11 year old Jack Russell Terrier

Diagnosis

Echocardiography – there was a large (at least 6 x 6 cm), lobulated mass in the left atrium that appeared to be arising from the left atrial lateral wall. It was causing marked left atrial enlargement. The mass did not appear to be arising from the interventricular septum. There was mitral regurgitation present. The left ventricle, right ventricle and right atrium were not enlarged. There was no tricuspid regurgitation, pulmonic or aortic stenosis present.

Assessment and recommendations – This is a large mass in an unusual location. Possible differential diagnosis include myxoma, myxosarcoma, ectopic thyroid carcinoma, fibroma(sarcoma), chondrosarcoma and leiomyosarcoma. There are limited treatment options available for any of these tumors in this location. The most definitive treatment would be attempted surgical removal with histology however this will require open heart surgery with cardiac bypass. The tumor is in a location where obstruction to pulmonary venous inflow may occur. If this occurs, congestive heart failure will result. Hence, owner monitoring of sleeping respiratory rate is advised. The tumor may also induced cardiac arrhythmias. There was no evidence of arrhythmia on physical examination today however, periodic reevaluation, especially if the syncopal episodes worsen is advised. Without surgical removal the prognosis is poor.