Diagnostic Performance of Coronary Angiography by 64-Row CT

Background & Methods

We conducted a multicenter study to examine the accuracy of 64-row, 0.5-mm multidetector CT angiography as compared with conventional coronary angiography in patients with suspected coronary artery disease. Nine centers enrolled patients who underwent calcium scoring and multidetector CT angiography before conventional coronary angiography. In 291 patients with calcium scores of 600 or less, segments 1.5 mm or more in diameter were analyzed by means of CT and conventional angiography at independent core laboratories. Stenoses of 50% or more were considered obstructive. The area under the receiver-operating-characteristic curve (AUC) was used to evaluate diagnostic accuracy relative to that of conventional angiography and subsequent revascularization status, whereas disease severity was assessed with the use of the modified Duke Coronary Artery Disease Index.

Results

A total of 56% of patients had obstructive coronary artery disease. The patient-based diagnostic accuracy of quantitative CT angiography for detecting or ruling out stenoses of 50% or more according to conventional angiography revealed an AUC of 0.93 (95% confidence interval [CI], 0.90 to 0.96), with a sensitivity of 85% (95% CI, 79 to 90), a specificity of 90% (95% CI, 83 to 94), a positive predictive value of 91% (95% CI, 86 to 95), and a negative predictive value of 83% (95% CI, 75 to 89). CT angiography was similar to conventional angiography in its ability to identify patients who subsequently underwent revascularization: the AUC was 0.84 (95% CI, 0.79 to 0.88) for multidetector CT angiography and 0.82 (95% CI, 0.77 to 0.86) for conventional angiography. A per-vessel analysis of 866 vessels yielded an AUC of 0.91 (95% CI, 0.88 to 0.93). Disease severity ascertained by CT and conventional angiography was well correlated (r = 0.81; 95% CI, 0.76 to 0.84). Two patients had important reactions to contrast medium after CT angiography.

Conclusion:

Multidetector CT angiography accurately identifies the presence and severity of obstructive coronary artery disease and subsequent revascularization in symptomatic patients.

The negative and positive predictive values indicate that multidetector CT angiography
cannot replace conventional coronary angiography at present.

N Engl J Med 2008;359:2324-36.

The second large-scaled multi-center study published in 2008 was the “Core-64-Study”. The results are somehow different compared with “Accuracy”, since the negative predictive value is lower than the positive predictive value. This is mainly due to the way of interpreting the CT scans with a fixed cut-off of 50% (diameter?) stenosis to define significant lesions. These data show, however, the limitation of cardiac CT which allows a solely morphologic look at the coronary tree. This can be performed, however, with high accuracy.

The authors conclude “ …In this international, multicenter study, we have demonstrated that coronary 64-row multidetector CT angiography is accurate in identifying coronary stenoses and characterizing disease severity in symptomatic patients who have coronary calcium scores of 600 or less. However, multidetector CT angiography cannot be used as a simple replacement for conventional coronary angiography, given its negative predictive value of 83% and positive predictive value of 91% in this population of patients. Further studies are needed to define the method’s precise role in the diagnostic algorithm for the evaluation of patients with suspected coronary artery disease…”.