64-slice CT unable to out-perform coronary angiography

Previous studies comparing CT coronary angiography with the current gold standard of coronary angiography have been limited by single-centre design and inherent bias in small studies.  This multi-centre, international study, CORE 64 (Coronary Artery Evaluation Using 64-Row Multidetector Computed Tomography Angiography) used central blinded analysis to evaluate the diagnostic accuracy of MDCT angiography involving 64 slice detectors and a slice thickness of 0.5mm in order to identify symptomatic patients with suspected CAD who should be referred for conventional coronary angiography. Patients with Agatston calcium scores>600 were pre-specified to be excluded from the analysis and entered into a registry. Patients were followed up for the interim occurrence of death, MI, stroke, revascularisation (percutaneous or surgical), hospitalisation for angina or heart failure and other serious adverse events at 7 and 30 days.

291 patients had calcium scores <600 and underwent MDCT and conventional angiography. Stenoses >50% were considered obstructive. 56% of patients had obstructive CAD. The patient-based diagnostic accuracy of quantitative CT for detecting or ruling out stenoses of 50% or more according to conventional coronary angiography revealed an AUC of 0.93 (95%CI 0.90-0.96), with a sensitivity of 85% (95% CI 79-90), specificity of 90% (95%CI 83-94), positive predictive value (PPV) of 91% (95%CI 86-95) and a negative predictive value (NPV) of 83% (95%CI 75-89). CT angiography was commensurate with conventional angiography in its ability to identify patients who subsequently required revascularisation: AUC 0.84 (95%CI 0.79-0.88) for MDCT compared to 0.82 (95%CI 0.77-0.86) for conventional coronary angiography. Assessment on an individual vessel basis of 866 vessels yielded an AUC of 0.91 (95% CI 0.88-0.93).Good correlation of disease severity assessment was seen between the 2 techniques (r=0.81, 95%CI 0.76-0.84).

Although this study suggests that MDCT can accurately diagnose obstructive CAD, the PPV of 91% and NPV of 83% suggest that it cannot replace conventional coronary angiography in symptomatic patients at this time.  The results suggest that MDCT should be considered in the context of other non-invasive stress tests although exposure to radiation is a concern in all methods involving radiography or nuclear isotopes. Further studies will be necessary to determine its precise role in diagnostic algorithms evaluating patients with suspected CAD.

  • Miller JM, Rochitte CE, Dewey M et al. Diagnostic performance of Coronary Angiography by 64-Row CT. N Engl J Med 2008;359:2324-6