Ventricular Septal Defect (VSD) in Dogs

Ventricular septal defect (VSD) is a hole in the heart left when the organ doesn’t form properly in utero. This birth defect affects many breeds of dogs and causes one side of the heart to work harder than the other. A dog with severe VSD will be exercise intolerant and short of breath — and could even collapse and die. Treatment ranges from medications to surgery.


In the mammalian embryo, the heart develops as a tube that separates into the four chambers that make up the pumping mechanism for the body’s blood (the right and left atria and right and left ventricles). With a VSD, the wall (or septum) between the two ventricles fails to fuse normally, leaving a hole in the heart’s inner wall.

Because blood needs to move in one direction through the heart, the presence of this defect means that some of the blood that enters the left side of the heart (after receiving oxygen from the lungs) gets shunted back to the right side of the heart instead of out to the rest of the body, as it’s meant to be. Ultimately, this defect means that the left side of the heart has to work harder to pump the amount of blood the body requires for normal functions — and that by doing so it might break down under the weight of this overload.

This disease is congenital (meaning puppies are born with it), but it occurs sporadically in several breeds, so there is some discussion among researchers about whether it is truly “genetic” or merely a failure of normal embryo development. The condition also varies in severity depending on the size and location of the hole between the two ventricles and whether there are any other defects involving the heart.

Symptoms and Identification

Some puppies have so small a defect in the wall between the ventricles that it spontaneously closes relatively early in life. These pups will not show symptoms, though they’ll typically have a heart murmur until the abnormal opening closes.

Others will suffer severe VSD, in which case a veterinarian can detect a heart murmur early on, though symptoms may not develop until later in life.

The most common symptoms are the result of the left side of the heart’s work overload. This will cause an enlargement of this side of the heart and clinical signs including shortness of breath, coughing, exercise intolerance, sudden death, or, less commonly, cyanosis (blue tinged discoloration of the gums, lips, or tongue as a result of inadequate oxygen supply).

Diagnosis of VSD is achieved through X-rays to see the enlargement of the heart, EKG (electrocardiogram) to pick up electrical changes as a result of the enlargement, and, most crucially, an echocardiogram (heart ultrasound) equipped with Doppler technology to identify the defect in the ventricular wall and the abnormal flow of blood there.

Affected Breeds

Unfortunately, VSD affects many breeds sporadically, and its method of inheritance has not been fully determined.


Drugs are the primary approach for dogs who show symptoms (remember, some may not). For more severe cases, however, drugs may be insufficiently effective.

In cases for which drug therapy is insufficiently effective, surgical options are available. However, surgery is relatively costly and generally available only at specialty referral centers.

Exercise restriction, a low-sodium diet, and weight management may be recommended for symptomatic VSD patients.


Preventing VSD requires removing affected dogs from the breeding pool.

This article has been reviewed by a Veterinarian.

Join the Conversation

Like this article? Have a point of view to share? Let us know!