MAGNETIC-RESONANCE RELAXATION-TIMES IN VENTRICULAR HYPERTROPHY INDUCED BY MYOCARDIAL-INFARCTION IN THE RAT

The purpose of this study was to evaluate changes in the proton nuclear magnetic resonance relaxation times (T-1 and T-2 after chronic infarction in the rat. Ligation of the left coronary artery was followed by various degrees of reduction in myocardial blood flow. The ligation induced infarction in the left ventricle and compensatory hypertrophy in the right ventricle, as evaluated by the ratio of right ventricle to body weight. The interventricular septum and the right ventricle did not become ischemic in this model and served as control areas. fn the infarcted left ventricle our results showed an increase in the T-1 and T-2 relaxation times after 15 and 30 days of ligation and a slight decrease after 60 days. A similar change in the T-1 values was observed in the right ventricle. In contrast, a persistent increase in the T-2 relaxation times was observed in the right ventricle and correlated with the ratio Of right ventricle to body weight (r = 0.54, P < 0.01). The observation that the magnetic resonance relaxation times in vitro are modified in the hypertrophic right ventricle after myocardial infarction could be important in interpreting magnetic resonance imaging in vivo. There was no relation between the changes in the relaxation times and the degree of myocardial ischemia.