DELAYED REDUCTION OF TISSUE WATER DIFFUSION AFTER MYOCARDIAL-ISCHEMIA

The apparent diffusion coefficient (ADC) of water after regional myoca rdial ischemia was measured in isolated, perfused rabbit hearts by usi ng magnetic resonance imaging (MRI) techniques. After ligation of the left anterior descending coronary artery, the ADC of the nonperfused r egion showed a gradual but significant decreasing trend over time, whe reas that of the normally perfused myocardium remained constant. Morph ological analysis revealed that the ADC decrease reflected the expansi on of a subregion of reduced ADC within the nonperfused myocardium. Th e dynamics of the diffusion change and the morphological progression o f the affected tissue suggest that the ADC decrease may be linked to t he onset of myocardial infarction, which is known to involve myocyte s welling. The ADC reduction provides a potentially valuable MRI tissue- contrast mechanism for noninvasively determining the viability of the ischemic myocardium and assessing the dynamics of acute myocardial inf arction.