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Aortic Stenosis

Aortic Stenosis - Heart Condition in Boxer Dogs 


The is one of the more common Boxer dog heart problems. This is a canine health condition in which there is a partial block to the normal flow of blood in the dog’s heart, as it flows out through the dog’s left ventricle through the aorta. Because of this blockage, the Boxer dog's heart must work much harder and faster than normal.

What are the Symptoms of This Canine Heart Condition?

• A heart murmur – this often is found during a routine exam at the veterinarian

In very serious cases, the symptoms of this canine health issue will mimic canine heart disease:

• The Boxer dog will become very tired and weak
• Decreased appetite
• Difficulty breathing
• Panting and/or coughing
• Fainting after exercise
• In very severe cases, the beating of the dog’s heart will be very clearly seen in the dog’s veins of the dog’s neck, even at complete rest or sleep

Is This Fatal to Dogs?

Yes, it can be. It is a tricky condition... Some Boxers have a mild case which does not affect life span at all... However, with others, it can be severe and fatal.  

Abnormal heart rhythms in a dog can lead to sudden death. 

Breeding / Hereditary Factors

A dog (either sire or dam) with a mild case can pass the disease to a litter in which a puppy or puppies contract a very serious case. For this reason, a dog with this should not be bred even if he/she has a mild case that is not affecting his/her quality of life.

Any dog that is being considered for breeding should be tested for this - along with Doppler studies (a particular type of ultrasound machine that uses sound waves to measure the flow of blood through a blood vessel) - by a board-certified canine cardiologist prior to any pairing.

Once a Boxer is cleared of this and is at least 1 year old, he/she is considered clear and can entered into a breeding program.


Once a heart murmur is detected, your Boxer dog should be referred to a canine heart specialist. One of the most important aspects will be to determine the severity of the murmur. 

Testing will be done to determine the exact location of the most intense area of the murmur and then the murmur will be graded on a scale of 0/6 to 6/6 (more ahead)


X-Rays - An X-ray of the dog's chest is usually performed. This is helpful to see the size and shape of the heart. Any abnormal enlargement of the heart's chambers can usually be spotted, which would indicate a more severe case.

EKG - An EKG is important as it will determine the severity of the heart's valve narrowing and it will measure electrical impulses to the Boxer's heart.

Ultrasound- With Aortic Stenosis, the left ventricle wall of the heart thickens. This test will measure the extent of the thickness and well as the internal dimensions of the heart.

Doppler Test - A Doppler test is a specialized ultrasound test that measures the flow of blood through a blood vessel. Of most concern, will be the left ventricle. The flow rate can tell you a lot. Flow is measured by meters per second.

If a dog has a flow that is LESS than 4 meters per second, he will usually live to full life expectancy and not have any major problems.

If a Boxer has a flow that is MORE than 5 meters per second, this is an indication that the dog will be affected by this disease; though all tests will be combined together to give the murmur a 'grade'.

This is the grading system:

0/6- This is considered to be very mild and will not affect quality of life or life span

1/6 and 2/6 - This is also in the mild category. 95% of Boxer dogs that are in the class will not develop symptoms that impede his/her health

3/6 and 4/6 - A murmur of this scale is considered to be moderate. Most Boxer puppies and dogs will not suffer from any symptoms; however 10 to 15% will. Dogs given a grade of either 3/6 or 4/6 should be watched closely and monitored often to check for possible problems and to see if the murmur worsens as the dog ages.

5/6 and 6/6- At this grading, the murmur is considered to be severe. Unfortunately, the majority of Boxer dogs that are graded with a 5/6 or 6/6 are likely to develop symptoms and may have shorter life spans. Medication will most certainly be given and the dog must be monitored on a regular basis. 


No matter what the degree of this health condition, a dog’s owner should:

• Make sure the Boxer dog does not endure excessive exercise; this is especially important in hot weather

• Keep the dog at the proper weight which will help ease stress on the dog’s heart


Surgery and cardiac catheterization, in which the affected area is removed is not done very often as it was in the past. Studies have shown that this procedure does not significantly extend the life span of affected dogs.

Beta-blocker medication for dogs may be prescribed if: 

• The Aortic stenosis is severe (graded as 5/6 or 6/6)
• There are signs of left ventricular hypertrophy (this means when the heart muscle cells become enlarged) 

• Dogs with signs of VPCs. (Ventricular Premature Complexes) 

Beta-blockers help a dog to tolerate exercise, reduce the stress on the dog’s heart and prevents abnormal heart rhythms. The 3 most commonly prescribed beta-blockers for Boxers with Aortic Stenosis heart murmurs are propranolol, atenolol and metoprolol.

Propranolol often sold under the brand names of Inderol®, Betachron® or Intensol® . It is available in tablet, injectable and liquid forms. While rare, the most common side effects are slowed heart rate, low blood pressure, weakness, diarrhea and/or difficult breathing. Owners should immediately report any side effects to their dog's veterinarian.

Atenolol is sold under the brand name of Tenormin® . It is given as tablets but is also available as injectable doses. While rare, the most common side effects are slowed heart rate, low blood pressure, weakness, diarrhea and/or vomiting. Owners should immediately report any side effects to their dog's veterinarian.

Metoprolol is sold under the brand name of Lopressor®. It is given as a tablet. While rare, the most common side effects are slowed heart rate, low blood pressure, weakness and/or vomiting. Owners should immediately report any side effects to their dog's veterinarian.

Note: Always follow the exact dosing instructions for any of these Aortic Stenosis medications, as an overdose can be toxic and sometimes fatal.


With 90% of Boxer dogs, the severity of the murmur will not worsen after the age of 2-years-old. With 10%, it will worsen over time. A dog should be checked every 6 months to 1 year, with testing done to see if there are any changes.  
See also:
What to feed a Boxer dog - If you are not 100% confident in what you are feeding your Boxer, have a look at these guidelines and recommendations. 
Boxer dog health issues- A list of the health conditions most likely to affect the Boxer dog breed. 
Boxer dog exercise requirements - Ensuring that your Boxer puppy or dog stays active for a healthy body and mind. 
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