4-DIMENSIONAL STRAIN IMAGING OF THE RIGHT VENTRICLE USING SPECKLE-TRACKING ECHOCARDIOGRAPHY: APPLICATION OF A NOVEL DEFORMATION PARAMETER

Abstract

Echocardiographic evaluation of right ventricular (RV) function is challenged by its asymmetric geometry. Two-dimensional (2D) RV strain imaging by speckle-tracking echocardiography (STE) has previously demonstrated feasibility and prognostic significance. Three-dimensional (3D) strain analysis is preferable because it is not slice-plane limited and provides vectored data in multiple orthogonal planes from a single acquisition. However, current 3D STE analysis software systems were designed for the more symmetrical geometry of the left ventricle. The purpose of this study was to demonstrate the feasibility of a novel 3D strain analysis approach for calculation of principal strain to characterize RV mechanical function. Twenty-eight patients underwent echocardiography inclusive of RV imaging acquired from standard transthoracic views with RV systolic function assessment using conventional 2D and 3D parameters. STE was performed by manual placement of endocardial RV contours from 3 echocardiographic views, and a 3D mesh model was generated using specialized software (Tomtec Imaging Systems, Germany). Off-line analysis was then performed using GIUSEPPE, a custom in-house made Matlab-based (Mathworks, USA) software. The 3D mesh model was then deformed according to the local velocity at each frame of the cardiac cycle. The deformed mesh elements allowed computation of contraction in the dominant direction, or peak principal strain amplitude (PPSA) (see Figure 1). Mean age of the study population was 49.8±14.6 years and 10 patients (36%) were female. RV chamber size and function by conventional echocardiographic assessment was normal for 20 patients (71%), while 4 (14%) had RV enlargement, 4 (14%) RV dysfunction and 3 (11%) RV hypertrophy. Mean RV end-diastolic volume, end-systolic volume, 3D ejection fraction (EF), 2D global peak longitudinal systolic strain (GLPSS) and tricuspid annular plane systolic excursion (TAPSE) were 70.4±23.5 mL, 35.2±13.1 mL, 49.8±9.6%, -22.5±7.1%, and 2.2±0.4 mm, respectively. RV 3D strain analysis was feasible in all subjects. Mean RV 3D PPSA was -25.0±3.5%. Correlation coefficients (p-value) for RV PPSA were significant with 3D EF (r=0.67, p<0.01), GLPSS (r=0.72, p<0.01) and TAPSE (r=0.68, p=0.02). In this pilot study we demonstrate the feasibility of 3D RV strain analysis by STE to characterize RV mechanical deformation using a novel software tool that is adaptable to the unique geometry of the RV. PPSA assessment by 3D RV strain correlated well with conventional measures of RV systolic function and represents a viable measure of global contractile deformation.