Simultaneous Evaluation of Infarct Size and Cardiac Function in Intact Mice by Contrast-Enhanced Cardiac Magnetic Resonance Imaging Reveals Contractile Dysfunction in Noninfarcted Regions Early After Myocardial Infarction

<jats:p> <jats:bold> <jats:italic>Background—</jats:italic> </jats:bold> The objective of this study was to noninvasively determine the effects of reperfused myocardial infarction (MI) on regional and global left-ventricular (LV) function 24 hours after MI in intact mice with contrast-enhanced cardiac MRI and a single, gradient-echo pulse sequence. </jats:p> <jats:p> <jats:bold> <jats:italic>Methods and Results—</jats:italic> </jats:bold> Twenty-three mice received baseline MRI scans followed by either 60 minutes of coronary occlusion (MI group, n=15) or thoracotomy without occlusion (sham group, n=8). Gadolinium-DTPA–enhanced magnetic resonance (MR) images were acquired 24 hours after surgery. Hearts were then excised for conventional infarct size determination via 2,3,5-triphenyl tetrazolium chloride (TTC) staining. In addition to infarct size, analysis of the MR images yielded left ventricular (LV) mass, LV end-systolic volume (LVESV), LV end-diastolic volume (LVEDV), LV ejection fraction (LVEF), cardiac output, and percent LV wall thickening (%WTh). Twenty-four hours after surgery, infarct size was 28.1±1.8% of LV mass by MRI and 27.5±1.7% by TTC ( <jats:italic>P</jats:italic> =NS). Bland-Altman analysis revealed close agreement between the results obtained by the 2 methods. MI had little effect on LVEDV but caused a 98% increase in LVESV (from 11.3 to 22.4 μL, <jats:italic>P</jats:italic> <0.05), which resulted in a significant reduction in LVEF (from 70% to 37%, <jats:italic>P</jats:italic> <0.05). Compared with LV regional function at baseline, %WTh 24 hours after MI was significantly depressed, not only in infarcted myocardium but also in regions remote from the infarct zone. In contrast, sham-operated mice showed a small but significant increase in %WTh 24 hours after surgery ( <jats:italic>P</jats:italic> <0.05). </jats:p> <jats:p> <jats:bold> <jats:italic>Conclusions—</jats:italic> </jats:bold> MRI can accurately assess both infarct size and cardiac function in intact mice early after large, reperfused MI, revealing the existence of contractile dysfunction in noninfarcted regions of the heart. </jats:p>