Sinus Bradycardia In Dogs: Symptoms, Causes, & Treatments

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Sinus bradycardia in dogs is an unusually low heart rate caused by impulses in the sinus node firing slower than normal. The sinus node is responsible for electrical impulses in the heart that cause it to beat or contract. Sinus bradycardia is most often a harmless or beneficial condition, and it is often present in athletic dogs, especially those that undergo athletic training. However, it can be dangerous when it is caused by a serious underlying medical condition, and it can even cause a loss of consciousness. If you see the symptoms of sinus bradycardia in your dog, it is helpful to consult your veterinarian so they can determine if it is benign or if there is a dangerous underlying cause. Here is what you should know about sinus bradycardia in dogs.

Symptoms Of Sinus Bradycardia In Dogs

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Sinus bradycardia is characterized by an abnormally low resting heart rate, though dogs’ normal heart rate can vary depending on age and size. Sinus bradycardia may be an issue in puppies with a heart rate lower than 160 beats per minute, large adult dogs with a heart rate lower than 60 beats per minute, or small adult dogs with a heart rate lower than 100 beats per minute. Your veterinarian will be able to help you determine if your dog’s heart rate is abnormally low.

Symptoms of sinus bradycardia in dogs may not be present at all if the condition is benign, especially in athletic dogs. However, symptoms may appear if there is an underlying cause. Some common symptoms of sinus bradycardia include the following.

  • Lethargy
  • Getting too exhausted during exercize
  • Slow breathing
  • Loss of muscle coordination
  • Seizures
  • Fainting

Causes Of Sinus Bradycardia In Dogs


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There are several possible causes of sinus bradycardia in dogs. Sinus bradycardia is usually harmless when the cause is athletic training, and it can even be beneficial, as the heart doesn’t have to work as hard to pump oxygen-filled blood throughout the body during exercise. Other causes may be more harmful. Here are a few possible causes of sinus bradycardia in dogs.

  • Hypothermia
  • Intubation during medical procedures
  • Being overly sedated
  • Hypothyroidism
  • Hypocalcemia
  • Pericarditis
  • Hypomagnesemia
  • Other neurological, respiratory, or gastrointestinal diseases

Sinus bradycardia is also more likely to appear in certain dog breeds. Cocker Spaniels, Dachshunds, Miniature Schnauzers, Pugs, and West Highland White Terriers all are more likely to have sinus bradycardia. Young dogs are also more likely to have the condition with the likelihood decreasing with age unless there is an underlying cause.

Treatments For Sinus Bradycardia In Dogs

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The treatment for sinus bradycardia in dogs depends on the underlying cause. If no cause is found and a dog is otherwise healthy, no treatment may be needed, and the dog may just need to be monitored for any changes. Otherwise, treatment is provided as needed by a veterinarian.

If a dog’s heart rate falls critically low, they may be hospitalized and placed on intravenous fluids. Should the sinus bradycardia be a symptom of a serious condition, exercise will likely be restricted, and medical or surgical treatments will be used to address the problem.

Has your dog ever had sinus bradycardia? What was the cause? Let us know in the comments below!