Relationship between Coronary Iodine Concentration Determined Using Spectral CT and the Outcome of Percutaneous Coronary Intervention in Patients with Chronic Total Occlusion
冠状动脉碘浓度与经皮冠状动脉介入治疗慢性完全闭塞患者预后的关系

Introduction 简介

Coronary chronic total occlusion (CTO) is an obstructive coronary artery disease for which patients are commonly referred for percutaneous coronary intervention (PCI) (1). The prevalence of CTO has been reported to be up to 30% among patients with a clinical indication of coronary angiography (2). Revascularization of the coronary arteries by PCI improves symptoms, quality of life, left ventricular function, and survival in patients with CTO (3). However, despite recent technological advances and improvements in interventional strategies, the success rate of PCI for the revascularization of CTO has remained low (4,5).
冠状动脉慢性完全梗塞(CTO)是一种阻塞性冠状动脉疾病,患者通常被转诊进行经皮冠状动脉介入术(PCI)(1)。CTO 的患病率被报告可高达 30%,其中有临床适应行冠状动脉造影的患者(2)。PCI 可改善 CTO 患者的症状、生活质量、左心室功能和存活(3)。然而,尽管近期技术进步和介入策略的改善,PCI 重建 CTO 的成功率仍较低(4,5)。

The pathologic characteristics of CTO encompass the presence of calcification, inflammation, and neovascularization within the totally occluded segment (6). The degree of calcification, negative remodeling, and the presence of necrotic core along the occluded segment of the CTO help explain the success rates of PCI for CTO (7). In particular, small microvessel recanalization and loose fibrous tissue of CTO lesions are associated with the success rate of PCI (8). Coronary CT angiography is a valuable imaging method for the characterization of CTO (9–11). In clinical practice, the scoring systems based on the coronary CT angiography manifestations of CTO have been used for treatment planning and proper selection of candidates for PCI. Li et al (12) reported that the presence of contrast enhancement within the occluded segment of the CTO on coronary CT angiograms may be associated with microvessel formation or recanalization of the lumen of the CTO. However, the visual assessment of contrast enhancement in the occluded segment of the CTO on coronary CT angiograms may be subjective, depending on the reader’s experience.
慢性全闭塞冠状动脉(CTO)的病理学特征包括钙化、炎症和新生血管形成(6)。CTO 闭塞段的钙化程度、负性重构和坏死病灶的存在有助于解释 PCI 对 CTO 的成功率(7)。特别是 CTO 病变小微管再通和松散的纤维组织与 PCI 的成功率相关(8)。冠状动脉 CT 血管造影是 CTO 表征的有价值的影像学方法(9–11)。在临床实践中,基于冠状动脉 CT 血管造影 CTO 表现的评分系统被用于治疗规划和 PCI 候选人的合适选择。Li 等人(12)报告,CTO 闭塞段冠状动脉 CT 血管造影中的对比剂强化可能与微血管形成或 CTO 管腔再通相关。但是,对 CTO 闭塞段冠状动脉 CT 血管造影中对比剂强化的视觉评估可能会受读者经验的影响而具有主观性。

Spectral CT based on the dual-energy CT technique can quantify iodine content, which is a major component of the contrast media used at coronary CT angiography (13,14). The quantification of iodine content by using the dual-energy CT technique may provide a more reliable evaluation of contrast enhancement than an assessment based on Hounsfield units (15). We hypothesized that the characterization of CTO at coronary CT angiography may benefit from iodine-specific reconstruction by using spectral CT. Thus, the objective of this study was to measure the coronary iodine concentration (CIC) of CTO lesions with coronary CT angiography by using spectral CT and to evaluate the feasibility of CTO-CIC in the assessment of the outcome of PCI for CTO.
基于双能 CT 技术的光谱 CT 可以定量测量碘含量,这是用于冠状动脉 CT 血管造影的对比剂的主要成分(13,14)。利用双能 CT 技术测量碘含量可能提供比基于修斯菲尔德单位的评估更可靠的对比增强评估(15)。我们假设,利用光谱 CT 进行碘特异性重建可能有助于冠状动脉 CT 血管造影对慢性完全闭塞(CTO)的表征。因此,本研究的目的是使用光谱 CT 测量 CTO 病变的冠状动脉碘浓度(CIC),并评估 CTO-CIC 在评估经皮冠状动脉介入术(PCI)CTO 治疗结果的可行性。

