Kim R J, Chen E L, Lima J A, Judd R M
Department of Medicine, Johns Hopkins Hospital, Baltimore, Md 21287-6568, USA.
Circulation. 1996 Dec 15;94(12):3318-26. doi: 10.1161/01.cir.94.12.3318.
Contrast medium-enhanced magnetic resonance images of acute, reperfused infarcts have shown hypoenhanced and hyperenhanced regions in areas of injured myocardium. The precise mechanisms that lead to these altered enhancement patterns are unknown. This study was designed to evaluate possible mechanisms and to relate altered enhancement patterns to myocardial perfusion and viability.
Thirteen rabbits underwent in situ coronary artery occlusion and reperfusion followed by isolated perfusion with cardioplegic solution. T1-weighted spin-echo images were acquired continuously during step changes in perfusate Gd-DTPA concentration. Regional blood flow was also measured by use of radioactive microspheres in all rabbits. There were marked differences in Gd-DTPA wash-in and washout time constants (wash-in, 0.8 +/- 0.1, 2.1 +/- 02, and 16.3 +/- 2.4 minutes, P < .001; washout, 1.6 +/- 0.1, 4.8 +/- 0.5, and 31.1 +/- 3.3 minutes, P < .001) in normal, infarct rim, and infarct core regions, respectively, resulting in differential enhancement of these regions. Microsphere flows in the infarct rim and core were 42.9 +/- 4.0% and 12.0 +/- 1.6% of normal myocardium and correlated well with washout time constants (r = .86, y = 0.77x - 0.002, P < .001), suggesting that these time constants index the severity of microvascular damage. In addition, spatial maps of washout time constants were produced. The extent of regions with abnormal time constants correlated well with triphenyltetrazolium chloride-determined infarct size (r = .94, y = 0.95x + 4.17, P < .001).
In contrast-enhanced magnetic resonance images of acute, reperfused rabbit infarcts, differential image intensity is primarily due to regional differences in contrast agent wash-in and washout time constants. These regional differences in time constants also indicate the extent and severity of myocardial injury.
急性再灌注梗死的对比剂增强磁共振图像显示，受损心肌区域存在低增强和高增强区域。导致这些增强模式改变的确切机制尚不清楚。本研究旨在评估可能的机制，并将增强模式的改变与心肌灌注和存活能力相关联。
13只兔子接受原位冠状动脉闭塞和再灌注，随后用心脏停搏液进行单独灌注。在灌注液中钆喷酸葡胺浓度发生阶跃变化时，连续采集T1加权自旋回波图像。所有兔子均使用放射性微球测量局部血流量。正常、梗死边缘和梗死核心区域的钆喷酸葡胺注入和洗脱时间常数存在显著差异（注入时间分别为0.8±0.1、2.1±0.2和16.3±2.4分钟，P<.001；洗脱时间分别为1.6±0.1、4.8±0.5和31.1±3.3分钟，P<.001），导致这些区域出现差异增强。梗死边缘和核心区域的微球流量分别为正常心肌的42.9±4.0%和12.0±1.6%，与洗脱时间常数密切相关（r=.86，y = 0.77x - 0.002，P<.001），表明这些时间常数可反映微血管损伤的严重程度。此外，还生成了洗脱时间常数的空间图。时间常数异常区域的范围与氯化三苯基四氮唑测定的梗死面积密切相关（r=.94，y = 0.95x + 4.17，P<.001）。
在急性再灌注兔梗死的对比增强磁共振图像中，图像强度差异主要归因于对比剂注入和洗脱时间常数的区域差异。这些时间常数的区域差异也表明了心肌损伤的程度和严重程度。
