Quantification of regional right ventricular strain in healthy rats using 3D spiral cine dense MRI

Statistical data from clinical studies suggests that right ventricular (RV) circumferential strain (E_cc) and longitudinal strain (E_ll) are significant biomarkers for many cardiovascular diseases. However, a detailed and regional characterization of these strains in the RV is very limited. In the current study, RV images were obtained with 3D spiral cine DENSE MRI in healthy rats. An algorithm for surface growing was proposed in order to fit irregular topology. Specifically, a new custom plugin for the DENSEanalysis program, called 3D DENSE Plugin for Crescent Organ, was developed for surface reconstruction and precise segmentation of organs with sharp curvature, such as the murine RV. The RV free wall (RVFW) was divided into three longitudinal thirds (i.e., basal, middle, and apical) with each one partitioned into circumferential fourths (i.e., anterior, anteriorlateral, inferiorlateral and inferior). Peak systolic strains were quantified for each segment and comparisons were performed statistically. The inclusion of a new plugin was able to generate global values for E_cc and E_ll that are in good agreement with previous findings using MRI. Despite no regional variation found in the peak E_cc, the peak E_ll exhibited regional variation at the anterior side of the RV, which is potentially due to differences in biventricular torsion at the RV insertion point and fiber architecture. These results provide fundamental insights into the regional contractile function of the RV in healthy rat and could act as a normative baseline for future studies on regional changes induced by disease or treatment.