Duchenne muscular dystrophy

Classic findings in Duchenne muscular dystrophy include resting sinus tachycardia, deep infero-lateral Q waves, and a tall R in lead V1 due to the underlying cardiomyopathy, which is often associated with posterobasal fibrosis of the left ventricle. Left atrial enlargement, as indicated by the prominent negative P wave in lead V1, and marked right axis deviation are also present.

Normal electrocardiogram showing normal sinus rhythm at a rate of 75 beats/minute, a PR interval of 0.14 seconds, a QRS interval of 0.10 seconds, and a QRS axis of approximately 75°.