congenital heart conditions in dogs

Congenital Heart Conditions In Pets | Boston Terrier dog being examined by a vet using stethoscope
Posted by Dr. Kim Smyth on Feb 13 2013

Today we’ll focus on congenital heart conditions that can affect our furry friends, describing a few of the most common ones, along with their clinical signs and treatments.

But first, it’s helpful to know a little bit about the basic anatomy of the normal heart, which is the same for two- and four-legged family members.. You know it’s located almost in the center of the chest (slightly to the left) and you know that its function is to pump blood, but it’s the intricacies of the pumping that may leave you wondering. Well, wonder no more!

What is the hearts responsibility?

The heart is responsible for pumping oxygen-rich blood out to the tissues of the body, nourishing muscles and vital organs. It also has to pump blood that has already delivered oxygen back to the lungs to get re-oxygenated. To make this easier, the heart is basically divided into two parts – the left heart, and the right heart.

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In the normal heart, the left side of the heart pumps fully oxygenated blood into the aorta, which delivers it to the body. The blood returns to the right side of the heart, which pumps it to the lungs to get oxygenated again. The blood then flows back into the left side, to be delivered to the body, and so on.

Once you understand how a normal heart works, it’s easier to see the problems that can occur when a heart has a congenital defect. Let’s start with two conditions involving stenosis (or narrowing) of the outflow tracts out of the heart.

Subaortic stenosis

Subaortic stenosis is a narrowing around the aortic valve. As you may have guessed, this is the valve that lies between the left heart and the aorta. When the outlet is narrowed, it makes it difficult for blood to smoothly pass through it, which makes it a little more difficult for the heart to pump efficiently. Overtime, as the left heart muscle has to work harder, it gets bigger and less flexible, causing a decrease in its pumping function as well as a decrease in its ability to properly fill with blood.

All of this can lead to fainting spells, arrhythmias and in some cases, sudden death, especially during exercise. As the left heart continues to grow, congestive heart failure can occur.

Breeds that are predisposed to subaortic stenosis include Golden Retrievers, Rottweilers, Newfoundlands, Great Danes, Boxers, German Shepherds and German Shorthair Pointers.

Pulmonic stenosis

Pulmonic stenosis is a similar narrowing around the pulmonic valve, which is found in the right side of the heart. When it is narrowed, it restricts the blood that goes from the right heart to the lungs. Just like in subaortic stenosis, when the right heart has to work harder, the muscle gets thicker, making it more difficult to pump and fill efficiently.

Most cases of pulmonic stenosis are mild and are not concerning, however, in severe cases, affected pets will tire easily with exercise and may faint and have a bluish tinge to their gums due to poor oxygenation. About 30% of severe cases have sudden death.

Boxers and Bulldogs are prone to a particular type of pulmonic stenosis due to possible anomalies in the structures of their blood vessels. Other breeds that are prone to pulmonic stenosis are Beagles, Chihuahuas, Cocker Spaniels, West Highland White Terriers, Mastiffs, Miniature Schnauzers and Keeshonds.


Pulmonic and aortic stenosis may first be suspected if your vet hears a murmur when he or she listens to your pet’s heart. X-rays may be taken to look for left- or right-sided heart enlargement or for other evidence of heart failure, such as fluid in the lungs. An ultrasound of the heart (echocardiogram) will measure the size of the heart chambers and the thickness of their walls and a definitive diagnosis of subaortic or pulmonic stenosis can be made from there.


Treatment of subaortic stenosis generally relies on medical therapy. Beta blockers keep the heart from racing, thereby avoiding some of the problems with abnormal heart rhythms and fainting. Surgical options exist, including trying to widen the stenosis with balloon valvuloplasty, but survival times are not drastically improved over just using beta blockers alone.

Unfortunately, there are no medications that specifically help pulmonic stenosis patients. However, most cases of pulmonic stenosis are mild and do not need to be treated. In severe cases, balloon valvuloplasty is preferred over other surgical options. In those more severe cases, treatment can become costly, so protecting your pet with Petplan pet insurance when she is healthy and free of heart trouble can give you the peace of mind that should trouble ever arise, you will be able to focus on her care, not the cost.

If you suspect your pet is having heart trouble, contact your vet immediately.

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