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Coronary Computed Tomography: Still Searching for a Reason to Believe

In a multicenter study, 64-row coronary CT performed well, but not well enough to justify its use as a first-line diagnostic tool.

Coronary computed tomography with 64 detectors has been heralded in some quarters as a noninvasive diagnostic tool that could replace conventional coronary angiography. To evaluate the accuracy of this technique, investigators compared results of 64-row coronary CT with those of conventional coronary angiography in 291 patients with Agatston calcium scores 600 who were evaluated for symptoms of coronary artery disease at nine centers. Eligible patients were aged 40 (median age, 59; 74% men) and were referred for coronary angiography.

Fifty-six percent of the participants had at least one obstructive stenosis (50%); 27% had single-vessel disease. The median time between the two tests was 10 hours. The sensitivity of coronary CT for the detection of an obstructive stenosis of 50% was 85% (95% confidence interval, 79–90), and its specificity was 90% (95% CI, 83–94). Coronary CT had a positive predictive value of 91% (95% CI, 86–95) and a negative predictive value of 83% (95% CI, 75–89). In a vessel-based analysis, coronary CT had a sensitivity of 75% (95% CI, 69–81), a specificity of 93% (95% CI, 90–94), a positive predictive value of 82% (95% CI, 77–86), and a negative predictive value of 89% (95% CI, 86–92). The mean radiation dose for CT was 13.8 mSv for men and 15.2 mSv for women.

Comment: Multidetector CT’s performance was reasonably close to that of the gold standard, coronary angiography, in patients with suspected CAD. The authors conclude, however, that the positive and negative predictive values of CT in this population are insufficient to recommend that the new technique replace conventional coronary angiography. In an accompanying perspective piece, Redberg and Walsh note that the study "does not advance our knowledge of the appropriate use and possible benefits of the technology." Until we have solid evidence of such benefits — and clarity about how best to incorporate the evidence into decision making — we should avoid the routine use of coronary CT to assess patients for CAD.

— Harlan M. Krumholz, MD, SM

Published in Journal Watch Cardiology November 26, 2008

Citation(s):

Miller JM et al. Diagnostic performance of coronary angiography by 64-row CT. N Engl J Med 2008 Nov 27; 359:2324.

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• Medline abstract (Free)

Redberg RF and Walsh J. Pay now, benefits may follow — The case of cardiac computed tomographic angiography. N Engl J Med 2008 Nov 27; 359:2309.

• Original article (Subscription may be required)
• Medline abstract (Free)