Cardiomyopathy in dystrophin-deficient hypertrophic feline muscular dystrophy

A colony of cats affected with hypertrophic feline muscular dystrophy was u sed to study the occurrence of cardiomyopathy associated with dystrophin de ficiency. Affected male and female cats, obligate carrier females, and unaf fected healthy littermates were followed from 12 weeks of age into adulthoo d. Thoracic radiography, 2-D echocardiography, and 2-D-derived M-mode echoc ardiography were performed at 3-month intervals until 12 months of age and regularly thereafter From 9 months of age, all affected cats had larger hea rts than normal and carrier animals. Left ventricular wall thickness in sys tole and in diastole and interventricular septal thickness in systole were greater in affected cats 12 months and older when compared with normal or h eterozygous animals (P < .05). The myocardium of affected cats was diffusel y hypoechoic and thickened. Multiple hyperechoic foci were in the myocardiu m and papillary musculature. Shortening fraction was normal in all cats. Ch anges seen in carrier females included enlargement and hyperechogenicity of the papillary musculature after the age of 2 years. Gross and light micros copic examination revealed left ventricular wall thickening with multiple f oci of mineralization in 2 of 5 hearts from dystrophin-deficient cats. Alth ough approximately 10% of the normal dystrophin amount was present in the s keletal muscle, dystrophin could not be detected in the myocardium. Early o nset concentric myocardial hypertrophy was present in all adult cats. Lesio ns were mainly localized in the myocardium of the left ventricular free wal l and interventricular septum, papillary musculature, and the endocardium. Clinical signs of heart Failure developed only infrequently in cats with hy pertrophic feline muscular dystrophy.