Validation of three-dimensional echocardiographic principal strain analysis for assessing left ventricular contractility: An animal study

Purpose: The three-dimensional (3D) principal strain represents the major direction and magnitude of the deformation by its definition and can be measured using 3D echocardiography. We aimed to validate 3D echocardiographic left ventricular (LV) global principal strains as an assessment of LV contractility by comparison with gold standard invasive measurements. Methods: In 14 beagles, the LV pressure–volume loop was recorded to invasively measure the end-systolic pressure–volume relationship (ESPVR) and dP/dt as reference indicators representing LV contractility. The echocardiographic image was obtained simultaneously, and endocardial motions and volume changes were extracted in the form of speckle-tracking point grids to calculate strains. High or low inotropic states were induced pharmacologically by using an intravenous infusion of dobutamine and esmolol, respectively. Results: The direction of 3D endocardial global principal strain (GP1S) appeared to be circumferential. The dP/dt showed the highest Pearson's correlation coefficients with GP1S (r = −0.845, P < 0.001), whereas ESPVR showed the best correlation with global secondary strain (GP2S; r = −0.819, P < 0.001). In comparison with GP1S and GP2S, global circumferential (GCS) and longitudinal strains (GLS) tended to correlate less with invasive measurements, respectively. LV ejection fraction showed excellent correlations with GP1S or GCS, but the correlation with GLS was relatively weak. The correlations between invasive measurements and GP2S or GLS were strengthened when strains were corrected by the LV residual volume ratio, whereas those of GP1S or GCS were weakened after correction. Conclusions: The principal direction of the LV endocardial contraction presents circumferential behavior reflecting LV volume change. The 3D principal strains derived from 3D echocardiography are reliable indicators for LV contractility and seem better than conventional strains.