The pericardium is a thin membrane that follows the contour of the heart and forms a sac-like structure. Most of the time, the sac is empty and the membrane serves as a lubricated surface inside which the heart can easily move. When fluid collects in that sac, the fluid is called pericardial effusion, which ultimately leads to cardiac tamponade. During cardiac tamponade, the fluid puts pressure on the heart to the point that the heart’s chambers cannot expand to fill with blood. If they cannot fill with blood, the heart cannot pump blood to the rest of the body.
The most common causes for pericardial effusion include bleeding from a heart base or right atrial tumor or idiopathic. Causes related to the abnormal growth of tissue (as found in hemangiosarcoma, mesothelioma, and, less commonly, lymphoma are also common. Other less common causes include: bleeding disorders; bacterial or viral infections; heart failure; low blood protein levels; or other ill-defined causes. Due to the impact on the heart, cases of pericardial effusion are often emergencies.
An echocardiogram is the best way to diagnose pericardial effusion and will show build up of fluid in the pericardial sac or indicate that the walls of the heart are moving abnormally (cardiac tamponade). Abnormal heart rhythms may be visible on an electrocardiogram.
Thoracic radiographs of the chest may show a very large, round heart; however, if the fluid accumulates rapidly, the size of the heart may be normal on the radiographs, at least initially. Abdominal ultrasound, blood work, including a complete blood count serum chemistry profile, and urinalysis may be needed to look for signs of underlying diseases processes.
Your pet may exhibit weakness, tiredness, intolerance to exercise, and decreased appetite. Other gastrointestinal signs such as gagging or vomiting may be present. Ascites, episodes of collapse, or difficulty breathing may also be present.
In a patient experiencing significant pericardial effusion and for emergency treatment, removing even a small amount of fluid with a needle or catheter relieves the pressure around the heart, which usually makes the patient feel much better. The benefits gained from performing pericardiocentisis usually outweigh the potential complications. This procedure is performed under local anesthesia on an outpatient basis. The fluid is often sent out for analysis to provide insight into the cause of this condition.
Prognosis varies depending on the underlying cause. Pericardial effusion may re-accumulate over a period of hours to months. The course of continued treatment of pericardial effusion largely depends on the cause. For patients with idiopathic pericardial effusion or sometimes those with pericardial effusion secondary to certain heart base tumors, surgical removal of a portion of the pericardium may be recommended. This allows the fluid that would be trapped within the pericardium to drain into the larger space of the chest cavity, and then be absorbed. In these cases, removal of a portion of the pericardium can offer a good prognosis. For patients with pericardial effusion secondary to a right atrial tumor, surgical removal of the pericardium is not recommended.
For these patients, periodic pericardiocentisis can be performed as needed for as long as the patient can maintain a good quality of life at home. On average, patients with right atrial tumors have a survival time of 2-4 months following diagnosis.
Idiopathic Pericardial Effusion: The underlying cause of this disease process is unknown. If the pericardial effusion keeps happening, then removing part of the pericardium may be necessary to eliminate the symptoms associated with this disease.
Hemangiosarcoma: This is a tumor typically associated with the heart’s right atrium/auricle. It is a fast growing tumor that metastasizes rapidly. If the tumor is surgically removable, then the best treatment option includes surgical removal of the tumor followed by chemotherapy. Chemotherapy alone, without removal of part of the pericardium, may decrease the tumor growth rate and effusion rate. Overall, the prognosis is poor.
Chemodectoma: This tumor is slow growing and slow to spread. Brachycephalic breed dogs are the breeds who most commonly have this tumor type.