Arrhythmia in Dogs (Abnormal Heart Rhythm): Should You Be Concerned?

| Updated: May 8, 2023
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Have you noticed your dog’s heart beating faster or slower than usual? Maybe you’ve felt a skipped beat or an irregular rhythm when you cuddled with your furry friend. If so, it’s possible your dog may have an arrhythmia that affects the heart’s electrical activity and causes abnormal heartbeats.

Arrhythmia is relatively common in dogs and is not always a cause for concern. An occasional irregular heartbeat may not cause any other health problems. However, because an irregular beat may be an early symptom of a more serious underlying condition, you should ask your veterinarian to check it out.

Types of arrhythmia in dogs

Arrhythmias are classified into different types based on their origin and pattern. The most common types of arrhythmias in dogs are:

  • Sinus arrhythmia: A normal variation in the heart rate that is associated with breathing. The heart rate increases when the dog inhales and decreases when the dog exhales. This type of arrhythmia is usually harmless and does not require any treatment. It is more common in brachycephalic breeds (those with short noses and flat faces) like bulldogs, pugs, and shih tzus.
  • Ventricular arrhythmia: An abnormal rhythm that originates from the heart’s lower chambers (ventricles). It can be caused by various factors such as heart disease, electrolyte imbalance, trauma, toxins, or genetic factors. This type of arrhythmia can be dangerous and may lead to decreased blood flow, collapse, or sudden death. It is more common in boxers, bulldogs, and German shepherds.
  • Atrial fibrillation: A rapid and irregular heart rhythm originating from the heart’s upper chambers (atria). It is associated with various conditions such as heart enlargement, thyroid disease, or other diseases. This type of arrhythmia can affect heart function and reduce blood flow. More commonly seen in large breeds like Great Danes, Doberman Pinschers, and Newfoundlands.
  • Sick sinus syndrome: A disorder of the sinus node (the heart’s natural pacemaker) causing alternating episodes of slow and fast heart rates. It can be caused by aging, inflammation, infection, or medication. This type of arrhythmia can cause weakness, fainting, or seizures. It is more common in older dogs and small breeds like schnauzers and dachshunds.

Symptoms of Arrhythmia in Dogs

The signs and symptoms of arrhythmia in dogs will vary, depending on the type, severity, and underlying cause of the arrhythmia. Some dogs may not show any symptoms at all, while others may experience:

  • Irregular heartbeat (detected by listening to the chest or feeling the pulse)
  • Weakness or fatigue
  • Reduced exercise tolerance or stamina
  • Shortness of breath or coughing
  • Pale gums or tongue
  • Collapse or loss of consciousness
  • Seizures or convulsions

If you notice any of these symptoms in your dog, contact your veterinarian as soon as possible. It may end up being a minor concern, but don’t take that chance! Arrhythmia can be a life-threatening condition if left untreated.

Causes of Arrhythmia in Dogs

Many possible factors can trigger or contribute to arrhythmia in dogs. A few are:

  • Congenital defects or inherited disorders: Some dogs are born with abnormal heart structures or genes that predispose them to arrhythmia.
  • Heart diseases or conditions: Any disease or condition that affects the structure or function of the heart can cause arrhythmia.
  • Systemic diseases or conditions: Any disease or condition that affects other organs or systems can also affect the heart rhythm. Such as thyroid disease, kidney disease, and electrolyte imbalances.
  • Trauma or injury: Any trauma or injury to the chest or heart can damage the heart’s electrical system and cause arrhythmia.
  • Toxins or medications: Some toxins or medications can affect the heart’s electrical activity and cause arrhythmia. For example, digoxin (a medication for heart failure), chocolate, caffeine, and xylitol (a sugar substitute).
  • Stress or anxiety: Some dogs may develop arrhythmia due to stress or anxiety.

Diagnosis of Arrhythmia in Dogs

To diagnose your dog’s arrhythmia, your vet will perform a physical examination and ask you about your dog’s medical history, symptoms, and lifestyle. Your veterinarian may also use various tests and procedures to detect and evaluate an arrhythmia, such as:

  • Electrocardiogram (ECG)
  • Echocardiogram
  • Blood tests
  • Chest X-rays

Treatment of arrhythmia in dogs

Treating an arrhythmia in dogs depends on the type, severity, and underlying cause of the arrhythmia. Some may not require any treatment, while others may need medication, surgery, or implantable devices. If your dog has an arrhythmia requiring treatment it may be one of these:

  • Sinus arrhythmia: Usually, no treatment is needed unless the dog has symptoms of poor blood flow or low oxygen levels. In that case, oxygen therapy or drugs to increase the heart rate may be given.
  • Ventricular arrhythmia: Antiarrhythmic drugs (e.g., sotalol, mexiletine) may be prescribed to suppress the abnormal beats and prevent life-threatening complications. Surgery or a defibrillator device may be needed in more severe cases to correct the underlying heart problem or restore a normal rhythm.
  • Atrial fibrillation: Rate-control drugs (e.g., diltiazem, atenolol, digoxin) can be used to slow down the heart rate and improve heart function. Cardioversion (electrical shock) may be attempted to restore a normal rhythm. Underlying causes such as thyroid disease or heart enlargement should also be treated.
  • Sick sinus syndrome: Pacemaker implantation may be the best option to regulate the heart rate and prevent symptoms. Antiarrhythmic drugs can also be used to control the fast episodes of arrhythmia.


Arrhythmia in dogs is a condition that affects the heart’s electrical activity and causes abnormal heartbeats, which are classified into different types based on their origin and pattern. Regular veterinary check-ups and monitoring are important for dogs with an arrhythmia or those at risk of developing it.

If you want to do your part to give your dog the best life possible. Keep them at a healthy weight, provide moderate exercise to prevent obesity and heart disease, and reduce stress or anxiety by providing a calm and comfortable environment.


Q: How can I tell if my dog has arrhythmia?

A: The best way to detect arrhythmia in your dog is to consult your veterinarian, who can perform various tests and procedures to diagnose it. However, you can also check your dog’s pulse or listen to their chest for any irregularities in their heartbeat. Look for signs of weakness, fatigue, coughing, pale gums, collapse, or seizures in your dog.

Q: What breeds are more prone to arrhythmia in dogs?

A: Arrhythmia can affect any breed and age of dogs, but some breeds (Boxers, Pugs, and Great Danes to name just a few) are more predisposed to developing certain types of arrhythmia. Similarly, older dogs have a higher risk of developing an arrhythmia.

Q: How can I prevent arrhythmia in my dog?

A: Some causes of arrhythmia in dogs are not preventable, such as congenital defects or inherited disorders. You can reduce the risk of other causes of arrhythmias by keeping your dog healthy and happy. Diet, nutrition, exercise, and stress relief are important in preventing many conditions.

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