Regional Dysfunction After Myocardial Infarction in Rats

Background— Detailed understanding of regional function after myocardial infarction (MI) is currently incomplete. We aimed at investigating regional myocardial strain and work in post-MI rats with and without heart failure. Methods and Results— Six weeks after induction of MI, 62 male Wistar-Hannover rats with a range of infarct sizes, plus 14 sham-operated rats, were examined by cine and phase-contrast magnetic resonance imaging. After magnetic resonance imaging, the rats were catheterized, and left ventricular pressures were recorded. Regional strain and work were calculated from the magnetic resonance imaging and pressure data. On the basis of end-diastolic left ventricular pressure, 34 MI rats were classified as nonfailing (MI NF ) and 28 MI rats as failing (MI CHF ). In the region remote to the infarct, the MI NF rats exhibited preserved strain and increased work compared with sham, whereas MI CHF had reduced longitudinal strain and no increase in work in this region. In the noninfarcted region adjacent to the infarct, MI CHF demonstrated substantially reduced work because of high levels of negative work. Conclusions— We have demonstrated a distinct difference in regional work between nonfailing and failing hearts after MI and offer novel insight into the relation between regional function and presence of congestion. Work analysis provided significant added value over strain analysis alone.