Clinical, epidemiological and echocardiographic features and prognostic factors in cats with restrictive cardiomyopathy: A retrospective study of 92 cases (2001‐2015)

BACKGROUND: Restrictive cardiomyopathy (RCM) is a common primary cardiomyopathy of cats. However, little information is available regarding prognostic variables in large populations of cats with RCM. OBJECTIVES: To characterize the epidemiological, clinical, and echocardiographic features of cats with RCM and to document their survival times and risk factors for cardiac death (CD). ANIMALS: Ninety‐two cats with RCM. METHODS: Retrospective study. Diagnosis of RCM was based on echocardiographic and Doppler criteria. Median survival time to CD and adjusted hazard ratios (HR) were estimated by the Kaplan‐Meier method and multivariate Cox models, respectively. RESULTS: The feline population (median age [interquartile range], 8.6 years [4.1‐12.4]; body weight, 4.0 kg [3.3‐4.7]) included 83 cats (90%) with the myocardial RCM form and 9 (10%) with the endomyocardial fibrosis RCM form. Most RCM cats (64/92, 70%) were symptomatic at the time of diagnosis, with dyspnea related to congestive heart failure in 57 of 64 cats (89%). The median survival time of the 69 cats with the myocardial RCM form and available follow‐up was 667 days (range, 2‐3710 days) considering CD. Independent of age, biatrial enlargement, and arrhythmias, increase of the left atrium (LA)‐to‐aorta (Ao) ratio (hazard ration [HR], 2.5 per 0.5‐unit increase; 95% confidence interval [CI], 1.5‐4.2; P < .001) and presence of severe LA enlargement (end‐diastolic LA : Ao ≥2; HR, 3.4; 95% CI, 1.3‐8.7; P = .01) were significantly associated with shorter time to CD. CONCLUSIONS AND CLINICAL IMPORTANCE: Cardiac death is common in RCM cats, and LA enlargement seems independently associated with decreased survival time in these cats.