Evaluation of Cardiac Phenotype in Horses with Type 1 Polysaccharide Storage Myopathy
Article first published online: 15 SEP 2012
Copyright © 2012 by the American College of Veterinary Internal Medicine
Journal of Veterinary Internal Medicine
Volume 26, Issue 6, pages 1464–1469, November/December 2012
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How to Cite
Naylor, R.J., Luis-Fuentes, V., Livesey, L., Mobley, C.B., Henke, N., Brock, K., Fernandez-Fuente, M. and Piercy, R.J. (2012), Evaluation of Cardiac Phenotype in Horses with Type 1 Polysaccharide Storage Myopathy. Journal of Veterinary Internal Medicine, 26: 1464–1469. doi: 10.1111/j.1939-1676.2012.00988.x
- Issue published online: 20 NOV 2012
- Article first published online: 15 SEP 2012
- Manuscript Accepted: 26 JUN 2012
- Manuscript Revised: 8 JUN 2012
- Manuscript Received: 19 MAR 2012
- Exertional rhabdomyolysis;
Type 1 polysaccharide storage myopathy (PSSM1), an equine glycogen storage disorder caused by a gain of function mutation (R309H) in the gene encoding glycogen synthase (GYS1), is associated with the accumulation of amylase-resistant alpha-crystalline polysaccharide inclusions within skeletal muscle. Several glycogenoses in humans have a cardiac phenotype, and reports exist of horses with PSSM and polysaccharide inclusions in cardiac muscle.
To investigate the hypothesis that horses with PSSM1 display a cardiac phenotype. Our objectives were to compare plasma cardiac troponin I (cTnI) concentration and the incidence of cardiac arrhythmias in PSSM1 homozygotes, heterozygotes, and control horses.
One hundred and twenty-five Belgian and Percheron horses under the same management were genotyped for the R309H GYS1 mutation. From these, 8 age-, breed-, and sex-matched cohorts of each genotype were identified. Plasma cTnI concentration and incidence of cardiac arrhythmias (determined by 24-hour Holter ECG) were compared between the groups.
Although some PSSM1-affected horses had mildly increased plasma cTnI concentrations, there was no significant difference in cTnI concentrations between groups. There were no significant differences in the incidence of ectopic beats, cardiac conduction intervals or mean heart rate between groups.
Conclusions and clinical importance
We found no evidence of clinically relevant cardiac myocyte injury or arrhythmias in horses with PSSM1. Additional study is required to determine whether myocardial function may be compromised in this disorder.