Transluminal Attenuation Gradient Research Articles

Assessment of coronary spasms with transluminal attenuation gradient in coronary computed tomography angiography.

To evaluate the imaging features of coronary spasm, including transluminal attenuation gradient (TAG) on coronary computed tomography angiography (CCTA), in patients with vasospastic angina (VA). A total of 43 patients with a high clinical likelihood of VA were included in the study. All the subjects underwent double CCTA acquisition: CCTA without a vasodilator ('baseline CT') and CCTA during continuous intravenous nitrate infusion ('IV nitrate CT'). A catheterized ergonovine provocation test was used to determine true VA patients. Coronary spasm is classified into focal- and diffuse-types according to morphological differences. We measured TAG and contrast enhancement of the proximal ostium (ProxHU) of each coronary artery for both the baseline and IV nitrate CT. Twenty-four patients (55.8%) showed positive results of coronary vasospasm on the provocation test. Thirty-eight vessels showed coronary spasms (29.5%): Focal-type in nine vessels (24%), and diffuse-type in 29 (76%). In the baseline CT, LCX showed significantly lower (steeper) TAG in spasm(+) vessels than in spasm(-) vessels, while LAD and RCA showed no significant differences in TAG. The ProxHU of LAD showed significantly lower values in spasm(+) vessels than in spasm(-) vessels, while the other vessels did not show significant differences in ProxHU. For IV nitrate CT, there were no significant differences in either the TAG and ProxHU between spasm(+) and (-) vessels for all the three vessel types. In subgroup analysis for spasm(+) vessels, diffuse spasms showed significantly lower TAG than focal spasms, while the ProxHU did not differ between the two types of spasm. A relatively large percentage of coronary spasms present as diffuse type, and the TAG values significantly differed according to the morphological type of the coronary spasm.

A Noninvasive Assessment of Flow Based on Contrast Dispersion in Computed Tomography Angiography: A Computational and Experimental Phantom Study.

Transluminal attenuation gradient (TAG), defined as the gradient of the contrast agent attenuation drop along the vessel, is an imaging biomarker that indicates stenosis in the coronary arteries. The transluminal attenuation flow encoding (TAFE) equation is a theoretical platform that quantifies blood flow in each coronary artery based on computed tomography angiography (CTA) imaging. This formulation couples TAG (i.e., contrast dispersion along the vessel) with fluid dynamics. However, this theoretical concept has never been validated experimentally. The aim of this proof-of-principle phantom study is to validate TAFE based on CTA imaging. Dynamic CTA images were acquired every 0.5 s. The average TAFE estimated flow rates were compared against four predefined pump values in a straight (20, 25, 30, 35, and 40 ml/min) and a tapered phantom (25, 35, 45, and 55 ml/min). Using the TAFE formulation with no correction, the flow rates were underestimated by 33% and 81% in the straight and tapered phantoms, respectively. The TAFE formulation was corrected for imaging artifacts focusing on partial volume averaging and radial variation of contrast enhancement. After corrections, the flow rates estimated in the straight and tapered phantoms had an excellent Pearson correlation of r = 0.99 and 0.87 (p < 0.001), respectively, with only a 0.6%±0.2 mL/min difference in estimation of the flow rate. In this proof-of-concept phantom study, we corrected the TAFE formulation and showed a good agreement with the actual pump values. Future clinical validations are needed for feasibility of TAFE in clinical use.

Transluminal attenuation gradient derived from coronary CT angiography to predict ischemia in SPECT myocardial perfusion imaging: Effect of coronary cross-sectional area

