The Diagnostic Performance And Clinical Application Of Cardiac CT In Coronary Artery Diseases

Objective : 1)With reference to invasive coronary angiography(ICA),to evaluate the diagnostic accuracy of in-stent restenosis(ISR)and Mehran classification of ISR by coronary computed tomography angiography(CCTA);2)To investigate the morphological characteristics of early and late stage of coronary chronic total occlusion(CTO)observed by coronary computed tomography angiography(coronary CTA);3)To study the predictive value of transluminal attenuation gradient(TAG)derived from diastolic phase of CCTA for identifying systolic compression of myocardial bridge(MB).Materials and Methods:1)Consecutive patients,who had implanted stents and underwent CCTA and ICA examinations within one month,were retrospectively included.Mehran classification was determined by CCTA and ICA to classify ISR lesions into four types: focal,diffuse intrastent,diffuse proliferative and total occlusion;2)We retrospectively analyzed patients who underwent coronary CTA and invasive coronary angiography and had at least one CTO with known duration.The following parameters were obtained in coronary CTA: calcification of occluded segment;stump morphology;lesion length;remodeling index;presence of intra-occlusion linear contrast enhancement and density of non-calcified CTO components.CT parameters were compared between early(duration?12 months)and late (duration>12 months)stage CTO subgroups;3)Consecutive patients with MB(confirmed by CCTA)without obstructive coronary artery disease were retrospectively enrolled.Patients were classified,on the basis of their CCTA findings,into three groups: those without systolic compression,those with systolic compression <50%,and those with systolic compression ?50%.TAG was defined as the linear regression coefficient between intraluminal attenuation in Hounsfield units(HU)and length from the vessel ostium.Other indices such as the length and depth of the MB were also recorded,and compared among the groups.Results: 1)Totally 570 stents in 320 patients with 94 ISR lesions were evaluated.According to patient-based(n=320)analysis,lesion-based(n=456)analysis and stent-based analysis(n=570),the specificity,sensitivity,NPV,PPV,and diagnostic accuracy of CCTA were 95.2%-96.9%,83.3%-96.3%,96.9%-98.5%,78.9%-88.9%,94%-96.2% respectively.In patients with stents?3mm(n=294),Mehran classification by CCTA correlated well with ICA's findings.The diagnostic accuracy of CCTA for Mehran classification class I,class II,class III and class IV was 87.2%,86.7%,66.7% and 88% respectively;2)One-hundred and twelve patients with 124 chronically occluded coronary arteries were analyzed.Fifty-nine patients had early stage CTOs(62 lesions)and 53 patients had late stage CTOs(62 lesions).Calcification was more severe in late-stage versus early CTOs(Agatston score: early stage,27.4 ±46.7 vs.late stage,58.3 ± 112.4;p = 0.049).Remodeling index was lower in late-stage CTOs(early stage,0.96 ± 0.2 vs.late stage,0.88 ± 0.22;p = 0.034).In patients with late stage CTO,the presence of intra-occlusion linear enhancement was more likely(45.2% vs 14.5%,p < 0.001),and the density of non-calcified components was significantly higher(85.4 ± 27.2 HU vs.65.7± 30.1 HU,p < 0.001).Stump morphology was not different between the two groups;3)In total,143 patients with 144 MBs were included.TAG was the lowest in MB patients with systolic compression ?50%(-19.9 ± 8.7 HU/10mm),followed by those with systolic compression <50%(-14.0 ± 4.8 HU/10mm),and those without systolic compression(-9.6 ± 6.2 HU/10 mm,p <0.001).ROC curve analysis determined the optimal cutoff value of TAG as-18.8 HU/10 mm(area under curve = 0.778,p < 0.001),which yielded higher sensitivity,specificity,positive predictive value,negative predictive value,and diagnostic accuracy(54.1%,90.4%,80.5%,72.8%,and 75%)over the other two parameters.Conclusion: 1)With reference to ICA,CCTA is a non-invasive method with high diagnostic accuracy for post-stenting patients,especially in those with stents caliber ?3mm.CCTA can be used for accurate classification of ISR patterns;2)Coronary CTA reveals differences between chronic total coronary occlusions of longer and shorter duration.A long duration is associated with focal calcification and negative remodeling,as well as intra-occlusion enhancement and a higher density of non-calcified components;3)TAG derived from diastolic phase could predict systolic compression of MB.In addition,with a cutoff value of-18.8 HU/10 mm,TAG was a better predictor of significant MB compression,compared to the length or depth of the MB.