Congenital supravalvular mitral stenosis in 14 cats.

Objectives: To describe the clinical features of congenital supravalvular mitral stenosis (SVMS) in cats.

Background: Supravalvular mitral stenosis is an uncommon congenital cardiac defect that has not been previously reported in a series of cats.

Animals: 14 cats with SVMS.

Methods: Medical records, relevant diagnostic studies and preserved pathology specimens were reviewed.

Results: Cats were presented over a wide age range (5 months-10 years; median 3 years); males (n = 9) and the Siamese breed were over-represented. Presenting complaints included respiratory distress (n = 6), hindlimb paralysis due to aortic thromboembolism (n = 5) and asymptomatic heart murmur (n = 3). Echocardiographic examination often identified pulmonary hypertension (PHT) (n = 7) and concurrent cardiac abnormalities (n = 7), especially partial atrioventricular septal defect (PAVSD) (n = 4). Status 12 months following diagnosis was known for 9 cats; 8 of these had died or were euthanized.

Conclusions: Cats with SVMS are usually presented as young adults for respiratory signs attributable to congestive heart failure, aortic thromboembolism or incidental murmur identification. Congestive heart failure, PHT and concurrent congenital cardiac abnormalities (specifically PAVSD) are common. Long-term prognosis for symptomatic cats is poor.