Comprehensive Ultrasound Imaging of Right Ventricular Remodeling Under Surgically Induced Pressure Overload in Mice

This study reports a new methodology for right heart imaging by ultrasound in mice under right ventricular (RV) pressure overload. Pulmonary artery constriction (PAC) or sham surgeries were performed on C57BL/6 male mice at 8 weeks of age. Ultrasound imaging was conducted at 2, 4 and 8 weeks post-surgery using both classical and advanced ultrasound imaging modalities including ECG-based kilohertz visualization, anatomical M-mode and strain imaging. Based on pulsed Doppler, the PAC group demonstrated dramatically enhanced pressure gradient in the main pulmonary artery (MPA) as compared to the sham group. By applying advanced imaging modalities in novel short axis views of the ventricles, the PAC group demonstrated increased thickness of RV free wall, enlarged RV chamber and reduced RV fractional shortening compared to the sham group. The PAC group also showed prolonged RV contraction, asynchronous inter-play between RV and left ventricle (LV), and passive leftward motion of the inter-ventricular septum (IVS) at early diastole. Consequently, the PAC group exhibited prolongation of LV isovolumic relaxation time, without change in LV wall thickness or systolic function. Significant correlations were found between the maximal pressure gradient in MPA measured by Doppler and the RV systolic pressure by catheterization, as well as the morphological and functional parameters of RV by ultrasound.