Types of Heart Tumors in Dogs
Heart tumors are quite rare in dogs. These abnormal growths may develop in and around the heart or they may be a result of a metastasis of a tumor from another part of the body. There are many types of cardiac tumors, but the most common types include hemangiosarcomas (HSA), aortic body tumors (chemodectoma and paraganglioma), and lymphoma. Keep reading to learn more about heart tumors in dogs, including symptoms, causes, and treatment options.
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Symptoms of Heart Tumors in Dogs
Although heart tumors in dogs are rare, they can cause life-threatening complications including obstruction of blood flow, pericardial effusion, congestive heart failure, and arrhythmias. These tumors can interfere with the normal function of the heart or cause bleeding into the pericardial sac. When normal heart function is compromised, it will eventually lead to poor circulation in the body and heart failure.
In most cases of heart tumors, the symptoms exhibited by affected dogs are mostly non-specific. The most common signs reported by dog owners include:
- Loss of appetite
- Neurologic signs
- Difficulty breathing
- Pot-bellied appearance
These symptoms are generally associated with heart failure which is often the result of a heart tumor.
Causes of Heart Tumors in Dogs
Heart tumors are classified as either primary or secondary, and benign or malignant. Cardiac tumors arise from heart tissues (primary tumors) or metastasize to the heart from another location (secondary tumors). In dogs, these tumors are typically primary and malignant.
This is a highly malignant tumor of the blood vessels. The tumor usually arises in the wall of the right atrium - the upper chamber on the right side of the heart. The presence of the tumor can damage the atrial wall and may lead to bleeding into the pericardium (pericardial effusion). Hemangiosarcomas are common in Golden Retrievers and German Shepherds.
Aortic Body Tumor
Next to hemangiosarcoma, the most common heart tumor in dogs is chemodectoma (also known as a neuroendocrine tumor, chromaffin cell tumor, aortic body tumor, and carotid body tumor).
Chemodectas (heart base tumors) are slow-growing and most don’t cause any problems until they grow big enough to interfere with the blood supply to the sac surrounding the heart (pericardial sac or pericardium). Although they are the second most common cardiac tumor in dogs, they are 10 times less common than hemangiosarcomas. The English Bulldog, Boxer, and Boston Terrier breeds develop these tumors most frequently, usually between 6 and 15 years of age.
These are small tumors that spread over the sac that surrounds the heart (pericardium) and chest wall. Mesotheliomas can cause the buildup of extra fluid around the heart (pericardial effusion) which can exert pressure on the heart. This can be lethal to dogs.
Other cardiac tumors that can occur in dogs include lymphosarcomas, fibrosarcomas, and rhabdomyosarcomas. These tumors can invade the heart’s muscular wall and decrease its ability to contract. Heart valves can also be affected which causes them to leak; this can eventually lead to heart failure.
Are some dog breeds more at risk for heart tumors?
While dogs of any age, gender, or breed can develop cardiac tumors, the following breeds have been reported to have higher heart tumor incidence:
- Golden retriever
- Afghan hound
- Irish water spaniel
- English setter
- French bulldog
- Scottish terrier
- Boston terrier
- Flat-coated retriever
- German shepherd
Diagnosing Heart Tumors in Dogs
Diagnosis of heart tumors in dogs is based on a combination of history, findings during the physical exam, and analysis of the clinical laboratory results.
At the veterinary clinic, your dog will undergo a thorough physical exam. Blood work will also be performed to determine baseline figures. This will include a complete blood count (CBC), biochemical blood profile, electrolyte panel, and urinalysis.
When a heart tumor is suspected by your veterinarian, several diagnostic procedures will be performed to allow visual examination of the heart. The first one is a chest x-ray. If the x-ray result shows an enlarged heart, an echocardiogram (ultrasound of the heart) and an electrocardiogram (ECG) are performed to determine if there are abnormalities in the conduction of electrical current in the heart muscles (which is responsible for heart contraction and beating).
An echocardiogram can also detect the presence of a tumor and its effects on heart structure and function. If a tumor is present, your vet may take a tissue sample for biopsy.
Laboratory tests and ultrasound of the abdomen are done to check for any signs of metastasis and if there are any effects on other systems of the body.
Depending on the results of these tests and procedures, additional tests may be indicated to arrive at a definite diagnosis.
Treatment Options for Dogs with Heart Tumors
Treatment of the tumor depends on the tumor type and may involve removal of the pericardial sac and chemotherapy. Surgical resection remains to be the recommended treatment of choice for most types of heart tumors in dogs. Regardless of whether the tumor is malignant or not, the procedure may be curative.
Surgical resection is curative for benign tumors. If the heart tumor is malignant, chemotherapy can also be administered. Dogs with heart base tumors benefit from the removal of the pericardial sac because these tumors grow very slowly. Unfortunately, even with treatment, many dogs with malignant heart tumors die.
Your veterinarian will advise you on the frequency of recheck visits and testing based on the chosen treatment protocol.
Dogs with hemangiosarcoma in the right atrium have a survival time that ranges from 0 to 229 days (average = 56 days).
For dogs with heart-based tumors, a retrospective study showed that the survival time ranged from 0 to 1,096 days (with an average of 213 days). Dogs that underwent pericardectomy (removal of a portion or all of the pericardial sac) had a significantly longer mean survival time (661 +/- 170 days) compared to dogs that were on medical treatment only.
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