Moderately reversible dilated cardiomyopathy in a cat with presumptive spontaneous primary hypothyroidism

Abstract A 7‐year‐old domestic shorthair cat was presented to a primary veterinarian for evaluation of polydipsia, hyporexia and an unkempt haircoat. The cat was diagnosed with hypothyroidism based on a serum total thyroxine measured at less than 0.5 µg/dL. The cat was prescribed levothyroxine. Two months later, the cat presented to the same primary veterinarian for respiratory signs and was diagnosed with congestive heart failure based on radiographic pulmonary oedema, cardiomegaly and an abnormal SNAP N‐terminal pro‐brain natriuretic peptide test. Furosemide was prescribed, and the cat was referred for cardiologist evaluation. Echocardiography 1 month later revealed four‐chamber dilation and systolic dysfunction, consistent with a diagnosis of dilated cardiomyopathy. Pimobendan (Vetmedin) and clopidogrel were prescribed. Over the following 19 months, the cat had routine echocardiographic and biochemical evaluations, which showed moderate improvement in cardiac structure and function while the cat maintained a euthyroid status on supplementation.