BackgroundCoronary computed tomography angiography (CCTA)-based transluminal attenuation gradient (TAG) was suggested to determine the functional significance of a stenosis. However, evidence that TAG acquired by wide-volume scanners can assess the hemodynamic significance of stenosis assessed by single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) is lacking. Moreover, coronary cross-sectional area may influence TAG. Hence, we aimed at assessing the diagnostic value of TAG to predict ischemia in SPECT-MPI and the correlation between TAG and the transluminal cross-sectional area gradient (TCG). MethodsPatients undergoing CCTA and SPECT-MPI for suspected coronary artery disease were included. TAG and TCG were calculated measuring the mean vessel attenuation and the cross-sectional area along major coronary vessels at 5-mm intervals. ResultsA total of 255 coronary arteries of 87 patients were included. TAG and TCG did not discriminate between coronary arteries with or without ischemia as assessed by SPECT-MPI (p = .44 and p = .25, respectively). The area under the curve to predict ischemia was not increased by adding TAG (0.88, 95% CI 0.83-0.92) or TCG (0.87, 95% CI 0.81-0.90) to CCTA alone (0.85, 95% CI 0.80-0.89). There was a significant correlation between TAG and TCG (r = 0.43; p < .001). ConclusionsCCTA-derived TAG and TCG do not offer any value in predicting ischemia assessed by SPECT-MPI. TAG is partly affected by differences in the coronary luminal area.

Estimation of coronary stenosis severity based on flow distribution ratios

We suggest improving minimally-invasive stenosis severity estimation, using a combination of existing geometry-based methods with Transluminal Attenuation Gradient measurements. Instead of local flow values, the method uses flow distribution ratios along the entire tree. The tree geometry is used to derive a lumped model and predict the ‘theoretical’ ratios in each bifurcation, while attenuation measurements are used for extracting ‘actual’ ratios. The discrepancies between the measured and the theoretical values are utilized to assess a functional degree of stenosis. Our experimental and numerical analyses show that the quantitative value of discrepancy is proportional to stenosis severity, regardless of boundary conditions.

New transluminal attenuation gradient derived from dynamic coronary CT angiography: diagnostic ability of ischemia detected by 13N-ammonia PET.

Coronary computed tomography angiography (CCTA) has low specificity for detecting significant functional coronary stenosis. We developed a new transluminal attenuation gradient (TAG)-derived dynamic CCTA with dose modulation, and we investigated its diagnostic performance for myocardial ischemia depicted by 13N-ammonia positron emission tomography (PET). Data from 48 consecutive patients who had undergone both dynamic CCTA and 13N-ammonia PET were retrospectively analyzed. Dynamic CCTA was continuously performed in mid-diastole for five cardiac cycles with prospective electrocardiography gating after a 10-s contrast medium injection. One scan of the dynamic CCTA was performed as a boost scan for conventional CCTA at the peak phase of the ascending aorta. Absolute TAG values at five phases around the boost scan were calculated. The dynamic TAG index (DTI) was defined as the ratio of the maximum absolute TAG to the standard deviation of five TAG values. We categorized the coronary territories as non-ischemia or ischemia based on the 13N-ammonia PET results. A receiver operating characteristic (ROC) analysis was performed to determine the optimal cutoff of the DTI for identifying ischemia. The DTI was significantly higher for ischemia compared to non-ischemia (8.8 ± 3.9 vs. 4.6 ± 2.0, p < 0.01). The ROC analysis revealed 5.60 as the optimal DTI cutoff to detect ischemia, with an area under the curve of 0.87, 85.7% sensitivity, and 76.2% specificity. TAG provided no additional diagnostic value for the detection of ischemia. We propose the DTI derived from dynamic CCTA as a novel coronary flow index. The DTI is a valid technique for detecting functional coronary stenosis.

Non-Invasive Assessment of Left Internal Mammary Artery Patency Using Transluminal Attenuation Gradient

Objective: This study aimed to discuss the value of using dual-source computed tomography (CT) to calculate the transluminal attenuation gradient (TAG) and TAG with corrected contrast opacification (TAG-CCO) and quantitatively evaluate left internal mammary artery (LIMA) patency. Method: A total of 32 patients accepting coronary artery bypass grafting were continuously assessed and examined by computed tomography angiography (CTA) of the LIMA before operation. TAG, TAG-CCO, and transluminal diameter gradient (TDG) were then calculated. Blood flow velocity in the LIMA was measured during the operation, and correlation analysis was carried out. Results: TAG, TAG-CCO, and TDG presented significantly positive correlations with blood flow velocity in the LIMA (r = 0.48 r = 0 56 and r = 0.65 respectively, p &lt; 0.05). Conclusion: The greater the absolute values of TAG and TAG-CCO, the lower the blood flow velocity in the LIMA; thus, evaluating LIMA patency presents a certain clinical value.

