Evaluation of Myocardial Viability with Delay-Enhanced Magnetic Resonance Imaging in the Ischemic Pig Models Compared with Histochemical and Pathological Analyses

Delayed-enhancement magnetic resonance imaging (DE-MRI) is quickly assuming an important role in the evaluation of myocardial viability. Most of recently published data support the concept that the hyper-enhanced regions have preserved irreversible ischemic injury. This study was to investigate the accuracy of DE-MRI in detecting acute myocardial infarction with special attention to the role played by edema in hyper-enhanced regions. We first made an acute myocardial infarction model in ten pigs, and DE-MRI scan was performed subsequently to observe hyper-enhanced segments, number of myocardial infarction and transmural extent of infarction. After MRI examination, the pigs' hearts were excised and studied by 2,3,5-triphenyltetrazolium chloride (TTC) staining and pathological staining for microscopy. The infarct segments were 30 detected by DE-MRI and 29 by TTC staining, and DE-MRI found an additional infarct zone in the apical lateral segment compared with the TIC staining. However, no statistically significant differences (P > 0.05) existed between the two methods in detecting the infarct zones. In judging myocardial infarction, DE-MRI correlated well with TTC staining (P < 0.05), and there was a good consistency between DE-MRI and TIC staining (Kappa > 0.75). However, the transmural extent of infarction judged by DE-MRI is greater than TTC staining (P < 0.05). Histopathological microscopy confirmed the existence of edema in acute myocardial infarction. DE-MRI may thus amplify the extent of myocardial infarction in the acute stage, and cellular and interstitial edema plays an important role in this aspect.