Materials and Methods 材料和方法

Study Population 研究人群

This retrospective study was approved by our institutional review board, and the requirement for informed consent was waived. Between June 2017 and July 2018, 70 consecutive patients with CTO who underwent coronary CT angiography and PCI sequentially within 1 month were retrospectively reviewed. The inclusion criteria were (a) a diagnosis of CTO confirmed at invasive coronary angiography and (b) previous imaging with preprocedural coronary CT angiography with spectral CT. The exclusion criteria were (a) the presence of a coronary stent at the occluded segment of the CTO (n = 9), (b) congestive heart failure (n = 8), or (c) an uninterpretable coronary CT angiographic examination (n = 3). Finally, 50 patients were enrolled into this study (Fig 1).
本回顾性研究已被我院伦理委员会批准,知情同意的要求已豁免。2017 年 6 月至 2018 年 7 月期间,70 名连续的冠状动脉闭塞(CTO)患者接受了冠状动脉 CT 血管造影和经皮冠状动脉介入治疗,并在 1 个月内完成。纳入标准是：(a)经侵入性冠状动脉造影确诊为 CTO,(b)既往有术前冠状动脉 CT 血管造影并包含光谱 CT 成像。排除标准为：(a)CTO 闭塞段有冠状动脉支架(n = 9)、(b)充血性心力衰竭(n = 8)或(c)冠状动脉 CT 血管造影无法评估(n = 3)。最终,50 名患者被纳入本研究(图 1)。

Figure 1:

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CT Image Reconstruction and Analysis
计算机断层扫描图像重建与分析

Coronary CT angiography data were transferred to an offline workstation (IntelliSpace Portal, version 9.0; Philips Medical Systems, Best, the Netherlands) for image analysis. The coronary CT angiography data were analyzed by two experienced radiologists (S.H.H. and J.Y.L.) with 15 years and 4 years, respectively, of experience in cardiac imaging. The reviewers were independently blinded to the clinical histories and outcomes of PCI. Any disagreement between the two reviewers was resolved by consensus.
冠状动脉 CT 血管造影数据被转移到离线工作站(IntelliSpace Portal, 9.0 版本; Philips 医疗系统, Best, 荷兰)进行图像分析。冠状动脉 CT 血管造影数据由两位经验丰富的放射科医生(S.H.H.和 J.Y.L.)分别具有 15 年和 4 年心脏影像学工作经验进行分析。评审者对患者的临床资料和 PCI 结果进行独立盲法评估。两位评审者之间的任何分歧都通过共识解决。

At coronary CT angiography, the CTO lesion was defined by the complete absence of luminal enhancement in the coronary artery. Furthermore, the anatomic characteristics of whole CTO lesions were assessed using the cross-sectional curved multiplanar reformatted images from coronary CT angiography. The reviewers recorded the presence or absence of high-risk coronary CT angiographic findings related to failed PCI in every CTO lesion. The high-risk coronary CT angiography manifestations of CTO consisted of (a) long CTO (with a total lesion length > 2 cm), (b) severe calcification (with calcifications ≥ 50% of the vessel cross-sectional area), (c) CTO bending (with an angle ≥ 45° at the occlusion site), and (d) blunt stump (without any tapered stump at the entry of the CTO) (Fig 2) (9).
在冠状动脉 CT 血管造影中,全闭塞病变由冠状动脉管腔内完全缺乏强化来定义。此外,使用冠状动脉 CT 血管造影的横断面曲面多平面重建图像评估了全部慢性完全闭塞病变的解剖特征。评审员记录了每个慢性完全闭塞病变与 PCI 失败相关的高危冠状动脉 CT 血管造影表现。慢性完全闭塞病变的高危冠状动脉 CT 血管造影表现包括(a)长闭塞(总病变长度>2 cm)、(b)严重钙化(血管横断面积中钙化≥50%)、(c)闭塞部位弯曲(角度≥45°)和(d)钝端(在闭塞部入口处无任何锥形端) (图 2) (9)。

Figure 2a:

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Figure 2b:

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Figure 2c:

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Figure 2d:

