In the developing embryo, the heart has four chambers. Walls (or septums) then form and separate the heart into four separate chambers: two atria and two ventricles. If the walls do not develop completely, holes may be left between the heart chambers. VSD is a congenital heart defect in which a hole remains between the two ventricles.  It is a rare congenital defect that often presents with no family history of the disease. The VSD is seen sporadically in several breeds of dogs. While there is thought to be a genetic component of the heart defect, none hast been identified.

During normal circulation, there is no mix in blood flow between the right and left ventricles. With a VSD, blood flow is shunted into the right ventricle rather than into circulation. Oxygenated blood normally exits the left ventricle to circulate through the body. In the case of the VSD, oxygenated and deoxygenated blood are combined, so the left ventricle must work harder to circulate blood through the body. Given the increased work of the left ventricle, the VSD can lead to heart failure. Additionally, body tissues may not receive an adequate amount of oxygen due to the mixing of the blood.

Puppies may show no signs of the heart defect. During a routine puppy examination, a heart murmur may be heard. In the case of a VSD, the heart murmur is typically very loud.   Diagnostic studies such as x-rays and ultrasounds are commonly used to determine the size and severity of the defect. Most defects are very small and the hole will likely spontaneously close within the first year of life. In this case, the puppy’s quality of life, and life span, is not affected. With larger VSDs, however, the symptoms of heart failure can be severe and even fatal. Puppies are initially treated with medications to prevent heart failure. In such cases where medications are not effective, surgery may be indicated. Local veterinarians will  refer puppies to specialized clinics for management of congenital heart defects. Very few clinics perform canine open heart surgery in the United States.

 Ventricular Septal Defect (VSD) is a congenital defect in which there is a hole in the wall that separates the left and right ventricle of the heart.  Blood may flow abnormally between the two ventricles causing the heart to work harder to circulate oxygenated blood through the body.

A loud heart murmur may be the only symptom of the VSD. With larger defects or as the puppy matures, symptoms may include:

Types   

Although the cause of the VSD is unknown, some suspect that there may be a genetic link to the congenital defect. In most cases, puppies present with a VSD without any prior family history of the heart defect. VSDs appears sporadically in many different breeds of dogs.

Diagnosis will be made likely during a routine puppy examination. If a heart murmur is noted, your puppy will require a follow up visit within 2 weeks. Some murmurs noted in puppies are minor, and will resolve within the next week or two of growth. If a loud murmur is heard, diagnosis will require a chest x-ray and an ultrasound to assess the source of the murmur. The ultrasound will also specify size of the defect and provide more information about heart function. In older puppies or dogs, symptoms such as cough, decreased activity tolerance, weight loss, and respiratory difficulty may suggest to the veterinarian a heart defect such as VSD. Many veterinarians do not have the equipment needed to perform this ultrasound test, so you may be referred to a veterinary specialist.

No treatment is required for most VSDs because the dog is asymptomatic. Such defects will not impact quality of life, nor expectancy.

Larger VSD’s may cause heart failure. In such cases, medications will be given to manage symptoms associated with heart failure. These may include diuretics and medications to strengthen the contractility of the heart.  In severe cases, when drug therapy is not effective, heart surgery may be warranted. These surgeries are performed at specialty centers, of which there are just a few in the United States. The puppy must be large enough to tolerate bypass surgery, and the surgery is cost-prohibitive in most cases.

To manage the care of a puppy with any type of heart defect, annual x-rays will be performed to assess the size of the heart and to evaluate the lungs for any signs of congestive heart failure. Follow up ultrasounds may be required to assess heart function. Pet owner vigilance will be required to report any changes in behavior or activity. A low-sodium diet may be recommended. Finally, activity level may need to be adjusted per veterinary advice.