Variabilidade da frequência cardíaca em pacientes com Distrofia Miot？nica tipo 1

background: cardiac involvement is common in myotonic dystrophy (md) patients. heart rate variability (hrv) is a simple and reliable technique that can be useful for studying the influence of the autonomic nervous system on the heart. objective: study heart rate variability in patients with type 1 md. methods: we studied hrv during 5-minute recordings in md patients and in a healthy control group. we analyzed frequency domains (lf and hf) in normalized units (nu) and sympathovagal balance, in the sitting and supine position. results: seventeen patients (10 men and 7 women) and seventeen matched healthy individuals (10 men and 7 women) were studied. sympathetic and parasympathetic modulations of the heart increased in male md patients from supine to sitting position in 19% of lfnu and the lf/hf ratio rose by 42.3%. in the sitting position, male md patients exhibited significantly higher sympathovagal balances in 50.9% compared to healthy control individuals. hrv was influenced by both gender and disease. gender influenced lfnu in the supine position while the lf/hf ratio and hfnu were affected in both positions. post hoc analyses showed that gender significantly impacts md patients and healthy individuals in different ways (p < 0.01). the low frequency domain in the sitting position (lfnu) was significantly influenced by the disease. conclusion: the results of this study suggest that the sympathetic drive in middle-aged male md patients who are not severely impaired and present moderate disease duration seems to be greater than in healthy matched individuals.