Recurrent steroid responsive hypertrophic obstructive cardiomyopathy in a Maine Coon.

A 5-year-old, neutered, female Maine Coon with history of eosinophilic enteritis presented for acute deterioration following placement of a subcutaneous ureteral by-pass. Physical examination revealed a new 4/6, left, parasternal, systolic heart murmur. Echocardiography diagnosed hypertrophic obstructive cardiomyopathy with severe left ventricular outflow tract obstruction. Resolution of the hypertrophic obstructive cardiomyopathy phenotype was observed after 3 months of treatment with corticosteroids (1–2 mg/kg/day) implemented for a concurrent chronic enteropathy. Myocardial thickening and moderate left ventricular outflow tract obstruction recurred after discontinuation of steroids. Again, resolution of the cardiac changes was observed after 1 month of treatment with tapering doses of corticosteroids (0.8–2 mg/kg/day). A second recurrence occurred when steroids were decreased to 0.25 mg/kg/day. Due to adverse effects, the dose was only increased to 0.4 mg/kg/day. During follow-up over the next 10 months, this treatment regimen resulted in stabilisation of the disease, with echocardiographic changes compatible with hypertrophic cardiomyopathy stage B1 and minimal left ventricular outflow tract obstruction.