Left Ventricular Postmyocardial Infarction Remodeling Studied by Combining MR-Tagging With Delayed MR Contrast Enhancement

Abstract

We sought to monitor the evolution of noninfarcted and infarcted myocardium function in the process of left ventricular (LV) remodeling after a reperfused myocardial infarction. Pigs (n = 8) were subjected to reperfused infarction. Magnetic resonance imaging (MRI) was performed at 3 days and 8 weeks after infarction. Regional circumferential shortening (Ecc) and principal strain L1 in the infarcted, peri-infarcted, and remote myocardium were evaluated by tagged cine MRI combined with matched late enhancement data (Gadolinium-DOTA-enhanced IR-GRE) Global LV function was evaluated by cine MRI. Animals were euthanized after the second imaging session and tissue samples from the different myocardial regions were obtained for histopathologic study. There was a significant deterioration in Ecc between the 3-day and 8-week studies in the peri-infarcted myocardium at apex (-9.9% +/- 4.5% to -6.5 +/- 3.9; P = 0.046) whereas it remained stable for all other regions at all levels. A trend toward improvement in Ecc existed in the infarcted myocardium when infarction transmurality was less than 50% of the LV wall (-7.5% +/- 0.8% to -12.2% +/- 2.9% P = 0.06). Ecc in infarcted myocardium was significantly inferior (P < 0.002) to that in remote and peri-infarcted myocardium at the apical level (2.7% +/- 2.6% vs. -14.4% +/- 3.3% and -9.9% +/- 4.5%, respectively). Global LV function substantially deteriorated after infarction and was associated with a significant LV dilation. These results confirm the hypothesis that scarred myocardium imposes additional functional burden to the peri-infarcted myocardium.