A 19-year-old male Siberian tiger was presented with inappetence and paralysis of hind limbs. In a computed tomography (CT) scan, intervertebral disk disease at L3–L4 was detected. Cardiac arrest occurred during the surgery. At autopsy, myxomatous mitral valve degeneration (MMVD) and eccentric hypertrophy of the left heart were noted. The diagnosis was congestive heart failure caused by MMVD. Microscopically, myocardial and pulmonary fibrosis were observed in addition to the disintegration of the fibrosa layer and accumulation of glycosaminoglycans and proteoglycans in the spongiosa layer of the mitral valve. This is the first case of congestive heart failure with MMVD in a Siberian tiger.

Hypertrophic cardiomyopathy (HCM) is recognized as the most common feline cardiac disease. Several studies have evaluated the population characteristics and survival time of cats with HCM; however, these reports included large numbers of asymptomatic HCM. The purpose of this study was to evaluate the characteristics and survival time of cats with symptomatic HCM admitted to emergency service. Medical records were examined to verify clinical diagnosis of HCM. Asymptomatic cats diagnosed with HCM were also excluded from the study. From a total of 13 cats, eight were classified in the arterial thromboembolism (ATE) group while the other five were in the congestive heart failure (CHF) group. Middle-aged (6 years, range 1.4~7 years) male cats (53.8%) were included in this study. Pelvic limb paralysis, depression, and respiratory distress were common clinical signs found in symptomatic HCM cats. Hematologic evaluation found that enzymes related to muscle damage and tissue necrosis were elevated in both groups and highly elevated in the ATE group. Left atrium was remarkably enlarged in ATE group cats. The median survival time of cats in the ATE group was significantly shorter than that of cats in the CHF group (P=0.002). Prospective investigation based on a large population would be required to clarify the effects of various factors on prognosis of HCM cats.