Prevalence of attenuated wavy fibers in myocardium of dogs with dilated cardiomyopathy

OBJECTIVE: To determine the prevalence of attenuated wavy fibers in the myocardium of dogs with and without dilated cardiomyopathy (DCM). DESIGN: Prevalence survey. ANIMALS: 70 dogs clinically suspected to have DCM (ie, fractional shortening < 25%, absence of echocardiographic lesions other than chamber dilatation, and radiographic or postmortem evidence of congestive heart failure) and 147 dogs with chronic valvular disease (n = 60), congenital heart disease (49), myocardial infarcts (23), myocarditis (8), or endocarditis (7). PROCEDURE: Echocardiography and electrocardiography were performed, and thoracic radiographs were obtained with dogs in left lateral recumbency. Necropsy specimens were examined for attenuated wavy fibers (ie, myocardial cells < 6 microns in diameter with a wavy appearance). RESULTS: 65 of 70 dogs clinically suspected to have DCM were confirmed to have the disease on postmortem examination, and 64 of 65 had attenuated wavy fibers. The remaining 5 dogs were found during postmortem examination to have heart disease other than DCM, and none had attenuated wavy fibers. Only 1 of 147 dogs with heart disease other than DCM had attenuated wavy fibers. CLINICAL IMPLICATIONS: Findings suggest that histologic examination for attenuated wavy fibers may be a useful postmortem test for DCM in dogs. The diagnosis was confirmed in 65 of 70 dogs suspected to have DCM on the basis of standard clinical criteria.