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Hemangiosarcoma of the Dog's Heart (Heart Cancer in Dogs)


Hemangiosarcoma of the dog's heart is a serious and rapidly spreading type of cancer. This type of cancer, originates from the excessive and uncontrolled growth of special cells, called vascularendothelial cells, which line small blood vessels. The causes of hemangiosarcoma in dogs still remain poorly understood, although there are chances that genetics may play a role. Hemangiosarcoma of the dog's heart, just like other forms of hemangiosarcomas, spread rapidly and therefore require quick intervention.

Hemangiosarcomas in Dogs 


Hemangiosarcoma is composed by the word "hemo” from the Greek word “ haima" or "haimatos" meaning “blood" and the word "sarcoma" coming from the Greek word "sárx" meaning flesh and "oma" meaning process. Put the words together and you have a malignant disease process of vascular origin.

Hemangiosarcomas are tumors that grow rapidly, are invasive (spreading easily to other body parts) and fragile because they are prone to break easily and bleed profusely when they do. They can arise in several regions of the dog's body region, but mostly originate from the dog's skin (canine cutaneous hemangiosarcoma), spleen (canine splenic hemangiosarcoma) and heart (canine cardiac hemangiosarcoma).

The exact symptoms observed in dogs tend to vary, but ultimately depend on the site of the original tumor and where it has spread. Sometimes, the initial signs of hemangiosarcoma are misinterpreted for advanced age.

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Undiagnosed or left untreated, the cancer quickly progresses and some dogs may die suddenly as a result of massive internal bleeding. Unfortunately, hemangiosarcoma is a common type of cancer that is especially seen in large and giant dog breeds with golden retrievers, Labrador retrievers, German shepherds, English setters, boxers and Doberman pinschers commonly affected.

heart anatomy dog

Hemangiosarcoma of the Dog's Heart 

Canine cardiac hemangiosarcoma is one of the most common cancers affecting the dog's heart, representing 69 percent of all cardiac cancers. To be more exact, this cancer affects the right auricle of the heart - also know as the right atrial appendage (RAA) and the right atrium (RA). Occasionally, the cancer may be found in the dog's left-sided cardiac chambers.

Affected dogs typically develop pericardial effusion which is the presence of "fluid around the heart." This abnormal accumulation of fluid and/or blood quickly fills up the pericardial cavity, and because of limited space in this location, increased intrapericardial pressure has a negative impact on heart function (cardiac tamponade), potentially leading to heart failure.

This is an emergency situation considering its life threatening consequences. First aid for cardiac tamponade involves insertion of a needle through the dog's chest wall and then into the pericardium, (which is the sac surrounding the heart) to remove the excess fluid. The procedure is known as "pericardiocentesis."

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Symptoms suggestive of hemangiosarcoma of the dog's heart include loss of appetite, weight loss, lethargy, collapse, presence of fluids in the dog's abdomen, exercise intolerance, labored breathing, cold paws and cough. These symptoms often occur as the result of the pericardial effusion (PE), cardiac tamponade and right-sided heart failure.

At the Vet's Office

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Veterinarians will collect the history of the dog, carefully noting the symptoms. A physical examination may or may not reveal abnormalities related to this cancer such as pale gums (seen in anemic dogs), labored breathing, increased heart rate and muffled heart sounds revealed upon listening to the heart with a stethoscope.

Blood work may sometimes point to the presence of possible hemangiosarcoma. Affected dogs may show abnormally low levels of red blood cells (anemia), low levels of platelets (thrombocytopenia) and a higher than normal number of neutrophils (a type of white blood cell).

The preferred imaging strategy used to diagnose dogs with hemangiosarcoma of the dog's heart remains echocardiography (an ultrasound of the heart). Masses on the dog's heart via ultrasound are more easily detected when pericardial fluid is present.

Sadly, by the time of diagnosis, the cancer has already spread to other organs. With cardiac hemangiosarcoma, spread is most likely to manifest in the lungs (40 percent), spleen (27 percent), liver (27 percent), and kidneys (13 percent). Chest X-rays can help the vet determine whether the cancer has spread to the dog's lungs, while an ultrasound of the abdomen can help detect spread to the dog's liver and spleen.

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Treatment and Prognosis 

Treatment for hemangiosarcoma of the dog's heart may include surgery followed by chemo (in may cases, doxorubicin) or palliative treatment in advanced cases meant to provide measures of temporary relief.

Palliative care may include the use of medications (antibiotics, glucocorticoids, diuretics, digitalis and anti-arrhythmic drugs) along with repeated pericardiocentesis (removal of the excessive fluid that has accumulated in the sac of the heart).

When it comes to survival times, statistics from a study show that dogs undergoing surgery (pericardectomy and tumor resection) had significantly longer survival times, compared to dogs receiving no treatment or receiving medical management alone. Dogs undergoing surgery followed by chemo though had significantly longer survival times (mean survival time of 164 days) compared to dogs that did not receive chemotherapy after surgery (mean survival of 46 days).


  • The Journal of Veterinary Medical Science, Epidemiological, Clinical and Pathological Features of Primary Cardiac Hemangiosarcoma in Dogs: A Review of 51 Cases, Shinya Yamamoto et al, 013 Nov; 75(11): 1433–1441
  • DVM360: Pericardial effusion: causes and clinical outcomes in dogs (Proceedings)
  • Weisse C., Soares N., Beal M. W., Steffey M. A., Drobatz K. J., Henry C. J. 2005. Survival times in dogs with right atrial HS treated by means of surgical resection with or without adjuvant chemotherapy: 23 cases (1986–2000). J. Am. Vet. Med. Assoc.226: 575–579. doi: 10.2460/javma.2005.226.575

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