Heart Cancer (Hemagiosarcoma) in Cats

Hemangisaroma of the Heart in Cats

A hemangiosarcoma of the heart is a tumor that originates in the blood vessels that line the heart. Hemangio refers to the blood vessels and sarcoma a type of aggressive, malignant cancer that arises from the connective tissues of the body. A hemangiosarcoma may originate in the heart, or it may have metastasized to the heart from another location in the body.

This tumor often will go undetected until complications arise. Because a hemangiosarcoma arises from the blood vessels, when it reaches an unsustainable size it will burst, often resulting in life threatening internal bleeding. Other typical symptoms relate to the size of the tumor interfering with the heart’s ability to function. The pumping of blood into or out of the heart organ may be blocked or slowed, resulting in an irregular heart rhythm; the pericardial sac that surrounds the heart may become filled with blood due to burst vessels, or with fluid that places restrictive pressure on the heart; or there may be a responsive abdominal swelling that puts pressure on the heart and other organs. In addition, the blood loss may lead to a regenerative anemia, with concurrent symptoms that can confound the initial diagnosis.

Symptoms and Types

Most symptoms are seen related to complications affecting heart rather than tumor itself.

  • Difficult breathing
  • Accumulation of fluid within abdominal cavity – visible abdominal distention
  • Accumulation of fluid within thoracic (chest) cavity
  • Sudden loss of consciousness/fainting (syncope)
  • Inability to perform routine exercises
  • Trouble with coordination (ataxia)
  • Irregular heart beats/arrhythmia
  • Enlargement of the liver
  • Lethargy
  • Malaise/depression
  • Loss of appetite (anorexia)
  • Weight loss


The exact cause is still unknown.


You will need to give your veterinarian a thorough history of your cat’s health, onset of symptoms, and any incidents of ill health, behavioral changes, or accidents that have recently taken place. The history you provide may give your veterinarian clues as to which organs are being primarily affected and which organs are being affected secondarily. Your cat’s age, breed, and the outward symptoms that are presenting will be the initial signals for a rough diagnosis.

Routine laboratory tests include a complete blood count, biochemistry profile, and urinalysis. The blood tests may reveal anemia, as often the blood loss will lead to a state of regenerative anemia, where the body is lacking in sufficient red blood cells, but is still capable of producing more of them – though it may not be able to keep with the demand.

Your veterinarian will want to take fluid samples from both the abdomen and the chest, by abdominocentesis and pericardiocentesis respectively, for cytological analysis. This can also be used to remove excess fluid so that your cat is more comfortable. Blood found in the fluid sample is a frequent sign of hemangiosarcoma, and failure of clotting in the blood when it is drawn is another telling indication, since the body is working hard to maintain its blood balance and is using the blood clotting factors too rapidly.

An electrocardiogram (ECG, or EKG) recording can be used to examine the electrical currents in the heart muscles, and may reveal any abnormalities in cardiac electrical conduction (which underlies the heart’s ability to contract/beat). Your veterinarian may also need to take a surgical tissue sample of the mass for examination (biopsy).

Visual diagnostic methods, such as x-rays and ultrasound of the thoracic (chest) and abdominal cavities may reveal variations in cardiac size and structure. Echocardiography is the most valuable tool for making accurate diagnosis. It will confirm the presence of fluid, structural abnormalities in the heart, the presence of a tumor mass or clot, and other aspects of tumors within the heart.


The prediction of a disease’s outcome in advance


The term for the membrane around the heart


A type of neoplasm that occurs in connective tissue


Fainting; the respiratory and circulatory systems are suspended for a time


An in-depth examination of the properties of urine; used to determine the presence or absence of illness


Pertaining to the chest


A tumor made up vascular tissue


A medical condition in which an animal is unable to control the movements of their muscles; may result in collapse or stumbling.


A condition of the blood in which normal red blood cell counts or hemoglobin are lacking.


Abdominocentesis is a procedure in which a needle is inserted into the abdomen of the animal to remove fluid. In most cases, abdominocentesis is used to make a diagnosis of some sort in a sick animal.


The process of removing tissue to examine it, usually for medical reasons.


The process of making something larger by dilating or stretching it

abdominal cavity

The space in the abdomen that holds the major digestive organs in an animal. Normally referred to as the area between the diaphragm and the pelvis. Also referred to as the peritoneal cavity.


A record of the activity of the myocardium


Something that becomes worse or life threatening as it spreads

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