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Defect of the Ventricular Septum in Dogs

Ventricular Septal Defect in Dogs

A ventricular septal defect (VSD) leads to abnormal communication within the ventricular septum, the wall dividing the heart’s lower chambers known as the ventricles. This causes blood to flow in an irregular manner from one side of the heart to the other. The extent and direction of this flow depend on factors such as the size of the defect, the relative resistances of pulmonary and systemic blood vessels, and the presence of any additional anomalies.

In dogs, most VSDs are located below the aortic valve (subaortic) and involve a hole in the right ventricle beneath the septal leaflet of the tricuspid valve. Typically, these defects are small and thus restrictive, meaning there is a maintained difference in pressure between the left and right ventricles. Moderate-sized VSDs are partially restrictive and can cause varying levels of high blood pressure in the right ventricle. On the other hand, large VSDs have openings equal to or larger than the open aortic valve in the left ventricle. They are nonrestrictive, and the pressure in the right ventricle matches the body’s blood pressure. Only moderate and large defects impose pressure on the right ventricle.

It’s worth noting that ventricular septal defects are relatively rare in dogs.

Symptoms and Types

Cats typically show no signs of the defect (asymptomatic). However, common symptoms associated with ventricular septal defects include:

  • Breathing difficulties
  • Exercise intolerance
  • Fainting
  • Coughing
  • Pale gums (only if pulmonary hypertension leads to a right-to-left shunt)
  • Elevated heart rate


The exact cause of ventricular septal defects is uncertain, although there is suspicion of a genetic basis.


Providing your veterinarian with a comprehensive history of your dog’s health and the onset of symptoms is essential. Your veterinarian will conduct a thorough physical examination of your pet, along with various tests including a complete blood profile, chemical blood profile, complete blood count, urinalysis, and an electrolyte panel to eliminate other potential diseases.

Imaging methods such as thoracic X-rays can aid in detecting larger VSDs, which may result in left (or generalized) heart enlargement due to increased blood flow through the heart. Additionally, signs of high blood pressure in the lungs, chronic heart failure, and right-to-left shunts may be visible.

A two-dimensional echocardiographic study, utilizing sonographic imaging to observe heart activity, can reveal heart enlargement. If the defect is moderate-sized or large, or if there are other concurrent heart abnormalities alongside VSD, the right side of the heart may also appear enlarged.


The majority of patients can receive treatment on an outpatient basis. Surgical repair of large shunts can be performed during cardiopulmonary bypass. Patients with moderate or large shunts may also undergo pulmonary artery banding as a palliative procedure, which alleviates some discomfort but does not cure the disease.

Living and Management

If your dog exhibits signs of congestive heart failure (CHF), it should have its activity restricted. Your veterinarian will provide guidance on an appropriate physical regimen. Additionally, your veterinarian may recommend implementing a strict low-sodium diet for your dog diagnosed with CHF to reduce pressure on the heart. Animals diagnosed with overt CHF typically have a life expectancy of 6 to 18 months with medical treatment. Pets with small shunts may lead a normal lifespan if there are no concurrent diseases posing a direct threat to their health.

Avoid breeding your dog if it has been diagnosed with a ventricular septal defect, as this defect is believed to be genetically transmitted. Your veterinarian will schedule regular follow-up appointments for your dog to monitor its progress, perform follow-up X-rays and ultrasound scans, and adjust medications or therapies as necessary.

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