2D and 3D Echocardiography-Derived Indices of Left Ventricular Function and Shape: Relationship With Mortality

Abstract

Objectives: This study hypothesized that left ventricular (LV) ejection fraction (EF) and global longitudinal strain (GLS) derived from 3-dimensional echocardiographic (3DE) images would better predict mortality than those obtained by 2-dimensional echocardiographic (2DE) measurements, and that 3DE-based LV shape analysis may have added prognostic value.

Background: Previous studies have shown that both LVEF and GLS derived from 2DE images predict mortality. Recently, 3DE measurements of these parameters were found to be more accurate and reproducible because of independence of imaging plane and geometric assumptions. Also, 3DE analysis offers an opportunity to accurately quantify LV shape.

Methods: We retrospectively studied 416 inpatients (60 ± 18 years of age) referred for transthoracic echocardiography between 2006 and 2010, who had good-quality 2DE and 3DE images were available. Mortality data through 2016 were collected. Both 2DE and 3DE images were analyzed to measure LVEF and GLS. Additionally, 3DE-derived LV endocardial surface information was analyzed to obtain global shape indices (sphericity and conicity) and regional curvature (anterior, septal, inferior, lateral walls). Cardiovascular (CV) mortality risks related to these indices were determined using Cox regression.

Results: Of the 416 patients, 208 (50%) died, including 114 (27%) CV-related deaths over a mean follow-up period of 5 ± 3 years. Cox regression revealed that age and body surface area, all 4 LV function indices (2D EF, 3D EF, 2D GLS, 3D GLS), and regional shape indices (septal and inferior wall curvatures) were independently associated with increased risk of CV mortality. GLS was the strongest prognosticator of CV mortality, superior to EF for both 2DE and 3DE analyses, and 2D EF was the weakest among the 4 functional indices. A 1% decrease in GLS magnitude was associated with an 11.3% increase in CV mortality risk.

Conclusions: GLS predicts mortality better than EF by both 3DE and 2DE analysis, whereas 3D EF is a better predictor than 2D EF. Also, LV shape indices provide additional risk assessment.

Keywords: left ventricular function; left ventricular shape; outcomes; risk assessment.

FIGURE 1. 3DE Volume and Deformation Analyses

Example of 3DE dataset of the left ventricle (top). Endocardial boundaries initialized in 3 cross-sectional views extracted from the 3D dataset (middle) are used to create a dynamic 3D cast of the ventricle (bottom, center), from which both dynamic volume (bottom, left) and longitudinal strain (LS) (bottom, right) are calculated. 3DE = 3-dimensional echocardiographic; Ch = channel; LV = left ventricular.

FIGURE 2. Global and Regional Shape Indices

Diagrammatic representation of the computation of sphericity and conicity shape indices of the left ventricle (top) and regional curvature of the 4 different ventricular walls (bottom). Abbreviations as in Figure 1.

FIGURE 3. Results of Survival Analysis for EF and Strain

Kaplan-Meier survival curves for 2DE- and 3DE-based LVEF and GLS, stratified by tertiles both for EF and GLS. 2DE = 2-dimensional echocardiography; EF = ejection fraction; GLS = global longitudinal strain; other abbreviation as in Figure 1

FIGURE 4. Results of Survival Analysis for Regional Shape Indices

Kaplan-Meier survival curves for regional shape indices: inferior wall (left) and septal wall (right) curvature, stratified by tertiles for each index.