Evaluation Of Ventricular Remodeling After Myocardial Infarction Using 3.0T Magnetic Resonance Diffusion Tensor Imaging

Objective: To evaluate the application value of 3.0 T magnetic resonance diffusion tensor imaging in ventricular remodeling after myocardial infarction, detect cardiac muscle fibers remodeling of myocardial infarction zone, peri-infarction zone and non-infarction zone, so as to explore the mechanism and heterogeneity of ventricular remodeling in different areas after myocardial infarction.Materials and methods:We chose 42 adult male rabbits, divided into normal group(n=5), sham-operation group(n=5) and myocardial infarction group(n=32).We established rabbit myocardial infarction models by ligating the left ventricular branch of coronary artery, while 7 died postoperative, 25 lived. The 25 survivors were put to death at postoperative 1 w, 2 w, 4 w, 8 w and 16 w, with 5 excised heart at each time-point respectively. The heart types were scanned in vitro diffusion tensor imaging and post-processed images by measuring the fractional anisotropy value and the mean diffusion coefficient of the myocardial infarction zone, peri-infarction zone and non-infarction zone. Meanwhile, by proceeding diffusion tensor tractography and reconstruction primary eigenvector maps in different areas, so as to display the alignment, tightness and continuity of myocardial fibers directly. We compared the difference of remodeling in myocardial infarction zone, peri-infarction zone and non-infarction zone by DTI.Results: There were differences in both the average FA and MD of infarction zone, peri-infarction zone and non-infarction zone after myocardial infarction, we analyzed the values in different areas by the pairwise comparison, the average FA and MD values both had statistically significance. From the infarction zone extending to the peri-infarction zone, and compensatory remodeling of the non-infarction zone, the average FA values were on the rise, while the average MD values were on the decline,both were significantly negative correlation(r=-0.791, p < 0.001). However, the correlation of FA and MD in different areas varied, in the infarction zone and peri-infarction zone, the FA had significantly negative correlation with the MD, withr=-0.638, p=0.001 and r=-0.607, p=0.003 respectively. While in the non-infarction zone, there was no correlation between the FA and MD(r =-0.062, p = 0.783).We also made pairwise comparison analysis in different areas according to the different groups respectively. In the normal group and sham-operation group, there were not statistically significant in the FA and MD between each other zone. In the1 w, 2 w, 4 w, 8 w and 16 w after myocardial infarction, the FA values all had statistically significant between each other zone. In the MD analysis, the results showed the MD in these pairwise areas, including the infarction zone with peri-infarction zone and peri-infarction zone with non-infarction zone in the postoperative 1 w group, three pairwise areas in the 2 w group, and peri-infarction zone with non-infarction zone in the 8 w group, had no statistical difference, while the remaining pairwise comparison had the statistical difference.Conclusion: The remodeling was heterogeneous among the infarction zone,peri-infarction zone and non-infarction zone after myocardial infarction. From the infarction zone extending to peri-infarction zone, and compensatory remodeling of the non-infarction zone, the degree of remodeling gradually changed, with the infarction zone the most obvious, which suggested that the integrity of the infarction zone had been damaged most seriously. Moreover, the FA in assessing the remodeling heterogeneity of different regions after myocardial infarction might be more stable and reliable compared with the MD.