Right Ventricular Architectural Remodeling and Functional Adaptation in Pulmonary Hypertension

Abstract

BACKGROUND: Global indices of right ventricle (RV) function provide limited insights into mechanisms underlying RV remodeling in pulmonary hypertension (PH). While RV myocardial architectural remodeling has been observed in PH, its effect on RV adaptation is poorly understood. METHODS: Hemodynamic assessments were performed in 2 rodent models of PH. RV free wall myoarchitecture was quantified using generalized Q-space imaging and tractography analyses. Computational models were developed to predict RV wall strains. Data from animal studies were analyzed to determine the correlations between hemodynamic measurements, RV strains, and structural measures. RESULTS: In contrast to the PH rats with severe RV maladaptation, PH rats with mild RV maladaptation showed a decrease in helical range of fiber orientation in the RV free wall (139º versus 97º; P =0.029), preserved global circumferential strain, and exhibited less reduction in right ventricular-pulmonary arterial coupling (0.029 versus 0.017 mm/mm Hg; P =0.037). Helical range correlated positively with coupling ( P =0.036) and stroke volume index ( P <0.01). Coupling correlated with global circumferential strain ( P <0.01) and global radial strain ( P <0.01) but not global longitudinal strain. CONCLUSIONS: Data analysis suggests that adaptive RV architectural remodeling could improve RV function in PH. Our findings suggest the need to assess RV architecture within routine screenings of PH patients to improve our understanding of its prognostic and therapeutic significance in PH.

Knowing All the Angles (on Right Ventricular Myocardial Remodeling)

“…In Sprague Dawley rats, however, they observed a different fiber remodeling pattern where the transmural helical range of myofiber angles was reduced, accompanied by circumferential reorientation of endocardial fibers, resulting in preserved circumferential RV wall strain and less severe reduction in RV coupling measured by TAPSE/ RVSP, compared to CDF animals. 4 In some ways, these findings may relate to what is known regarding left ventricular fiber angle and systolic twisting. The left ventricle (LV) also has a helical organization to myofibers that has been implicated in systolic twisting motion that contributes to ejection and is diminished in remodeling accompanying cardiomyopathy.…”

“…The article by Mendiola et al 4 in the current issue of the journal takes us one significant step closer in understanding this complex question. This multidisciplinary group of investigators examined RV myofiber angle remodeling via new technology: magnetic resonance imaging diffusion-weighted imaging.…”

Improved right ventricular strain estimation in rats using anisotropic diffusion filtering

“…The images used for speckle tracking were obtained from 2D parasternal echocardiography in a male Sprague-Dawley Sugen-hypoxi rat (n = 1) at the third-week timepoint post Sugen5416 injection. 2 SA and 4-CH images were acquired in one session (Fig. 1a).…”

“…Clinical diagnosis of cardiovascular diseases (CVDs), by and large, has relied on the evaluation of organ-level functional markers such as ejection fraction and end-systolic pressure. 1,2 The inclusion of medical imaging data in delineating cardiac motion has been a vital addition to standard clinical practice. In addition to the conventional diagnostic markers, the development of tissue-level measures of contractility through cardiac strain estimation has advanced the in-vivo assessment of CDVs.…”

“…B-mode short-axis (SA) and four-chamber (4-CH) images of the RVFW were acquired for a Sugen-hypoxia rodent model of pulmonary hypertension. 2,14 Subsequently, acoustic shadows were observed, and the images were subjected to the edge-enhancing anisotropic diffusion (EED) filter. Cardiac strains were then evaluated using both the unprocessed and filtered images.…”