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Heart Cancer (Hemagiosarcoma) in Dogs

4 min read

Hemangisaroma of the Heart in Dogs


Where 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 of the heart is a tumor that originates in the blood vessels that line the heart. This is the most common cardiac tumor seen in dogs. A hemangiosarcoma may originate in the heart, or it may have metastasized to the heart from another location in the body. It is most commonly reported in mid to large size breeds, such as boxers, German shepherds and golden retrievers, and in older dogs – six years and older.


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 dog'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 dog'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 dog 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.




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