Tachycardia-induced cardiomyopathy in a cat

A 10-year-old male castrated Domestic Shorthair cat was evaluated for an asymptomatic tachyarrhythmia noted two weeks prior. Electrocardiography revealed a normal sinus rhythm with atrial premature complexes and paroxysms of supraventricular tachycardia with a heart rate between 300 and 400 min-1. Echocardiography was unremarkable, and concentrations of circulating cardiac troponin I, T4, and blood taurine were within reference ranges. The cat was treated with sotalol (2.1 mg/kg q12h, PO) but the arrhythmia was insufficiently controlled as determined during several re-examinations within a two-year time period. Twenty four months after initial presentation atrial fibrillation with fast ventricular response rate (200 to 300 min-1) was diagnosed, along with severe eccentric chamber remodeling and systolic dysfunction. The cat developed congestive heart failure and cardiogenic shock and was euthanized nearly 27 months after the first exam. Gross and histopathologic findings ruled out commonly seen types of primary myocardial disease in cats. The persistent nature of the tachyarrhythmia, the progressive structural and functional cardiac changes, and comparative gross and histopathologic post-mortem findings are consistent with the diagnosis of tachycardia-induced cardiomyopathy.