Bradycardia means a heart rate slower than expected for the situation. A calm or athletic dog can have a slower resting pulse without being sick. A dog with an abnormal electrical rhythm, however, may not circulate enough blood and can develop weakness or fainting. A heart-rate number alone cannot determine safety.
Symptoms that make a slow pulse concerning
Weakness, sudden exercise intolerance, episodic collapse, fainting, unusual tiredness and reduced responsiveness all merit prompt veterinary attention. If a dog collapses, has trouble breathing, does not respond normally or appears severely weak, seek emergency care. These signs can have causes other than bradycardia, but they are not appropriate for home experimentation.
Why dogs can have low heart rates
Normal sleep, physical conditioning, medications, electrolyte disturbances and certain illnesses may lower heart rate. Some dogs develop conduction problems, such as high-grade atrioventricular block or sick sinus syndrome, which interfere with the heart’s usual electrical signaling. A slow pulse may also accompany certain systemic medical emergencies.
How a vet diagnoses the problem
An examination and electrocardiogram (ECG) help distinguish normal slowing from an arrhythmia. Blood tests, blood pressure, imaging and an extended heart-rhythm monitor may be indicated depending on the dog’s symptoms. Owners can note the timing of fainting episodes and medications, but a phone app or wearable reading is not a substitute for an ECG.
What treatment may involve
Treatment is directed at the cause. Some problems resolve when another illness is treated or a medication is adjusted under veterinary supervision. Dogs with serious persistent conduction disorders may need a pacemaker; others may need additional monitoring. Do not attempt to raise a dog’s heart rate with supplements, caffeine or unprescribed drugs.
Questions for the cardiology team
- Is the rate appropriate when my dog is asleep and active?
- Does the ECG show an abnormal rhythm or a normal variation?
- Could any prescribed medications contribute?
- Would a Holter monitor or specialist consultation help?
- What symptoms mean I should go to an emergency hospital?
Because fainting can reflect serious heart or non-heart problems, record episodes and seek assessment rather than assuming an older dog is simply slowing down. For broader triage, read Does My Pet Need a Vet Right Now?
Reference: Merck Veterinary Manual, Heart Disease: Conduction Abnormalities in Dogs and Cats. This is not individualized cardiology advice.
This article is for general education and is not a substitute for care from your own veterinarian. Learn about The Pet Vet and our editorial policy.