Atrial Fibrillation in a Cow with Bovine Leukemia

Abstract

A Holstein dairy cow suffering from lymphosarcoma was diagnosed electrocardiographically as atrial fibrillation. In the pathological examination, tumor cells have invaded both atria diffusely. The leukemic infiltration laid immediately adjacent to and surrounded the sinoatrial (SA) node, but did not involve the node. Onset of atrial fibrillation in this case was considered to be associated with the SA node which was isolated from myocardial fibers of the right atrium by the lesions.