Todayโs path rounds are on ๐ญ๐๐ญ๐ซ๐๐ฅ๐จ๐ ๐ฒ ๐จ๐ ๐ ๐๐ฅ๐ฅ๐จ๐ญ!
๐๐ก๐๐ญ ๐ข๐ฌ ๐ข๐ญ?
๐๐๐ญ๐ซ๐๐ฅ๐จ๐ ๐ฒ ๐จ๐ ๐
๐๐ฅ๐ฅ๐จ๐ญ is a combination of four ๐๐จ๐ง๐ ๐๐ง๐ข๐ญ๐๐ฅ (present at birth) defects in the heart, leading to abnormal blood flow. This condition is quite rare, but interesting!
๐๐ก๐จ ๐ ๐๐ญ๐ฌ ๐ข๐ญ?
Any species can get this!
๐๐ก๐๐ญ ๐๐๐ฎ๐ฌ๐๐ฌ ๐ข๐ญ?
Tetralogy means ๐๐จ๐ฎ๐ซ ๐ฐ๐จ๐ซ๐ค๐ฌ, and is most often used in literature (i.e. it comes after a trilogy 
). In the case of tetralogy of Fallot, the โfour worksโ are the four different congenital abnormalities present in the disease. These defects are:
1. ๐๐๐ง๐ญ๐ซ๐ข๐๐ฎ๐ฅ๐๐ซ ๐ฌ๐๐ฉ๐ญ๐๐ฅ ๐๐๐๐๐๐ญ, a hole in the separation between the two halves of the heart.
2. ๐๐ฎ๐ฅ๐ฆ๐จ๐ง๐ข๐ ๐ฌ๐ญ๐๐ง๐จ๐ฌ๐ข๐ฌ, or narrowing of the valve that opens and closes to regulate blood entering the lungs for oxygenation.
3. ๐๐ฏ๐๐ซ๐ซ๐ข๐๐ข๐ง๐ ๐๐จ๐ซ๐ญ๐, or an aorta that emerges from both sides of the heart, rather than just the left side.
4. ๐๐ข๐ ๐ก๐ญ ๐ฏ๐๐ง๐ญ๐ซ๐ข๐๐ฎ๐ฅ๐๐ซ ๐ก๐ฒ๐ฉ๐๐ซ๐ญ๐ซ๐จ๐ฉ๐ก๐ฒ, or thickening of the muscle wall on the right side of the heart.
This combination of abnormalities is typically a ๐ฌ๐ฉ๐จ๐ซ๐๐๐ข๐ (random) occurrence, however it has been found to have a genetic link in Keeshond breed dogs.
๐๐ก๐ฒ ๐ข๐ฌ ๐ญ๐ก๐ข๐ฌ ๐ ๐ฉ๐ซ๐จ๐๐ฅ๐๐ฆ?
The main issue with tetralogy of Fallot is ๐ก๐ฒ๐ฉ๐จ๐ฑ๐ข๐, or inadequate oxygenation of the blood. The main cause of this is inadequate delivery of blood to the lungs from the pulmonary stenosis, preventing proper oxygenation. This effect is enhanced by the ventricular septal defect, which allows deoxygenated blood to cross into the left side of the heart, mix with oxygenated blood, and be delivered to the body. This poorly oxygenated mixture is not very helpful for the tissues that desperately need oxygen!
In order to try and compensate for the lack of oxygen, the kidneys produce ๐๐ซ๐ฒ๐ญ๐ก๐ซ๐จ๐ฉ๐จ๐ข๐๐ญ๐ข๐ง, a hormone that stimulates red blood cell production. Ultimately, this results in ๐ฉ๐จ๐ฅ๐ฒ๐๐ฒ๐ญ๐ก๐๐ฆ๐ข๐, or having too many red blood cells. The blood becomes viscous and thick, and cannot flow into smaller vessels. This can lead to seizures and ๐๐ญ๐๐ฑ๐ข๐ (irregular gait).
๐๐จ๐ฐ ๐ข๐ฌ ๐ข๐ญ ๐๐ข๐๐ ๐ง๐จ๐ฌ๐๐?
Often, the main clinical sign a veterinarian will see on physical exam is ๐๐ฒ๐๐ง๐จ๐ฌ๐ข๐ฌ, or blue tissue. This is because the animal doesnโt have enough oxygen in their blood, which makes the blood appear red! These animals also have a history of collapse, seizures, and difficulty breathing. To confirm the diagnosis, ๐๐๐ก๐จ๐๐๐ซ๐๐ข๐จ๐ ๐ซ๐๐ฉ๐ก๐ฒ (ultrasound of the heart) can be used to identify the abnormalities directly.
๐๐จ๐ฐ ๐ข๐ฌ ๐ข๐ญ ๐ญ๐ซ๐๐๐ญ๐๐?
Although there are surgical procedures that can help, this is very rarely done in our animal patients. Sometimes, these animals are managed with medication to improve their quality of life. However, this disease has an extremely poor prognosis, so euthanasia is often the outcome for these patients.
๐๐ก๐จ๐ญ๐จ๐ฌ
1-4) Examples of the lesions of tetralogy of Fallot!
5) A pig example of cyanosis.
๐๐จ๐ฎ๐ซ๐๐๐ฌ
Maxie, G. Jubb, Kennedy and Palmerโs Pathology of Domestic Animals, Volume 3. Sixth Edition.
Tou SP. Tetralogy of Fallot in Animals. Merck Veterinary Manual 2020.
Photos 1-5 ยฉ Noahโs Arkive contributors Ramos-Vera, Harrington, Andreasen, Domingo licensed under CC BY-SA 4.0.
