From the Biomedical Imaging Science Department, Leeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds, and Leeds Teaching Hospitals NHS Trust, Clarendon, Way, Leeds LS2 9JT, England (A.D., C.K., I.T., A.C., L.A.E.B., C.E.D.S., T.P.C., P.G.C., N.J., P.P.S., E.L., J.P.G., J.E.S., S.P., E.D.); and Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland (C.T.S., S.K.).
Radiology. 2021 Apr;299(1):86-96. doi: 10.1148/radiol.2021203208. Epub 2021 Feb 9.
Background Cardiac diffusion tensor imaging (cDTI) allows for in vivo characterization of myocardial microstructure. In cDTI, mean diffusivity and fractional anisotropy (FA)-markers of magnitude and anisotropy of diffusion of water molecules-are known to change after myocardial infarction. However, little is known about regional changes in helix angle (HA) and secondary eigenvector angle (E2A), which reflects orientations of laminar sheetlets, and their association with long-term recovery of left ventricular ejection fraction (LVEF). Purpose To assess serial changes in cDTI biomarkers in participants following ST-segment elevation myocardial infarction (STEMI) and to determine their associations with long-term left ventricular remodeling. Materials and Methods In this prospective study, 30 participants underwent cardiac MRI (3 T) after STEMI at 5 days and 3 months after reperfusion (National Institute of Health Research study no. 33963 and Research Ethics no. REC17/YH/0062). Spin-echo cDTI with second-order motion-compensation (approximate duration, 13 minutes; three sections; 18 noncollinear diffusion-weighted scans with values of 100 sec/mm [three acquisitions], 200 sec/mm [three acquisitions], and 500 sec/mm [12 acquisitions]), functional images, and late gadolinium enhancement images were obtained. Multiple regression analysis was used to assess associations between acute cDTI parameters and 3-month LVEF. Results Acutely infarcted myocardium had reduced FA, E2A, and myocytes with right-handed orientation (RHM) on HA maps compared with remote myocardium (mean remote FA = 0.36 ± 0.02 [standard deviation], mean infarcted FA = 0.25 ± 0.03, < .001; mean remote E2A = 55° ± 9, mean infarcted E2A = 49° ± 10, < .001; mean remote RHM = 16% ± 6, mean infarcted RHM = 9% ± 5, < .001). All three parameters (FA, E2A, and RHM) correlated with 3-month LVEF ( = 0.68, = 0.59, and = 0.53, respectively), with acute FA being independently predictive of 3-month LVEF (standardized β = 0.56, = .008) after multivariable analysis adjusting for factors, including acute LVEF and infarct size. Conclusion After ST-segment elevation myocardial infarction, diffusion becomes more isotropic in acutely infarcted myocardium as reflected by decreased fractional anisotropy. Reductions in secondary eigenvector angle suggest that the myocardial sheetlets are unable to adopt their usual steep orientations in systole, whereas reductions in myocytes with right-handed orientation on helix angle maps are likely reflective of a loss of organization among subendocardial myocytes. Correlations between these parameters and 3-month left ventricular ejection fraction highlight the potential clinical use of cardiac diffusion tensor imaging after myocardial infarction in predicting long-term remodeling. © RSNA, 2021
背景 心脏扩散张量成像（cDTI）可用于对心肌微观结构进行体内特征描述。在 cDTI 中，水分子扩散的大小和各向异性的平均扩散系数和分数各向异性（FA）标志物在心肌梗死后已知会发生变化。然而，对于螺旋角（HA）和次特征向量角（E2A）的局部变化知之甚少，这些变化反映了层状薄片的方向，并且与左心室射血分数（LVEF）的长期恢复有关。目的 评估 ST 段抬高型心肌梗死（STEMI）患者接受 cDTI 生物标志物的连续变化，并确定它们与长期左心室重构的关系。材料与方法 在这项前瞻性研究中，30 名患者在再灌注后 5 天和 3 个月时（国家卫生研究院研究编号 33963 和研究伦理编号 REC17/YH/0062）接受了心脏 MRI（3T）检查。采用自旋回波 cDTI 进行二阶运动补偿（大致持续时间 13 分钟；三个部分；18 个非共线扩散加权扫描， 值为 100 sec/mm [三次采集]、200 sec/mm [三次采集]和 500 sec/mm [12 次采集]）、功能图像和晚期钆增强图像。采用多元回归分析评估急性 cDTI 参数与 3 个月 LVEF 的关系。结果 在急性梗死心肌中，与远隔心肌相比，FA、E2A 和 HA 图上右旋取向的心肌细胞（RHM）减少（远隔心肌平均 FA = 0.36 ± 0.02[标准差]，梗死心肌平均 FA = 0.25 ± 0.03， <.001；远隔心肌平均 E2A = 55° ± 9，梗死心肌平均 E2A = 49° ± 10， <.001；远隔心肌平均 RHM = 16% ± 6，梗死心肌平均 RHM = 9% ± 5， <.001）。所有三个参数（FA、E2A 和 RHM）均与 3 个月 LVEF 相关（ = 0.68， = 0.59， = 0.53），急性 FA 在多变量分析中调整急性 LVEF 和梗死面积等因素后，独立预测 3 个月 LVEF（标准化 β = 0.56， =.008）。结论 在 ST 段抬高型心肌梗死后，急性梗死心肌中的扩散变得更加各向同性，表现为 FA 降低。E2A 的降低表明心肌薄片在收缩期无法采用通常的陡峭取向，而 HA 图上的 RHM 减少可能反映了心内膜下心肌之间组织的丧失。这些参数与 3 个月 LVEF 的相关性突出了心肌梗死后心脏扩散张量成像在预测长期重构方面的潜在临床应用。
