Abstract
A 10-year-old spayed West Highland white terrier, which had previously been implanted with a pacemaker because of Sick Sinus Syndrome type III, was diagnosed ashaving a spleen tumor. Six months after the implantation and a splenectomy was performed. Consequently, the dog experienced no paroxysmal tachycardia after the pacemaker implantation, even when given perioperative anesthesia load and surgical stress.