Echocardiographic and electrocardiographic effects of atenolol versus sotalol in dogs with severe subaortic stenosis.

BACKGROUND

Subaortic stenosis (SAS) is a commonly diagnosed canine congenital cardiac defect, with severe forms of carrying a poor long-term prognosis. To date, an effective treatment strategy has not been developed in veterinary medicine. This study sought to determine if sotalol, a class III antiarrhythmic, may have salient echocardiographic and antiarrhythmic benefits for medical management for dogs affected with severe SAS.

METHODS

Ten dogs diagnosed with severe SAS were enrolled in this prospective, double-blinded, crossover study. Dogs underwent physical exam, non-invasive blood pressure measurement, electrocardiography, echocardiography, and 24-h Holter monitoring. Diagnostics were repeated 12-16 days following randomization to oral atenolol (0.5-1 mg/kg) or sotalol (1-2 mg/kg) twice daily. After a medication taper and four-day washout, dogs were crossed-over to the alternate study medication, and the diagnostics were repeated in 12-16 days. Linear and multinomial mixed models were developed to evaluate the effects of treatments on echocardiographic and electrocardiographic variables.

RESULTS

Indices of left ventricular systolic function were reduced based on the volumetric assessment when dogs received sotalol compared to atenolol. No difference was noted between groups in left ventricular systolic function based on the linear assessment. No difference was observed in the reduction in left ventricular outflow tract velocity. No significant differences were observed between treatment groups for any variable on 24-h Holter monitor.

CONCLUSIONS

Sotalol may be a viable therapy to consider for dogs with severe SAS based on this pilot study. A larger, prospective study is necessary to investigate further.