Added Value of Transluminal Attenuation Gradient to Qualitative CCTA Ischemia Detection as Determined by 13N-ammonia PET Quantitative Myocardial Perfusion.

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.

The transluminal attenuation gradient does not add diagnostic accuracy to coronary computed tomography.

A method for improving the accuracy of coronary computed tomography angiography (CCTA) is highly sought after as it would help to avoid unnecessary invasive coronary angiographies. Measurement of the transluminal attenuation gradient (TAG) has been proposed as an alternative to other existing methods, i.e. CT perfusion and CT fractional flow reserve (FFR). To evaluate the incremental value of three types of TAG in high-pitch spiral CCTA with invasive FFR measurements as reference. TAG was measured using two semi-automatic methods and one manual method. A receiver operating characteristic (ROC) analysis was made to determine the usefulness of TAG alone as well as TAG combined with CCTA for detection of significant coronary artery stenoses defined by an invasive FFR value ≤0.80. A total of 51 coronary vessels in 37 patients were included in this retrospective study. Hemodynamically significant stenoses were found in 13 vessels according to FFR. The ROC analysis TAG alone resulted in areas under the curve (AUCs) of 0.530 and 0.520 for the semi-automatic TAG and 0.557 for the manual TAG. TAG and CCTA combined resulted in AUCs of 0.567, 0.562 for semi-automatic TAG, and 0.569 for the manual TAG. The results from our study showed no incremental value of TAG measured in single heartbeat CCTA in determining the severity of coronary artery stenosis degrees.

Correlation of Transluminal Attenuation Gradientdistal with Corrected Contrast Opacification with Anterior Coronary Atherosclerosis

Objective To explore the correlation between the transluminal attenuation gradient with corrected contrast opacification(TAG-CCO)and the severity of atherosclerotic stenosis in the anterior segment of myocrardial bridge(MB). Methods The imaging data of 200 patients diagnosed with left anterior descending branch(LAD)single MB and coronary atherosclerosis in the anterior segment of MB were retrospectively analyzed.According to MB types,the patients were divided into two groups:incomplete and complete.There were some significant differences in TAG-CCO between patients with the same degree of coronary atherosclerosis(mild,moderate,and severe stenosis)in two groups.The relationships among groups with different degrees(mild,moderate,and severe stenosis)of the same type of MB were further compared. Results Among 84 patients with complete MB,36,30,and 18 patients had mild,moderate,or severe coronary atherosclerosis in the anterior segment of MB;among 116 patients with incomplete MB,45,42,and 29 patients had mild,moderate,or severe coronary atherosclerosis in the anterior segment of MB.In the complete MB group,the TAG-CCO in the anterior segment of MB subgroups were(-0.0086±0.0014)/10 mm,(-0.0170±0.0180)/10 mm,and(-0.0230±0.0026)/10 mm,respectively,in mild,moderate,and severe subgroups(F = 404.728, P<0.001).In the incomplete MB group,the TAG-CCO of patients with mild,moderate and severe coronary stenosis in the anterior segment of MB were(-0.0039±0.0011)/10 mm,(-0.0100±0.0140)/10 mm,and(-0.0160±0.0020)/10 mm,respectively,and the difference among the different stenosis groups was statistically significant(F = 17.756, P < 0.001);the TAG-CCO of patients with mild(t = 16.519, P < 0.001),moderate(t = 2.570, P = 0.012)and severe anterior segment coronary stenosis(t = 10.714, P < 0.001)were significantly lower in the complete MB group than in the incomplete MB group. Conclusions TAG-CCO is correlated with the MB type and the degree of anterior coronary artery stenosis.Thus,TAG-CCO can be used as a predictive indicator for the degree of atheroscleratic stenosis in the anterior segment of MB.

