Abstract 11163: Biomechanics of Left Ventricular Remodeling in a Chronic Swine Model of Myocardial Infarction

Introduction: Adverse left ventricular (LV) remodeling after a myocardial infarction (MI) is an insidious process whose severity predicts future decompensated heart failure, morbidity and mortality. Our understanding of LV remodeling has been extensive at the molecular level, but little is known of the biomechanical changes that occur as the LV remodels, dilates, thins, and potentially has rearranged myofibers. In this study, we developed a chronic swine model of post-MI remodeling and used cardiac MRI to assess biomechanics of the remodeling LV after 10 weeks of infarction. Methods: Fourteen Yorkshire swine (n=14) were induced percutaneously with an MI by acute thrombosis of the left circumflex artery with ethanol infusion ( Fig.A1-A2 ), and the animals were survived. Echocardiography and MRI was performed at baseline and at 10 weeks to assess LV function and biomechanics, respectively. MRI was performed on a 3T Siemens scanner, with short axis CINE and tagged imaging ( Fig.A3-A4 ). LV strain, twist and torsion from short-axis tagged images and compared between baseline and 10 week values. Results: Survival rate after the infarction was 85.71%. Ejection fraction reduced from 54.79±5.52% at baseline to 47.29±8.36% 10 weeks post-MI (p=0.023) ( Fig.A5 ). LV end diastolic volume, end systolic volume and sphericity index were significantly elevated ( Fig.A6-A8 ). Radial strain values showed an increasing trend at 10 weeks after an MI, compared to baseline values ( Fig.B3 ). Circumferential strain values showed a decreasing trend by 10 weeks after MI compared to baseline values ( Fig.B4 ). Both ventricular twist and torsion were reduced compared to baseline, but the trend was more evident with LV torsion ( Fig.B5-B6 ) . Conclusions: After an MI of the postero-lateral wall, reduced ejection fraction and dilatation were observed as expected. LV radial strain was increased but circumferential strain, twist, and torsion of the left ventricle were significantly diminished.