A 7-year-old 4.7-kg (10.3-lb) neutered male Russian Blue cat was examined by the referring veterinarian because of lethargy and inappetence of 2 days' duration. Cardiac auscultation revealed the only abnormality identified during physical examination, which was an irregular cardiac rhythm with a frequency of approximately 300 beats/min and interrupted with periods of distinctly lower (albeit undocumented) frequency. The cat had no history of cardiac abnormalities. The cat was immediately referred to the emergency service of a veterinary teaching hospital.
At the referral evaluation, the cat was bright, alert, and responsive and had a body condition score of 5/9. No signs