ABC | Volume 114, Nº3, March 2020

Original Article Sousa et al. Software: analysis of strain curves Arq Bras Cardiol. 2020; 114(3):496-506 Figure 2 – Left ventricular strain, left atrial strain, and echocardiographic curves with division into cardiac cycle phases. Eighteen strain curves corresponding to 18segments of the left ventricle, six left atrial strain curves, and one electrocardiographic signal. Colors of the strain and strain rate curves correspond to those attributed to the segments by the proprietary software; MVC: mitral valve closure; AVO: aortic valve opening; AVC: aortic valve closure; MVO: mitral valve opening. after participants signed an informed consent form. The study was approved by the Ethics Committee of the institution (CAEE approval number 91350318.4.0000.5483). The time of opening and closing of the mitral and aortic valves were registered. Some test results showed more than one event time registered; tests with discrepancies of time higher than 10 ms were excluded. The cardiac cycle with the best image quality in the apical three- four- and two-chamber view was selected. In case of three cycles with poor-quality image, the last cycle was selected. The endocardial board was defined by delineation of the region of interest using the option Q-analysis of the EchoPAC software. A visual inspection of the tracking quality was made, which was confirmed by the “approve” option, and finally the GLS_EchoPAC value was registered. In case of poor-quality tracking (by visual inspection), this process was repeated. Tests with two or more segments with suboptimal quality were excluded. The raw data of the strain curves were extracted using the “Store Trace” option, which generates .txt files that are used in data processing in D-Station. The GLS was chosen as a parameter of validation of measurement equivalence in the EchoPAC processing (a well‑established technique – gold standard) and the D-station (the proposed technique), showed in Table 1. Methods used in the analyses: a) Normality test of GLS obtained by EchoPAC, D-Station and the differences (EchoPAC – D-Station), using a graphical method (Q-Q plot), followed by a statistical method (Shapiro-Wilk test) to confirm normality assumption found by the graphical method; b) Graphs of GLS by EchoPAC and D-Station in case of equality or coefficient of correlation (Pearson’s correlation or Spearman’s correlation for normal and non-normal distribution, respectively, of EchoPAC andD-Station data); c) Test of the hypothesis of difference between GLS values by EchoPAC and D-Station GLS, paired data, level of significance of 5% by Student’s t-test or the non-parametric Wilcoxon test in case of normal and non-normal distribution of data, respectively. d) Agreement test by Bland-Altman plot 9,10 The Stats and the BlandAltmanLeh packages of the R software version 3.5.2 (2018-12-20) were used, which has the necessary commands and outputs for p-value calculation and Bland-Altman analysis. Validation criteria From the clinical point of view, the criteria used to determine whether D-Station can be used as an alternative method to EchoPAC (equivalence), were the following: 498