The Effects of a Vasodilator on Transluminal Attenuation Gradient at Coronary Computed Tomography Angiography.

ObjectiveTo evaluate the effects of vasodilators on contrast enhancement and transluminal attenuation gradient (TAG) of coronary arteries at coronary computed tomography angiography (CCTA).Materials and MethodsWe retrospectively reviewed CCTA scans of patients who underwent double-acquisition CCTA; CCTA without a vasodilator, and CCTA during a intravenous (IV) infusion of nitrate. Among them, we enrolled 19 patients who had no significant atherosclerotic lesions or coronary spasms. In the control group, 28 patients were enrolled who showed normal coronary arteries on CCTA, which was acquired by a conventional method (sublingual vasodilator). We measured the TAG and Hounsfield units for each of the three major epicardial coronary arteries (reported as ‘ProxHU’) and then compared the results between the nitrate administration methods (CT without vasodilator [CTpre], CT with IV vasodilator [CTiv], and CT with sublingual vasodilator [CTsub]).ResultsThe mean TAG showed a significant difference between the coronary arteries (right coronary artery [RCA] > left anterior descending artery [LAD] > left circumflex artery [LCX], p < 0.05), while there was no difference in ProxHU of each coronary artery in all three types of nitrate administration methods (p > 0.05). The TAG of CTpre group showed steeper slope than those of vasodilator groups (CTiv and CTsub) on LAD and LCX ([LAD: CTpre = −22.1 ± 6.66, CTiv = −16.76 ± 5.78, and CTsub = −16.47 ± 5.78, p = 0.005], [LCX: CTpre = −31.26 ± 17.43, CTiv = −23.74 ± 14.06, and CTsub = −20.94 ± 12.15, p = 0.051]), while that of RCA showed no significant differences (p = 0.600). When comparing proxHU, CTiv showed higher proxHU than that of CTpre or CTsub, especially on LCX (CTpre = 426.7 ± 68.3, CTiv = 467.9 ± 84.9, and CTsub = 404.9 ± 63.3, p = 0.013). ProxHU showed a negative correlation with TAG on all three of methods (r = −0.280, p < 0.001).ConclusionTAG in CCTA was significantly affected by vasodilator administration. Both TAG and ProxHU of coronary arteries tend to increase with vasodilator administration on CCTA.

CT FFR for Ischemia-Specific CAD With a New Computational Fluid Dynamics Algorithm: A Chinese Multicenter Study

ObjectivesThe aim of this study was to validate the feasibility of a novel structural and computational fluid dynamics–based fractional flow reserve (FFR) algorithm for coronary computed tomography angiography (CTA), using alternative boundary conditions to detect lesion-specific ischemia. BackgroundA new model of computed tomographic (CT) FFR relying on boundary conditions derived from structural deformation of the coronary lumen and aorta with transluminal attenuation gradient and assumptions regarding microvascular resistance has been developed, but its accuracy has not yet been validated. MethodsA total of 338 consecutive patients with 422 vessels from 9 Chinese medical centers undergoing CTA and invasive FFR were retrospectively analyzed. CT FFR values were obtained on a novel on-site computational fluid dynamics–based CT FFR (uCT-FFR [version 1.5, United-Imaging Healthcare, Shanghai, China]). Performance characteristics of uCT-FFR and CTA in detecting lesion-specific ischemia in all lesions, intermediate lesions (luminal stenosis 30% to 70%), and “gray zone” lesions (FFR 0.75 to 0.80) were calculated with invasive FFR as the reference standard. The effect of coronary calcification on uCT-FFR measurements was also assessed. ResultsPer vessel sensitivities, specificities, and accuracies of 0.89, 0.91, and 0.91 with uCT-FFR, 0.92, 0.34, and 0.55 with CTA, and 0.94, 0.37, and 0.58 with invasive coronary angiography, respectively, were found. There was higher specificity, accuracy, and AUC for uCT-FFR compared with CTA and qualitative invasive coronary angiography in all lesions, including intermediate lesions (p < 0.001 for all). No significant difference in diagnostic accuracy was observed in the “gray zone” range versus the other 2 lesion groups (FFR ≤0.75 and >0.80; p = 0.397) and in patients with “gray zone” versus FFR ≤0.75 (p = 0.633) and versus FFR >0.80 (p = 0.364), respectively. No significant difference in the diagnostic performance of uCT-FFR was found between patients with calcium scores ≥400 and <400 (p = 0.393). ConclusionsThis novel computational fluid dynamics–based CT FFR approach demonstrates good performance in detecting lesion-specific ischemia. Additionally, it outperforms CTA and qualitative invasive coronary angiography, most notably in intermediate lesions, and may potentially have diagnostic power in gray zone and highly calcified lesions.