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For evaluating the CIC (Fig 3), the cross-sectional virtual monoenergetic image obtained at 60 keV and the iodine-no-water map obtained perpendicular to the coronary artery centerline were reconstructed for each CTO lesion. On the virtual monoenergetic image obtained at 60 keV, the regions of interest (ROIs) were manually drawn at the proximal CTO (at 2 mm from the entry of the CTO, excluding the calcification) and the reference vessel (at the unaffected vessel immediately proximal to the CTO within a 1-cm interval). The ROI at the reference vessel covered the entire vessel lumen. The ROI at the proximal CTO represented the largest noncalcified area in the occluded segment of the CTO. The ROI area of the reference segment (reference ROI area, in millimeters squared) and the ROI area of the proximal CTO (CTO-ROI area, in millimeters squared) were recorded. Thereafter, the CICs of the reference vessel (reference CIC, in milligrams per milliliter) and the proximal CTO (CTO-CIC, in milligrams per milliliter) were measured by applying the ROIs to the iodine-no-water maps. Eventually, the reviewers measured the reference areas, CTO area, reference CIC, and CTO-CIC by using the virtual monoenergetic image obtained at 60 keV and iodine-no-water map from coronary CT angiography (Fig 3).
对于评估 CIC (图 3),每个 CTO 病变处获得了 60 keV 虚拟单能量图像和与冠状动脉中心线垂直的碘-无水图像。在 60 keV 获得的虚拟单能量图像上,手动勾画了感兴趣区(ROI)在近端 CTO(距 CTO 入口 2 mm,不包括钙化)和参考血管(在 CTO 近端未受影响的血管内,1 cm 范围内)。参考血管的 ROI 覆盖整个血管腔。近端 CTO 的 ROI 表示 CTO 闭塞段中最大的非钙化区域。记录了参考段的 ROI 面积(参考 ROI 面积,平方毫米)和近端 CTO 的 ROI 面积(CTO-ROI 面积,平方毫米)。此后,通过将 ROI 应用于碘-无水图,测量了参考血管的 CIC(参考 CIC,毫克/毫升)和近端 CTO 的 CIC(CTO-CIC,毫克/毫升)。最终,评审员使用 60 keV 虚拟单能量图像和冠状动脉 CT 血管造影的碘-无水图(图 3)来测量参考面积、CTO 面积、参考 CIC 和 CTO-CIC。

Figure 3a:

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Figure 3b:

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Figure 3c:

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Results 结果

All 50 patients with CTO (mean age, 65 years ± 13; range, 37–89 years; 40 men [mean age, 62 years ± 13; range, 37–89 years] and 10 women [mean age, 74 years ± 10; range, 60–86 years]) were included (Table 1). Depending on the outcome of PCI, 34 (68%) and 16 (32%) of the 50 patients were assigned to the successful PCI and failed PCI groups, respectively. When considering clinical histories that included smoking, hypertension, diabetes mellitus, and dyslipidemia, no significant difference was observed in their incidence between the successful PCI and failed PCI groups (Table 1). The mean dose–length product of coronary CT angiography was 410 mGy · cm ± 75 (range, 310–489 mGy · cm), which corresponded to 5 mSv ± 3 (range, 4–7 mSv). PCI was performed in all patients at a mean interval of 4 days ± 2 (range, 2–7 days) after coronary CT angiography.
所有 50 名 CTO 患者(平均年龄 65 岁±13 岁;年龄范围 37-89 岁;40 名男性[平均年龄 62 岁±13 岁;年龄范围 37-89 岁]和 10 名女性[平均年龄 74 岁±10 岁;年龄范围 60-86 岁])都被纳入表 1。根据 PCI 的结果,50 名患者中有 34 名(68%)和 16 名(32%)分别被分到成功 PCI 组和失败 PCI 组。当考虑吸烟、高血压、糖尿病和血脂异常等临床史时,这两组之间没有显著差异表 1。冠状动脉 CT 血管造影的平均剂量长度积为 410 mGy·cm±75(范围 310-489 mGy·cm),相当于 5 mSv±3(范围 4-7 mSv)。所有患者在冠状动脉 CT 血管造影后 4 天±2 天(范围 2-7 天)内进行了 PCI。

