Acquired aortic and mitral stenosis characterized by valvular fibroelastosis in a dog

Left-sided congestive heart failure was diagnosed in a 2.6-kg 13-year-old neutered male Yorkshire terrier by compatible clinical signs and findings on thoracic radiographs. Echocardiography revealed left atrium enlargement, left ventricular concentric hypertrophy, and thickening and stenosis of the mitral and aortic valves (AVs). A hypercoagulable state, chronic kidney disease, and a portal vein thrombus were identified. Medical management and balloon valvuloplasty of the AV provided good quality of life for nine months since diagnosis, but ultimately, recurrent episodes of pulmonary oedema and acute kidney injury led to attempted mitral balloon valvuloplasty which resulted in cardiac arrest and death. Postmortem examination revealed thickening of the mitral and aortic leaflets with loss of normal stratification and the presence of large areas of fibroelastic tissue and accumulation of myxoid tissue. Hypertrophy of cardiomyocytes was also observed and was considered secondary to aortic stenosis and not due to primary myocardial disease. Histopathological examination revealed fibroelastic changes affecting both the mitral valve and AV leaflets. These findings were considered atypical for more common forms of acquired valvular disease. This case report describes the clinical presentation, diagnostic approach, interventional management, and pathological features of an unusual case of acquired combined aortic and mitral stenosis in a dog and discusses similarities and differences with other conditions associated with comparable valvular abnormalities.