In vivo quantification of myocardial stiffness in hypertensive porcine hearts using MR elastography

Abstract

Purpose To determine alteration in left ventricular (LV) myocardial stiffness (MS) with hypertension (HTN). Cardiac magnetic resonance elastography (MRE) was used to estimate MS in HTN induced pigs and MRE-derived MS measurements were compared against LV pressure, thickness and circumferential strain. Materials and Methods Renal-wrapping surgery was performed to induce HTN in 8 pigs. LV catheterization (to measure pressure) and cardiac MRI (1.5T; gradient echo-MRE and tagging) was performed pre-surgery at baseline (Bx), and post-surgery at month 1 (M1) and month 2 (M2). Images were analyzed to estimate LV-MS, thickness and circumferential strain across the cardiac cycle. The associations between end-diastolic (ED) and end-systolic (ES) MS and i) mean LV pressure; ii) ED and ES thickness respectively; and iii) circumferential strain were evaluated using Spearman’s correlation method. Results From Bx to M2, mean pressure, MRE-derived stiffness, and thickness increased while circumferential strain decreased significantly (slope test, p≤0.05). Both ED and ES MS had significant positive correlation with i) mean pressure (ED MS: ρ =0.56; p=0.005 and ES MS: ρ =0.45; p=0.03); ii) ED thickness (ρ =0.73; p<0.0001) and ES thickness (ρ =0.84; p<0.0001) respectively; but demonstrated a negative trend with circumferential strain (ED MS: ρ =0.31 and ES MS: ρ =0.37). Conclusion This study demonstrated that in HTN porcine model, MRE-derived MS increased with increase in pressure and thickness.

Relative identifiability of anisotropic properties from magnetic resonance elastography

“…Isotropic myocardial shear stiffness has successfully been measured from MRE experiments 11,15,16,[66][67][68] and so it is assumed that sufficient wave propagation can be achieved experimentally. However, the loading applied to the LV model in this experiment is idealised and does not necessarily represent the true harmonic motion that would occur in the left ventricle during cardiac MRE.…”

Cardiovascular magnetic resonance elastography: A review

“…Renal wrapping surgery was performed in porcine animals to induce hypertension and hypertrophy, which eventually leads to heart failure. Cine MRE data and invasive pressure measurements were obtained at baseline, 1 month and 2 months post‐surgery . This study demonstrated that MRE‐derived stiffness increased linearly with thickness and pressure, and also showed that stiffness during end‐systole and end‐diastole was significantly higher at months 1 and 2 compared with baseline (Figure ) …”

“…The first harmonic displacement field is obtained by performing the Fourier transform along the temporal dimension of the external waves with a temporal frequency equal to the mechanical excitation frequency in the data acquired with multiple phase offsets to obtain the stiffness maps. 7,46,47,57,62,[67][68][69] Before computing the stiffness maps using the aforementioned inversion strategies, several preprocessing methods are typically performed to remove undesired components from the phase data. Shear waves are of primary interest when estimating the shear stiffness, and therefore the longitudinal waves are removed using the curl operator 62 or bandpass filtering.…”

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.…”

“…12 MR elastography (MRE) is a novel noninvasive technique to measure the spatial stiffness of soft tissues. [13][14][15][16][17][18][19][20][21][22][23][24][25][26] MRE images are generated through a three-step process. First, noninvasive vibrations are applied to tissues by a driver that transmits waves.…”