Rishniw M., Tobias A.H., Marks S.L., et al.
A I3-year-old spayed female domestic shorthair cat was admitted for routine vaccination. The owner was not aware of any problem with the cat at the time of examinatlon. An arrhlthmia was ausculted, but the remainder of the physical examination was unremarkable. An ECG was performed as part of the diagnostic evaluation (Fig 1). Thoracic radiography revealed mild cardiomegaly, but pulmonary edema or pleural effusion was not evident. The owner declined use of echocardiography for the cat. High baseline thyroxine concentration was found on serum biochemical evaluation (11.6 ug/dl; reference range, 1.6 to 3.1 ug/ldl).