Surgical correction of left auricular aneurysm herniation through a pericardial defect in a dog with atrial fibrillation and mitral valve disease

Pericardial defect is a rare condition, with risk of cardiac chamber strangulation or incarceration. Surgical correction is recommended when clinical signs are unmanageable and to decrease the risk of thromboemboli. A 15-year-old, 4.1-kg, spayed female Shih Tzu dog presented to the hospital with a 6-month history of weakness and syncope episodes. The dog had been diagnosed with degenerative mitral valve disease 9 years earlier. Thoracic radiographs, echocardiography and computed tomography indicated a left auricular herniation through a pericardial defect. Clinical signs were temporarily controlled with pimobendan, benazepril and clopidogrel, until the syncope episodes returned along with atrial fibrillation (unresponsive to oral digoxin). Surgical correction (auriculectomy and partial pericardiectomy) was performed via thoracotomy. Atrial fibrillation reverted to normal sinus rhythm following surgery and recovery was uneventful. The patient survived, arrhythmia-free, for 25 months postoperatively. Syncope episodes never resolved.