Objective: T he aim of this study was to demonstrate that transluminal contrast attenuation gradient (TAG), a new CT imaging-derived marker of functional significance of a coronary stenosis, is associated with the vulnerability degree of atheromatous coronary plaques.
Methods: The study enrolled 72 patients (36 with unstable angina and 36 age and gender-matched with stable angina) who underwent cardiac computed tomography angiography (CTA) for complex plaque characterization and assessment of vulnerability features.
Results: Based on CT features, 32 plaques (34.5%) were classified as vulnerable plaques (VP) and 60 plaqu-es (57%) as non-vulnerable (nVP). TAG values were 41.7 +/- 27.2 HU/cm in VP and 20.1 +/- 10.3 HU/ cm in nVP (p=0.04), while the degree of stenosis was comparable (p=0.7 for VP vs. nVP). In both the group with unstable angina and in the total population of the study, TAG values above 20 HU/cm were associated with a higher plaque vulnerability, as demonstrated by a higher amount of plaque burden (107.9±81.1 mm³ vs. 63.6±29.1 mm³, p=0.03 for unstable angina and 94.2±63.8 mm³ vs. 60.1±23.7 mm³, p=0.04 for the total population), and volume of plaque with CT density be-low 30 HU (31.8±19.9 mm³ vs. 3.1±1.5 mm³, p<0.0001 for unstable angina and 75.7±50.6 mm³ vs. 49.9±9.8 mm³, p=0.04 for the total population). ROC analysis identified a good sensitivity of a TAG value above 20 HU/mm for predicting plaque vulnerability in the glo-bal study population (AUC=0.7, sensitivity 87% and specificity 66%).
Conclusions: Vulnerable coronary plaques exhibit a significantly higher functional significance as compa-red with the stable ones having a similar morphologic pattern, as demonstrated by a higher contrast attenua-tion gradient along the coronary plaques, determined by CTA.