Tumors in the heart are fairly rare in dogs, and even rarer in cats. As with most cancers, these tumors occur in older pets, and there is some evidence that German Shepherds and Golden Retrievers are at increased risk.

Heart tumors can arise directly from heart tissue, or can spread from other locations via metastasis. The most common heart tumors are hemangiosarcomas, which arise from abnormal growth of blood vessels. Hemangiosarcomas are most commonly located in the right atrium, and they tend to bleed into the pericardium  (the sac surrounding the heart). This sac fills with fluid (a condition known as tamponade) and constricts the heart, interfering with the ability of the heart to pump the blood effectively to the rest of the body. Heart tumors can also weaken the heart muscle or interfere with conduction of the electrical impulses that maintain normal heart rhythm, leading to potentially dangerous arrhythmias.

Dogs with heart tumors tend to show signs of weakness, fatigue, or lethargy, as a result of diminished heart function. Affected dogs may collapse and die suddenly from ruptured blood vessels or serious arrhythmia. Diagnosis is usually based on history, physical exam, chest x-rays, and/or ultrasound. Dogs with heart tumors often have muffled heart sounds (because of the pericardial fluid surrounding the heart) and a weak, rapid pulse. X-ray or ultrasound images often show an enlarged and/or rounded heart silhouette. Your veterinarian may recommend an electrocardiogram to look for conduction problems in the heart, and possibly aspirating some fluid from the pericardial sac to examine its composition and characteristics. Additional tests (e.g., blood work) may be necessary in order to rule out other illnesses.

Some heart tumors can be surgically removed, while others respond to chemotherapy. These treatments require specialized expertise, and your vet may refer you to a veterinary teaching hospital or specialty practice. Draining fluid from the pericardial sac can provide temporary relief of symptoms, and drugs can be used to address arrhythmias. However, the prognosis is guarded, and heart tumors are often fatal.

Q&A

Can dogs and cats get tumors of the heart?

Yes, but heart-based tumors are rare in dogs, and even rarer in cats. These tumors can arise directly from heart tissue, or can travel to the heart from other locations in the body.

What are the signs of heart tumors?

Dogs with heart tumors are usually tired and weak from diminished heart function. They may also collapse and die suddenly.

How are heart tumors diagnosed?

Diagnosis is usually based on history, physical exam, chest x-rays, and/or ultrasound. Your vet may also wish to aspirate some fluid from the sac surrounding the heart to examine its composition and characteristics.  

How are heart tumors treated?

Some heart tumors can be surgically removed, while others respond to chemotherapy. Draining fluid from the sac surrounding the heart can provide temporary relief of symptoms. However, the prognosis is guarded, and this condition is often fatal.

Written and reviewed by John A. Bukowski, DVM, MPH, PhD
and Susan E. Aiello, DVM, ELS