Transient third‐degree atrioventricular block with type 1 isorhythmic atrioventricular dissociation with accrochage during anaesthesia in a dog

Abstract An 8‐year‐old, male, neutered, mixed‐breed dog presented for treatment of a left medial patellar luxation. Thirty minutes following the induction and maintenance of general anaesthesia, a second‐degree atrioventricular block was identified, rapidly progressing to third‐degree atrioventricular block with type 1 isorhythmic atrioventricular dissociation. As the dog's non‐invasive blood pressure remained normal, no intervention was implemented, and the dog was found to have returned to sinus rhythm with repeat electrocardiography the next day. The inciting cause of the conduction disturbance is hypothesised to be a result of anaesthetic drugs and/or relatively increased vagal tone.