ABC | Volume 113, Nº2, August 2019

Original Article Maia et al Global Longitudinal Strain in Functional Capacity Arq Bras Cardiol. 2019; 113(2):188-194 in patients with systolic HF. The aim of this study was to correlate GLS value with functional parameters of CPET and to assess if GLS could predict systolic HF patients that were more appropriated to be referred to heart transplantation according to CPET criteria. Methods This is an observational, prospective cross-sectional study, guided by the recommendations of the STROBE Statement. 14 This study was approved by the Ethics and Research Committee of our Institution under number 1507992. The study population consisted of adults (21-65 years), both sexes, diagnosed with HF in functional class II and III by the New York Heart Association (NYHA), sedentary, with systolic dysfunction (LVEF <45%) assessed by transthoracic echocardiography performed until one month before they had been referred for cardiopulmonary program and recruited for this study. Data were collected between January, 2015 and March, 2016. Exclusion criteria were: deformity in the face to prevent the coupling of the CPET mask, orthopedic and neurological diseases that could preclude the execution of CPET, psychological problems restricting them to respond to the questionnaire, functional class IV HF or hospitalization due to cardiac decompensation in the last three months, unstable angina, myocardial infarction or cardiac surgery up to three months before the study; forced expiratory volume on the first one second/forced vital capacity <70% of predicted characterizing obstructive respiratory disorder. To ensure standardization, a single examiner performed the exams. None of them had access to the patients’ other evaluations results. The researchers responsible for data collection were not responsible for carrying out the examinations, thus ensuring the blinding of the study. Cardiopulmonary exercise test All patients in the study underwent CPET by the method ramp on a treadmill ( Centurium300 , Micromed, Brazil) through ErgoPC Elite® software associated with the electrocardiogram (Micromed, Brazil) with 12 channels. Respiratory variables were evaluated by a gas analyzer (Cortex - Metalyzer II, Germany) and obtained in conditions of standard temperature, pressure and dry (STPD), breath‑by‑breath, with the patient breathing in a face mask without leaks during exercise. During the test, functional capacity, maxVO 2 measured in METs, the maximum VE/VCO 2 , VE/VCO 2 slope, T 1/2 VO 2 and HRR were evaluated. Echocardiography All echocardiograms were performed according to ASE. 14 Patients underwent the two-dimensional echocardiography, using an ultrasound system Vivid I (GE Medical Systems, Horten, Norway) with a multifrequency transducer from 2.5 to 5 MHz. After the echocardiogram, a strain analysis technique was performed using an echocardiogram analysis software (EchoPAC, GE Medical Systems, Horten, Norway, version 10.0). The images in the longitudinal sections were analyzed (4 chambers, 3 chambers and 2 chambers). 15 A region of interest was applied automatically by the software and, if necessary, was adjusted manually. The strain analysis software performed the analysis. Patients were excluded when more than two segments were considered to have insufficient quality for monitoring by the analysis system. 16 Statistical analysis To calculate the sample, G*Power 3 software was used, 17 in which we chose the post hoc option with α = 0.05 and two-tailed hypothesis. Thus, the two most important ergospirometric variables were chosen for the study population: maxVO 2 and VE/VCO 2 slope. We found an effect size of 0.81 (R 2 = 0.67) for the maxVO 2 and 0.71 (R 2 = 0.51) for the VE/VCO 2 slope. We observed for both variables a power of 99% with a total sample of 25 patients. Patients were later divided into two groups according to values of maxVO 2 and VE/VCO 2 slope found to CPET: Group 1 - maxVO 2 > 14mL/kg/min and/or VE/VCO 2 slope < 35; and Group 2 - maxVO 2 < 14mL/kg/ min and VE/VCO 2 slope > 35 (IIa class indication criteria for heart transplantation). 16 The data was presented by absolute and percentage frequencies for categorical variables; by the mean and standard deviation for parametric quantitative variables; and by median and interquartile range for non-parametric variables. Shapiro-Wilk test was applied to verify if the quantitative data were normals. For comparison of parametric variables, we used the Student t-test for independent samples and for non-parametric variables the Mann-Whitney test. To compare categorical variables, we used the chi-square non-parametric test. In the second step, the correlation between the values of the GLS strain index with ergospirometric variables was performed by using the Pearson coefficient for parametric and Spearman variables for non-parametric variables. The Receiver Operating Characteristic (ROC) curve was performed to evaluate the GLS's ability to predict maxVO 2 < 14 mL/kg/min and VE/VCO 2 slope > 35. P value inferior to 0.05 was considered statistically significant. Data were entered in an EXCEL spreadsheet and statistical software used for statistical calculations was the SPSS (Statistical Package for Social Sciences) version 23. Results During the study period, 39 patients with HF were referred to the cardiopulmonary rehabilitation program. Of these, 10 were not included because of a LVEF higher than 45%, one patient for presenting inadequate acoustic window for subsequent analysis of the GLS and two patients due to arrhythmia. Therefore, 26 patients (mean age, 47±12 years, 58% men) participated in this study, Table 1. Regarding the CPET results the average maxVO 2 was 19.09 ± 9,52 mL/kg/min and the VE/VCO 2 slope was 39.43 ± 9.91. The mean HRR and T 1/2 VO 2 were respectively, 19.65±17.42 bpmand 168.61±43.90s. By echocardiography, the mean LVEF was 28.0 ± 8.6% and mean GLS index was -7.5 ± 3.92 % for all studied patients, Table 1. 189