The severity of skeletal and cardiac myopathy in myotonic dystrophy correlates with age and CTG repeat length, suggesting a similar mechanism causing a time-dependent degenerative process.

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and in the sinoatrial node associated to myocyte hypertrophy 7. Patients with greater skeletal muscle impairment are older and experience heart problems more frequently 8. The autonomic nervous system plays a crucial role in heart rate (HR) modulation. A decrease in its variability is a predictor of morbidity and mortality 9,10. Earlier research found that healthy women showed greater vagal dominance over HR, which seems to account for their enhanced cardioprotection compared to men, although these differences decrease with age 11. The study of heart rate variability (HRV) has therefore been proposed as a simple, inexpensive and non-invasive method that provides information on neurocardial integrity. A number of investigations on the overall function of the autonomic nervous system in patients with MD show that the presence of autonomic neuropathy is highly unlikely 1,12,13. However, studies on autonomic modulation of HR in patients with MD have obtained conflicting results 14-18. The present study aimed to evaluate the possible differences in autonomic modulation of HR between the sexes for patients with MD and healthy individuals in different body positions and the influence of interaction between sex and disease on autonomic modulation of HR in different body positions.

The case of a 66-year-old woman with myotonic dystrophy is presented. This patient underwent implantation of an insertable loop recorder as a participant in a clinical trial. At 1-month follow-up, interrogation of the insertable loop recorder revealed multiple episodes of wide complex tachycardia. She underwent electrophysiologic study, which revealed moderate His-Purkinje disease, focal atrial tachycardia, monomorphic ventricular tachycardia, and ventricular fibrillation. Successful radiofrequency ablation of the focal atrial tachycardia and implantation of a dual-chamber implantable cardioverter defibrillator was performed.