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What is Heart Racing?

There are many reasons why your dog's heart may race. Your dog may have just completed an activity which may have caused overexertion. If your dog is otherwise healthy, it is normal for his heart to race. However, if you find that your dog has been experiencing a racing heart on a normal basis, even in his resting phase, it is important to have him checked out by your veterinarian. Heart racing in dogs may be caused by the following:

  • Subaortic stenosis
  • Pulmonic stenosis
  • Poisoning

Why Heart Racing Occurs in Dogs

Subaortic Stenosis

Subaortic stenosis occurs when the outlet underneath the aortic valve narrows, causing the heart to overwork and placing a strain the entire cardiovascular system. In subaortic stenosis, fibrous tissue forms near the left ventricle under the aortic valve. The issue blocks the blood flow, creating a dangerous obstruction in the heart. Many dogs are born with this defect and the condition can worsen as your dog ages. Some of the symptoms to look out for in subaortic stenosis include:

  • Lethargy
  • Racing heart/difficulty breathing
  • Weakness

Your dog's heart may race due to different factors or certain medical conditions. In subaortic stenosis, obstruction is causing the damage within your dog's heart. Due to the obstruction, your dog's heart may race easily. The narrowing of the obstruction may range anywhere from mild to severe. In severe cases, your dog's heart may be forced to overexert itself which can be harmful. Subaortic stenosis may be present at birth and can appear within your dog's first year.

Pulmonic Stenosis

Pulmonic stenosis occurs when the semilunar valves of the heart do not function up to standard. Pulmonic stenosis is an abnormality of the heart that prevents the heart from beating normally. In pulmonic stenosis, the valve has developed in such a way that it is too thick to function or it may be fused together, preventing the valve to properly open or close. Your dog may not experience any symptoms with pulmonic stenosis. However, if your dog has an advanced case of pulmonic stenosis, he may experience the following:

  • Weakness
  • Lethargy
  • Resistance to active activity
  • Heart failure
  • Collapse

In pulmonic stenosis, the condition is congenital and breed specific. 


Poisoning due to human error in the administration of heart medicine, or by the ingestion of toxic plants with effects on the heart can cause your pet’s heart to race. Your veterinarian will use medical means to eliminate the toxins from your dog’s system. The lasting effects on the heart will depend on the severity of the poisoning.



What to do if your Dog is Heart Racing

If you notice your dog's heart racing and he hasn't been diagnosed with a medical condition, it is important to seek veterinarian attention to avoid prolonging any damage. 

Your veterinarian will want to perform a physical examination and use a stethoscope to listen for a heart murmur. Other tests to determine whether your dog's racing heart is caused by subaortic stenosis or pulmonic stenosis are chest x-rays, electrocardiogram, and echocardiogram. These tests will help to determine whether there is any fluid accumulation in the lung, find any irregularities in the heart, and assess the direction of blood flow. 

Your veterinarian may prescribe medications to help reduce the workload of the heart. Surgery may be an option if your dog's obstruction is severe and he is an eligible candidate. Your veterinarian will suggest ways to help maintain a calm lifestyle for your dog and make possible lifestyle adjustments. 

Toxicity affecting the heart will be diagnosed by clinical signs and laboratory tests that can determine the level of poisoning and direct the veterinarian as to the steps for detoxification and supportive care.



Prevention of Heart Racing

Your veterinarian may offer suggestions to help maintain your dog's quality of life and avoid overexertion of his heart. You will also be provided with symptoms and signs to look out for in case your dog begins to suffer from his condition. 

In the case of poisonous or hazardous substances of any kind, including medication, household cleaners, plants and insecticides, keeping them out of reach of your companion is essential.



Cost of Heart Racing

Treatment for heart racing in dogs can drastically vary depending on your dog's condition, your location, and your veterinarian. For example, treating subaortic stenosis can range anywhere from $1800 to $5000. The average cost of treating subaortic stenosis is $2500.00. An intensive medical condition such as pulmonic stenosis can range from $2500 to $7000 with the average cost for treatment at $4500.



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