Avaliação clínica, eletrocardiográfica e do sistema nervoso autônomo de pacientes com Distrofia muscular de Duchenne

Abstract

Introduction: Duchenne Muscular Dystrophy (DMD) is a rare inherited degenerative neuromuscular disease. This recessive disorder is X-linked, with alterations in the dystrophin gene and skeletal muscle and cardiac involvement. Given the paucity of this topic, there is a relevance of studies on it. Objectives: To assess the clinical profile, electrocardiographic and autonomic changes in children and adolescents with DMD, and to compare the latest changes with those of a healthy age-matched group. Methods: This is an observational, prospective and cross-sectional study with 27 patients with DMD (mean age 11.9 years), who underwent clinical and laboratory evaluation, in addition to digital monitoring by Holter. The electrocardiogram (ECG) with a 200% increase was evaluated by two independent observers. Heart rate variability (HRV) was performed in the domain of time in 24 h and of frequency (by Fourier transformation) for 10 min in the supine and sitting positions. The healthy group was composed of 9, also male, with a mean age of 11.0 years. Results: The mean age at diagnosis was 5.6 years, 12 patients (44.4%) required a wheelchair and 8 (29.6%) required ventilatory support. The means of the variables were 99.3 bpm for HR; 101.8/68.5 mmHg for blood pressure; 21.5 kg/m2 for body mass index and 0.60 for left ventricular ejection fraction (0.34 to 0.71). 18 patients (66.6%), carvedilol 11 (40.7%), corticoids 22 (81.4%), spironolactone 4 (14.8%) and cholecalciferol 13 were using (48.1%). Pearson's coefficient for ECG measurements ranged from 0.43 to 0.94. The R/S ratio was increased in 5 patients (18.5%); QT interval dispersion of 35.6 ms and the corrected QT interval (Bazett) of 413.8 ms. Fragmented QRS alterations in the inferior and high lateral regions were observed in 6 patients (22.2%), pathological Q wave in the same regions in 8 (29.6%), and right bundle branch conduction disorder in 4 (14.8 %). When changing from the supine to sitting position, there was a 10% increase in HR (p=0.004), with no change in the HRV spectral analysis, both in normalized units and in ms2 (paired test). There was no influence of treatment on HRV in both domains. Comparing DMD patients with the healthy group, the means were 877.2 and 1826.0 ms2, respectively, for the low frequency (LF) component (p=0.03, Student's t test); 488.7 and 2188.5 for the high frequency (HF) (p<0.0001) and 2.7 and 0.7 for the ratio between the components (p=0.002). Conclusions: Patients with DMD presented alterations in the inferior and high lateral regions (Q wave and fragmented QRS), prominent R waves and increased R/S ratio in V1. There was autonomic dysfunction, with lower vagal tone. Despite the increase in HR, there was no adequate response with the change in position. Treatment with cardioprotective drugs did not influence HRV.