ABC | Volume 113, Nº5, November 2019

Original Article Saraiva et al. Normal values for new echocardiographic techniques Arq Bras Cardiol. 2019; 113(5):935-945 by self-description. The study was conducted at Instituto Nacional de Infectologia Evandro Chagas (INI), from Fundação Oswaldo Cruz, located in the city of Rio de Janeiro, Brazil . INI is a public institution dedicated to clinical research on infectious diseases and a reference center for diagnosis and treatment of Chagas’ disease. This article is derived fromour project “Analysis of the cardiac performance by new echocardiographic techniques in patients with Chagas disease”. 4,5 We used a convenience sample. Echocardiography Studies were performed using phased-array ultrasound system (Vivid 7, GEMedical Systems, Milwaukee, WI) equipped with M4S phased-array and 1.5- to 4-MHz 4 matrix-array transducers. Cardiac dimensions measured by M-mode and 2D echocardiography and Doppler measurements were obtained as recommended. 1,6 Echocardiograms were reviewed offline and two-dimensional ε and 3DE analyses were performed with software Echopac PC workstation version 108.1.12 (GE Medical Systems) with a 4D LV volume analysis plug-in (Tomtec Imaging Systems Gmbh). The same software designed to calculate LV ε was used to analyze RV and LA ε . All 2D clips analyzed were acquired at high frame rate (>60 frames/s). Studies were acquired by one echocardiographer and analyzed by two echocardiographers. Two-dimensional strain analysis LA strain analysis LA ε was determined as previously described 7 using apical 4- and 2-chamber views. P-wave onset was used as the reference point, which enabled the recognition of peak positive global LA ε (LAScd), which corresponded to LA conduit function, peak negative global LA ε (LASct), which corresponded to LA contractile function, and the sumof those previous values (LASr), which corresponded to LA reservoir function. Two-dimensional LV and RV strain analysis LV global longitudinal ε (LV-GLS), LV global circumferential ε (LV-GCS) and LV global radial ε (LV-GRS) were calculated as previously described. 4,5 LV-GCS and LV-GRS were the average of the peak average for LV-GCS and LV-GRS obtained at short-axis views at the basal, mid and apical levels. LV-GLS was the average of the peak average for LV-GLS obtained at 4-, 2- and 3-chamber views. If tracking quality was not good in two segments of the same acoustic window, that view was excluded from global LV ε calculation. RV longitudinal ε (RV-GLS) was calculated using focused 4-chamber apical view. RV free wall ε (RV-fwLS) was calculated as the average of the basal, mid and apical RV free wall segments. Left ventricular torsion calculation LV torsion and twist were calculated as previously described. 5 LV twist was defined as the net difference of LV rotation (LVrot) between apical and basal short-axis planes obtained from STE analysis and LV torsion as the LV twist divided by the end-diastolic LV longitudinal length. Counterclockwise LVrot as viewed from apex was expressed as a positive value. LA and LV volume and function analyses by 3DE 3DE 4-beat full volume images were acquired during breath hold in end expiration from apical views. Volume rate varied from 17 to 25 volumes/s. LA 3D images were analyzed as previously described. 5 The software showed maximum and minimum LA volume and pre-contraction LA volume was obtained from analysis of time-volume curves. Total LA emptying fraction was calculated as [(maximum LA volume – minimum LA volume)/maximum LA volume] x 100. Active LA emptying fraction was calculated as [(pre-contraction LA volume – minimum LA volume)/pre- contraction LA volume] x 100. Passive LA emptying fraction was calculated as [(maximum LA volume – pre-contraction LA volume)/maximum LA volume] x 100. LV volume and 3D LV ejection fraction were measured using a similar approach. 5 Statistical analysis Calculations were done using the software package MedCalc 12.5.0.0. Continuous variables were expressed as mean ± standard deviation and discrete variables as absolute and percentage values. Echocardiographic variables passed standard tests of normality (Kolmogorov- Smirnov test). Normally distributed data were compared by unpaired Student’s t-tests. Discrete variables were compared by contingency tables. Correlation between age and echocardiographic parameters was tested by Pearson’s correlation and classified according to Zegers et al. 8 Stepwise multiple regression analysis was used to analyze independent correlation between echocardiographic indexes and age, gender, body mass index (BMI) and ethnicity. Interobserver and intraobserver agreements were determined after offline re-analysis of recorded clips of 15 randomly selected subjects and assessed by Bland-Altman analysis. P values < 0.05 were considered significant. Results Participants A total of 296 adult subjects with negative Chagas disease serology were screened fromMarch 2010 to November 2013, and from May 2016 to July 2017. After applying exclusion criteria, 77 subjects (36 men; 46.7%) were included (Figure 1). Regarding age groups, 39 participants were 18 to 39 years old, 35 participants were 40 to 60 years old and 3 participants were 60 years old or older. Most subjects were born in the Southeast and Northeast of Brazil and were white. Distribution by state was as follows: 24 were born in Rio de Janeiro, 7 in Minas Gerais, 1 in Espírito Santo, 12 in Bahia, 9 in Paraíba, 8 in Ceará, 5 in Pernambuco, 5 in Alagoas, 1 in Piauí, 1 in Sergipe and 4 in Pará. There was no significant difference in age, BMI, place of origin and ethnicity distribution between men or women (Table 1). 936