Right Ventricular Deformation Analyses Using a Three-Dimensional Speckle-Tracking Echocardiographic System Specialized for the Right Ventricle

Abstract

Background: Given the complex morphologic nature of the right ventricle, three-dimensional (3D) approaches would be more appropriate for assessing right ventricular (RV) function than two-dimensional approaches. Thus, the investigators have developed a novel 3D speckle-tracking echocardiographic (STE) system specialized for the right ventricle. The aim of this study was to assess the characteristics of RV global and regional deformation as well as changes on stress tests using the 3D STE system in experimental studies.

Methods: In 10 sheep, sonomicrometry crystals were implanted to validate 3D STE data in the RV endocardium of seven RV segments, including the basal and mid anterior, lateral and inferior wall, and outflow free wall. Full-volume 3D STE data sets and sonomicrometric data were acquired at baseline, during pulmonary artery banding (PAB)-induced moderate (peak RV pressure > 40 mm Hg) and severe (peak RV pressure > 60 mm Hg) RV pressure increases, and during propranolol infusion. The 3D STE area change ratio (ACR), longitudinal strain (LS), and circumferential strain (CS) were measured, and RV global and all segmental deformation data were compared between baseline and stress tests. To assess clinical feasibility, 30 control subjects and 11 patients with pulmonary arterial hypertension were enrolled.

Results: All combined 3D STE data were significantly correlated with the sonomicrometric data (ACR, R(2) = 0.88; LS, R(2) = 0.84; CS, R(2) = 0.82; P < .001). In all seven segments, the 3D STE data correlated with the sonomicrometric data (R(2) = 0.72-0.90, P < .001). Global ACR and LS data showed significant differences among baseline, moderate PAB, and severe PAB; however, CS differed only between baseline and severe PAB. The magnitudes of segmental deformation in the free wall were larger than those in the septum and apex under all conditions (P < .05) except LS during severe PAB. Segmental analyses also showed similar responses during stress tests; the ACR in each segment differed significantly between conditions. In all but the apical segments, LS showed significant reductions from moderate PAB; in contrast, CS was significantly reduced with severe PAB in all segments. In this clinical study, the acquisition rate of adequate images for analysis of the RV outflow tract was lower (75.6%) compared with the rate in other segments (from 85.4% to 100%). However, the pulmonary arterial hypertension group had lower RV global deformation values than the control group (ACR and LS, P < .001; CS, P = .003), the ACR and LS in basal and middle segments differed significantly between groups, and the outflow and apex did not differ.

Conclusions: A novel 3D STE system specialized for the right ventricle is reliable for RV deformation analyses and may provide additional information about RV global and segmental function. The clinical feasibility of this system is acceptable.

Keywords: Cardiac function; Right ventricle; Speckle-tracking echocardiography; Three-dimensional echocardiography.