Paroxysmal atrioventricular block in a mixed-breed dog

An 11-year-old female mixed-breed dog was presented with syncopal episodes occurring up to 10 times a day for 3 months. The owner reported events lasting for approximately 15 s, during which the dog would fall into lateral recumbency, have muscle tremors and show intense salivation. After the event, the animal was disorientated for a few seconds before full recovery. A surface electrocardiogram was obtained, during which an episode of syncope occurred, with a paroxysmal atrioventricular block lasting 10.5 s. The event was characterised as an intrinsic pause-dependent paroxysmal atrioventricular block associated with cardiogenic syncope type 1E. The dog received aminophylline 10 mg/kg every 8 hours and the frequency of syncopal episodes decreased until it died of non-cardiac causes 3 months later. There is little information on paroxysmal atrioventricular blocks in dogs, and further electrocardiographic event characterisation may the influence choice of therapy in individual cases.