EN
Atrial fibrillation is one of the commonest arrhythmia in dogs and humans. It accompanies organic heart diseases but also other pathologies, e.g. hyperthyroidism. The aim of the study was to determine the frequency of the occurrence of atrial fibrillation, its potential causes and the relationship between electrocardiographic changes and other results of cardiological examination in dogs with this arrhythmia. From 1456 dogs referred to cardiological examination in the years 2001-2006, 521 dogs (35.78%) demonstrated arrhythmias. Atrial fibrillation was detected in 51 dogs, which accounts for 3.5% of all the examined dogs and 9.7% of the dogs with arrhythmias. In 49 cases atrial fibrillation was permanent. The mean age of all the examined dogs was 7.55 ± 3.6. However, it was significantly higher in the animals from II group (10.64 ± 3) as compared to those of I group (6.6 ± 3.2). Atrial fibrillation is dominant in dogs with a body weight exceeding 25 kg, which accounted for 72.55% of the examined group and are predisposed to dilated cardiomyopathy. Permanent atrial fibrillation is a common arrhythmia in dogs and it is accompanied by ventricular tachycardia, regardless of the etiology of the atrial fibrillation. Paroxysma atrial fibrillation is a very rare arrhythmia in dogs. Atrial fibrillation tends to occur in large breed dogs more frequently in the course DCM than in small dogs.