Unusual Presentation of Aortic Valve Infective Endocarditis in a Dog: Aorto-Cavitary Fistula, Tricuspid Valve Endocarditis, and Third-Degree Atrioventricular Block

SIMPLE SUMMARY: In dogs, infective endocarditis represents a rare but clinically relevant disease that typically involves the aortic and/or mitral valve. Transthoracic echocardiography plays an essential role in the diagnosis, prognosis, and monitoring of such a condition. Typical echocardiographic signs of disease progression include left-sided cardiac dilatation and extension of aortic and/or mitral vegetative lesions. Nevertheless, unexpected complications can sometimes develop, especially in the case of the erosion of the periannular tissue caused by lytic enzymes produced by bacteria. This case report describes the coexistence of multiple, uncommon complications of aortic valve infective endocarditis in a dog, namely, aorto-cavitary fistula, tricuspid valve endocarditis and third-degree atrioventricular block. In this study, the combination of the ante mortem (clinical and echocardiographic) and post mortem (gross pathology and histopathology) findings allowed us to gain detailed information on the disease process, its atypical complications, and the associated emodynamic consequences. ABSTRACT: A 2-year-old Boxer with a history of subaortic stenosis and immunosuppressant therapy developed aortic valve infective endocarditis. On echocardiographic examination with simultaneous electrocardiographic tracing, multiple uncommon periannular complications of the aortic valve endocarditis were found, including aorto-cavitary fistula with diastolic left-to-right shunt, tricuspid valve endocarditis, and third-degree atrioventricular block. Necropsy confirmed the above echocardiographic findings. Although aortic valve endocarditis represents a well-known disease entity in dogs, the dynamic nature of this condition may allow development of complex and uncommon echocardiographic features.