Transluminal attenuation gradient in coronary computed tomography angiography for determining stenosis severity of calcified coronary artery: a primary study with dual-source CT.

OBJECTIVES

To evaluate the diagnostic accuracy of transluminal attenuation gradient (TAG) for stenosis severity of calcified lesions assessed by coronary computed tomography angiography (CCTA).

METHODS

One hundred seven patients who underwent CCTA and coronary angiography (CAG) were enrolled. TAGs of 309 major epicardial coronary arteries were measured. The impact of plaque composition, Agatston scores, and lesion length ratio on TAG were analyzed. Diagnostic performance vs. CAG of TAG, CCTA, and combined TAG/CCTA were evaluated, and incremental value of TAG for reclassification of CCTA stenosis severity in calcified lesions was also analyzed.

RESULTS

TAG decreased consistently with stenosis severity. TAG was significantly lower in coronary arteries with calcification scores >300 and lesion length ratios >2/3. TAG improved diagnostic accuracy of CCTA (c-statistic =0.982 vs. 0.942, P = 0.0001) in calcified lesions, and the sensitivity, specificity, positive, and negative predictive values of TAG cutoff ≤ -11.33 were 72 %, 91 %, 88 %, and 78 %, respectively. The addition of TAG to CCTA resulted in significant reclassification (NRI =0.093, P = 0.022) in calcified vessels.

CONCLUSIONS

Measurement of TAG may improve diagnostic performance and reclassification of CCTA in coronary stenosis caused by calcified lesions.

KEY POINTS

• TAG decreased as calcification scores and lesion length increased. • TAG markedly improved the diagnostic performance of CCTA for calcified lesions. • TAG improved reclassification of coronary artery stenosis severity in CCTA.