Does vessel length impact transluminal attenuation gradient in 320-slice coronary CT angiography? Correlation with invasive angiography

This study aimed to investigate the influence of vessel length on transluminal attenuation gradient (TAG) and establish a new index, VLN-TAG (VLN-TAG (HU/100mm2) = TAG (HU/10mm)/vessel length (10mm)), to estimate the diagnostic value using 320-slice computed tomography (CT). A total of 150 coronary arteries from 52 patients who underwent single-beat scanning using 320-slice CT and invasive coronary angiography (ICA) within 2weeks were retrospectively enrolled. TAG was obtained from the major three epicardial vessels, and its interrelation with the measured length of the vessels was evaluated by Pearson correlation and regression analyses. The changes in TAG and VLN-TAG were compared with the corresponding stenosis severities ascertained by ICA using repeated measures ANOVA. TAG had a significant interrelation with the measured length of the vessels (r = 0.644, p < 0.001). Neither TAG nor VLN-TAG with different stenosis degrees of < 50, 50-70, and 70-99% on ICA had significant difference among the three groups. Plaque composition had no influence on VLN-TAG in all groups. The combined TAG or VLN-TAG and coronary computed tomography angiography (CCTA) assessment did not significantly change the area under the curve compared with using CCTA only. In the calcified vessels group, adding VLN-TAG to CCTA improved the specificity (92.86 vs 85.71%). Vessel length is an important factor impacting TAG. TAG does not offer an incremental diagnostic value compared with CCTA only for detecting coronary stenosis. • Transluminal attenuation gradient (TAG) does not improve the diagnostic value of CCTA. Vessel length impacts TAG, but VLN-TAG does not improve the diagnostic value of CCTA. • Plaque composition had no influence on VLN-TAG in all groups of stenosis degrees. There may be a minimal improvement in specificity when VLN-TAG is applied to the calcified vessels group.

Evaluating the relationship between myocardial bridge of the left anterior descending branch and atherosclerosis of coronary artery using transluminal attenuation gradient on CT

