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 in the annulus of the mitral and tricuspid valves. In contrast, Shedeed et al. 11 found no significant differences in these variables between controls and a group with asthma or between the different degrees of asthma severity. A number of studies have demonstrated that patients with asthma exhibit diastolic dysfunction. 9,11,12 Indeed, in the current study significant differences between the controls and the group with asthma were found regarding myocardial diastolic velocities E' and A’ as well as the E'/A' ratio evaluated in the tricuspid annulus. Similar results were found in the mitral valve annulus, with a reduction in myocardial velocity during early diastole and an increase in myocardial velocity during atrial contraction. A significant increase in the IVRT was also found in the group with asthma, contributing to a significant increase in the MPI. In contrast, the increase in the MPI of the left ventricle occurred at the cost of a reduction in systolic velocity in the ventricle. The clinical phenotype of asthma may differentially affect myocardial performance. Zedan et al. 12 compared the MPI of children with asthma according to the phenotype (predominance of shallow breathing or wheezing as the clinical manifestation) and found that those with shallow breathing had a higher MPI. In the present study, the asthmatic children and adolescents were evaluated in a single group based only on the clinical and spirometric diagnosis of asthma. In the current study, MIP was similar in both groups, despite the significant reductions in FEV 1 and Tiffeneau index in the asthmatic group. The results of studies involving inspiratory muscle strength in asthmatic children and adolescents are conflicting. Some studies show that there is no difference, 25 26 and other studies show that the strength of the inspiratory muscles of children and adolescents with asthma is reduced relative to their peers. 27 Similar results were observed in inspiratory muscle endurance. Endurance test was similar in the control and asthmatic groups. However, exertion dyspnea evaluated at the end of the endurance test was significantly more intense in the group with asthma, suggesting that this variable may have a discriminative value between healthy individuals and those with asthma when submitted to the same level of inspiratory muscle overload. There is a number of determinant factors of inspiratory muscle endurance, such as contraction strength and duration, shortening velocity, the relationship between baseline inspiratory pressure (IP) and MIP (IP/MIP) and the inspiratory flow pattern adopted by patients during the evaluation. 28 Further studies are needed to clarify the greater shortness of breath in the group with asthma. The 6MWT is considered a safe, easy-to-administer method for the evaluation of sub-maximum exercise capacity in healthy children and adolescents, 29 as well as those with respiratory diseases. 30-32 Similar to the results of Basso et al. 31 and Soares et al., 27 in the present study, no significant difference between groups was found regarding the distance walked or the cardiovascular variables analyzed before and after the 6MWT. In the same way, studies using other functional capacity assessment methods, such as the shuttle walking test 33 and cardiopulmonary exercise test 34 also did not observe a difference between asthmatic children and adolescents and control group. Quality of life is one of the most important outcomes in the evaluation of patients with chronic disease. In the present study, this aspect was evaluated using a generic questionnaire as well as a specific questionnaire for children and adolescents with asthma. Regarding the generic questionnaire, quality of life was similar in both groups with regard to most domains, except the score on the physical domain, which was significantly lower in the group with asthma. In agreement with data described by Basaran et al. 35 and Andrade et al., 30 the mean score on the asthma-specific questionnaire was 5.67 ± 0.23, which indicates a good quality of life among the children and adolescents studied in the present investigation. Limitations of the study The small sample size could be considered a limitation of the present study. However, even with the small number of participants, it was possible to demonstrate changes in conventional and tissue echocardiographic variables among the children and adolescents with asthma in comparison to the control group. Another limitation regards the evaluation of functional capacity. The 6MWT is considered a sub-maximal exercise test for measuring physical functional capacity. It is possible that the variables analyzed on a maximum cardiopulmonary stress test would be more sensitive in detecting differences in functional capacity between individuals considered healthy and those with asthma. A third limitation was the failure to evaluate the breathing pattern adopted during the respiratory muscle endurance test. The record of inspiratory flow allows the evaluation of inspiratory time, expiratory time, total cycle and the inspiratory time/total cycle ratio, as performance on the endurance test can vary depending on the breathing pattern adopted. The precise mechanism to clarify the difference in exertion dyspnea between healthy individuals and those with asthma during the inspiratory muscle endurance test needs to be determined. Conclusion Patients with asthma presented significant changes in diastolic velocities of the myocardium and the MPI of both ventricles, but with no repercussions regarding exercise capacity evaluated using the 6MWT. Further studies are needed to confirm these findings and to evaluate the clinical implications of these abnormalities. Acknowledgement This work was supported by the Funda ão Lucas Machado (FELUMA), Faculdade Ciências M dicas-Minas Gerais, Pós‑Gradua ão em Ciências da Saúde and Clínica Conrad. Camilla R de Paula, undergraduate student received support from Funda ão de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG.), Brazil. We are thankful to Isabel Cristina Gomes for additional statistical assistance. Author contributions Conception and design of the research: Rodrigues‑Machado MG; Acquisition of data: De-Paula CR, Magalhães GS, 237