Functional changes in Duchenne muscular dystrophy: a 12-month longitudinal cohort study.

OBJECTIVE: The aim of the study was to assess different outcome measures in a cohort of ambulant boys with Duchenne muscular dystrophy (DMD) over 12 months in order to establish the spectrum of possible changes in relation to age and steroid treatment. METHODS: The study is a longitudinal multicentric cohort study. A total of 106 ambulant patients with DMD were assessed using the 6-minute walk test (6MWT) and North Star Ambulatory Assessment (NSAA) at baseline and 12 months. Clinical data including age and steroid treatment were collected. RESULTS: During the 12 months of the study, we observed a mean decline of 25.8 meters in the 6MWT with a SD of 74.3 meters. On NSAA, the mean decline was 2.2 points with a SD of 3.7. Not all the boys with DMD in our cohort showed a decline over the 12 months, with young boys showing some improvement in their 6MWT and NSAA scores up to the age of 7. NSAA and the 6MWT had the highest correlation (r = 0.52, p < 0.001). CONCLUSIONS: This study provides longitudinal data of NSAA and 6MWT over a 12-month period. These data can be useful when designing a clinical trial.

Usefulness of heart rate variability as a predictor of sudden cardiac death in muscular dystrophies.

Sudden cardiac death, or cardiac arrest, is a major health problem, causing about 166,200 deaths each year among adults in the United States. It may be caused by almost all known heart diseases. Most cardiac arrests occur when the diseased heart begins to exhibit rapid and/or chaotic activity, such as ventricular tachycardia or fibrillation. Some are due to extreme slowing of the heart. All these events are called life-threatening arrhythmias. Arrhythmogenic cardiomyopathy is a frequent feature in several muscular dystrophies with a potential risk of cardiac sudden death. Among the measures able to predict the propensity to develop life-threatening arrhythmias, heart rate variability is an accepted non invasive measurement of cardiac autonomic modulation. The use of heart rate variability to measure the extent of changes in autonomic nervous system is an established risk stratification procedure in different diseases. In fact numerous studies have demonstrated the positive prognostic power of altered heart rate variability values to predict all-cause mortality, cardiac events, sudden cardiac death and heart transplantation. Usefulness of heart rate variability as a predictor of sudden cardiac death in muscular dystrophies has been reviewed.