Electrical cardioversion of sustained ventricular tachycardia in three Boxers

2 spayed female (8 and 9 years old) and 1 sexually intact male (6.5 years old) Boxers were treated because of sustained ventricular tachycardia by electrical cardioversion.

Physical examination of the 8-year-old female Boxer revealed tachycardia (heart rate, 250 beats/min), weak femoral pulses, pale mucous membranes, panting, and lethargy. The 6.5-year-old male Boxer had similar physical examination findings, with the addition of a syncopal event. Analysis of the ECG rhythm strips for the 8- and 6.5-year-old dogs indicated a right ventricular origin of the ventricular tachycardia. The 9-year-old female Boxer was being treated with an IV constant rate infusion of lidocaine hydrochloride because of ventricular arrhythmias during the initial examination; physical examination re-vealed weakness, pale mucous membranes, prolonged capillary refill time, weak femoral pulses, and tachycardia (heart rate, 265 beats/min). Analysis of the ECG rhythm strip for the 9-year-old Boxer indicated a left ventricular origin of the ventricular tachycardia.

Pharmacological cardioversion treatment was unsuccessful in all 3 Boxers; however, electrical cardioversion by use of a biphasic defibrillator synchronized to conduct 30 J of energy during the peak of the QRS complex was successful in each dog. The electrical cardioversion procedure was performed 2 times (5-day interval between procedures) in the 9-year-old female as a result of relapse of the ventricular tachycardia condition.

Results and follow-up monitoring suggested electrical cardioversion of sustained ventricular tachycardia may be a safe and effective treatment in Boxers that are unresponsive to medical treatment.