Abstract
A 13-years-old female Shiba-breed dog was seen because of syncope and wobbling motion. A monitoring scalar electrocardiography showed high frequency sinus arrests and atropine test was positive. Oral atropine sulfate had been administered for the treatment. Afterwards, the clinical sign had disappeared. On the 378th day, syncope relapsed again and atropine test became negative. Based on the results of electrocardiography and atropine test, Sick Sinus Syndrome was strongly suspected. Administration of cilostazol, which is a phosphodiesterase inhibitor, and enalapril maleate resulted in an immediate disappearance of the clinical signs again. Monitoring holter electrocardiography was conducted before and after the treatment. The cilostazol therapy couldn't increase the total daily heat-beat counts. However, frequency of sinus arrest that exceeds 6 seconds decreased, and the maximal period of sinus arrest was favorably shortened.
