Quantification of myocardial stiffness using magnetic resonance elastography in right ventricular hypertrophy: initial feasibility in dogs

IntroductionMyocardial stiffness is an important determinant of cardiac function and is currently invasively and indirectly assessed by catheter angiography. This study aims to demonstrate the feasibility of quantifying right ventricular (RV) stiffness noninvasively using cardiac magnetic resonance elastography (CMRE) in dogs with severe congenital pulmonary valve stenosis (PVS) causing RV hypertrophy, and compare it to remote myocardium in the left ventricle (LV). Additionally, correlations between stiffness and selected pathophysiologic indicators from transthoracic echocardiography (TTE) and cardiac magnetic resonance imaging were explored.MethodsIn-vivo CMRE was performed on nine dogs presenting severe congenital PVS using a 1.5 T MRI scanner. T1-MOLLI, T2-prepared-bSSFP, gated-cine GRE-MRE and LGE (PSIR) sequences were used to acquire a basal short-axis slice. RV and LV-free-wall (FW) stiffness measurements were compared against each other and also correlated to ventricular mass, RV and LV FW thickness, T1 and T2 relaxation times, and extracellular volume fraction (ECV). Peak transpulmonary pressure gradient and myocardial strain were also acquired on eight dogs by TTE and correlated to RV-FW systolic stiffness. Potential correlations were evaluated by Spearman's rho (rs).ResultsRV-FW stiffness was found to be significantly higher than the LV-FW stiffness both during end-systole (ES) (p = 0.002) and end-diastole (ED) (p = 0.029). Significant correlations were observed between RV-FW ES and LV-FW ED stiffness versus ECV (rs =0.75; p-value = 0.05). Non-significant moderate correlations were found between LV-FW ES (rs = 0.54) and RV-FW ED (rs = 0.61) stiffness versus ECV. Furthermore, non-significant correlations were found between RV or LV-FW stiffness and the remaining variables (rs < 0.54; p-value > 0.05).ConclusionThis study demonstrates the feasibility of determining RV stiffness. The positive correlations between stiffness and ECV might indicate some interdependence between stiffness and myocardial extracellular matrix alterations. However, further studies are warranted to validate our initial observations.