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

Abstract

To determine alteration in left ventricular (LV) myocardial stiffness (MS) with hypertension (HTN). Cardiac MR 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. Renal-wrapping surgery was performed to induce HTN in eight pigs. LV catheterization (to measure pressure) and cardiac MRI (1.5 Tesla; 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. 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). This study demonstrated that, in a HTN porcine model, MRE-derived MS increased with increase in pressure and thickness. 1 J. Magn. Reson. Imaging 2017;45:813-820.