P927Early left ventricular remodeling in a rat model of chronic myocardial infarction

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Post-infarct remodeling has been divided into an early (<72h) and a late (>72h) phase. Although the late phase has been studied extensively, relatively little is known about the early phase.Purpose: To characterize the time course of early LV remodeling subsequent to myocardial infarction (MI).Methods: 7 Sprague-Dawney rats were subjected to LAD ligation (MI) and 7 to sham surgery (SHAM). 3D high-frequency ultrasound imaging was performed at baseline and 1,2,3 and 7 days post surgery by acquiring a stack of 2D short-axis images at end-systole and end–diastole. Hereto, the transducer was automatically translated over a distance of 24mm in steps of 0.5mm. LV volumes were estimated by fitting endo- and epicardial surfaces to contours manually drawn in a select number of slices.Results: At baseline, LV end-diastolic (EDV), end-systolic volumes (ESV) and LV dimensions were comparable for both groups. Following SHAM no significant changes were found. In the MI group, ESV increased significantly at 7d compared to baseline (0.212±43 vs. 0.057±13 mL, p<0.05). LV anterior wall thickness progressively decreased over 1week post surgery (0.87±0.14 vs. 1.44±0.15mm, p<0.05) along with preserved LV posterior wall thickness. EDV and stroke volume (SV) values for both groups are shown in the figure.Conclusion: At day 1 a profound drop in SV, associated with a loss of myocardial function, with apparent structural changes in the infarct zone (reduced diastolic anterior wall thickness) was observed. In the following days the ventricle dilates, resulting in an improved SV and cardiac output. Dilation may thus be a mechanism to lower wall stress and thereby recover ejection performance.

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