Quantitative study of cardiac MR T 1 mapping/iECV in patients with aortic insufficiency / 中华放射学杂志

ABSTRACT

Objective:To explore the clinical value of T 1 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 T 1 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 T 1 mapping, post-contrast T 1 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 T 1 mapping, post-contrast T 1 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 T 1 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.