ABC | Volume 110, Nº3, March 2018

Original Article De-Paula et al Impact of asthma on ventricular function Arq Bras Cardiol. 2018; 110(3):231-239 to walk as fast as possible along a 30-meter flat corridor marked every three meters and received standardized verbal encouragement every 30 seconds by the same evaluator. A second evaluator remained at one of the extremities of the track to assist in the data collection at the beginning and end of the test. Blood pressure (BP), respiratory rate (RR), heart rate (HR), SpO 2 , and the Borg dyspnea score at rest and during exertion were the variables measured at the beginning and end of the test. The 6MWT was performed twice, with a 30-minute rest interval between tests. The test on which the participant travelled the longer distance was considered in the statistical analysis. The criteria for interrupting the test were extreme weariness, SpO 2 less than 85% or any other discomfort. The participant was told that the test could be interrupted at any type if he/she felt any discomfort. Dyspnea at rest and during exertion was evaluated using the modified Borg scale, 17 which is scored from 0 to 10 points based on verbal responses that correspond to no or maximum shortness of breath, respectively. Evaluation of quality of life Quality of life was evaluated using the Pediatric Quality of Life Inventory TM version 4.0 (PedsQL 4.0). 18,19 Self-assessments were available for the following age groups: 5 to 7, 8 to 12 and 13 to 18 years. The items on the forms for each age group are similar, differing only in terms of the use of language adequate to the level of development. The quality of life of the group with asthma was also evaluated using the Paediatric Asthma Quality of Life Questionnaire (PAQLQ), 20 which has been translated and culturally adapted to Brazilian Portuguese for children and adolescents aged 7 to 17 years. 21 Evaluation of baseline physical activity Physical activity was evaluated using the Physical Activity Questionnaire – Child (PAQ-C), 22 which measures the level of physical activity of children and adolescents in the previous week. Evaluation of echocardiographic variable A single pediatric cardiologist who was blinded to the respiratory status of the participants performed the echocardiogram. The exam was performed with the participant positioned in left lateral and dorsal decubitus. The Toshiba echocardiograph was used with variable frequency transducers from 2.0 to 7.0 MHz. At least five consecutive beats were obtained from the parasternal window to determine the inner diameters of the ventricles. The exams were recorded and analyzed offline by two specialists in pediatric echocardiography. The left and right ventricular functions were assessed by two-dimensional echocardiography: M-mode, color-flow imaging, standard pulsed-wave Doppler and TDI, according to guidelines of the American Society of Echocardiography. The following data were collected for statistical evaluation: measurements of aortic dimension, left atrium, right ventricle anterior wall, right ventricular end-diastolic dimension, interventricular septum, left ventricular end-diastolic dimension, left ventricular systolic dimension and left ventricle posterior wall obtained by the Mmode paraesternal long and short axis view. There was no patient with congenital heart disease and all of them had symmetric left ventricular systolic function. The apical four-chamber view enables studying blood inflow through the atrioventricular valves. The early (E) and late (A) diastolic velocities of mitral and tricuspid valves and E/A ratio were used to evaluate biventricular filling function. TDI was used to evaluate cardiac load and determine the myocardial performance index (MPI). The left ventricular TDI was achieved at the lateral wall through the mitral annulus, whereas the right ventricular TDI was achieved through the tricuspid lateral annulus. The recordings of peak early (E’) and late (A’) diastolic velocities, E´/A´ ratio, systolic (S´) annular velocity, isovolumetric relaxation time (IVRT) and isovolumetric contraction time (IVCT) were obtained in the apical four-chamber view. MPI is defined as the IVCT and IVRT divided by the ejection time (ET) (Figure 1). The right ventricular systolic function was assessed by fractional area change (FAC), derived from tricuspid lateral annular systolic velocity wave (S’) and tricuspid annular plane systolic excursion (TAPSE). Pulmonary systolic arterial pressure (PSAP) was also estimated using two methods. Pulsed-wave Doppler tracing across the pulmonary valve was performed using the pulmonary acceleration time (PAT) by left parasternal short-axis view (Figure 2). The normal profile is symmetrical in shape. When pulmonary pressure and pulmonary vascular resistance are high, the peak occurs earlier. The other method was measuring maximal tricuspid regurgitation velocity, applying the modified Bernoulli equation to convert this value into pressure values and adding the estimated right atrial pressure (RAP). Normal RAP was considered 5 mmHg. PSAP = tricuspid regurgitation gradient + RAP. PSAP = (Vmax² x 4) + RAP. Normal systolic arterial pressure is up to 30 mmHg at rest and up to 40 mmHg during exercise. Sample size In order to calculate the sample size, we considered as objective to test the equality of the means of the mitral E-wave velocity among the groups of asthmatic patients and controls. 23 In order to detect a minimum difference of 4.7 cm/s between means, with a significance of 5%, minimum power of 80%, and variance based on a previous study, 9 it was necessary to obtain a ratio of 0.9 between controls/asthmatics, corresponding to 20 asthmatic children and 18 controls. Statistical analysis The Kolmogorov-Smirnov test was used to determine the normality of the data. The variables were expressed as central tendency (mean and median) and variability (standard error of the mean or interquartile range-IQR). When appropriate, either the non-paired t-test or the Mann-Whitney test was used for the comparison of the different variables analyzed, and either Pearson’s or Spearman’s correlation coefficient were calculated to evaluate associations between the independent variables and response variable. All analyses were performed with the GraphPad Prism software (version 5.0, GraphPad Software, Inc., 233