ABC | Volume 110, Nº6, June 2018

Original Article Behavior of Blood Pressure Variables in Children and Adolescents with Duchenne Muscular Dystrophy Fabiane R. R. H. Marui, Henrique Tria Bianco, Maria Teresa N. Bombig, Natascha G. F. Palmeira, José M. Thalenberg, Fernando Focaccia Povoa, Maria Cristina de O. Izar, Francisco Antonio H. Fonseca, Acary S. B. de Oliveira, Rui M. S. Povoa Universidade Federal de São Paulo, São Paulo, SP - Brazil Mailing Address: Henrique Tria Bianco • Setor de Lípides, Aterosclerose, Biologia Vascular e Hipertensão Arterial. Disciplina de Cardiologia da Universidade Federal de São Paulo (UNIFESP). Rua Loefgren, 1350. Postal Code 04040-001, Vila Clementino, São Paulo, SP – Brazil E-mail: henriquetria@uol.com.br Manuscript received July 14, 2017, revised mansucript October 24, 2017, accepted Novembe 16, 2017 DOI: 10.5935/abc.20180085 Abstract Background: Duchenne muscular dystrophy is an X-chromosome-linked genetic disorder (locus Xp21). Involvement of the cardiovascular system is characterized by fibrous degeneration/replacement of myocytes with consequent ventricular hypertrophy and arterial hypertension. Objective: To assess, by using 24-hour ambulatory blood pressure monitoring, the behavior of blood pressure variables in children and adolescents with a confirmed diagnosis of Duchenne muscular dystrophy. Methods: Prospective observational cohort study, which selected 46 patients followed up on an outpatient basis, divided according to age groups. Blood pressure was classified according to the age percentile. The monitoring interpretation includes systolic and diastolic blood pressure means, systolic and diastolic blood pressure loads, and nocturnal dipping. The blood pressure means were calculated for the 24-hour, wakefulness and sleep periods. Nocturnal dipping was defined as a drop in blood pressure means during sleep greater than 10%. The significance level adopted was p < 0.05. Results: Nocturnal dipping for systolic blood pressure was present in 29.9% of the participants. Approximately 53% of them had attenuated nocturnal dipping, and 15%, reverse nocturnal dipping. The age groups of 9-11 years and 6-8 years had the greatest percentage of attenuation, 19.1% and 14.9%, respectively. Regarding diastolic blood pressure, nocturnal dipping was identified in 53.2% of the children, being extreme in 27.7% of those in the age group of 6-11 years. Conclusions: The early diagnosis of blood pressure changes can allow the appropriate and specific therapy, aimed at increasing the life expectancy of patients with Duchenne muscular dystrophy. (Arq Bras Cardiol. 2018; 110(6):551-557) Keywords: Cardiovascular Diseases / genetics; Muscular Dystrophy, Duchenne / genetics; Hypertension; Child; Male. Introduction Duchennemuscular dystrophy (DMD) is an X-chromosome- linked genetic disorder that affects approximately 1 in every 3500 live-born boys. 1 It is clinically characterized by progressive and irreversible muscle weakness consequent to dystrophin deficiency or absence. It is the most frequent neuromuscular disease in human beings, and, although predominating in the male sex, it is occasionally reported in females due to inactivation or abnormalities of the X chromosome. That anomaly is present in the short arm of the X chromosome ( locus Xp21 ). Its global prevalence can reach 63 cases per one million individuals. Duchenne muscular dystrophy has a high spontaneous mutation velocity, and approximately one third of the cases are estimated to be due to new mutations. 2-4 The first clinical signs manifest at an early age as frequent falls, difficulty climbing stairs, running and getting up from a lying or sitting position, and mainly calf hypertrophy. The muscle impairment is symmetric, initiates in the pelvic girdle muscles (hip and legs) and reaches the upper limbs. In addition, cardiomyopathy is frequent in DMD. While some studies have estimated its incidence in 25% at the age of 6 years, and 59% at the age of 10 years, others have reported its beginning at the age of 14 and 15 years. 5,6 Cardiac involvement occurs in 90% of the patients, being the cause of death in 50% of them. However, its clinical identification can be hindered by severe muscle weakness and thoracic deformities. Cardiac histological changes include hypertrophy of myocytes and myocardial fibrosis, with replacement with connective and fatty tissues. 7 Dystrophin deficiency or absence in cardiomyocytes hinders the function of membrane ion channels, notably in sarcolemma, which is activated by stretching, responding to mechanical stress. When cardiomyocytes, with or without dystrophin deficiency, are stretched during ventricular filling, the ion channels do not open properly, increasing calcium influx. Excessive intracellular calcium activates a group of calcium-induced proteases, the calpains, which degrade troponin I and hinder contraction. 8-10 The importance of the cardiomyopathy in children with DMD has grown in past decades, mainly due to the increase in survival, consequent to advances in ventilatory 551