Cardiac leiomyoma associated with advanced atrioventricular block in a young dog.

A 1 year old intact female Labrador retriever dog presented for evaluation of syncope caused by severe bradycardia. Advanced atrioventricular block was diagnosed. A mass infiltrating the interventricular septum and the tricuspid annulus was identified with echocardiography. Histopathological evaluation of the mass was consistent with cardiac leiomyoma, and immunohistochemical staining for smooth muscle actin confirmed the diagnosis. To the authors' knowledge, this is the first report of cardiac leiomyoma in the canine species.

Immunohistochemical evidence for expression of fast-twitch type sarco(endo)plasmic reticulum Ca2+ ATPase (SERCA1) in German shepherd dogs with dilated cardiomyopathy myocardium.

OBJECTIVES: Dilated cardiomyopathy (DCM) is one of the most common acquired canine heart diseases. It is particularly common in large and giant breed dogs. Although a great deal is known about the clinical progression and manifestations of the disease, the underlying cellular and molecular mechanisms remain poorly understood. One widely held belief is that calcium-handling abnormalities are critically involved in the disease process. This study investigates the changes in expression of the sarco(endo)plasmic reticulum calcium ATPase (SERCA) isoforms in DCM myocardium from German shepherd dogs. ANIMALS, MATERIALS AND METHODS: Affected tissue samples were obtained from German shepherd dogs with DCM, euthanized for intractable congestive heart failure while normal myocardial tissue samples were obtained from German shepherd dogs, euthanized for non-cardiovascular reasons. Tissue microarrays containing normal and DCM myocardium samples were prepared, immunostained with SERCA1 and SERCA2 antibodies and analyzed. RESULTS: We were able to demonstrate, for the first time, that while there is little change in the expression of the cardiac isoform (SERCA2), there is clear expression of the fast-twitch skeletal muscle isoform SERCA1 in the myocardium of dogs diagnosed with DCM. CONCLUSION: We propose that SERCA1 expression is evidence of a natural adaptive response to the impaired Ca2+ handling thought to occur in German shepherd dogs with DCM and heart failure.