Heart rate variability and hypercapnia in Duchenne muscular dystrophy.

OBJECTIVE: To investigate the relationship between heart rate variability and hypercapnia. PATIENTS AND METHODS: We measured the coefficient of variation of R-R interval (CVrr) and arterial blood gas pressures in 73 patients with Duchenne muscular dystrophy. RESULTS: CVrr was negatively correlated with arterial partial pressure of carbon dioxide (PaCO(2)). In patients whose CVrr was larger than 5%, 84% of them had no hypercapnia while the other 16% had hypercapnia (PaCO(2) >45 mmHg). In contrast, 27% of those with CVrr smaller than 3% had no hypercapnia, 73% had hypercapnia and 47% had severe hypercapnia (PaCO(2) >50 mmHg). CONCLUSION: We first showed that CVrr was negatively correlated with PaCO(2), and propose that abnormally low CVrr indicates respiratory insufficiency in patients with Duchenne muscular dystrophy.

Mental retardation and lifetime events of Duchenne muscular dystrophy in Japan.

OBJECTIVE: This study investigated the relationship between mental retardation and lifetime events in patients with Duchenne muscular dystrophy (DMD). METHODS: The data on mental retardation and ages of lifetime events (first walking, loss of ambulation, introductions of ventilator support and tube nutrition and death) were collected retrospectively, and the relationships between the factors were analyzed. PATIENTS: Among 194 DMD patients admitted to our hospital between 1995 and 2007, 74 patients underwent evaluation of their intelligence quotient (IQ). RESULTS: Twenty-eight patients (38%) demonstrated mental retardation (IQ<70). DMD patients with mental retardation started walking later, required ventilator and tube nutrition support earlier, and died earlier than those without mental retardation. CONCLUSIONS: Since the prognosis of DMD patients with mental retardation was worse than that of those without mental retardation, more careful treatment is necessary for DMD patients with mental retardation.