Aims Microvascular dysfunction in hypertrophic cardiomyopathy (HCM) is predictive of clinical decline, however underlying mechanisms remain unclear. Cardiac diffusion tensor imaging (cDTI) allows in vivo characterization of myocardial microstructure by quantifying mean diffusivity (MD), fractional anisotropy (FA) of diffusion, and secondary eigenvector angle (E2A). In this cardiac magnetic resonance (CMR) study, we examine associations between perfusion and cDTI parameters to understand the sequence of pathophysiology and the interrelation between vascular function and underlying microstructure. Methods and results Twenty HCM patients underwent 3.0T CMR which included: spin-echo cDTI, adenosine stress and rest perfusion mapping, cine-imaging, and late gadolinium enhancement (LGE). Ten controls underwent cDTI. Myocardial perfusion reserve (MPR), MD, FA, E2A, and wall thickness were calculated per segment and further divided into subendocardial (inner 50%) and subepicardial (outer 50%) regions. Segments with wall thickness ≤11 mm, MPR ≥2.2, and no visual LGE were classified as ‘normal’. Compared to controls, ‘normal’ HCM segments had increased MD (1.61 ± 0.09 vs. 1.46 ± 0.07 × 10−3 mm2/s, P = 0.02), increased E2A (60 ± 9° vs. 38 ± 12°, P < 0.001), and decreased FA (0.29 ± 0.04 vs. 0.35 ± 0.02, P = 0.002). Across all HCM segments, subendocardial regions had higher MD and lower MPR than subepicardial (MDendo 1.61 ± 0.08 × 10−3 mm2/s vs. MDepi 1.56 ± 0.18 × 10−3 mm2/s, P = 0.003, MPRendo 1.85 ± 0.83, MPRepi 2.28 ± 0.87, P < 0.0001). Conclusion In HCM patients, even in segments with normal wall thickness, normal perfusion, and no scar, diffusion is more isotropic than in controls, suggesting the presence of underlying cardiomyocyte disarray. Increased E2A suggests the myocardial sheetlets adopt hypercontracted angulation in systole. Increased MD, most notably in the subendocardium, is suggestive of regional remodelling which may explain the reduced subendocardial blood flow.

中文翻译：

---

使用心脏弥散磁共振成像对肥厚型心肌病进行表型分析：微血管功能障碍与微结构变化之间的关系

目的 肥厚性心肌病 (HCM) 的微血管功能障碍可预测临床衰退，但潜在机制仍不清楚。心脏扩散张量成像 (cDTI) 允许通过量化平均扩散率 (MD)、扩散分数各向异性 (FA) 和二次特征向量角 (E2A) 来对心肌微观结构进行体内表征。在这项心脏磁共振 (CMR) 研究中，我们检查了灌注和 cDTI 参数之间的关联，以了解病理生理学的顺序以及血管功能和底层微结构之间的相互关系。方法和结果 20 名 HCM 患者接受了 3.0T CMR，包括：自旋回波 cDTI、腺苷应激和静息灌注图、电影成像和晚期钆增强 (LGE)。10 个对照接受了 cDTI。心肌灌注储备 (MPR), MD, 计算每个节段的 FA、E2A 和壁厚，并进一步分为心内膜下（内部 50%）和心外膜下（外部 50%）区域。壁厚≤11 mm、MPR ≥2.2 且无可见 LGE 的节段被归类为“正常”。与对照组相比，“正常”HCM 节段增加了 MD（1.61 ± 0.09 对比 1.46 ± 0.07 × 10−3 mm2/s，P = 0.02），增加了 E2A（60 ± 9° 对比 38 ± 12°，P < ; 0.001)，FA 减少（0.29 ± 0.04 对比 0.35 ± 0.02，P = 0.002）。在所有 HCM 节段中，心内膜下区域比心外膜下区域具有更高的 MD 和更低的 MPR（MDendo 1.61 ± 0.08 × 10−3 mm2/s 对比 MDepi 1.56 ± 0.18 × 10−3 mm2/s，P = 0.003，MPRendo 1.85 ± 0.83， MPRepi 2.28 ± 0.87，P < 0.0001)。结论 在 HCM 患者中，即使在壁厚正常、灌注正常且无瘢痕的节段中，扩散也比对照组更各向同性，表明存在潜在的心肌细胞紊乱。增加的 E2A 表明心肌小片在收缩期采用过度收缩的角度。增加的 MD，尤其是在心内膜下，提示局部重塑，这可以解释心内膜下血流减少。