Institute for Biomedical Engineering, University and ETH Zurich, Gloriastrasse 35, Zurich, 8092, Switzerland.
Department of Cardiology, University Hospital Zurich, Zurich, Switzerland.
J Cardiovasc Magn Reson. 2019 Sep 5;21(1):56. doi: 10.1186/s12968-019-0563-2.
In-vivo cardiovascular magnetic resonance (CMR) diffusion tensor imaging (DTI) allows imaging of alterations of cardiac fiber architecture in diseased hearts. Cardiac amyloidosis (CA) causes myocardial infiltration of misfolded proteins with unknown consequences for myocardial microstructure. This study applied CMR DTI in CA to assess microstructural alterations and their consequences for myocardial function compared to healthy controls.
Ten patients with CA (8 AL, 2 ATTR) and ten healthy controls were studied using a diffusion-weighed second-order motion-compensated spin-echo sequence at 1.5 T. Additionally, left ventricular morphology, ejection fraction, strain and native T1 values were obtained in all subjects. In CA patients, T1 mapping was repeated after the administration of gadolinium for extracellular volume fraction (ECV) calculation. CMR DTI analysis was performed to yield the scalar diffusion metrics mean diffusivity (MD) and fractional anisotropy (FA) as well as the characteristics of myofiber orientation including helix, transverse and E2A sheet angle (HA, TA, E2A).
MD and FA were found to be significantly different between CA patients and healthy controls (MD 1.77 ± 0.17 10 vs 1.41 ± 0.07 10 mm/s, p < 0.001; FA 0.25 ± 0.04 vs 0.35 ± 0.03, p < 0.001). MD demonstrated an excellent correlation with native T1 (r = 0.908, p < 0.001) while FA showed a significant correlation with ECV in the CA population (r = - 0.851, p < 0.002). HA exhibited a more circumferential orientation of myofibers in CA patients, in conjunction with a higher TA standard deviation and a higher absolute E2A sheet angle. The transmural HA slope was found to be strongly correlated with the global longitudinal strain (r = 0.921, p < 0.001).
CMR DTI reveals significant alterations of scalar diffusion metrics in CA patients versus healthy controls. Elevated MD and lower FA values indicate myocardial disarray with higher diffusion in CA that correlates well with native T1 and ECV measures. In CA patients, CMR DTI showed pronounced circumferential orientation of the myofibers, which may provide the rationale for the reduction of global longitudinal strain that occurs in amyloidosis patients. Accordingly, CMR DTI captures specific features of amyloid infiltration, which provides a deeper understanding of the microstructural consequences of CA.
体内心血管磁共振（CMR）扩散张量成像（DTI）可用于成像患病心脏中心肌纤维结构的改变。心脏淀粉样变性（CA）导致错误折叠的蛋白质对心肌微观结构造成浸润，其后果未知。本研究应用 CMR DTI 对 CA 患者进行研究，以评估与健康对照组相比，微观结构的改变及其对心肌功能的影响。
10 名 CA 患者（8 名 AL，2 名 ATTR）和 10 名健康对照者接受了 1.5T 扩散加权二阶运动补偿自旋回波序列的检查。所有受试者均获得左心室形态、射血分数、应变和固有 T1 值。在 CA 患者中，在给予钆对比剂后重复 T1 映射以计算细胞外容积分数（ECV）。进行 CMR DTI 分析以获得标量扩散指标平均扩散率（MD）和各向异性分数（FA）以及肌纤维取向特征，包括螺旋、横向和 E2A 片层角（HA、TA、E2A）。
与健康对照组相比，CA 患者的 MD 和 FA 差异有统计学意义（MD 1.77±0.17×10-3mm/s 比 1.41±0.07×10-3mm/s，p<0.001；FA 0.25±0.04 比 0.35±0.03，p<0.001）。MD 与固有 T1 具有极好的相关性（r=0.908，p<0.001），而 FA 与 CA 人群中的 ECV 具有显著相关性（r=-0.851，p<0.002）。在 CA 患者中，HA 表现出更向心性的肌纤维取向，同时 TA 标准差和绝对 E2A 片层角更高。发现壁内 HA 斜率与整体纵向应变呈强相关性（r=0.921，p<0.001）。
CMR DTI 显示 CA 患者与健康对照组相比，标量扩散指标有明显改变。升高的 MD 和降低的 FA 值表明 CA 中的心肌排列紊乱，弥散度更高，与固有 T1 和 ECV 测量值密切相关。在 CA 患者中，CMR DTI 显示肌纤维呈明显的向心性取向，这可能是淀粉样变性患者出现整体纵向应变降低的原因。因此，CMR DTI 可以捕获淀粉样蛋白浸润的特定特征，从而更深入地了解 CA 的微观结构后果。
