New-onset atrial fibrillation and flutter in a mechanically ventilated dog with bronchopneumonia.

A 3-year-old intact male English bulldog was presented to a veterinary teaching hospital because of respiratory distress secondary to bronchopneumonia and brachycephalic obstructive airway syndrome. Due to severe hypoxemia, the dog was mechanically ventilated. He developed atrial flutter and atrial fibrillation during hospitalization. The arrhythmias were suspected to be secondary to the systemic inflammation, severe brachycephalic obstructive airway syndrome, and high vagal tone without underlying cardiac pathology identified by echocardiography. Considering the hemodynamic instability of the dog, cardioversion was attempted. The arrhythmias were refractory to conventional treatments, discontinuation of pro-arrhythmic medications, and trials of Class I and II antiarrhythmics. Cardioversion occurred 2 h following oral sotalol administration after the dog received a diltiazem infusion for 30 h, and the dog recovered successfully. After the dog was discharged and prescribed sotalol that was subsequently discontinued, he did not experience any recurrence of arrhythmias during follow-up examinations. Key clinical message: To the authors' knowledge, this is the first report of a medical cardioversion of atrial flutter and atrial fibrillation in a mechanically ventilated dog with bronchopneumonia. Clinicians should be aware of the risk of acute cardiac events in dogs with systemic inflammation, such as bronchopneumonia, especially in brachycephalic breeds with high vagal tone.