Objective—To evaluate the effect of 4 antiarrhythmic
treatment protocols on number of ventricular premature
complexes (VPC), severity of arrhythmia, heart
rate (HR), and number of syncopal episodes in Boxers
with ventricular tachyarrhythmias.
Design—Randomized controlled clinical trial.
Procedure—Dogs with > 500 VPC/24 h via 24-hour
ambulatory ECG (AECG) were treated with atenolol
(n = 11), procainamide (11), sotalol (16), or mexiletine
and atenolol (11) for 21 to 28 days. Results of pre- and
posttreatment AECG were compared with regard to
number of VPC/24 h; maximum, mean, and minimum
HR; severity of arrhythmia; and occurrence of syncope.
Results—Significant differences between pre- and
posttreatment number of VPC, severity of arrhythmia,
HR variables, or occurrence of syncope were not
observed in dogs treated with atenolol or procainamide.
Significant reductions in number of VPC,
severity of arrythmia, and maximum and mean HR
were observed in dogs treated with mexiletineatenolol
or sotalol; occurrence of syncope was not significantly
different between these 2 treatment groups.
Conclusions and Clinical Relevance—Treatment
with sotalol or mexiletine-atenolol was well tolerated
and efficacious. Treatment with procainamide or
atenolol was not effective. (J Am Vet Med Assoc 2002;221:522–527)