细胞外容积预测慢性冠状动脉完全闭塞患者血运重建后的心肌收缩功能恢复

Extracellular volume fraction for the assessment of myocardial functional outcome after revascularization in the patients with coronary chronic total occlusion

目的前瞻性研究细胞外容积(ECV)定量能否预测慢性冠状动脉完全闭塞(CTO)血运重建6个月后的局部收缩功能恢复。方法2014年4月到2015年3月,前瞻性纳入复旦大学附属中山医院30例CTO患者,于基线及经皮冠状动脉介入治疗(PCI)血运重建术后6个月行心脏MR检查。扫描序列包括电影、对比剂增强前后纵向弛豫时间定量成像(T1mapping)和延迟增强。商用CVI42软件计算射血分数(EF)和节段室壁增厚率(SWT),SWT<45%定义为节段运动功能障碍。按照美国心脏学会(AHA)16分段法,将位于CTO血管供血区且术前存在运动功能障碍的心肌节段纳入后续分析,分别计算每一节段的细胞外容积(ECV)、梗死透壁程度(TEI)和未强化心肌的厚度(RIM)。依据冠状动脉造影的Rentrop分级法评估侧支循环形成情况,将心肌节段分为两组:侧支循环形成良好和侧支循环形成不良。采用Wilcoxon符号秩检验比较基线和随访SWT的差别;配对t检验比较基线和随访射血分数的差别。以SWT较基线水平增加>10%作为节段性功能恢复的参考标准,ROC分析比较各基线MR参数预测心肌局部功能恢复的诊断效能。采用混合线性模型分析侧支循环形成情况与SWT的关系。二元logistic回归分析确定预测节段心功能恢复的独立预测因子。结果PCI术后,运动功能障碍的心肌节段的平均SWT从基线的21.6%(9.7%,33.3%)上升至38.4%(19.0%,51.2%),差异具有统计学意义(Z=-6.869,P<0.001),EF较基线有明显增加(分别为54.5%±8.5%和50.7%±6.6%,t=-5.706,P<0.001)。ECV预测节段性功能恢复的截断值、ROC下面积、敏感度和特异度分别为34.7%、0.86、91%和66%;ECV的ROC下面积高于TEI和RIM(ROC下面积分别为0.75和0.73,P值均<0.01)。侧支循环形成良好较侧支循环形成不良的心肌节段具有更高的随访SWT[46.6%(36.6%,64.2%)和33.5%(12.8%,47.8%),F=5.791,P=0.02]。logistic回归分析显示节段ECV值是评价局部收缩功能恢复的独立预测因子(OR=0.83,95%置信区间0.77~0.89,P<0.001)。结论在CTO患者中,ECV是预测血运重建后局部收缩功能恢复的可靠指标。基线侧支循环形成情况与血运重建术后的局部收缩功能相关。

Objective Myocardial functional outcome after revascularization of coronary chronic total occlusion (CTO) was prospectively predicted using extracellular volume fraction (ECV) based on cardiovascular magnetic resonance (CMR). Methods Thirty patients with CTO underwent CMR before and 6 months after percutaneous coronary intervention (PCI) were enrolled. The CMR scan protocol included cine, pre-contrast and post-contrast T1 mapping and late gadolinium enhancement (LGE). Ejection fraction (EF) and segmental wall thickening (SWT) were calculated using CVI 42 software. SWT less than 45% indicated myocardial segment dysfunction. According to the American Heart Association (AHA) scientific statement, the dysfunctional segments assigned to CTO vessel were selected, and three baseline imaging markers, ECV, transmural extent of infarction (TEI) and unenhanced rim thickness (RIM) were respectively evaluated. The myocardial segments were divided into two subgroups, group with well-developed collaterals and group with poorly-developed collaterals, based on the collateral circulation using Rentrop classification. Baseline and follow-up values of SWT and EF were evaluated using paired Student′s t-test. Using an increase in SWT>10% as standard reference, ROC analysis was conducted to describe the predictive performance of baseline markers. A mixed linear model was used to probe the relationship between collateral circulation and SWT. Stepwise logistic regression analysis was used to determine the independent predictors of regional functional recovery. The differences of EF between poorly-developed and well-developed collaterals were compared by Student t test. Results The baseline mean segmental wall thickening (SWT) of the dysfunctional segments increased from 21.6%(9.7%, 33.3%) to 38.4%(19.0%, 51.2%) after PCI (Z=-6.869, P<0.001), and EF was also significantly higher compared with baseline (54.5%±8.5% vs. 50.7%±6.6%, t=-5.706, P<0.001). ECV showed good performance in predicting functional recovery with cutoff value 34.7%, area under ROC curve (AUC) 0.86, sensitivity 91%, and specificity 66%. The AUC of ECV was superior to TEI and RIM (AUC: 0.75 and 0.73, all P value<0.01). The segments with well-developed collaterals were associated with a higher SWT at follow-up [46.6%(36.6%, 64.2%) vs. 33.5%(12.8%, 47.8%),F=5.791, P=0.02]. Logistic regression analysis demonstrated that mean segmental ECV was the only independent predictors of regional functional outcome after PCI (OR=0.83, 95% confidence interval: 0.77-0.89;P<0.001). Conclusions ECV by CMR may provide incremental value for the prediction of regional functional recovery in CTO patients, and baseline collateral circulation correlates with the regional systolic function after revascularization.