ABC | Volume 110, Nº6, June 2018

Original Article Marui et al Blood pressure variables in Duchenne muscular dystrophy Arq Bras Cardiol. 2018; 110(6):551-557 and orthopedic supports. 11 In the absence of ventilatory intervention, death usually occurs by the end of the second or beginning of the third decade. Diastolic dysfunction can be present even before systolic dysfunction is detected. The use of drugs that act on the renin-angiotensin-aldosterone axis, such as angiotensin‑converting-enzyme inhibitors or angiotensin‑receptor blockers, should be considered, aiming at reducing afterload before symptom onset. 12 Ambulatory Blood Pressure Monitoring (ABPM) allows indirect and intermittent blood pressure (BP) recording for 24 hours, during wakefulness and sleep. In adults, ABPM is a well-established diagnostic and follow-up method, considered “gold standard” in BP assessment. 13 In 2008, the American Heart Association (AHA) published recommendations for the use of ABPM in the pediatric population, which were reviewed in 2014. 14,15 Many recommendations of ABPM use for adults can be applied to children. Because of the difficulty of conducting randomized clinical trials in the pediatric population, the recommendations used are based on expert opinions. However, it is worth considering some aspects, such as equipment selection, which should be light (weight between 168 and 457 grams), with appropriate cuff size. 16 The use of corticosteroid, known to increase BP, has been widely studied. Left and/or right ventricular hypertrophy can cause arterial hypertension (AH) and/or pulmonary hypertension or mitral and/or tricuspid regurgitation, sometimes culminating in ventricular failure. 17,18 A study by Braat et al. has assessed the renal function of 20 individuals with DMD and undergoing ABPM, 9 of whom had elevated BP (over the 95th percentile), 8 of whom were on corticosteroids, and 13 had no nocturnal dipping (ND), 10 of whom were on corticosteroids. 19 Knowing BP behavior in such patients is fundamental, mainly because it enables early treatment, contributing to improve the quality of life, aiming at reducing the high morbidity rates of those patients. Thus, our study aimed at assessing the behavior of BP variables, by using 24-hour ABPM, in children and adolescents diagnosed with DMD, followed up at a university-affiliated outpatient clinic specialized in muscular dystrophies. Methods This is a descriptive study comprising all 46 boys with a confirmed diagnosis of DMD followed up on an outpatient basis. Because DMD is a rare disease, we chose to assess all children and adolescents followed up on a university-affiliated outpatient clinic. The boys were divided into five age groups, considering the distribution of normal BP levels for age, according to the previously reported AHA suggestion. 14,15 The research project was approved by the local Ethics Committee, the information was provided by the parents or guardians, and written informed consent was provided by all participants. Prior to ABPM, the patients’ clinical history was collected, and the height and weight measured in the children who could walk, while, for wheelchair-bound patients, historical height was used. Blood pressure was measured at the medical office with the OMROM digital device (HEM 742INT ® model) and appropriate cuff size, respecting the proportion width/ length 1:2, corresponding to 40% of arm circumference and at least 80% of its length. The Spacelabs 90207 ® ABPM monitor was installed on the “nondominant” arm, with appropriate cuff size, by a trained nurse, and programmed to take BP every 15 minutes during wakefulness and every 30 minutes during sleep. The parents/guardians received a diary to record the most important events in 24 hours, mainly the bedtime and wake-up time. The following variables were assessed inABPM interpretation: systolic and diastolic BP (SBP and DBP, respectively) means; systolic and diastolic blood pressure loads (SBPL and DBPL, respectively); and ND. The SBP and DBP means were calculated for the 24-hour, wakefulness and sleep periods. The SBPL and DBPL were calculated considering the proportion of readings over the 95th percentile. Nocturnal dipping was defined as a drop greater than 10% in BP means during sleep. All parameters were compared to the normal range values to determine whether BP was normal or elevated, as was the presence or absence of ND. In addition, ND was stratified as follows: “present”, BP drop during sleep between 10% and 20% as compared to wakefulness; “absent”, no BP drop during sleep; “attenuated”, BP drop > 0% and < 10% during sleep; “reverse”, BP during sleep higher than that during wakefulness; and “extreme”, BP drop > 20%. Statistical analysis The continuous variables with normal distribution were presented as means ± standard deviation, while those without normal distribution were presented as medians and interquartile range. The categorical variables were presented as absolute numbers and percentages. The significance level adopted in the statistical analyses was 0.05. Kolmogorov- Smirnov test was used to assess the normality of the variables, and Pearson chi-square test was used to assess the association between corticosteroid use and BP classification. We used as comparator the BP values of the 95th percentile from the AHA recommendations, as shown in Table 1, which classified children and adolescents according to age groups. Values of p <0.05 were considered significant. All statistical analyses were performed with the SPSS software, version 17.0 (SPSS Inc. Chicago, IL, USA) ® . Results Table 2 shows the major characteristics of the participants with DMD. Of the 46 children, 57.4% were wheelchair- bound, 69.6% were on corticosteroids, and 6.4% had been previously diagnosed with AH, as reported by their parents/guardians. The diagnosis of DMD was established at around 7 years of age, while the first symptoms appeared approximately at the age of 2.7 years. Other family members were reported to have DMD in 6.4% of the cases. A significant part (63.8%) of the participants was undergoing specific physical therapy, and 40.5% used some type of respiratory support, such as artificial manual breathing unit (AMBU) and/or bilevel positive airway pressure (bipap). Table 3 shows BP behavior, distribution of the SBP and DBP means with their respective standard deviations in the five age groups, as well as SBPL and DBPL. Regarding SBP, 552