In vivo magnetic resonance elastography to estimate left ventricular stiffness in a myocardial infarction induced porcine model

Purpose To estimate change in left ventricular (LV) end‐systolic and end‐diastolic myocardial stiffness (MS) in pigs induced with myocardial infarction (MI) with disease progression using cardiac magnetic resonance elastography (MRE) and to compare it against ex vivo mechanical testing, LV circumferential strain, and magnetic resonance imaging (MRI) relaxometry parameters (T1, T2, and extracellular volume fraction [ECV]). Materials and Methods MRI (1.5T) was performed on seven pigs, before surgery (Bx), and 10 (D10), and 21 (D21) days after creating MI. Cardiac MRE‐derived MS was measured in infarcted region (MIR) and remote region (RR), and validated against mechanical testing‐derived MS obtained postsacrifice on D21. Circumferential strain and MRI relaxometry parameters (T2, T1, and ECV) were also obtained. Multiparametric analysis was performed to determine correlation between cardiac MRE‐derived MS and 1) strain, 2) relaxometry parameters, and 3) mechanical testing. Results Mean diastolic (D10: 5.09 ± 0.6 kPa; D21: 5.45 ± 0.7 kPa) and systolic (D10: 5.72 ± 0.8 kPa; D21: 6.34 ± 1.0 kPa) MS in MIR were significantly higher (P < 0.01) compared to mean diastolic (D10: 3.97 ± 0.4 kPa; D21: 4.12 ± 0.2 kPa) and systolic (D10: 5.08 ± 0.6 kPa; and D21: 5.16 ± 0.6 kPa) MS in RR. The increase in cardiac MRE‐derived MS at D21 (MIR) was consistent and correlated strongly with mechanical testing‐derived MS (r(diastolic) = 0.86; r(systolic) = 0.89). Diastolic MS in MIR demonstrated a negative correlation with strain (r = 0.58). Additionally, cardiac MRE‐derived MS demonstrated good correlations with post‐contrast T1 (r(diastolic) = –0.549; r(systolic) = –0.741) and ECV (r(diastolic) = 0.548; r(systolic) = 0.703), and no correlation with T2. Conclusion As MI progressed, cardiac MRE‐derived MS increased in MIR compared to RR, which significantly correlated with mechanical testing‐derived MS, T1 and ECV. Level of Evidence: 1 J. Magn. Reson. Imaging 2017;45:1024–1033