Discrete subaortic stenosis in Newfoundland dogs: association of infective endocarditis.

Necropsy findings are described in eight Newfoundland dogs from the same colony with discrete subaortic stenosis. Infective endocarditis involving the aortic valve occurred in four dogs and in each it proved fatal. Damage to the aortic valve cusps by the jet of blood ejected through the discretely narrowed left ventricular outflow tract predisposes to the development of infective endocarditis in both dogs and human beings with discrete subaortic stenosis. Severe abnormality of the intramural coronary arteries in the ventricular septum, which also occurs in patients with hypertrophic cardiomyopathy, was present in all eight dogs. Myocardial fiber disorganization and asymmetric septal hypertrophy, two other findings observed in patients with hypertrophic cardiomyopathy, were absent in each of the eight Newfoundland dogs with discrete subaortic stenosis.