Heart disease changes in Irish wolfhounds with atrial fibrillation

Abstract

OBJECTIVES: To evaluate gross and histopathologic lesions in Irish wolfhounds (IWs) with atrial fibrillation (AF) and/or primary dilated cardiomyopathy (DCM) in different stages of disease. METHODS: Twenty-six formalin-fixed IW hearts were studied. Clinical diagnosis was based upon results of their most recent cardiovascular examinations including electrocardiography and echocardiography and categorized as normal (n = 4); preclinical (asymptomatic) DCM with AF (n = 6); DCM with congestive heart failure and AF (n = 4); AF with left ventricular reverse remodeling after DCM diagnosis (n = 3); AF without DCM (n = 7); and DCM with sinus rhythm (n = 2). All hearts were evaluated by one pathologist (HA) blinded to the clinical diagnosis. RESULTS: Ten of 15 DCM hearts showed mild to moderate multifocal myocardial fibrosis with variable diffuse adipocyte infiltration within the left and right ventricular myocardium. In five DCM hearts, there were no histopathological findings identified. Right atrial appendages from AF dogs with and without DCM had significantly more myocardial fibrosis and adipocyte infiltration compared with normal hearts and compared to left atrial appendages. CONCLUSIONS: Gross and histological findings in the ventricular myocardium of IWs with clinical diagnosis of DCM were variable; in some dogs, histopathology was normal. In IWs, the etiology of DCM might be different from that in other breeds with conditions causing functional impairment rather than evident histological changes. Right and left atrial appendages from IWs with AF displayed substantial pathology (interstitial fibrosis and adipocytes) most prevalent in the right atrial appendages which may be correlated to the pathogenesis of AF. These preliminary findings merit further study.