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 Echocardiography is a non-invasive, relatively safe, cost effective and easily accessible method for the right ventricle assessment. Tissue Doppler imaging (TDI) has been demonstrated to furnish a quantitative measure of regional velocities in the myocardium as well as systolic and diastolic intervals. 8 TDI can detect subclinical abnormalities of the right ventricle in a phase when conventional echocardiographic findings are still within normal ranges, 8 thereby enabling the detection of right ventricular dysfunction in the early stage of a disease. 9-11 Recent studies on young adults with asthma have employed TDI and found subclinical diastolic dysfunction directly related to the severity of the condition, suggesting that this imaging technique has greater predictive value than conventional echocardiography for the evaluation of right ventricular function 9 . Similar findings have been reported for children and adolescents in the stable phase of asthma. Shedeed et al. 11 evaluated children and adolescents aged 5 to 15 years with mild to severe asthma and found that TDI demonstrated right ventricular dysfunction that was positively correlated with the severity of the condition, despite the conventional echocardiogram being apparently normal. Likewise, Ozdenir et al. 10 found a negative correlation between right ventricular dysfunction and peak expiratory flow in children with asthma, suggesting that TDI has important diagnostic value for the early detection and monitoring of heart repercussions in children with asthma. The clinical phenotype of asthma can differentially affect myocardial performance. Children with asthma and a predominance of shallow breathing exhibit more severe myocardial dysfunction than those with a predominance of wheezing as the manifestation of the condition. 12 The aim of the present study was to compare heart function, quality of life, physical activity level, functional exercise capacity and inspiratory muscle strength/endurance in young patients with mild-to-moderate asthma and healthy controls to determine the impact of this condition on echocardiographic variables. Methods Study population Male and female children and adolescents from10 to 16 years with mild to moderate asthma were enrolled in the present study. Asthma severity was established based on the guidelines of the Global Strategy for AsthmaManagement and Prevention. 13 The control group comprised of children and adolescents considered healthy. The groups were matched for sex and age. Inclusion criteria The group with asthma comprised children and adolescents with clinical and spirometric diagnosis of asthma, for more than 30 days with no history of acute upper or lower airway infection or exacerbation of the condition. The participants in the control group had a normal clinical history and normal lung function. Exclusion criteria Children and adolescents with acute or chronic lung disease, major thoracic deformities, neuromuscular, cardiovascular, digestive, rheumatic, osteoarticular or genital-urinary disorders, genetic syndromes or any adverse health conditions that limited the safe performance of the tests proposed in the protocol were excluded from the study. Evaluation protocol Height (meters) and weight (kilograms) were measured using an anthropometric scale (Filizola TM , São Paulo, SP, Brazil). The tests were conducted in two steps. Step 1 – spirometric analysis was performed to confirm the diagnosis and classification of asthma. Next, the quality of life and baseline physical activity questionnaires were administered. The strength and endurance of the inspiratory muscles were then measured. Functional capacity was evaluated using the six-minute walk test (6MWT) 30 minutes after the evaluation of the inspiratory muscles. Step 2 – Echocardiography was performed. The order of the two steps was determined randomly and a maximum interval of 15 days was respected between steps. Pulmonary function test The spirometric variables analyzed were forced vital capacity (FVC), forced expiratory volume in the first second of FVC (FEV 1 ) and the Tiffeneau index (FEV 1/ FVC). The group with asthma was also submitted to the bronchodilator test 20 minutes after the inhalation of salbutamol (400 μg/dose) distributed in four inhalations of 100 μg with a one-minute period between inhalations. Predicted values were analyzed and described using the equations proposed by Polgar and Promadhat. 14 An increase in FEV 1 equal to or greater than 12% of the predicted after the administration of salbutamol confirmed the variable limitation to airflow. Evaluation of maximum inspiratory pressure Maximum inspiratory pressure (MIP) was evaluated using an analog pressure gauge (MDI® model MVD300, Porto Alegre, Brazil) beginning from residual volume. At least five reproducible measurements were taken and the maneuvers were repeated until the two highest measurements did not differ by more than 5%. 15 The highest measurement was used to establish the load for the evaluation on inspiratory muscle endurance. Evaluation of inspiratory muscle endurance Inspiratory muscle endurance was evaluated after the determination of MIP, using a modified version of the protocol proposed by Sette et al. 16 Inspiratory muscle endurance was defined as the maximum time tolerated of spontaneous breathing with a load corresponding to 30% of MIP until exhaustion, which was defined as the inability to overcome inspiratory resistance in two consecutive attempts. The criteria for interrupting the test were intense weariness, dizziness, discomfort, cheek pain or peripheral oxygen saturation (SpO 2 ) less than 85%. Evaluation of functional capacity using the 6MWT The 6MWT was performed based on the guidelines of the American Thoracic Society. The participant was instructed 232