Pacemaker Implantation in a Dog with Concurrent Sick Sinus Syndrome and a Splenic Tumor

Abstract

A 12-year-old neutered female Miniature Schnauzer weighing 5.1 kg was presented for a syncope evaluation (Day 1). Bradyarrhythmia was noted on auscultation, so a decision was made to initiate a series of clinical and laboratory tests. There was nothing unusual about the hematology and serum biochemistry results, including the thyroid hormone values, other than anemia and elevated triglyceride. The abdominal ultrasound revealed a splenic mass, and sinus bradycardia and sinus arrest were noted in the electrocardiograms. The Holter monitor and atropine response tests were performed, and these confirmed that syncope was indeed caused by sick sinus syndrome. On Day 15, pacemaker implantation and splenectomy were performed simultaneously. Syncope did not occur again after surgery. A histopathological evaluation of the splenic mass was performed, and hemangiosarcoma was diagnosed. The dog was put on adjuvant doxorubicin and cyclophosphamide chemotherapy, but ultimately died at home on Day 358.