Regional deformation and contractile function in canine right ventricular free wall

Abstract

We used biplane cinefluorgraphy to study the regional deformation and local contractile function of the canine right ventricular free wall (RVFW) among the inflow, midventricular, and outflow regions. For a region delimited by three neighboring markers, under the assumption of homogeneous deformation, we identified the magnitudes and directions of principal shortening or elongation and changes in area every 16.7 ms. Furthermore, we extended this approach to study the alterations of these parameters during RV afterload increase by applying pulmonary artery (PA) occlusion. Results show that, at both control and PA occlusion states, the outflow region was subjected to maximal fractional area reduction (AR) and maximal time rate of fractional area reduction (ARR) during systole, with no differences between inflow and midventricular regions (P less than 0.05). At the control state, the percent AR and the corresponding value for ARR were 27% and 179%/s at the outflow, 19% and 112%/s at the midventricular, and 15% and 107%/s at the inflow region, respectively. During PA occlusion, they became 21% and 115%/s at the outflow, 14% and 97%/s at the midventricular, and 15% and 102%/s at the inflow region, respectively. Statistically, only the outflow region deformation was affected by PA occlusion (P less than 0.05). For the control state, we also compared the direction of regional principal shortening at end systole to the local transmural myocardial fiber orientations. The directions were found to correspond closely to the mean of all local transmural fiber orientations. This suggests that the regional RVFW deformation we measured is the combined deformation behavior from all the local participating myofibers.

Deficiency of Actinin-Associated LIM Protein Alters Regional Right Ventricular Function and Hypertrophic Remodeling

“…The amount of maximum strain measured (on average about 17%) was similar to previously measured RV strains in the conscious dog, 3,18,23 despite the substantially slowed heart rate in the anesthetized mouse in this study (250 bpm) compared with a conscious mouse (500-600 bpm). The literature contains conflicting results regarding regional strain differences.…”

“…The literature contains conflicting results regarding regional strain differences. We found that strains were somewhat lower in the sinus region than the outflow tract region, which is consistent with some previous studies, 3,21 but disagrees with others. 18,27 The reasons for these discrepancies are not clear, but are likely due to differences in preparation such as in marker placement and open-vs. closed-chest measurements.…”

Three-dimensional motion reconstruction and analysis of the right ventricle using tagged MRI

“…One-dimensional relative motion data has been gathered by tracking pairs of radiopaque beads tracked with biplane cineradiography [30,51) or pairs of crystals with ultrasound [28]. By implanting several markers close together on the same ventricular surface (e.g., endocardium), researchers have been able to derive biaxial, or in-plane, deformations [17,6,341. The human RV has been studied using the noninvasive MRI tissue tagging method.…”

Three-dimensional systolic kinematics of the right ventricle

“…A potentially important means of detecting and evaluating RV dysfunction is to quantitatively analyze changes in its motion. However, because of its thin wall and asymmetric geometry, the normal three-dimensional (3-D) motion and deformation of the RV are not yet well understood.Early studies (4,5,14,19,20,24) used implanted radiopaque markers to provide limited knowledge about RV motion, mostly in animals. Recently, imaging modalities, such as echocardiography, computed tomography, and conventional magnetic resonance imaging (MRI), have provided a noninvasive means of studying the RV (3, 7, 12).…”