Objective To evaluate the relationship between concurrent myocardial bridge at anterior descending branch and the formation of coronary atherosclerosis plaques by using transluminal attenuation gradient (TAG). Methods A total of 198 patients underwent coronary CTA in Renji Hospital of Shanghai Jiaotong University School of Medcine from June 2017 to March 2018 and the results showed the anterior descending myocardial bridge. The data were retrospectively analyzed. All patients completed the coronary CTA with 320-row detector CT. According to the manifestations of myocardial bridge on CTA,the patients were divided into deep and superficial myocardial bridge groups. According to whether the patients were complicated with coronary atherosclerotic plaques,they were divided into isolated myocardial bridge group and myocardial bridge with coronary atherosclerotic plaque group. The thickness and length of myocardial bridge,the volume of coronary atherosclerotic plaques at the site of myocardial bridge,the pre-bridge and post-bridge TAG values,and the K ratio were recorded. Independent sample t test (normal distribution) or Mann-Whitney U test (skewed distribution) was used to compare the difference of measurement data among different groups. χ2 test was used to compare the difference of enumeration data among different groups. Pearson correlation test was used to analyze the correlation among pre-bridge and post-bridge TAG values,K ratio,thickness and length of myocardial bridge and plaque volume. The influence of above indexes on plaque occurrence was analyzed by binary logistic regression analysis. The relationship between main influence indexes and plaque formation was analyzed by receiver operating characteristic curve (ROC). Results Ninety nine patients had isolated myocardial bridge,99 with myocardial bridge and coronary atherosclerotic plaques,27 with superficial myocardial bridge and 171 with deep myocardial bridge. All atherosclerotic plaques occurred in pre-bridge and the mean volume of plaques was (91.6±83.0)mm3. The differences in sex,age,height,body weight and body mass index werenot statistically significant between isolated myocardial bridge group and myocardial bridge with coronary atherosclerotic plaque group (all P>0.05). The difference in pre-bridge TAG value was statistically significant between the isolated myocardial bridge group and myocardial bridge with coronary atherosclerotic plaque group (all P 0.05). The difference in pre-bridge and post-bridge TAG values and K value was not statistically significant between the superficial group and the deep group (all P>0.05). There was a weak negative correlation (r=-0.205,-0.316,-0.339,respectively,P 0.05). The area under curveof plaque formation promoted by pre-bridge TAG value was 0.582. When the diagnostic critical value was-37.26 HU/mm,the sensitivity and specificity of pre-bridge TAG value in plaque formation were 31.31% and 81.82%,respectively. Conclusion The TAG value of anterior descending bridge is an independent risk factor for plaque occurrence. The abnormal TAG value of anterior descending myocardial bridge can be detected early by CTA. Key words: Coronary vessels; Tomography, X-ray computed; Transluminal attenuation gradient; Myocardial bridge

VALUE OF TRANSLUMINAL ATTENUATION GRADIENT FROM CORONARY CTA TO IDENTIFY VESSEL-SPECIFIC CORONARY ISCHEMIA: RESULTS FROM THE PROSPECTIVE, MULTICENTER, INTERNATIONAL CREDENCE TRIAL

Prior studies have reported discordant findings for the utility of transluminal attenuation gradient (TAG) to diagnosis vessel-specific ischemia. In the prospective, multicenter, international CREDENCE trial, 612 patients underwent non-emergent invasive angiography with FFR in all 40-90% stenoses.

Clinical feasibility of catheter-directed selective intracoronary computed tomography angiography using an extremely low dose of iodine in patients with coronary artery disease.

This study aimed to evaluate the clinical feasibility of catheter-directed selective computed tomography angiography (S-CTA) in patients with coronary artery disease (CAD). We prospectively enrolled 65 patients diagnosed with CAD who underwent conventional computed tomography angiography (C-CTA). C-CTA was performed with 60-90mL of contrast medium (370mg iodine/mL), whereas S-CTA was performed with 15mL of contrast medium and 17.19mg iodine/mL. Luminal enhancement range, homogeneity of luminal enhancement, image quality, plaque volume (PV), and percent aggregate plaque volume (%APV) were measured. Paired Student's t test, Wilcoxon rank-sum test, and Pearson's correlation coefficient were used to compare two methods. Luminal enhancement was significantly higher on S-CTA than on C-CTA (324.4 ± 8.0Hounsfield unit (HU) vs. 312.0 ± 8.0HU, p < 0.0001 in the per-vessel analysis). Transluminal attenuation gradient showed a significantly slower reduction pattern on S-CTA than on C-CTA (-0.65HU/10mm vs. -0.89HU/10mm, p < 0.0001 in the per-vessel analysis). Image noise was significantly lower on S-CTA than on C-CTA (39.6 ± 10.0HU vs. 43.9 ± 9.4HU, p < 0.0001). There was excellent correlation between S-CTA and C-CTA with respect to PV and %APV (r = 0.99, r = 0.98, respectively). S-CTA might be useful in facilitating atherosclerotic plaque analysis and providing guidance for complex lesions such as chronic total occlusion, particularly in cases in which on-site procedure planning is required. • Selective computed tomography angiography (S-CTA) can serve as an intraprocedural computed tomography angiography protocol. • S-CTA was performed with low dose of iodine compared with conventional computed tomography angiography. • S-CTA enables on-site atherosclerotic plaque analysis.