Table 1: Clinical Characteristics of the Study Cohort
表 1：研究队列的临床特征

In the comparison of coronary CT angiography manifestations (Table 2), the right coronary artery was the most common location of CTO. However, there was no significant difference of PCI result among the locations of CTO. The failed PCI group showed significantly greater incidence of severe calcification (11 of 16 [69%] vs 12 of 34 [35%]; P = .55), blunt stump (10 of 16 [62%] vs six of 34 [18%]; P = .001), and long (>2 cm) CTO (12 of 16 [75%] vs 15 of 34 [44%]; P = .04) compared with the successful PCI group. In the quantitative assessment of the reference vessel at coronary CT angiography, no significant difference was noted in the reference area between the failed PCI and successful PCI groups (mean, 6.4 mm² ± 2.3 vs 5.9 mm² ± 2.1, respectively; P = .42). In contrast, the failed PCI group showed significantly less reference CIC than did the successful PCI group (mean, 11.8 mg/mL ± 3.7 vs 14.5 mg/mL ± 4.1; P = .03). In the quantitative assessment of proximal CTO with coronary CT angiography, no significant difference was observed in the CTO-ROI area between the failed PCI and successful PCI groups (mean, 5.0 mm² ± 1.9 vs 5.2 mm² ± 1.7; P = .35). In contrast, the failed PCI group showed significantly less CTO-CIC than did the successful PCI group (mean, 1.3 mg/mL ± 0.9 vs 5.2 mg/mL ± 2.5; P < .001). In the reproducibility of the coronary CT angiography analysis (Table 3), the intraclass correlation coefficients of the CTO-ROI area and CTO-CIC were 0.7 or greater, indicating good reproducibility.
在冠脉 CT 血管造影表现的比较(表 2)中,右冠状动脉是 CTO 最常见的位置。然而,不同 CTO 位置间的 PCI 结果没有显著差异。失败 PCI 组严重钙化的发生率明显更高(11/16 [69%]比 12/34 [35%]; P = .55),钝头(10/16 [62%]比 6/34 [18%]; P = .001),以及长(>2 cm)CTO(12/16 [75%]比 15/34 [44%]; P = .04),与成功 PCI 组相比。在冠脉 CT 血管造影的参考血管的定量评估中,失败 PCI 组和成功 PCI 组的参考面积没有显著差异(平均值,6.4 mm² ± 2.3 比 5.9 mm² ± 2.1; P = .42)。相反,失败 PCI 组的参考 CIC 明显低于成功 PCI 组(平均值,11.8 mg/mL ± 3.7 比 14.5 mg/mL ± 4.1; P = .03)。在对近端 CTO 进行冠脉 CT 血管造影的定量评估中,失败 PCI 组和成功 PCI 组的 CTO-ROI 面积没有观察到显著差异(平均值,5.0 mm² ± 1.9 比 5.2 mm² ± 1.7; P = .35)。相反,失败 PCI 组的 CTO-CIC 明显低于成功 PCI 组(平均值,1.3 mg/mL ± 0.9 比 5.2 mg/mL ± 2.5; P < .001)。在冠脉 CT 血管造影分析的再现性(表 3)中,CTO-ROI 面积和 CTO-CIC 的级内相关系数为 0.7 或以上,表明良好的重复性。

Table 2: Comparison of Coronary CT Angiography Manifestations between Successful PCI and Failed PCI
表 2: 成功经皮冠状动脉介入治疗和失败经皮冠状动脉介入治疗的冠状 CT 血管造影表现对比

Table 3: Reproducibility of the Coronary CT Angiography Parameters
表 3: 冠状动脉 CT 血管造影参数的可重复性

In the assessment of failed PCI (Figs 4, 5), the area under the receiver operating characteristic curve for CTO-CIC was 0.89 (P < .001). When the cutoff point of low CTO-CIC was set at 2.5 mg/mL to predict failed PCI, the sensitivity was 87% (14 of 16), specificity was 79% (27 of 34), positive predictive value was 67% (14 of 21), and negative predictive value was 93% (27 of 29). In the reproducibility of low CTO-CIC (Table 3), the κ values of low CTO-CIC were 0.6 or greater, indicating fair-to-good reproducibility. Finally, the coronary CT angiographic findings at the CTO proximal entry (severe calcification, blunt stump, and low CTO-CIC) were used as input variables for the multivariable logistic regression analysis (Table 4). In this analysis, low CTO-CIC (odds ratio, 27.0; 95% confidence interval: 4.9, 147.6; P < .0001) was an independent factor for failed PCI.
在对失败 PCI 进行评估(图 4、5)时,CTO-CIC 的受试者工作特征曲线下面积为 0.89(P < .001)。当将 low CTO-CIC 的截断点设定为 2.5 mg/mL 以预测失败的 PCI 时,敏感性为 87%(14/16),特异性为 79%(27/34),阳性预测值为 67%(14/21),阴性预测值为 93%(27/29)。在 low CTO-CIC 的可重复性(表 3)中,low CTO-CIC 的 κ 值为 0.6 或更大,表示可重复性为良好到优秀。最后,使用 CTO 近端入口的冠状动脉 CT 血管造影结果(严重钙化、钝头和 low CTO-CIC)作为输入变量进行多变量 logistic 回归分析(表 4)。在此分析中,low CTO-CIC(比值比为 27.0;95%置信区间:4.9, 147.6;P < .0001)是导致 PCI 失败的独立因素。

