colleagues concluded. "However, CT angiography shows a trend toward higher diagnostic performance."