Nilesh R. Ghugre1, Mihaela Pop1, Jennifer Barry1, Beiping Qiang1, John J. Graham2, Kim Connelly2, Alexander J. Dick1,3, Graham A. Wright1
1Imaging Research, Sunnybrook Health Sciences Centre, Toronto, ON, Canada; 2Division of Cardiology, St. Michael's Hospital, Toronto, ON, Canada; 3University of Ottawa Heart Institute, Ottawa, ON, Canada
The type and extent of infarction encountered clinically [transmural, hemorrhagic, heterogeneous, with microvascular obstruction (MVO)] is primarily determined by the severity of the initial ischemic insult. The purpose of our study was to evaluate longitudinal fluctuations in edema (T2), hemorrhage (T2*) and vasodilatory function (stress-induced T2 changes) in infarcted and remote territories of porcine myocardium subjected to different ischemic durations: 45 min and 90 min followed by reperfusion. The 90 min group produced hemorrhagic transmural infarcts with MVO while infarction in the 45 min group was non-transmural, non-hemorrhagic and heterogeneous. MRI parameters revealed faster resolution of edema and earlier restoration of vasodilatory function in less severe infarcts, potentially indicating reduced adverse remodeling. Understanding the in vivo pathophysiological mechanisms after acute myocardial infarction in the clinical setting will be key in predicting functional recovery and assessing the efficacy of novel therapies.