October 27, 2015 – Computed tomography angiography (CTA) scans of the heart’s vessels are far better at spotting clogged arteries that can trigger a heart attack than the commonly prescribed exercise stress that most patients with chest pain undergo, according to a recent study1 by Johns Hopkins researchers.
While single-photon emission computed tomography (CT)-acquired myocardial perfusion imaging (SPECT-MPI) is frequently used for the evaluation of CAD, coronary CTA has emerged as a valid alternative. The researchers designed a study comparing the accuracy of SPECT-MPI and CTA for the diagnosis of CAD in 391 symptomatic patients who were prospectively enrolled in a multicenter study after clinical referral for cardiac catheterization.
They looked at the area under the receiver operating characteristic curve to evaluate the diagnostic accuracy of CTA and SPECT-MPI for identifying patients with CAD, which they defined as the presence of ≥1 coronary artery with ≥50% lumen stenosis by quantitative coronary angiography. Radiation doses were 3.9 mSv for CTA and 9.8 for SPECT-MPI. Sensitivity to identify patients with CAD was greater for CTA than SPECT-MPI (0.92 versus 0.62, respectively; P<0.001), resulting in greater overall accuracy (area under the receiver operating characteristic curve, 0.91 versus 0.69. Results were similar in patients without previous history of CAD (area under the receiver operating characteristic curve, 0.92 versus 0.67, and also for the secondary end points of ≥70% stenosis and multivessel disease, as well as subgroups, except for patients with a calcium score of ≥400 and those with high-risk anatomy in whom the overall accuracy was similar because CTA's superior sensitivity was offset by lower specificity in these settings.
Image: While coronary angiograms remain the ‘gold standard’ for detecting coronary artery stenosis (significant narrowing of the arteries which could require stents or bypass surgery), Coronary CTA may confidently exclude coronary stenosis in a number of patients thus avoiding the need for an invasive angiogram.2
Based on these results, the authors concluded that CTA is more accurate than SPECT-MPI for the diagnosis of CAD as defined by conventional angiography and may be underused for this purpose in symptomatic patients.
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