Animal models of primary myocardial diseases.

Feline and canine cardiomyopathies (primary myocardial diseases) were reviewed and divided into three groups based on the clinical, hemodynamic, angiocardiographic, and pathologic findings: (1) feline and canine hypertrophic cardiomyopathy, (2) feline and canine congestive (dilated) cardiomyopathy, and (3) feline restrictive cardiomyopathy. All three groups consisted predominantly of mature adult male cats and dogs. Cardiomyopathy in the hamster and turkey was also reviewed. The most common presenting signs were dyspnea and/or thromboembolism in the cat, systolic murmurs with gallop rhythms on auscultation, cardiomegaly with (groups 1 and 3) or without (group 2) pulmonary edema, abnormal electrocardiograms, elevated left ventricular end-diastolic pressures, and angiocardiographic evidence of mitral regurgitation with left ventricular concentric hypertrophy (group 1), left ventricular dilatation (group 2), or midventricular stenosis (group 3). Some cats in groups 1 and 3 also had evidence of left ventricular outflow obstruction. The principal pathologic findings in all of the cats and dogs were left atrial dilation, hypertrophy, increased septal:left ventricular free wall thickness ratio with disorganization of cardiac muscle cells (group 1); dilatation of the four chambers with degeneration of cardiac muscle cells (group 2); and extensive endocardial fibrosis and adhesion of the left ventricle (group 3). Aortic thromboembolism was commonly observed in the cats of all three groups. These clinical and pathologic findings indicate that cardiomyopathy in the cat or dog is similar to the three forms of cardiomyopathy in humans (hypertrophic, congestive, and restrictive).