Feasibility and reproducibility of systolic right ventricular strain measurement by speckle-tracking echocardiography in premature infants

Abstract

Background: Right ventricular (RV) systolic function is an important prognostic determinant of cardiopulmonary pathologies in premature infants. Measurements of dominant RV longitudinal deformation are likely to provide a sensitive measure of RV function. An approach for image acquisition and postacquisition processing is needed for reliable and reproducible measurements of myocardial deformation by two-dimensional (2D) speckle-tracking echocardiography. The aims of this study were to determine the feasibility and reproducibility of 2D speckle-tracking echocardiographic measurement of RV peak global longitudinal strain (pGLS) and peak global longitudinal strain rate in premature infants and to establish methods for acquiring and analyzing strain.

Methods: The study was designed in two phases: (1) a training phase to develop methods of image acquisition and postprocessing in a cohort of 30 premature infants (born at 28 ± 1 weeks) and (2) a study phase to prospectively test in a separate cohort of 50 premature infants (born at 27 ± 1 weeks) if the methods improved the feasibility and reproducibility of RV pGLS and peak global longitudinal strain rate measurements to a clinically significant level, assessed using Bland-Altman analysis (bias, limits of agreement, coefficient of variation, and intraclass correlation coefficient).

Results: Strain imaging was feasible from 84% of the acquisitions using the methods developed for optimal speckle brightness and frame rate for RV-focused image acquisition. There was high intraobserver (bias, 3%; 95% limits of agreement, -1.6 to +1.6; coefficient of variation, 2.7%; intraclass correlation coefficient, 0.97; P = .02) and interobserver (bias, 7%; 95% limits of agreement, -4.8 to +4.73; coefficient of variation, 3.9%; intraclass correlation coefficient, 0.93; P < .05) reproducibility, with excellent linear correlation between the two pGLS measurements (r = 0.97 [P < .01] and r = 0.93 [P < .05], respectively).

Conclusions: This study demonstrates high clinical feasibility and reproducibility of RV pGLS and RV peak global longitudinal strain rate measurements by 2D speckle-tracking echocardiography in premature infants and offers methods for image acquisition and data analysis for systolic strain imaging that can provide a reliable assessment of global RV function.

Keywords: 2D; CI; CV; Coefficient of variation; Confidence interval; DTI; Doppler tissue imaging; Global longitudinal strain; ICC; Intraclass correlation coefficient; LOA; Limits of agreement; PMA; Peak global longitudinal strain; Peak global longitudinal strain rate; Postmenstrual age; Premature infants; ROI; RV; Region of interest; Right ventricle; Right ventricular; STE; Speckle-tracking echocardiography; Systolic function; Two-dimensional; pGLS; pGLSr.

Copyright © 2013 American Society of Echocardiography. Published by Mosby, Inc. All rights reserved.

Figures

Figure 1

Three specific landmarks, one apical and two basal, are identified in the right ventricle (RV) focused image to delineate a “sail sign” around the inside of the endocardial boarder. These three landmarks are: A) the trigonal crux at the basal septal side of the trianular plane. B) the apical point at the apical junction of the septum and RV free wall (RVFW), and C) the lateral hinge point of the tricuspid valve at the basal RVFW side of the trianual plane and the RVFW.

Figure 2

Strain imaging of the right ventricle in a premature infant using speckle-tracking echocardiography. The segmental strain is graphically presented by six different color-code curves and the global longitudinal strain by the white dotted curve. The peak of the average curve of all the segments (the dotted curve) was considered as peak global longitudinal strain (pGLS).

Figure 3

Cine-loop images of (A) RV focused 4 chamber echocardiographic view and (B) Standard apical four chamber view showing the six segmental strain curves graphically and the dotted line representing global longitudinal strain. (A) Longitudinal systolic strain curves obtained from the RV focused apical four-chamber view. The segmental strain curves are and synchronized. The RV focused view allows for proper tracking of the RVFW basal segment (red strain curve) by the software program and generates the highest longitudinal strain value. (B) Longitudinal systolic strain curves obtained from standard apical four-chamber view. In this view, the segmental strains are not synchronous at the basal region (red strain curve) of the RVFW because of an over excursion and inability of the software algorithm to properly track this segment.

Figure 4

Feasibility flow chart for (a) Training phase and (b) Study phase.

Figure 4

Feasibility flow chart for (a) Training phase and (b) Study phase.

Figure 5

Bland-Altman plot of (A) intraobserver and (B) interobserver peak global longitudinal strain (pGLS) variability showing mean percentage bias (fine dotted line) and 95% limits of agreements (thick dotted lines).

Figure 6

Bland-Altman plot of (A) intraobserver and (B) interobserver peak global longitudinal strain rate (pGLSr) variability showing mean percentage bias (fine dotted line) and 95% limits of agreements (thick dotted lines).

Figure 7

Relationship between intra- and interobserver pGLS and pGLSr. (A) Correlation between the strain values measured by the same observer (intraoberver strain correlation). (B) Correlation between the strain values measured by two different observers (interobserver strain correlation). (C) Correlation between the strain rate values measured by the same observer. (Intraobserver strain rate correlation). (D) Correlation between the strain rate values measured by the same observer (interobserver strain rate correlation).

Figure 8

Configuration of Imaging system: (A) overall gain settings and TGC are set to produce images in which the brightness of the mid-myocardial regions of the septum and RVFW represent mid-level gray values to make it appear brighter than that typically used in (B) conventional echocardiography to have clear endocardial and epicardial borders.