ECG of the month

A 13-year-old 2.4-kg (5.3-lb) spayed female domestic shorthair cat was examined by a referring veterinarian because of lethargy, inappetence, and signs of right forelimb pain when ambulating. Radiographic findings for the right forelimb were suggestive of lameness as a result of historic trauma.. The owners of the cat elected for conservative workup of the problem, and supportive pain management was instituted with administration of buprenorphine hydrochloride. Nine days later, the cat was taken to a veterinary teaching hospital’s emergency service for evaluation of persistent lethargy, inappetence, and lameness. On examination of the cat, there was concern for shock with hypothermia (rectal temperature, 36.7°C [98.1°F]), and borderline bradycardia (heart rate, 140 beats/min) and dull mentation were noted. A cardiac arrhythmia or murmur was not detected, and femoral pulses were reported as fair and synchronous with the heartbeat bilaterally. The cat was assessed as being 5% dehydrated and had mild generalized muscle wasting. The initial diagnostic evaluation included a CBC and serum biochemical analysis. The results of the CBC were unremarkable. Serum biochemical abnormalities included moderate azotemia (BUN concentration, 106 mg/dL [reference range, 12 to 39 mg/ dL]; creatinine concentration, 3.2 mg/dL [reference range, 0.5 to 2.1 mg/dL]), moderate hyperphosphatemia (8.9 mg/dL; reference range, 3.3 to 7.8 mg/dL), and severe hypermagnesemia (6.6 mg/dL; reference range, 1.6 to 2.4 mg/dL). Abdominal ultrasonography revealed an infiltrative kidney lesion, a jejunal mass, and a hepatic mass. Microscopic examination of ultrasound-guided fine-needle aspirate specimens of the kidney and liver lesions revealed a predominantly lymphocyte population. The lymphocytes were medium to large, consistent with lymphoma. During the diagnostic workup, 6-lead ECG was performed. The cat was subsequently euthanized by IV injection of pentobarbital sodium, and postmortem examination confirmed a diagnosis of lymphoma. There were no pathological changes in the heart identified during postmortem examination.