NAVLE（北美执业兽医考题）Day 584

A 11-year old male castrated Golden Retriever presents for collapse with muffled heart sounds on examination. You ultrasound the heart and obtain the following image; the right atrium (RA) and right ventricle (RV) are labeled. A large mass is seen in the right atrioventricular groove with pericardial effusion. What is the likely diagnosis?

一只11岁的雄性已绝育金毛犬由于昏厥和体格检查时心音不清前来就诊。你为其做了心超并且得到了以下的图像；右心房和右心室已标出。房室沟内可见一个巨大的肿块，伴随心包积液。可能的诊断是什么？