ABSTRACT
OBJECTIVES: Right atrial aneurysms have been reported in bovine species, but a clear aetiopathogenesis has never been elucidated. ANIMALS: One thousand and seventy-nine veal calves (6-9 months old) and 313 beef cattle (10-24 months old) housed in intensive livestock farming systems and regularly slaughtered were included in the present study. METHODS: Hearts were externally examined and the identified right atrial aneurysms were submitted for gross and histopathological investigations. RESULTS: Right atrial aneurysms, which involved the right auricle, were detected in both veal calves (4.63%) and beef cattle (8.63%). Two types of aneurysms were observed: one type showing communications with the atrial lumen, the other one having no connections with it. Aneurysms communicating with the atrial lumen were characterized by endocardial fibrosis, whereas the other ones showed arterial characteristics (intimal fibromuscular hyperplasia and medial elastic fibre and fibrous tissue deposition). CONCLUSIONS: Considering the similarities with the right atrial aneurysms reported in people, the aneurysms communicating with the atrial lumen were considered to be caused by an inherent atrial weakness (so called 'loci minoris resistentiae' areas). On the contrary, the aneurysms with no communications with the atrial lumen, whose localization suggested an origin from the intramural coronary arteries of the pectinate muscles, may be subsequent to systemic hypertension due to intensive livestock farming conditions.
