Overview

• A highly metastatic malignant tumor of the vascular endothelium.
• The most common cardiac tumor in dogs.
• Can be a primary or metastatic site.
• Most tumors involve the right atrium or right auricular appendage.
• Metastasis can be multi-organ including lungs, kidneys, muscle, peritoneum, etc.

Signalment

• Dog and rarely cat.
• German shepherds, Labrador retrievers, golden retrievers predisposed.
• Typically middle-aged to older animals.
• Possible slight predisposition for male dogs.

Signs

• Signs most commonly related to pericardial effusion, cardiac tamponade, and right-sided congestive heart failure.
• Historical findings-include collapse, lethargy, weakness, anorexia, cough, dyspnea, vomiting, and exercise intolerance.
• Physical examination findings-include muffled heart and lung sounds, arrhythmias, pulse deficits, pulsus paradoxus, jugular vein distention, and hepatomegaly.

Causes & Risk Factors

• Dogs-genetic abnormalities including overexpression of the oncoprotein STAT3, mutations within tumor suppressor genes p53 and PTEN, and overexpression of angiogenic factors such as vascular endothelial growth factor and angiopoietins.
• Cats-none identified.

Differential Diagnosis

• Other cardiac neoplasia
• Idiopathic hemorrhagic pericardial effusion
• Other causes of right heart failure or arrhythmias

CBC/Biochemistry/Urinalysis

• Regenerative anemia
• Thrombocytopenia
• Poikilocytosis-acanthocytes, schistocytes, spherocytes
• Leukocytosis characterized by mature neutrophilia

Other Laboratory Tests

Coagulation panel (PT, PTT, D-dimers, fibrinogen)-criteria for DIC present in up to 50% of patients.

Imaging

• Radiography-thoracic radiographs may reveal the presence of a globoid cardiac silhouette, pleural effusion, and pulmonary metastasis.
• Ultrasonography-abdominal ultrasonography can be used to screen for visceral metastatic disease or primary splenic or hepatic lesions, omental nodules, and free abdominal fluid (hemoabdomen).
• Echocardiography-useful for identifying and removing pericardial effusion and determining the location and extent of tumor involvement.
• Advanced imaging-cardiac-gated MRI or CT scan can be used to help determine surgical resectability.

Diagnostic Procedures

• Definitive diagnosis requires a tissue biopsy.
• Thoracoscopy can be used to visualize the tumor and obtain pericardial biopsies.
• Cytologic evaluation of pericardial fluid rarely provides a definitive diagnosis.
• Electrocardiography may reveal arrhythmias.

Pathologic Findings

• Gross findings-solitary hemorrhagic, friable masses within the right side of the heart.
• Histopathology findings-atypical mesenchymal cells forming irregular blood-filled vascular spaces within a tumor mass. Often abundant necrosis and hemorrhage.

Drug(s)

• Doxorubicin (30 mg/m² IV dogs >15 kg; 1 mg/kg IV dogs <15 kg q2–3 weeks for 5 cycles).
• Metronomic cyclophosphamide (12.5–15 mg/m² PO q24h) in combination with an NSAID (e.g., piroxicam 0.3 mg/kg PO q24h) may be used concurrent or as an alternative to doxorubicin.

Contraindications/Possible Interactions

• Doxorubicin administration can lead to gastrointestinal, bone marrow, cardiac, renal, hypersensitivity, and extravasation toxicities.
• Doxorubicin can lead to cumulative cardiotoxicity in dogs.
• Cyclophosphamide can lead to sterile hemorrhagic cystitis in dogs.
• NSAIDs can lead to gastrointestinal toxicity and liver/kidney damage.

Patient Monitoring

• Physical examinations, blood work, thoracic radiographs, and cardiac ultrasounds every 2–3 months after the completion of therapy.
• If treated with metronomic chemotherapy, monthly urinalysis recommended to screen for sterile hemorrhagic cystitis.

Prevention/Avoidance

N/A

Possible Complications

Congestive heart failure secondary to pericardial effusion and cardiac tamponade.

Expected Course and Prognosis

• Prognosis guarded to poor, increased risk for acute death due to cardiac tamponade or fatal arrhythmias.
• Median survival <1 month without treatment, ∼4 months with doxorubicin, possibly longer if tumor resection performed.

Associated Conditions

N/A

Age-Related Factors

N/A

Zoonotic Potential

N/A

Pregnancy/Fertility/Breeding

Chemotherapy drugs may be carcinogenic and mutagenic.

Abbreviations

• DIC = disseminated intravascular coagulation
• HSA = hemangiosarcoma
• PT = prothrombin time
• PTT = partial thromboplastin time