Viable myocardium in reperfused acute myocardial infarction: Rest and stress first-pass MR imaging

Feasibility of identifying viable myocardium in rest and stress magnetic re sonance imaging (MRI) was evaluated using 3 hr occlusion and 30 min reperfu sion model of left anterior descending (LAD) coronary artery in 12 felines. At rest MRI, viable myocardium confirmed by 2,3,5-triphenyl tetrazolium ch loride (TTC)staining showed rapid signal intensity (SI) rise followed by gr adual decline not significantly different from normal myocardium that the t wo hyperperfused regions were distinguishable only from the hypoperfused no nviable myocardium. At stress MRI, hyperemia induced perfusion change was m ost pronounced in normal myocardium with earlier and greater peak enhanceme nt followed by brisk 'washout' phase while minimally augmented enhancement in viable myocardium was still in 'washin' phase. From these findings, it w as concluded that viable myocardium is identified in rest and stress MRI as redistributing hypoperfusion compared to persistent hyper-perfusion of the normal myocardium and the persistent hypo-perfusion of the nonviable myoca rdium.