This is the first report of paroxysmal atrioventricular block with Wenckebach cycles in a dog exhibiting syncope. The patient was a 1-year-old female Shiba Inu referred to our hospital with chief complaints of exercise intolerance, dizziness during walking, and tongue discoloration. Pacemaker implantation was performed based on the clinical presentation and Holter electrocardiogram findings. In this case, long-term management was successfully achieved for 13 years and 3 months (Age 15 years old) after the placement of pacemaker. A histopathological examination revealed that no abnormalities in the conduction system were detected that could explain the arrhythmia. Consequently, the arrhythmia was suspected to have been caused by vagus nerve stimulation.
