Remodeling of the Ischemia-Reperfused Murine Heart: 11.7-T Cardiac Magnetic Resonance Imaging of Contrast-Enhanced Infarct Patches and Transmurality

Our laboratory has published the first evidence obtained from fast low-angle-shot cine magnetic resonance imaging (11.7 T) studies demonstrating secondary myocyte death after ischemia/reperfusion (IR) of the murine heart. This work provides the first evidence from 11.7-T magnet-assisted pixel-level analysis of the post-IR murine myocardial infarct patches. Changes in function of the remodeling heart were examined in tandem. IR compromised cardiac function and induced LV hypertrophy. During recovery, the IR-induced increase in LV mass was partly offset. IR-induced wall thinning was noted in the anterior aspect of LV and at the diametrically opposite end. Infarct size was observed to be largest on post-IR days 3 and 7. With time (day 28), however, the infarct size was significantly reduced. IR-induced absolute signal-intensity enhancement was highest on post-IR days 3 and 7. As a function of post-IR time, signal-intensity enhancement was attenuated. The threshold of hyperenhanced tissue resulted in delineation of contours that identified necrotic (bona fide infarct) and reversibly injured infarct patches. The study of infarct transmurality indicated that whereas the permanently injured tissue volume remained unchanged, part of the reversibly injured infarct patch recovered in 4 weeks after IR. The approach validated in the current study is powerful in noninvasively monitoring remodeling of the post-IR beating murine myocardium.