ABSTRACT
The pericardium forms a double-layered sac around the heart; it is attached to the great vessels at theheart base. Diseases involving the pericardium and intrapericardial space can disrupt normal cardiac function, most often by impairing cardiac filling. Clinical evidence of this occurs most often in dogs, subsequent to the development of cardiac tamponade. Pericardial effusion as a primary disorder is less common in cats and in horses, compared to dogs. Pericardial effusion accumulates with many cardiac tumors and it often causes cardiac tamponade. Mass lesions that involve the heart or heart base can obstruct venous return or impede ejection of blood from the right ventricle. Peritoneopericardial diaphragmatic hernia (PPDH) is the most common congenital pericardial malformation in dogs and cats. Abnormal embryonic development, probably of the septum transversum, allows persistent communication between the pericardial and peritoneal cavities at the ventral midline.
