Schulich Heart Program, Sunnybrook Health Sciences Centre, Toronto, ON, Canada.
Physical Sciences Platform, Sunnybrook Research Institute, Toronto, ON, Canada.
Magn Reson Imaging. 2021 Jun;79:1-4. doi: 10.1016/j.mri.2021.02.011. Epub 2021 Feb 27.
The purpose of our study was to assess whether T2 MRI identifies the infarcted myocardium or the true area-at-risk (AAR) and whether edema is present in the salvageable region following acute myocardial infarction (MI). The study involved a porcine model of MI with a coronary occlusion model of either 60 min or 90 min. Imaging was performed on a 3T MRI pre-occlusion and at day 3 post-MI. Prior-MI, myocardial perfusion territory (MPT) maps were obtained under MRI via direct intracoronary injection of contrast agent. Post-MI, edema extent was quantified by T2 mapping while infarction and microvascular obstruction (MVO) were assessed by late gadolinium enhancement (LGE). Anatomically registered short-axis slices were analyzed for MPT, T2-AAR and infarct areas and T2 relaxation values. Animals were divided into groups with (MVO+) and without MVO (MVO-). T2-AAR area was significantly greater than infarct area in both groups. In the MVO+ group, T2-AAR and MPT were comparable and highly correlated, whereas, in the MVO- group, T2-AAR significantly underestimated MPT without any trend. T2 values in the salvageable myocardium were found to be significantly higher than those in remote myocardium. Our methodology offers the advantage that all images are acquired within the same MRI reference as opposed to complex co-registration with gross pathology. Our study suggests that edema may expand beyond the infarct zone over the entire ischemic bed. T2-AAR may be more clinically relevant than true AAR by perfusion territory since it identifies the "salvageable" myocardium.
我们的研究目的是评估 T2 MRI 是否能识别梗死心肌或真正的危险区(AAR),以及在急性心肌梗死(MI)后,是否存在可挽救区域的水肿。该研究涉及 MI 的猪模型,采用 60 分钟或 90 分钟的冠状动脉闭塞模型。在闭塞前和 MI 后第 3 天进行 3T MRI 成像。在 MI 之前,通过直接冠状动脉内注射造影剂在 MRI 下获得心肌灌注区域(MPT)图。在 MI 之后,通过 T2 映射量化水肿程度,通过晚期钆增强(LGE)评估梗死和微血管阻塞(MVO)。对解剖学上注册的短轴切片进行 MPT、T2-AAR 和梗死区域以及 T2 弛豫值的分析。动物分为有 MVO(MVO+)和无 MVO(MVO-)两组。在两组中,T2-AAR 面积明显大于梗死面积。在 MVO+组中,T2-AAR 和 MPT 是可比的,且高度相关,而在 MVO-组中,T2-AAR 明显低估了 MPT,且没有任何趋势。可挽救心肌中的 T2 值明显高于远隔心肌中的 T2 值。我们的方法具有优势,因为所有图像都是在同一 MRI 参考框架内获得的,而不是与大体病理学进行复杂的配准。我们的研究表明,水肿可能会在整个缺血床上扩张到梗死区之外。T2-AAR 可能比通过灌注区域的真正 AAR 更具有临床相关性,因为它可以识别“可挽救”的心肌。