Partial pericardial defect with left auricular herniation in a dog with syncope.

Pericardial defects are rare in both people and dogs. They may be congenital or acquired in origin, and partial or total in extent. Commonly, pericardial defects are incidental findings at autopsy; however, diagnostic methods such as thoracic radiography and echocardiography can be useful in the ante mortem diagnosis of pericardial defects. This report describes the first case of a dog with syncope, supraventricular tachycardia, and a partial left pericardial defect with herniation of the left auricle for which extensive ante mortem diagnostic information was available. Partial absence of the pericardium should be considered in dogs with disproportionate enlargement of cardiac chambers for which other congenital and acquired heart diseases are ruled out.