Heart Sac Inflammation (Pericarditis) in Dogs

By PetMD Editorial on Sep. 24, 2008

Pericarditis in Dogs

Pericarditis describes a condition where the dog's pericardium becomes inflamed. The pericardium is made up of two layers: a fibrous outer layer and a membranous inner layer that adheres closely to the heart. Within the sac is a layer of pericardial fluid made up of serum, a watery fluid that serves to keep the surfaces of the membranous sac and heart moist. The body's membranes will also secrete serum when they detect inflammation of the surrounding tissues and organs.

When either of the layers of the pericardium becomes inflamed, the natural reaction is for the membranes to produce more serum, which leads to an excess of serum in the pericardium. The buildup of fluid compresses the heart, placing too much pressure on it, and on the surrounding tissue, typically leading to more inflammation and further swelling.

Pericarditis can affect both dogs and cats. If you would like to learn more about how this disease affects cats, please visit this page in the PetMD health library.

Symptoms and Types

Right-sided congestive heart failure is the usual outcome of pericarditis. Other symptoms include:

  • Anorexia
  • Lethargy
  • Fluid buildup in the abdomen
  • Difficulty breathing
  • Weak pulse
  • Increased heart rate
  • Collapse

Dogs will usually progress to a hemorrhagic pericarditis (blood in the heart sac), which can lead to a life-threatening buildup of fluid in the heart sac, and tamponade (compression of the heart by the fluid in the heart sac). Hemorrhagic pericarditis is seen in medium to large-breed dogs that are young to middle-aged.


May be diagnosed as idiopathic or agnogenic (meaning that it is not related to anything in particular, and is of unknown cause). The only apparent problem may be that there is excess fluid buildup, with seemingly nothing else to explain the disease.

  1. Blunt or penetrating trauma
  2. Bacterial infection:
    • Tuberculosis: a mycobacterial disease that affects the lungs
    • Nocardiosis: infection that causes lesions on the lungs; may spread to other parts of the body
    • Pasteurella spp.: infection of the respiratory tract
    • Actinomycosis: invasion that causes lumpy tumors in the neck, chest, abdomen, and around the face and mouth; also called "lumpy jaw"
  3. Fungal infection:
    • Coccidioidomycosis: fever, red bumps on skin, and respiratory infection; common in hot, dry climates


Your veterinarian will perform a thorough physical exam on your dog, including a blood chemical profile, a complete blood count, a urinalysis, and an electrolyte panel to look for an underlying cause, or systemic illness. If bacterial based pericarditis is suspected, your veterinarian will take a fluid sample of the pericardial effusion for aerobic and anaerobic culture. That is, examination of tissue that lives with oxygen, and tissue that lives without oxygen.

Thoracic radiograph images (chest X-rays), and echocardiogram images are essential for an accurate visual diagnosis. Other, less sensitive tests which might still supply useful information about the heart are cardiac catheterization, where a tube is inserted into an artery or vein in the arm or leg, and then threaded up into the chambers of the heart; and electrocardiogram, which records the heart's electrical muscle activity. Both tests measure functionality: blood pressure and flow, rhythm, and how well the heart muscle is pumping.


Treatment will depend on the underlying cause of the pericarditis. All dogs with this disease will need to be hospitalized in an intensive care unit. Chemotherapy will be prescribed if there are cancerous neoplastic (abnormal tissue growth) conditions, and bacterial infections will be treated with the appropriate antibiotics. A pericardectomy surgery to remove part of the pericardium may also be necessary.

Living and Management

This condition will sometimes reoccur. If signs of illness return at anytime after taking your dog home, call your veterinarian immediately for advisement.

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