What you need to know about heart attacks in dogs

What you need to know about heart attacks in dogs

The heart muscle is called the myocardium. An infarction is the obstruction of the blood supply to an organ or region of tissue. Myocardial infarction, which literally means ‘heart tissue damage or death’, is the medical term for a heart attack that is deadly and needs immediate medical attention.

When blood – which transports oxygen and nutrients – is unable to reach a certain part of the heart muscle, tissue damage and tissue death occur, preventing the affected part to effectively pump blood throughout the body.

Fortunately canine heart attacks are rare, however, risks rise when heart disease, certain genetic factors or abnormalities from birth are present.


  • Tumour(s): When a tumour grows on or around the heart vasculature (blood vessels), it can block blood flow to the heart muscle
  • Hypothyroidism: When the thyroid gland fails to produce thyroxine hormone which turns food into fuel for the body
  • Nephrotic Syndrome: Kidney disease which results in kidney damage can lead to loss of protein that helps prevent blood clots from forming which can cause canine heart attack
  • Bacterial infection: Blood flow to the heart muscle can be hindered due to inflammation and blockage caused by infection
  • Vasculitis: Inflammation of blood vessels can be caused by infection, immune-mediated disease or other injury to endothelial linings
  • Atherosclerosis: It’s rare in dogs, but plaque buildup can restrict blood flow and even lead to artery rupture
  • Coronary artery disease: Although also very rare in dogs, damage or disease in the heart’s major blood vessels can happen with severe hypothyroidism and associated with high serum cholesterol levels


Not all dogs have the same symptoms and there’s little or no warning before it can happen. The following symptoms are associated with canine heart attack:

  • Seizure
  • Rigidity
  • Collapse
  • Head tilt
  • Lethargy
  • Vomiting
  • Weakness
  • Lameness
  • Immobility
  • Confusion/anxiety
  • Slight fever (over 39.4 °Celsius)
  • Panting, abnormal breathing or breathing problems
  • Increased heart rate (large breeds: 100+ beats p/min; small breeds: 140+ beats p/min)
  • Sudden death

Heart disease in pets may lead to fainting (syncope) which can be confused for a heart attack, but it doesn’t necessarily cause permanent damage.


In order for a veterinarian to make a diagnosis, a dog owner will need to provide the veterinarian with a detailed description of the signs and symptoms observed, along with a comprehensive health history. A physical examination, with a focus on the cardiovascular system, will also need to take place. Tests, which can help to determine the cause of the heart attack, include:

  • Check thyroid gland function
  • Check kidney and metabolic function with urinalysis
  • Check for infection with complete blood count (CBC)
  • Check kidney and liver function with biochemistry and blood culture
  • Chest X-ray: View heart size and check for fluid around the heart and possible masses
  • Electrocardiography (ECG): Review cardiac electrical impulses and measures arrhythmias
  • Echocardiography: Check for fluid or masses around the heart, examine heart valve function, heart muscle and pericardial health

TIP: Ask your veterinarian about a holter monitor/ambulatory ECG for monitoring heart health at home.


  1. Stay calm and contact a veterinarian immediately.
  2. Keep other pets and children away from your dog.
  3. Food or water intake could be dangerous so rather prevent it.
  4. Minimise or eliminate stimuli because it could contribute to panic.
  5. To comfort your dog, you can wrap him/her in a blanket if it’s not a hot day.
  6. CPR is not recommended, unless you’re professionally trained and know it’s necessary.
  7. You can attempt to record heart rate to determine if it improves. Ask your veterinarian how.
  8. Safely and comfortably transport your dog to the veterinary if he or she collapses.


There are various courses of action to consider. The best option will depend on the affected dog and severity of the heart attack. One or a combination of the following could be recommended to regain and maintain normal heart activity:

  • Resuscitation
  • Supportive care
  • Diet improvements
  • Pacemaker implants
  • Adjustment in activity
  • Surgery (if there’s a mass)
  • Antiarrhythmic medications
  • Hospitalisation (to monitor heart)
  • Thyroid replacement medications
  • Antibiotics for infection or inflammation
  • Preventative or supportive care for renal conditions
  • Blood thinners (to improve circulation)
  • Other medications

Accurate diagnosis and appropriate treatment can help dogs live long, happy lives after a heart attack.


The recovery will depend on how serious the heart attack was (extent and duration), what caused it and how the cause(s) can be treated. For some causes, treatment may have to continue for the rest of the dog’s life. Regular check-ups, tests and monitoring may also be necessary. The pet owner could benefit from learning how to check vital signs at home.


About 10% of all dogs suffer from heart disease. Mitral valve disease (MVD) is the most common form of heart disease in dogs and dilated cardiomyopathy (DCM) is the second most common form of heart disease in dogs.

For more information about heart conditions in dogs, visit our conditions and diseases section.

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