Figure 4:

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Figure 5a:

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Figure 5b:

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Figure 5c:

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Table 4: Multivariable Predictors of Failed PCI for CTO
表 4：慢性完全闭塞冠状动脉介入治疗失败的多变量预测因素

Discussion 讨论

We assessed the CIC of proximal CTO (CTO-CIC) on the iodine-no-water map from coronary CT angiography by using spectral CT just before PCI. Our results showed that patients with a failed PCI had significantly lower mean CTO-CIC than those who underwent a successful PCI (P < .001). Furthermore, the optimal cutoff for low CTO-CIC related to failed PCI was set at 2.5 mg/mL. At multivariable analysis, the low CTO-CIC of 2.5 mg/mL or less was independently associated with failed PCI for CTO.
我们在冠状动脉 CT 血管造影仪上使用光谱 CT 技术,在 PCI 手术前评估了近端慢性闭塞冠状动脉(CTO-CIC)的碘含量。我们的结果显示,PCI 手术失败的患者,平均 CTO-CIC 显著低于手术成功的患者(P < .001)。此外,与 PCI 手术失败相关的低 CTO-CIC 的最佳阈值被设定为 2.5 mg/mL。在多变量分析中,CTO-CIC 值≤2.5 mg/mL 独立与 PCI 手术失败相关。

Many CT features have been identified for defining the treatment strategies for the revascularization of CTO (11,19). In particular, calcification of the CTO lesion is closely associated with difficulty in achieving a successful PCI for CTO. It poses difficulties at all steps of the procedure, hampering successful guidewire passage, lesion predilatation, and adequate stent expansion (20,21). Extensive and large calcifications are the most important reasons for the low success rate of PCI for CTO (20,21). A cross-sectional calcium area of 50% or more serves as the best cutoff value for predicting PCI failure (10). The results of our study reconfirmed that severe calcifications of occluded coronary arteries are independently associated with failed PCI for the treatment of CTO. Interestingly, the absence of severe calcification does not always guarantee successful PCI. Thus, a comprehensive assessment of CTO characteristics, beyond calcifications, has been emphasized for ensuring better treatment strategies for patients with CTO.
许多 CT 特征已被确定为定义 CTO 再血管化治疗策略(11,19)。特别是,CTO 病变的钙化与成功进行 PCI 的难度密切相关。它在整个操作过程中造成困难,阻碍导丝通过成功、病变预扩张和适当的支架扩张(20,21)。广泛和大面积的钙化是 PCI 治疗 CTO 低成功率的最重要原因(20,21)。横断面钙化面积 50%或更多被视为预测 PCI 失败的最佳截断值(10)。我们研究的结果再次确认,严重钙化的闭塞冠状动脉独立与 PCI 治疗 CTO 失败相关。有趣的是,严重钙化的缺乏并不总能保证 PCI 成功。因此,除了钙化,全面评估 CTO 特征对于确保 CTO 患者更好的治疗策略很重要。

