Myocardial contractility assessment based on 3D echocardiography

Background

Left ventricular (LV) volumes and ejection fraction (EF) are important parameters for the diagnosis and prognosis of patients with heart disease (1-3). They can be evaluated using different noninvasive imaging techniques. Currently two-dimensional echocardiography (2DE) is the most widely used. However, 2DE depends on the observer’s interpretation and heart analysis is limited to a small number of anatomical views.

Real time three-dimensional echocardiography (RT-3DE) provides greater nearness to real anatomy (4, 5). It was compared with 64 slice-ultrafast cardiac tomography and a good correlation between LVEF, end-diastolic volume and end-systolic volume (r: 0.7888, r: 0.7695, r: 0.8119, p<0.0001, respectively) was found (6,7). When RT-3DE was compared with CMR to calculate LV volumes and EF, it was comparable and superior to 2D-echo (8).

LVEF depends not only on LV contractility but on other parameters as well such as pre-load and after-load. The direct evaluation of contractility would be valuable. New three-dimensional wall motion tracking (3D-WMT) technology provides a novel approach to analyzing the left ventricle (LV) and a new concept to assess its function.

Advantages of 3D-WMT

• Time sparing

It is one of the main advantages of 3D-WMT because all segments are calculated in a single analysis step. Within 20 seconds, the result of the 3D WMT is available providing a variety of parameters to evaluate the myocardial function.

• Real movement in 3D space

2D and 3D-WMT are also different in that 2D-WMT employs 2D movement or the projection of 3D movement into a 2D plane, whereas 3D tracking assesses real movement in 3D space, not just a projection. 3D-WMT can be used for regional wall motion analysis of the entire LV and allows to obtain real 3D indices and to assess 3D wall motion specifically with an improved integration of heart structure. It is capable of displaying results for the entire myocardium using a single dataset to assess truly global LV, new indices (eg, twist, torsion), true 3D strain, and a host of other previously unobserved parameters (11) (Figure 1). With this method, all vectors of tissue are tracked within the full volume. It provides a better vector calculation, which is more adequate for clinical scanning conditions and there is no loss of the speckle particle in 3D. The 3D-WMT technique is a simple, feasible, and reproducible method to measure longitudinal, circumferential, and radial strain values (8, 9).

• Information regarding LV volume

3D-WMT not only provides information regarding the segmentary analysis of the left ventricular myocardium, it also provides a robust evaluation of LV volume during the heart cycle. The detection of the endocardium for wall motion purposes is used to obtain the inner dimensions of the LV 3D shape and the myocardial volume. The system informs on LV volumes and LVEF, and the related volume curves are presented time-aligned with the segmental parametric imaging curves (Figure 2). The 3D shapes can be corrected when needed in 5 orthogonal planes. Thus, the assessment of LV volume is anatomicaly correct and robust.

Applications

3D-WMT has a promising role in the evaluation of different heart diseases such as dilated cardiomyopathy, LV asynchrony evaluation, and ischemic heart disease (12-14).

Area tracking

Area tracking is a new parameter of regional and global LV function provided by 3D-WMT on the ARTIDA premium class ultrasound system from Toshiba Medical Systems. Area Tracking reflects the 3D radial strain and is based only on endocardial changes, which makes the method very sensitive for detecting ischemic reactions in the myocardium which are most detectable in the sub-endocardial layers (Figure 3). This new parameter reflects the deformation of the endocardial surface during LV contraction and relaxation. This application in combination with stress echo is a very promising tool to quantify stress echo readings.





























Figure 1: Different parameters (longitudinal strain, rotation, circumferential strain and torsion-basal) displayed in different formats.

Figure 2: Final representation of a normal heart, after automatic software detection of endocardium and epicardium.














Figure 3: This polar map shows the area tracking analysis in a patient with a severely depressed left ventricular ejection fraction.