A groundbreaking study published in Neuromuscular Disorders has revealed that adult patients with Duchenne muscular dystrophy (DMD) who maintain their ability to walk for longer periods demonstrate significantly better cardiac function in adulthood, regardless of their genetic profile.
The research, focusing on left ventricular ejection fraction (LVEF), found that patients who experienced loss of ambulation (LOA) after age 12 had a five-fold reduction in the risk of developing severe cardiac dysfunction, defined as LVEF below 40%.
Clinical Impact and Patient Outcomes
The study examined 84 adult DMD patients receiving glucocorticoid therapy, with an average age of 22 years at final assessment. The mean age at loss of ambulation was 12.6 years, with over half the patients receiving daily deflazacort treatment. Notably, 29 patients (34.5%) showed LVEF lower than 40% at their last assessment, while the majority were receiving standard cardioprotective medications.
Statistical analysis revealed a clear correlation between extended ambulation and cardiac function. For each additional year of walking ability, patients demonstrated higher odds of maintaining better LVEF percentages (linear regression estimate, 1.49 [95% CI, 0.13-2.84; P = .03]).
Respiratory Function and Cardiac Outcomes
The study also examined respiratory parameters, with 51.1% of patients requiring ventilatory support. Despite varying respiratory conditions among participants, the age at respiratory thresholds did not impact the relationship between ambulation age and cardiac function. This suggests that the cardiac benefits of prolonged ambulation persist independently of respiratory status.
Long-term Implications for DMD Management
Particularly striking was the difference in cardiac outcomes between early and late LOA groups. Patients who lost ambulation before age 11.29 years developed significant cardiac dysfunction (LVEF <40%) more than five years earlier than those who maintained ambulation beyond age 11.92 years (adjusted mean survival time 19.08 vs. 24.29 years, P < .001).
These findings carry significant implications for DMD treatment strategies, especially as new therapeutic approaches targeting skeletal muscle preservation continue to emerge. The research suggests that interventions aimed at prolonging ambulation may offer additional cardiac benefits, challenging previous concerns about potential negative cardiac effects of extended walking periods.
Future Treatment Considerations
The study's results provide valuable insights for clinicians and researchers developing therapeutic strategies for DMD patients. The clear association between prolonged ambulation and better cardiac outcomes supports the development of treatments focused on maintaining motor function, suggesting such approaches may offer dual benefits for both skeletal muscle and cardiac health.