CTO of the coronary artery is defined as the total occlusion of the vessel at invasive angiography, with complete interruption of antegrade blood flow. However, CTO lesions at angiography are not always totally occluded. CTO lesions can include a shortly tapered stump, which may represent a high iodine concentration at the entry of the CTO on the iodine map. Furthermore, histologic studies reported that complete occlusion was noted in only 22% of all angiographic CTO lesions (7). At histologic analysis, microvessels (vessel diameter < 200 µm) surrounding loose fibrous tissue may be present in the angiographic CTO. These microvessels and loose fibrous tissue are amenable to PCI owing to the ease with which the wire can penetrate the CTO lesion. Coronary CT angiography can also be used to help identify features that may be overlooked at invasive angiography. Li et al (12) suggested that visible intrathrombus contrast enhancement on coronary CT angiograms could help predict better PCI outcomes for CTO. We hypothesize that the low iodine concentration as found in our study may represent a lack of tissue composition amenable to PCI.
冠状动脉完全闭塞(CTO)的定义是在侵入性血管造影检查中,血管完全中断而无前向血流。然而,在血管造影检查中,CTO 病变并非总是完全闭塞。CTO 病变可包括一个短而尖锐的残端,这可能代表 CTO 入口处高浓度碘的表现。此外,组织学研究报告,仅 22%的血管造影 CTO 病变存在完全闭塞(7)。在组织学分析中,可能存在环绕疏松纤维组织的微血管(血管直径<200μm)。这些微血管和疏松纤维组织有利于经皮冠状动脉介入治疗(PCI),因为导丝可以很容易地穿透 CTO 病变。冠状动脉 CT 血管造影也可用于帮助识别在侵入性血管造影中可能被忽视的特征。Li 等人(12)提出,在冠状动脉 CT 血管造影中可见的血栓内部对比剂增强可有助于预测 CTO 的 PCI 结果。我们假设,在我们的研究中发现的低碘浓度可能代表了不适合 PCI 的组织成分。

Dual-energy CT can help improve material differentiation by using two different x-ray energy spectra (22). Spectral CT allows dual-energy data acquisition with the use of unique dual-layer energy-resolving detectors (14). More importantly, dual-energy evaluation can be performed retrospectively after spectral CT in all clinical cases. Recently, authors of spectral CT studies have assessed the incremental diagnostic value of iodine quantification (22). When using spectral CT, the iodine-no-water map showing iodine density can be generated using known attenuation properties at high and low energies, which represents the iodine concentration in each voxel (13). The iodine-no-water map reconstructed by using dual-energy techniques also provides excellent resolution of images, with improved iodine contrast-to-noise ratio. In fact, a previous study reported that the use of an iodine map increased the readers’ confidence in detecting the abnormal presence of contrast media, particularly from endoleaks in patients in whom aortic stent graft had been placed (23). This study showed that the quantification of iodine concentration even in small vessels, such as the coronary artery, had the potential to predict failed PCI in patients with CTO.
双能量 CT 可以通过使用两种不同的 X 射线能量谱来帮助改善材料识别(22)。光谱 CT 允许使用独特的双层能量解析探测器进行双能量数据采集(14)。更重要的是,双能量评估可以在所有临床病例中在光谱 CT 后进行回顾性分析。最近,光谱 CT 研究的作者评估了碘定量的增量诊断价值(22)。使用光谱 CT 时,可以使用已知的高低能量衰减特性生成显示碘密度的碘-无水图,该图代表每个体素中的碘浓度(13)。使用双能量技术重建的碘-无水图还提供了出色的图像分辨率,并改善了碘对比度噪声比。实际上,先前的一项研究报告称,使用碘图增加了读者检测对比剂异常存在(特别是在已植入主动脉支架的患者出现内漏时)的信心(23)。这项研究表明,即使在像冠状动脉这样的小血管中,碘浓度的定量也有可能预测 CTO 患者 PCI 失败。

Our study had several limitations. First, this retrospective study had biases caused by case selection, operator expertise, resources, and image quality of the coronary CT angiograms. Second, a small number of patients and a relatively low portion of failed antegrade PCI could be critical limitations in the generalization of the results of this study. Another limitation of this study was the lack of pathologic correlation. Further validation of the iodine concentration with the histologic morphology of the CTO lesion is desirable. Therefore, further experimental and clinical studies with larger data sets are warranted to define the exact nature of iodine concentration at the site of coronary occlusion and to assess its clinical significance.
我们的研究存在几个局限性。首先,这项回顾性研究存在由病例选择、操作者专业水平、资源和冠状动脉 CT 血管造影图像质量造成的偏差。其次,较少的患者数量以及相对较低的前向经皮冠状动脉介入治疗失败率可能成为本研究结果推广的关键局限性。本研究的另一个局限性是缺乏病理学相关性。进一步验证碘浓度与冠状动脉完全闭塞病变的组织学形态非常值得期待。因此,需要进行更多基于更大数据集的实验性和临床性研究,以确定冠状动脉闭塞部位碘浓度的确切性质,并评估其临床意义。

In conclusion, by using spectral CT for coronary angiography before PCI for CTO, a low CIC (≤ 2.5 mg/mL) at the entry of the CTO lesion is associated with failure of successful antegrade PCI for the management of CTO.