ABSTRACT
BACKGROUND AND OBJECTIVES: Cardiovascuar MR using contrast enhancement has recently been reported to be useful for diagnosing myocarditis. It is also well known that irreversible myocardial injury by epicardial coronary artery flow obstruction spreads from the endocardium to the epicardium in a wave-front pattern with a time-dependent manner. We investigated characteristics of the patterns of contrast-enhanced MR imaging according to the underlying myocardial injury mechanism. SUBJECTS AND METHODS: Of all 275 patients who underwent coronary angiogram at our hospital due to cheat pain and elevated cardiac enzymes between October, 2002 and August, 2003, 48 patients who underwent cardiac MR were enrolled in this study. We retrospectively analyzed the pattern of delayed hyperenhancement according to presence or absence of a documented infarct related artery. Endomyocardial biopsies were done in selected patients. RESULTS: Contrast MR images of all patients showed delayed hyperenhancement. The study group was divided into 2 groups according to whether the areas of hyper-enhancement were involved in the sub-endocardial portion (endocardial sparing pattern, ESP) or not. In 8 patients (Group A, 17%) who showed the endocardial sparing pattern on contrast MR, the findings of coronary angiogram were all normal. In 40 patients (Group B, 83%), who did not show the endocardial sparing pattern on contrast MR, 39 patients (97.5 %) had an infarct related artery on coronary angiogram (p=0.001). Endomyocardial biopsies were performed in 3 patients of group A. The findings of the 3 biopsies were 2 cases of definite myocarditis and 1 case of myocardial degeneration. CONCLUSION: The endocardial sparing pattern of myocardial injury demonstrated by delayed enhancement MR imaging was very useful to predict the presence of an infarct related artery in patients with myocardial necrosis that has been determined by elevated cardiac enzymes. This result can be a useful clue to determine the nature of the underlying injury mechanism such as ischemic or non-ischemic.