January 19, 2023 Author : José Roquette Tetralogy of Fallot, also known as TOF, is a congenital heart disease , that is, it is present at birth. It occurs in about 4 out of 10 000 newborns; It represents about 7% of all congenital heart defects. The exact cause of TOF is not known, but: In many cases of tetralogy of Fallot, there are no other anomalies and in some of these, genetic mutations have been identified; In about 15% of cases, tetralogy of Fallot occurs in people with genetic syndromes such as Down syndrome (trisomy 21), Alagille, and DiGeorge syndrome. Heart defects in tetralogy of Fallot Tetralogy of Fallot is associated with four heart defects : 1. Obstruction to the outflow of blood from the right ventricle Under normal conditions, the pulmonary valve connects the right ventricle to the pulmonary artery, which carries blood to the lungs for oxygenation. In tetralogy of Fallot: There are alterations in the tissues and structures close to the pulmonary valve and this valve may also be narrowed (stenosis), blocking the flow of blood to the pulmonary artery; Thus, the blood flow for oxygenation in the lungs is less than desirable. 2. Interventricular communication Under normal conditions, the right and left ventricles are kept separated by the interventricular septum. The right ventricle contains deoxygenated blood, which is pumped to the lungs. The left ventricle contains oxygenated blood, which is pumped into the aorta and general circulation. In tetralogy of Fallot: A hole or defect in the interventricular septum allows blood from the two ventricles to mix; Blood flowing into the general circulation may have less than desirable oxygen content. 3. Poor insertion of the aorta into the heart Under normal conditions, the aorta transports oxygenated blood from the left ventricle to the general circulation. In tetralogy of Fallot: The insertion of the aorta is close to the defect that connects the two ventricles; This position further facilitates blood flow with less oxygen than is desirable for the aorta and general circulation. 4. Right ventricular wall thickening In a normal heart, the wall of the left ventricle is thicker than that of the right ventricle because the pressure which this generates is higher. In tetralogy of Fallot: The increases pressure and overload of the right ventricle wall is thicker, which causes the right intraventricular pressure to be high and the blood to flow in the right ventricle-left ventricle direction. Symptoms and diagnosis Tetralogy of Fallot can be diagnosed before or after birth, sometimes even in adulthood because, depending on its severity, it may or may not have symptoms . The main symptoms of tetralogy of Fallot are: Skin, lips, and nail beds with a bluish color (cyanosis); Determination of oxygen in the blood (oximetry) with values below normal; Characteristic heart murmur, which is detected on auscultation. The symptoms may not be constant, in older children crisis may occur, sometimes with loss of consciousness and which may require rapid intervention. Some patients adopt the squatting position as this makes them feel better. When tetralogy of Fallot is suspected, an echocardiogram is usually requested to confirm or exclude heart defects. Other frequently ordered medical exams are chest X-ray and electrocardiogram. Regardless of its severity, when tetralogy of Fallot is diagnosed, treatment is essential. An untreated tetralogy of Fallot has a poor prognosis. Treatment of tetralogy of Fallot Definitive treatment of tetralogy of Fallot involves a cardiac surgery , which, depending on its severity, may or may not be preceded by other interventions aimed at maintaining the outflow of blood from the right ventricle and its pulmonary oxygenation. In babies, definitive surgery can be performed between 3-6 months of age and includes eliminating the obstruction to right ventricle blood flow and closing the communication between the ventricles. All children undergoing TOF correction surgery need long-term follow-up by a cardiologist experienced in congenital heart disease . Surgical correction of tetralogy of Fallot has very good long-term results, with a survival rate of over 90% after 25 years. About one-third of adults may need reoperation to replace the pulmonary valve. Meet the cardiac surgery team from Hospital da Luz network. The content published in the Health Guide is intended for the general public and is provided for informational and educational purposes only. It does not replace individual medical assessment, diagnosis, or personalized clinical advice from a qualified healthcare professional. The content is produced or reviewed by physicians and other healthcare professionals at Hospital da Luz and is based on the knowledge available at the time of publication or the most recent update, as indicated at the beginning of each item.
