心血管MR T1mapping/iECV定量分析在主动脉瓣关闭不全评价中的价值

目的探讨心脏MR(CMR)定量技术纵向弛豫时间定量成像/心肌细胞外容积分数指数(T₁ mapping/iECV)对主动脉瓣关闭不全(AI)患者的临床价值,并探索其与传统心功能参数的相关性。方法回顾性收集2012年5月至2016年2月在中国医学科学院阜外医院经影像及临床资料确诊为慢性AI患者36例。所有患者均接受CMR常规扫描序列、初始及增强后T₁ mapping检查,CMR图像经后处理分析,计算主动脉瓣反流分数、钆对比剂延迟强化(LGE)质量分数、心肌细胞外容积分数(ECV)和iECV。基于CMR反流分数结果,将AI患者分为轻度组(9例)、中度组(14例)和重度组(13例)。3组AI患者初始及增强后T₁值、ECV及iECV等计量资料比较采用单因素方差分析,进一步两两比较采用LSD检验;心血管相关病史、纽约心脏协会(NYHA)心功能分级及LGE阳性率等计数资料比较采用χ2检验或Fisher确切概率法;左心室常规功能参数LVEF与iECV的相关关系采用Spearman相关分析。结果3组AI患者年龄、性别、心血管相关病史差异无统计学意义(P均>0.05)。3组不同反流程度AI患者比较:(1)3组患者LGE阳性率总体差异有统计学意义(P=0.023),随着主动脉瓣反流分级程度增高,替代性纤维化发生率增加。(2)3组患者初始T₁值、增强后T₁值及ECV总体差异均无统计学意义(H值分别为1.815、0.929、2.496,P均>0.05)。3组iECV总体差异有统计学意义(H=16.725,P<0.001),重度组iECV值明显高于其他2组(P<0.05)。iECV与LVEF呈负相关(r=-0.649,P<0.001)。结论无创性CMR定量参数技术T₁ mapping/iECV能识别不同反流程度AI患者发生弥漫性心肌纤维化的程度,并与传统心功能参数LVEF有较高的相关性,具有反映左心室功能失代偿前可逆阶段的潜力。

Quantitative study of cardiac MR T1 mapping/iECV in patients with aortic insufficiency

Objective To explore the clinical value of T₁ mapping/indexed extracellular volume fraction(iECV)quantified with cardiac MR(CMR)parameters,and its correlation with traditional indicators of myocardial dysfunction in aortic insufficiency(AI)patients.Methods A total of 36 patients clinically and radiologically diagnosed with chronic AI in our hospital between May 2012 and February 2016 were retrospectively selected.All AI patients underwent conventional CMR protocol,native and post T₁ mapping.CMR parameters,such as aortic regurgitant fraction(RF),late gadolinium enhancement(LGE)mass fraction,myocardial extracellular volume fraction(ECV)and iECV.Based on the values of aortic RF,AI patients were divided into mild AI group(9 cases),moderate AI group(14 cases)and severe AI group(13 cases).The clinical characteristics were teased from the patients′electronic medical records.Univariate analysis of variance was used to compare the measurement data of native T₁ mapping,post-contrast T₁ mapping,ECV,and iECV.LSD test was used for pair wise comparison between the mild AI,moderate AI and severe AI groups.Data about cardiovascular history,New York Heart Association(NYHA)heart function classification,and LGE were compared by chi-square test or Fisher exact test.The correlation between left ventricle ejection fraction(LVEF)and iECV was evaluated by Spearman correlation analysis.Results There was no difference in age,sex,cardiovascular history among the three groups.Comparison of patients with different severity of AI in the three groups:(1)There was statistically significant difference in the LGE positive rate among the three groups(P=0.023),while the myocardial replacement of fibrosis increased with the grade of aortic regurgitation.(2)There was no statistically significant difference in the measurement data of native T₁ mapping,post-contrast T₁ mapping,ECV among the three groups(H=1.815,0.929,2.496,all P values>0.05),while the diffuse myocardial fibrosis tended to increase with the degree of aortic regurgitation.There was statistically significant difference in iECV among the three groups(H=16.725,P<0.001).The measurement data of iECV in the severe AI group was significantly higher than those in the other two groups(P<0.05).LVEF value was inversely correlated with iECV(r=-0.649,P<0.001).Conclusions Quantitative T₁ mapping/iECV can serve as a parameter to noninvasively identify diffuse myocardial fibrosis in AI patients of different severities.It changes with LVEF and can manifest the reversible stage of left ventricular decompensation.