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.