Heart Tumors in Dogs

Tumors may develop in or around the heart, arising either directly from the heart tissue or spreading from another part of the body. Hemangiosarcoma is the most common form of heart tumor found in dogs, although it is rare overall. Large breed dogs like the Golden Retriever are more prone to the condition. The prognosis for dogs with hemangiosarcoma is poor, but prompt surgical treatment prior to metastasis may increase your dog’s odds of survival.

Hemangiosarcoma is rare but aggressive and is the most common type of heart tumor found in dogs. Tumors affect the heart’s ability to pump blood, which leads to weakness and lethargy. If hemangiosarcoma is left untreated, the tumor may rupture, filling the sac around the heart with blood and resulting in sudden collapse.

Some dogs with heart tumors show mild to no clinical signs while others may have more severe symptoms depending on the extent of the cancer. Symptoms are primarily nonspecific and include:

• Lethargy
• Difficulty breathing
• Weakness
• Pain
• Collapse

Symptoms that relate to the heart and may correlate to the tumor, versus the tumor itself:

• Loss of coordination
• Loss of appetite, disinterest in treats or snacks
• Accumulation of fluid within the chest cavity, abdominal cavity, or visible abdomen stretching
• Weight loss

Types

Heart tumors may arise from heart tissue or may metastasize from other areas of the body. The most common type of heart tumors are hemangiosarcomas, which typically involve the right side of the heart. Other types include:

Much as with other cancer types, there is currently no known cause for heart tumors in dogs. There is a predisposition in certain large breed dogs, such as German Shepherds, Golden Retrievers, and Labrador Retrievers, but heart tumors may develop in any dog. The condition typically affects middle-aged to older dogs.

As with any veterinarian visit, it's especially important to provide the veterinarian a thorough history of your dog's recent health. This should include behavioral changes, accidents (interaction with wildlife, sprained leg, getting into the pantry), living patterns, and any illnesses that may have gone unreported.

Because heart tumors are not detectable on the surface, asymptomatic dogs are usually diagnosed when they receive radiographs as part of the diagnostic process for another condition. However, if your dog is exhibiting unusual behavior or general weakness, the veterinarian will conduct basic tests as part of the initial examination. These may include blood work and a urinalysis, along with an electrocardiogram if the veterinarian suspects heart problems.

Heart tumors are typically diagnosed through a combination of history, physical findings, and clinical laboratory analysis. The presence of the tumor can be confirmed with a chest radiograph or with echocardiography, which uses sound waves to create an image of the heart. Depending on the location and extent of the heart tumor, the veterinarian may recommend further testing to support the diagnosis of heart tumors and to discover if metastasis is present. These tests include a complete blood count and biochemistry profile, cytological analysis, imaging, and analysis of fluids withdrawn from the abdomen. If the veterinarian encounters a particularly interesting, rare, or developed case, she may refer you to a specialized cancer doctor, or oncologist. 

Treatment plans will vary depending on the location of the tumor, the extent of metastasis, and the overall condition of your dog. Hemangiosarcoma carries a poor prognosis if left untreated, as the tumor may lead to bleeding below the pericardium, which is a thin membrane that encloses the heart. This places additional pressure on the heart and may prevent it from pumping blood. As part of treatment, the veterinarian may need to drain the blood from beneath the pericardium so that the heart can resume to its normal function.

Surgery and chemotherapy are both potential options for treating a heart tumor. In either case, the veterinarian will most likely refer you to a specialist to address the condition. Surgical treatment is not usually recommended, especially with hemangiosarcoma, as the tumors will most likely have metastasized by the time of diagnosis. However, if the tumor is small and has not yet spread, surgery may be able to remove it completely.

Chemotherapy can control the tumor’s growth and limit metastasis, and certain types of heart tumors may respond to the medication.

If your dog underwent surgery successfully, you should now focus on providing a safe, quiet place where he or she can recover. Limit physical activity, and inspect the surgical site daily for signs of infection.

Following either surgery or chemotherapy, the veterinarian will need to examine your dog again in order to ensure that the tumors are either gone or are under control. Unfortunately, heart tumors can be aggressive, and hemangiosarcoma is not often curable. Most dogs with hemangiosarcoma do not live long even with treatment. If your dog is diagnosed with hemangiosarcoma, you may wish to focus on maintaining your dog’s quality of life with advice from the veterinarian.