Cardiac MRI is a noninvasive diagnostic tool using nonionizing radiation that is widely used in patients with ST-segment elevation myocardial infarction (STEMI). Cardiac MRI depicts different prognosticating components of myocardial damage such as edema, intramyocardial hemorrhage (IMH), microvascular obstruction (MVO), and fibrosis. But how do cardiac MRI findings correlate to histologic findings? Shortly after STEMI, T2-weighted imaging and T2* mapping cardiac MRI depict, respectively, edema and IMH. The acute infarct size can be determined with late gadolinium enhancement (LGE) cardiac MRI. T2-weighted MRI should not be used for area-at-risk delineation because T2 values change dynamically over the first few days after STEMI and the severity of T2 abnormalities can be modulated with treatment. Furthermore, LGE cardiac MRI is the most accurate method to visualize MVO, which is characterized by hemorrhage, microvascular injury, and necrosis in histologic samples. In the chronic setting post-STEMI, LGE cardiac MRI is best used to detect replacement fibrosis (ie, final infarct size after injury healing). Finally, native T1 mapping has recently emerged as a contrast material–free method to measure infarct size that, however, remains inferior to LGE cardiac MRI. Especially LGE cardiac MRI–defined infarct size and the presence and extent of MVO may be used to monitor the effect of new therapeutic interventions in the treatment of reperfusion injury and infarct size reduction.

© RSNA, 2021

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心脏 MRI 是一种使用非电离辐射的无创诊断工具，广泛用于 ST 段抬高型心肌梗死 (STEMI) 患者。心脏 MRI 描绘了心肌损伤的不同预后成分，例如水肿、心肌内出血 (IMH)、微血管阻塞 (MVO) 和纤维化。但是心脏 MRI 结果与组织学结果有何关联？STEMI 后不久，T2 加权成像和 T2* 映射心脏 MRI 分别描绘了水肿和 IMH。急性梗塞的大小可以用晚期钆增强 (LGE) 心脏 MRI 确定。T2 加权 MRI 不应用于划定危险区域，因为 T2 值在 STEMI 后的前几天动态变化，并且 T2 异常的严重程度可以通过治疗进行调节。此外，LGE 心脏 MRI 是可视化 MVO 的最准确方法，其特征是组织学样本中的出血、微血管损伤和坏死。在 STEMI 后的慢性环境中，LGE 心脏 MRI 最适合用于检测替代纤维化（即损伤愈合后的最终梗死面积）。最后，原生 T1 映射最近成为一种无需对比材料的测量梗死面积的方法，但仍然不如 LGE 心脏 MRI。特别是 LGE 心脏 MRI 定义的梗死面积和 MVO 的存在和范围可用于监测新治疗干预措施在治疗再灌注损伤和梗死面积缩小方面的效果。LGE 心脏 MRI 最适合用于检测替代性纤维化（即损伤愈合后的最终梗死面积）。最后，原生 T1 映射最近成为一种无需对比材料的测量梗死面积的方法，但仍然不如 LGE 心脏 MRI。特别是 LGE 心脏 MRI 定义的梗死面积和 MVO 的存在和范围可用于监测新治疗干预在治疗再灌注损伤和梗死面积缩小方面的效果。LGE 心脏 MRI 最适合用于检测替代性纤维化（即损伤愈合后的最终梗死面积）。最后，原生 T1 映射最近成为一种无需对比材料的测量梗死面积的方法，但仍然不如 LGE 心脏 MRI。特别是 LGE 心脏 MRI 定义的梗死面积和 MVO 的存在和范围可用于监测新治疗干预措施在治疗再灌注损伤和梗死面积缩小方面的效果。

©北美放射学会，2021

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