Anatomical and Functional Computed Tomography for Diagnosing Hemodynamically Significant Coronary Artery Disease: A Meta-Analysis

ObjectivesThis meta-analysis determined the diagnostic performance of coronary computed tomography (CT) angiography (CTA), CT myocardial perfusion (CTP), fractional flow reserve CT (FFRCT), the transluminal attenuation gradient (TAG), and their combined use with CTA versus FFR as a reference standard for detection of hemodynamically significant coronary artery disease (CAD). BackgroundCTA provides excellent anatomic, albeit limited functional information for the evaluation of CAD. Recently, various functional CT techniques emerged to assess the hemodynamic consequences of CAD. MethodsThis meta-analysis was performed in adherence to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. PubMed, EMBASE, and Web of Science were searched from inception until September 7, 2017. Bayesian random effects analysis was used to compute pooled sensitivity, specificity, and the summary receiver-operating characteristic curve of the index tests and compare them with the FFR as a reference standard. Analyses were performed on vessel and patient levels. Because CTA has excellent sensitivity, specificity was considered most relevant. Individual FFRCT values were collected. ResultsOverall, 54 articles and 5,330 patients were included. At vessel level, pooled specificity of CTP (0.86; 95% confidence interval [CI]: 0.76 to 0.93), FFRCT (0.78; 95% CI: 0.72 to 0.83) and TAG (0.77; 95% CI: 0.61 to 0.89) were substantially higher than that of CTA (0.61; 95% CI: 0.54 to 0.68). The addition of FFRCT, CTP, and TAG to CTA resulted in high to excellent specificities (0.80 to 0.92). The summary receiver-operating characteristic curve at vessel level yielded superior diagnostic accuracy for CTP, FFRCT, and combined CTA and CTP, compared with CTA. A subanalysis of on-site versus off-site FFRCT revealed no substantial differences between the sensitivity (0.84 vs. 0.85) and specificity (0.80 vs. 0.73) of the 2 techniques. In a second subanalysis, dynamic CTP showed higher sensitivity (0.85 vs. 0.72), but had a lower specificity (0.81 vs. 0.90) than static CTP. ConclusionsCTP and FFRCT demonstrated a substantial improvement in the identification of hemodynamically significant CAD compared with CTA; therefore, their integration to clinical workflow before revascularization is recommended.

P1711Non-invasive coronary physiology based on computational analysis of intracoronary transluminal attenuation gradient

P1711Non-invasive coronary physiology based on computational analysis of intracoronary transluminal attenuation gradient

The transluminal attenuation gradient in coronary CT angiography

OBJECTIVE: Results of the use of the transluminal attenuation gradient (TAG) at coronary CT angiography (CCTA) to predict hemodynamically significant disease vary widely. This study tested whether diagnostic performance of TAG to predict fractional flow reserve (FFR) ≤ 0.8 is improved when applied separately to subsets of coronary arteries that carry similar physiological flow. METHODS: 28 patients with 64 × 0.5 mm CCTA and invasive FFR in ≥1 major coronary artery were retrospectively evaluated. Two readers assessed TAG in each artery. The receiver operating characteristic (ROC) area under the curve (AUC) was used to assess the diagnostic performance of TAG to detect hemodynamically significant disease following a clinical use rule [negative: FFR > 0.8 or ≤ 25% diameter stenosis (DS) at invasive catheter angiography; positive: FFR ≤ 0.8 or ≥ 90% DS at invasive catheter angiography]. ROC AUC was compared for all arteries pooled together, vs separately for arteries carrying similar physiological flow (Group 1: all left anterior descending plus right-dominant left circumflex; Group 2: right-dominant RCA plus left/co-dominant left circumflex). RESULTS: Of the 84 arteries, 30 had FFR measurements, 30 had ≤25% DS and 13 had ≥90% DS. 11 arteries with 26-89% DS and no FFR measurement were excluded. TAG interobserver reproducibility was excellent (Pearson r = 0.954, Bland-Altman bias: 0.224 Hounsfield unit cm). ROC AUC to detect hemodynamically significant disease was higher when considering arteries separately (Group 1 AUC = 0.841, p = 0.039; Group 2 AUC = 0.840, p = 0.188), than when pooling all arteries together (AUC = 0.661). CONCLUSION: Incorporating information on the physiology of coronary flow via the particular vessel interrogated and coronary dominance may improve the accuracy of TAG, a simple measurement that can be quickly performed at the time of CCTA interpretation to detect hemodynamically significant stenosis in individual coronary arteries. Advances in knowledge: The interpretation of TAG may benefit by incorporating information regarding which coronary artery is being interrogated.

