The mdx mouse is a model of Duchenne muscular dystrophy (DMD). As many DMD patients die of cardiac failure, we investigated whether mdx mice exhibited clinically relevant cardiac phenotypes. We applied a recently developed method for noninvasively recording electrocardiograms (ECGs) to study male mdx mice (n = 15) and control mice (n = 15). The mdx mice had significant tachycardia and decreased heart rate variability, consistent with observations in DMD patients. Heart rate was nearly 15% faster in mdx mice than control mice (P < 0.05). The rate-corrected QT interval duration and PR interval were shorter in mdx compared to control mice (P < 0.05). The muscarinic antagonist atropine significantly increased heart rate and decreased PR interval in C57 mice. In contrast, atropine significantly decreased heart rate and increased PR interval 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. Baseline ECGs and contrary responses to muscarinic blockade by atropine in mice deficient in neuronal nitric oxide synthase (nNOS) suggest that the autonomic dysfunction in mdx mice may be independent of decreased myocardial nNOS. These electrocardiographic findings in dystrophin-deficient mice may provide new bases for diagnosing, understanding, and treating DMD patients.

Background: The rapid increase in the development of mouse models is resulting in a growing demand for non-invasive physiological monitoring of large quantities of mice. Accordingly, we developed a new system for recording electrocardiograms (ECGs) in conscious mice without anesthesia or implants, and created Internet-accessible software for analyzing murine ECG signals. The system includes paw-sized conductive electrodes embedded in a platform configured to record ECGs when 3 single electrodes contact 3 paws.

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A late-onset case of propionic acidaemia with favourable response to restriction of dietary protein is described. During a keto-acidotic crisis, this patient demonstrated unexpectedly low concentrations of propionic acid and glycine in blood and urine but increased urinary output of some secondary metabolites.