What are the common symptoms of cardiac hemangiosarcoma in dogs and cats?

Common signs include lethargy, reduced activity, rapid breathing, and coughing. Symptoms may appear intermittently; monitor closely and report any changes to your vet.

How do vets usually diagnose cardiac hemangiosarcoma?

Diagnosis combines physical examination, chest X-ray, echocardiography, and ECG; biopsy or CT may be arranged when needed to confirm the diagnosis.

What are the treatment options and typical prognosis?

Treatment focuses on chemotherapy or targeted therapy combined with supportive care; outcomes and prognosis vary depending on tumour location, metastasis, and overall health — discuss options thoroughly with your vet.

What information should I bring to the vet appointment?

Bring videos of your pet's gait and breathing, a log of when symptoms occurred, previous test reports, and a current medication list to speed up the assessment.

How much do the tests and treatment usually cost?

Costs vary by clinic and region — ask your vet for an estimate before proceeding.

Disease Guide

Cardiac Hemangiosarcoma in Dogs and Cats: Symptoms, Diagnosis & Care Guide [2025]

Cardiac hemangiosarcoma is a highly malignant tumour that commonly causes pericardial effusion and cardiac tamponade. Prognosis is very poor, with a median survival time of only weeks to a few months.

Take 1 minute to check the symptoms first

Last updated: 2026/01/05

Pethealthmap Editorial Team

Sources: ACVIM, AVMA, National Taiwan University Veterinary College

When to See a Vet

Requires Immediate Emergency Care

•Extremely labored breathing with obvious open-mouth panting
•Sudden collapse or brief loss of consciousness with slow recovery
•Gums or oral mucous membranes appear noticeably blue or pale white

Schedule a Clinic Visit Soon (within 24–72 hours)

•Persistent rapid breathing but still able to move around, with fatigue
•Noticeably reduced activity, reluctance to play or walk
•Repeated vomiting or significantly reduced appetite

01What symptoms indicate a problem?

Cardiac hemangiosarcoma in dogs and cats often presents primarily as changes in energy level and breathing; symptoms may be intermittent and variable.

Lethargy, noticeably reduced activity, or reluctance to play
Weakness, appearing unsteady or lacking strength when standing or walking
Reduced appetite or persistent refusal to eat, with possible weight loss
Repeated vomiting or digestive discomfort that is worse than usual
Persistent or recurring cough, including increased coughing at night
Rapid breathing, laboured breathing, or open-mouth breathing should be monitored closely

Seek emergency care immediately if you notice the following symptoms:

⚠️ Severely laboured breathing with obvious open-mouth gasping
⚠️ Sudden collapse or brief loss of consciousness with slow recovery
⚠️ Noticeably pale or bluish gums or oral mucous membranes

02How to assess abnormalities at home: key observations and emergency criteria

Carefully observing and recording your pet's condition at home before visiting the vet allows the vet to assess the situation and changes more quickly.

Note the dates and times when symptoms first appeared and when they worsened
Record short videos of your pet's gait, laboured breathing, and coughing to bring to the clinic
Observe and record the frequency, content, and circumstances of each vomiting episode
Test and record changes in breathlessness and stamina after a short walk
Record changes in appetite, water intake, and willingness to eat
If acute symptoms occur, prepare to transport your pet to a specialist hospital immediately

03How will the vet make a diagnosis? Common diagnostic tests

The vet will build on a physical examination, combining imaging and necessary tests to evaluate cardiac, thoracic, and overall health status.

Physical examination

auscultation of heart sounds, lung sounds, and full-body assessment

Chest X-ray

assess heart size and check for pleural or pericardial effusion

Cardiac ultrasound (echocardiography)

examine cardiac masses, chambers, and functional status

Electrocardiogram (ECG)

evaluate heart rhythm and electrical activity for abnormalities

Tissue biopsy

sampling when necessary to confirm the pathological nature of the mass

CT scan

used for thoracic and tumour localisation in complex cases or staging assessments

04What treatment and care is needed after diagnosis? Medication, diet, and care guide

Treatment typically involves an oncology evaluation followed by chemotherapy or supportive care, with regular follow-up appointments to monitor imaging and clinical status.

Oncology assessment to determine suitability for chemotherapy or targeted therapy and plan the treatment course
Use medication and supportive therapy to manage symptoms and improve quality of life
Dietary adjustments and weight management to reduce the burden on the heart
Home care: avoid strenuous activity and maintain a calm, comfortable environment
Carry out scheduled imaging, blood work, and cardiac function monitoring
Long-term follow-up is recommended at a cardiac or oncology specialist hospital

05What to prepare before the vet visit: key information to help the vet assess quickly

Record short videos: gait, laboured breathing, and coughing (front and side views)

Note the timing and frequency of the first episode and any worsening for reference

Carry out a brief exercise test and record any breathlessness or fainting

If collapse or bluish discolouration has occurred, record the time and duration of each episode

Bring previous test reports and a current medication list

Book an appointment at a specialist clinic capable of performing echocardiography and advanced imaging

This content is for reference only and cannot replace a professional veterinary diagnosis. If your pet shows signs of illness, please seek veterinary care promptly.