This case reports a mongrel dog referred to a veterinarian due to tiredness and syncope episodes. Atrial fibrillation and ventricular premature complex were observed during electrocardiographic exam. The anti-arrhythmic treatment was not effective and the dog died from syncope. At necropsy, a mass invading the internal area of the left atrium was evidenced in the base of the heart. The occurrence of chemodectoma was histologically exhibited. Infiltrations in the atrial myocardium caused alterations in the miocites and produced reentrant circuits and/or atrial depolarization ectopic points.
dog; atrial fibrillation; chemodectoma; neoplasic infiltration
