Duchenne muscular dystrophy: prevalence and patterns of cardiac involvement

In about 10% cases of Duchenne muscular dystrophy (DMD), death is due to cardiac dysfunction. The recognition of cardiomyopathy in DMD is thus important.

To assess cardiac involvement in DMD patients by clinical, radiographic, electrocardiographic (ECG) and echocardiographic monitoring and correlate clinical parameters, CPK levels, presence of gene deletion and steroid therapy with cardiac involvement.

Thirty patients beyond 6 years age, with DMD in advanced stage disease/non-ambulatory were recalled. A detailed clinical evaluation, CPK levels, gene deletion studies were carried out. Cardiac investigations included Chest X-ray, 12 lead ECG and echocardiography.

Nineteen patients were non-ambulatory at the time of enrollment. Symptoms or signs suggestive of cardiac dysfunction were seen in only 10%. Gene deletion was identified in 70.3%. Around one-third patients had cardiomegaly. ECG abnormalities were present in 93.3% patients and commonest abnormality was R > 4 mm in V1. Ejection fraction (EF) < 55% was observed in 64.2% and EF < 50% in 17.8%.

Cardiomyopathy of DMD is characterized by lack of symptoms and few physical signs. Presence of subtle changes like sinus tachycardia may suggest early cardiac involvement. Thus echocardiography is required for evaluation of cardiac dysfunction. Presence of gene deletion was associated with higher CT ratio. Older children have been found to have higher heart rates. No other significant correlation with clinical parameters, CPK levels, genotype and steroid therapy was observed. Early detection possibly leads to appropriate treatment thus reducing the morbidity.