Pericardial effusion is often idiopathic, neoplastic, or hemorrhagic in origin. Right atrial tumors are the most common cause of pericardial effusion of neoplastic origin. The vast majority of right atrial tumors are hemangiosarcomas.^1-3 Other tumors include mesothelioma of the pericardium and heart-base tumor. Golden retrievers and Labrador retrievers are the two most common breeds reported with this condition.^4-7 Other causes of pericardial effusion include bacterial pericarditis, heart failure, clotting disorders, and uremic pericarditis.⁸

The increased pressure in the pericardial sac causes tamponade, which restricts the expansion of the ventricles. The right ventricle has a thinner myocardial wall; it is therefore more vulnerable, leading to the onset of right heart failure in the majority of cases.⁹

Symptoms vary from one individual to another and can include lethargy (75%), ascites (69%), dyspnea (55%), anorexia (53%), syncope (24%), and coughing (20%). These signs are usually associated with muffled heart sounds. Pericardial effusion, especially if rapidly increasing, is life threatening.¹⁰

Because masses originating on the right atrium are almost exclusively hemangiosarcomas, they carry a very poor prognosis.^1-3 Surgical resection does not prolong survival because most of those tumors have metastasized at the time of diagnosis. However, it can help palliate the risk of acute hemorrhage; clinical signs of pericardial effusion, and cardiac tamponade.

Echocardiography is the most effective imaging technique for the diagnosis of pericardial effusion. It is a valuable tool to differentiate among heart-base tumor, right atrial masses, and idiopathic pericardial effusion. The specificity and sensitivity of the examination are good for the detection of atrial masses (82% and 99%, respectively).^11,12 However, echocardiography does not allow a histologic diagnosis. Also, it is difficult to determine from echocardiography if surgical resection of the mass is technically possible.¹⁰

Advanced imaging techniques, in particular magnetic resonance imaging, have been advocated as diagnostic tools but have not yet proven superior to echocardiography in determination of neoplastic versus non-neoplastic origin of pericardial effusion.¹³

Abdominal ultrasonography is indicated to look for the presence of suspected hemangiosarcoma, particularly in the spleen.

Fluid analysis of pericardial effusion, including measurement of the pH and cytologic examination, rarely provides any certainty regarding the neoplastic or idiopathic nature of the effusion.¹⁴

Echocardiography does not allow evaluation of the margin and cannot demonstrate if the tumor is resectable or not with video-assisted thoracoscopic surgery (VATS) or thoracotomy. Therefore, VATS and pericardioscopy is becoming a diagnostic tool for improved decision making.