Contrast opacification difference of mural artery and the transluminal attenuation gradient on coronary computed tomography angiography for detection of systolic compression of myocardial bridge.

Myocardial bridges (MB) have traditionally been considered a benign condition, but recent studies have demonstrated that the clinical complications can be dangerous. The transluminal attenuation gradient (TAG) obtained from coronary computed tomography angiography (CCTA) data (Retrospective ECG-triggered method) has been used in detecting significant stenosis in coronary artery caused by atherosclerosis. Contrast opacification difference (COD) was the parameters calculated as the change between attenuation of mural artery and the median attenuation of presumptive vessel segment; it was evaluated along with TAGstandardized (TAGs) and MB length for predicting MB with systolic compression (MB-SC) in patients diagnosed as MB in left anterior descending coronary artery (LAD) by CCTA or invasive coronary angiograph (ICA). A total of 107MB patients were divided into three groups based on systolic compression (SC), including: Group 1 (MB without SC); Group 2 (MB with mild SC); and Group 3 (MB with significant SC). ANOVA and Kruskal-Wallis analysis indicated TAGs showed the most significant differences for MB identification. This study revealed that TAGs decreasing and COD increasing were dominated in MB with significant SC. COD had a higher sensitivity and a higher negative predictive value for detecting MB with significant SC than TAGs.

The transluminal attenuation gradient in coronary CT angiography for the detection of hemodynamically significant disease: can all arteries be treated equally?

Results of the use of the transluminal attenuation gradient (TAG) at coronary CT angiography (CCTA) to predict hemodynamically significant disease vary widely. This study tested whether diagnostic performance of TAG to predict fractional flow reserve (FFR) ≤0.8 is improved when applied separately to subsets of coronary arteries that carry similar physiological flow. 28 patients with 64×0.5 mm CCTA and invasive FFR in ≥1 major coronary artery were retrospectively evaluated. Two readers assessed TAG in each artery. The receiver operating characteristic (ROC)area under the curve (AUC) was used to assess the diagnostic performance of TAG to detect hemodynamically significant disease following a clinical use rule [negative: FFR>0.8 or ≤25% diameter stenosis (DS) at invasive catheter angiography; positive: FFR≤0.8 or ≥90% DS at invasive catheter angiography]. ROC AUC was compared for all arteries pooled together, vs separately for arteries carrying similar physiological flow (Group 1: all left anterior descending plus right-dominant left circumflex; Group 2: right-dominant RCA plus left/co-dominant left circumflex). Of the 84 arteries, 30 had FFR measurements, 30 had ≤25% DS and 13 had ≥90% DS. 11 arteries with 26-89% DS and no FFR measurement were excluded. TAG interobserver reproducibility was excellent (Pearson r=0.954, Bland-Altman bias: 0.224 Hounsfield unitcm-1). ROC AUC to detect hemodynamically significant disease was higher when considering arteries separately (Group 1 AUC=0.841, p=0.039; Group 2 AUC=0.840, p=0.188), than when pooling all arteries together (AUC=0.661). Incorporating information on the physiology of coronary flow via the particular vessel interrogated and coronary dominance may improve the accuracy of TAG, a simple measurement that can be quickly performed at the time of CCTA interpretation to detect hemodynamically significant stenosis in individual coronary arteries. Advances in knowledge: The interpretation of TAG may benefit by incorporating information regarding which coronary artery is being interrogated.