Abstract
Transluminal attenuation gradient (TAG) represents the slope of intraluminal contrast that decreases along a coronary vessel during coronary computed tomography angiography (CCTA). The aim of this study was to determine the added value of TAG to qualitative CCTA assessment of significant stenosis (>50%) detecting ischemia as determined by stress myocardial blood flow (MBF) or myocardial flow reserve (MFR) measured by positron emission tomography (PET). Individual contributions of TAG, qualitative assessment and the impact of calcium score were also investigated. Methods: We studied 38 consecutive patients that were referred due to suspected or known coronary artery disease (CAD). All patients underwent a two-phase hybrid 13N-ammonia PET/CT and CCTA. Results: TAG and presence of qualitatively assessed significant stenosis, but not calcium score, were associated with stress myocardial blood flow (MBF) and myocardial flow reserve (MFR). The area under the curves (AUC) of the linear predictor model including qualitative assessment and TAG was superior to the AUC of separate qualitative assessment or TAG for the detection of ischemia according to stress MBF (AUCs were: 88% vs. 79% and 77%; p = 0.01 and p = 0.01, respectively). Conclusions: TAG combined with qualitative CCTA assessment improved ischemia detection.
Highlights
Transluminal attenuation gradient (TAG) is a measurement representing the downslope gradient of intraluminal contrast along a coronary vessel
More negative values of TAG representing a steep decrease of contrast have been frequently reported in patients with coronary artery disease (CAD); TAG has been proposed as a parameter to identify hemodynamically significant stenosis [2,3,4]
TAG has been proposed as a simple procedure to aid the detection of significant stenosis and to increase diagnostic accuracy of coronary computed tomography angiography (CCTA), considering that its calculation can be performed with standard CCTA data without an additional protocol [2]
Summary
Transluminal attenuation gradient (TAG) is a measurement representing the downslope gradient of intraluminal contrast along a coronary vessel. More negative values of TAG representing a steep decrease of contrast have been frequently reported in patients with coronary artery disease (CAD); TAG has been proposed as a parameter to identify hemodynamically significant stenosis [2,3,4]. One study has reported a tendency of TAG to increase the diagnostic value of CCTA in ischemia detection as defined by 15 O-water positron emission tomography (PET) [7]. It is still unknown whether TAG improves ischemia detection when combined with qualitative CCTA assessment and whether calcium score influences TAG parameters. There is no literature comparing TAG to quantitative myocardial perfusion parameters obtained with 13 N-ammonia PET, such as stress myocardial blood flow (MBF) and/or myocardial flow reserve (MFR)
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