Hypertrophic cardiomyopathy in an aged dog.

A 14-year-old female Yorkshire terrier was presented with the complaint of cardiac murmur and convulsive seizure. Thickened mitral valve, left atrial enlargement, excess motions of the left ventricular (LV) free wall and the ventricular septum, and tricuspid, mitral and aortic valve regurgitations were recognized on echocardiography. Follow-up echocardiography revealed the progression of concentric LV hypertrophy and LV outflow obstruction. Clinical symptoms associated with cardiac failure did not develop during the observation period. The pathological examination of the heart revealed that the dog had the morphological hallmarks of hypertrophic cardiomyopathy: massive ventricular hypertrophy, disorganization of cardiac muscle cells, interstitial myocardial fibrosis, and abnormal intramural coronary arteries.