Abstract 15431: Transluminal Attenuation Gradient in Coronary Computed Tomography Angiography Does Not Predict Hemodynamic Significance of Coronary Artery Stenosis: Comparison Against FFR
Background: Transluminal attenuation gradient (TAG) is defined as the contrast opacification gradient across the length of a coronary artery at coronary computed tomography angiography (CCTA). Preliminary data suggest that TAG may provide additional functional information. Interpretation of TAG is hampered when utilizing multiple heartbeat reconstruction algorithms, resulting in timing dependent perturbation of contrast delivery. Furthermore, measurements are disrupted by dense mural calcifications. Two correction models have been proposed based on either dephasing of contrast delivery by relating coronary density to corresponding descending aortic opacification (TAG-CCO) or exclusion of dense calcified coronary segments (TAG-ExC). The current study evaluates the incremental value of TAG, TAG-CCO, and TAG-ExC over CCTA alone using fractional flow reserve (FFR) as gold standard.
Methods and Results: Eighty-five patients with an intermediate probability of coronary artery disease (CAD) were prospectively included. All patients underwent step-and-shoot 256-slice CCTA covering cardiac volume during two separate R-R intervals. TAG, TAG-CCO, and TAG-ExC analysis were performed prior to invasive coronary angiography in conjunction with FFR measurements of all major coronary branches. Thirty-four (40%) patients were diagnosed with obstructive CAD (i.e. FFR ≤ 0.80). On a per vessel analysis (n=253), 59 lesions (23,3%) were graded hemodynamically significant. Diagnostic accuracy of CCTA (diameter stenosis ≥ 50%) was 95, 75, 98, and 54% on a per vessel basis for sensitivity, specificity, NPV, and PPV, respectively. TAG and TAG-ExC were comparable for obstructive vs. non-obstructive vessels (-13.5±17.1 vs. -11.6±13.3, p=0.36, and -13.1±15.9 vs. -11.4±11.7 HU/10mm, p=0.77, respectively). TAG-CCO was significant lower in hemodynamically significant CAD (-0.050±0.051 vs. -0.036±0.034, p=0.03). ROC analysis did not display any incremental value of TAG parameters over CCTA.
Conclusions: TAG analysis does not improve diagnostic accuracy of 256-slice CCTA for predicting hemodynamically obstructive CAD. Corrections for multiple consecutive heartbeat acquisition and dense mural calcification does not influence TAG outcome.
- © 2013 by American Heart Association, Inc.