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

Abstract

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 MRI relaxometry parameters (T1, T2, and extracellular volume fraction (ECV)). Methods MRI (1.5T) was performed on 7 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 using mechanical testing-derived MS obtained post-sacrifice on D21. Circumferential strain and MRI relaxometry parameters (T2, T1, and ECV) were also obtained. Multi-parametric analysis was performed to determine correlation between cardiac MRE-derived MS and i) strain, ii) relaxometry parameters, and iii) mechanical testing. Results Mean diastolic (D10:5.09±0.6kPa; D21:5.45±0.7kPa) and systolic (D10:5.72±0.8kPa; D21:6.34±1.0kPa) MS in MIR were significantly higher (p<0.01) compared to mean diastolic (D10:3.97±0.4kPa; D21:4.12±0.2kPa) and systolic (D10:5.08±0.6kPa; and D21:5.16±0.6kPa) 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.

Cardiovascular magnetic resonance elastography: A review

“…Myocardial infarcts were created in a porcine animal model . CMRE was performed pre‐surgery (baseline) and at 10 days and 21 days post‐surgery.…”

“…A linear relationship was observed at end‐systole (ES) and at end‐diastole (ED) between MRE‐derived stiffness and mechanical testing by pooling both infarcted myocardium and remote normal myocardium. Reproduced with permission from Mazumder et al…”

“…CMRE was performed to assess myocardial contractility based on the stiffness estimates in a porcine animal model . First, baseline CMRE was performed during end‐systole using a cine MRE sequence, and then epinephrine was intravenously injected to increase the heart rate and myocardial contractility.…”

“…CMRE was performed pre‐surgery (baseline) and at 10 days and 21 days post‐surgery. After all imaging had been performed on the 21st day, the animals were euthanized and the strips of infarct and remote normal myocardium were analyzed using mechanical testing to obtain the stiffness measurements . As can be seen in Figure , a significant increase in CMRE‐derived stiffness of the infarct zone was observed from baseline to 10 days and 21 days post‐surgery, whereas the stiffness of the remote normal myocardium remained unchanged.…”

Quantification of breast stiffness using MR elastography at 3 Tesla with a soft sternal driver: A reproducibility study

“…MR elastography (MRE) is a novel noninvasive technique to measure the spatial stiffness of soft tissues . MRE images are generated through a three‐step process.…”