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 (PaCO2). In patients whose CVrr was larger than 5%, 84% of them had no hypercapnia while the other 16% had hypercapnia (PaCO2 >45 mmHg). In contrast, 27% of those with CVrr smaller than 3% had no hypercapnia, 73% had hypercapnia and 47% had severe hypercapnia (PaCO2 >50 mmHg). Conclusion We first showed that CVrr was negatively correlated with PaCO2, and propose that abnormally low CVrr indicates respiratory insufficiency in patients with Duchenne muscular dystrophy.