Long-term management of high-grade atrioventricular block using cilostazol in a cat

CASE SUMMARY: A 12-year-old neutered female domestic shorthair cat was admitted for syncope. Clinical signs and electrocardiography revealed high-grade atrioventricular (AV) block. Treatment with cilostazol ameliorated the clinical signs and arrhythmia. However, the high-grade AV block recurred on several occasions. After 640 days, the cat presented again with clinical deterioration owing to reoccurrence of the arrhythmia and it died 11 days later. Histopathological examination revealed a loss of conduction cells within the His bundle. RELEVANCE AND NOVEL INFORMATION: To our knowledge, this is the first report of high-grade AV block treated with cilostazol in a cat. Treatment with cilostazol prolonged survival for 650 days without pacemaker implantation. Histological findings suggested that the AV block was related to fibrosis of the impulse conduction system.