Assessment of cardiac autonomic function in patients with Duchenne muscular dystrophy using short term heart rate variability measures.

BACKGROUND

Duchenne muscular dystrophy (DMD) is a hereditary neuromuscular disorder frequently associated with progressive cardiac dysfunction, and is one of the common causes of death in these children. Early diagnostic markers of cardiac involvement might help in timely intervention. In this study we compared the short term HRV measures of DMD children with that of healthy subjects.

METHOD

One hundred and twenty-four genetically confirmed boys with DMD and 50 age matched controls were recruited. Error-free, electrocardiogram was recorded in all subjects at rest in the supine position. HRV parameters were computed in time and frequency domains. Time domain measures included standard deviation of NN interval (SDNN), and root of square mean of successive NN interval (RMSSD). Frequency domain consisted of total, low frequency and high frequency power values. Ratio of low frequency and high frequency power values (LF/HF) was determined using customized software.

RESULTS

HRV parameters were significantly altered in DMD children as compared to healthy controls. Following parameters [mean (SD)] were reduced in DMD as compared to controls; RMSSD (in ms) [52.14 (33.2) vs 64.64 (43.2); p = 0.038], High frequency component (nu) [38.77 (14.4) vs 48.02 (17.1); p = 0.001] suggesting a loss of vagal tone. In contrast, measure of sympathovagal balance LF/HF [1.18 (0.87) vs 0.89 (0.79); p = 0.020] was increased in DMD group.

CONCLUSION

In this cross sectional study we have demonstrated alteration in autonomic tone in DMD. Loss of vagal tone and an increase in sympathetic tone were observed in DMD children. Further prospective studies are required to confirm the utility of these measures as predictors of adverse cardiac outcome in DMD.