Mechanisms for Arrhythmias in Duchenne Cardiomyopathy
The substrate for arrhythmias in DMD remains under investigation. Progressive myocardial fibrosis may produce scar which disrupts normal myocardial electrical coordination. Fibrosis manifests as late gadolinium enhancement (LGE) on cardiac magnetic resonance (CMR) imaging, most often involving the posterobasal subepicardial muscle. Advanced disease features LGE expanding to the inferior and lateral wall, with increasing thickness of affected myocardium5,6. Electrocardiogram (ECG) abnormalities in DMD were described greater than 50 years ago and in general are thought to mirror the pattern of myocardial injury7. Altered electrical activation (depolarization) results in changes to the QRS complex voltage and are commonly identified8,9. Fragmented QRS complexes in adults represent heterogeneous myocardial activation in both ischemic and non-ischemic cardiomyopathy have been associated with arrhythmic events and sudden cardiac death10. Specifically in the DMD population, QRS fragmentation is associated with both left ventricular systolic dysfunction and ventricular ectopy burden11.