Intracoronary Transluminal Attenuation Gradient in Coronary CT Angiography for Determining Coronary Artery Stenosis

Abstract

Coronary computed tomography angiography (CTA) assessment of calcified or complex coronary lesions is frequently challenging. Transluminal attenuation gradient (TAG), defined as the linear regression coefficient between luminal attenuation and axial distance, has a potential to evaluate the degree of coronary stenosis. We examined the value of TAG in determining the stenosis severity on 64-slice coronary CTA. The value of TAG of 370 major coronary arteries was measured from 7,263 intervals of 5-mm length. Compared with coronary CTA and invasive coronary angiography, TAG decreased consistently and significantly with maximum stenosis severity on a per-vessel basis, from -1.91 ± 4.25 Hounsfield units/10 mm for diameter stenosis of 0% to 49% to -13.37 ± 9.81 Hounsfield units/10 mm for diameter stenosis of 100% (p < 0.0001). Adding TAG to the interpretation of coronary CTA improved diagnostic accuracy (p = 0.001), especially in vessels with calcified lesions (N = 127; net reclassification improvement 0.095; p = 0.046). TAG appears to be able to contribute to improved classification of coronary artery stenosis severity in coronary CTA, especially in severely calcified lesions.

Diagnostic performance of transluminal attenuation gradient and fractional flow reserve by coronary computed tomographic angiography (FFRCT) compared to invasive FFR: a sub-group analysis from the DISCOVER-FLOW and DeFACTO studies

“…Meanwhile, TAG assesses only a drop in contrast across a stenotic lesion in the coronary vessel in the rest condition and does not take into account the complex array of variables that are used by FFR CT to model flow reserve from the rest CCTA. Therefore, abnormality by TAG is likely to be associated with severe anatomic stenosis [24] as well as limited coronary flow [23], and TAG may fail to detect stenosis that limits flow as assessed by invasive FFR during pharmacologic stress but does not reduce resting coronary flow. This underlying mechanism may also explain why the combination of TAG and CCTA stenosis did not provide a greater diagnostic performance over CCTA stenosis alone in the current study and the aforementioned study [20].…”

A Comparative Preliminary Study on CT Contrast Attenuation Gradient Versus Invasive FFR in Patients with Unstable Angina

“…18 Despite of a multitude of studies that assessed the role of CTA in evaluating plaque vulnerability, according to our knowledge there are no published data so far regarding the role of CTA in assessing vulnerability markers in relation to the functional significance of a coronary lesion. [19][20][21][22][23] FFR remains the gold standard for assessing the hemodynamic significance of a coronary artery stenosis; however, this remains an invasive technique that could prove to be unnecessary in cases with no significant lesions.…”

Almanac 2014: Cardiovascular Imaging.

“…Zamijećeno je da se gradijenti zamućenosti transluminalnog kontrasta (TAG) smanjuju u skladu s procjenom protoka TIMI ljestvicom. 39 Međutim, ova metoda ovisi o više čimbenika poput EF lijeve klijetke, stopa bolus kontrasta, brzina koronarnog toka i koncentracija i volumen kontrasta. Zbog nedavnih napredaka u računalnoj dinamici toka, predviđanje koronarnog toka i pritiska, i po tome izračunavanje FFR specifičnih za lezije (FFRCT, FFR CT technique) su moused, and from the maximum slope of the tissue time-attenuation curve, MBF was calculated.…”

“…Transluminal contrast attenuation gradients (TAG) have been reported to decrease in accordance with Thrombolysis in Myocardial Infarction (TIMI) flow grade. 39 However, this technique is dependent on a multiple factors such as left ventricular EF, contrast bolus rates, coronary flow velocity and contrast concentration and volumes. Owing to recent advances in computational flow dynamics, prediction of coronary flow and pressure, and thereby calculation of lesion-specific FFR (FFRCT, FFR CT technique) have been possible from typically acquired static CT images.…”