Tetralogy Of Fallot: A Ventricular Septal Defect What causes the blue discoloration of your petโ€™s tongues, gums and membranes?

Tetralogy Of Fallot: A Ventricular Septal Defect Photo by Adam Kontor: https://www.pexels.com/photo/adult-german-shepherd-lying-on-ground-333083/

Tetralogy of Fallot is a congenital heart defect in puppies, kittens, and foals. It's one of the most common causes of blue discoloration of these young animals' tongues, gums, and membranes.

The tetralogy of Fallot is also called a ventricular septal defect, which is seen in more than 50% of cats with a congenital heart defect. It's an umbrella term for four defects that happen at the same time:

  • The septum, a wall separating two heart chambers, doesn’t develop fully in the womb; This is called ventricular septal defect (VSD). A hole in this wall allows oxygen-poor blood from the right ventricle to mix with oxygen-rich blood from the left ventricle. This can make your baby breathless and tired after exercise or crying.

  • A hole called a ventricular septal defect develops in this wall. In it, a hole in the heart wall between the heart's lower left and upper right chambers (ventricles). This causes blood to mix usually but also causes overproduction of red blood cells.

  • Overriding aorta – a more significant than the standard opening between the left ventricle and where it meets your aorta (the main artery exiting from your heart). This can cause pressure on both sides of this opening, which leads to trouble with circulation in other parts of your body.

  • The mixing effect means the animal's bloodstream has too much-oxygenated blood. A hole in the wall between the two ventricles allows blood to mix between them, which causes too much-oxygenated blood to go directly to the lungs and pick up more oxygen than usual. This is called the mixing effect or shunting effect.

To adapt, more blood goes from the left ventricle directly through the pulmonary artery to pick up more oxygen before going back through lung capillaries into tiny blood vessels called pulmonary veins, where it returns into circulation. This extra blood flow puts pressure on pulmonary arteries, causing them to grow thicker or become distorted. 

Tetralogy Of Fallot Is A Congenital Heart Defect

Tetralogy of Fallot is a congenital heart defect in puppies, kittens, and foals. It's one of the most common causes of blue discoloration of these young animals' tongues, gums, and membranes. The tongue may be tinged with a bluish color that varies from faint to intense, depending on how serious it is. 

Some pets have a normal pink or red tongue with tiny blueness, while others have almost no pigmentation left. So if you notice your pet with a bluish tint to their mouth or paws, take them to your veterinarian immediately. 

The Treatment Of Tetralogy Of Fallot In Pets

The treatment of tetralogy of Fallot in pets is similar to the treatment for humans. The only definitive treatment for tetralogy of Fallot is surgery, which involves opening up the chest and fixing the problem. This will require your pet to be under general anesthesia or a sedative like Acepromazine, so you should talk to your vet if you need help with how to go about it. 

Medication For Treating Tetralogy Of Fallot

What pet medications are used to treat TOF? The specific medications used will depend on the symptoms being treated. The goal of treatment is to keep the heart from getting worse and prevent complications from developing. Your vet may recommend Benazepril to treat heart failure and high blood pressure.

There are also options like Pimobendan for dogs and cats, which can help reduce the complications caused by valvular insufficiency. Vetmedin for dogs and cats is also a great option, as this pet medication is specifically used to treat pets with congestive heart failure.

It is also essential to keep your pet calm and relaxed, as we do not want them to have high blood pressure. You can get your pet calming treats for dogs and cats, but if it is getting difficult to manage them just with calming treats, you can also get pet medication like Clomicalm or Adaptil. 


Tetralogy of Fallot is a congenital heart defect that can be diagnosed at birth or shortly thereafter. The disease causes blue-colored gums, tongues, and membranes in animals like puppies and kittens. Owners need to know what this means to get treatment for their pets as soon as possible.

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