Arrhythmias in DMD
Despite a compelling substrate and abnormal conduction system tissue,
arrhythmia burden in DMD is generally attributed to accumulated cardiac
injury and systolic dysfunction. The most common finding on ambulatory
monitoring of patients with DMD is sinus tachycardia. Often in response
to pulmonary pathology or cardiac dysfunction, atrial arrhythmias
including flutter and fibrillation may develop7. In a
study of 151 patients with dystrophinopathy (Duchenne and Becker’s),
arrhythmias were significantly associated with decreased function, as
well as independently with increased age20. In the
study over 300 Holter monitor studies from Texas Children’s Hospital
were evaluated, and burden of supraventricular tachycardia (SVT),
ventricular tachycardia (VT), or frequent ventricular premature
contractions (VPCs) were noted. Overall, 44% of patients with DMD and
57% of patients with BMD had arrhythmias, with clinically significant
arrhythmia, either SVT or VT, occurring in 10% and 25% of those
patients respectively20. Though PR interval and QRS
disturbances have demonstrated the progressive impact of dystrophin
deficiency on cardiac conduction, complete atrioventricular block is
rare21,22. There was correlation between atrial
arrhythmias and sudden cardiac death in dystrophin-deficient
cardiomyopathies controlling for decreased systolic function. In fact
atrial arrhythmias were present in 68% of all holter monitors in one
study on 235 patients with DMD23. Non-sustained atrial
tachycardia, including frequent premature atrial contractions, are more
common in patients with decreased systolic function. None of the
patients experienced sustained atrial tachycardia and just 5 patients
(2%) experienced ventricular tachycardia. Other rare arrhythmias
including bundle branch reentry ventricular tachycardia, have been
noted7,23. Atrial fibrillation and flutter, certainly
common in the adult dilated cardiomyopathy population, is much rarer in
children. When these occur, increased cardiac rhythm monitoring and
treatment with standard antiarrhythmic therapies is
recommended2.