The mdx mouse is a model of Duchenne muscular dystrophy. The present invention describes that mdx mice exhibited clinically relevant cardiac phenotypes. A non-invasive method of recording electrocardiograms (ECGs) was used to a study mdx mice (n=15) and control mice (n=15). The mdx mice had significant tachycardia, consistent with observations in patients with muscular dystrophy. Heart-rate was nearly 15% faster in mdx mice than control mice (P0.01). ECGs revealed significant shortening of the rate-corrected QT interval duration (QTc) in mdx mice compared to control mice (P0.05). PR interval duration were shorter at baseline in mdx compared to control mice (P0.05). The muscarinic antagonist atropine significantly increased heart-rate and decreased PR interval duration in C57 mice. Paradoxically, atropine significantly decreased heart-rate and increased PR interval duration in all mdx mice. Pharmacological autonomic blockade and baroreflex sensitivity testing demonstrated an imbalance in autonomic nervous system modulation of heart-rate, with decreased parasympathetic activity and increased sympathetic activity in mdx mice. These electrocardiographic findings in dystrophin-deficient mice provide new bases for diagnosing, understanding, and treating patients with Duchenne muscular dystrophy.
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