Fallot Tetralogy (Tetralogy of Fallot)

 Fallot Tetralogy is characterized by four particular defects of the heart occurring together.

  • The four defects of the heart occurring together results in poorly oxygenated blood circulating in the body.
  • Heart murmur and cyanosis (bluish tint to the skin resulting from lack of oxygen in the blood) of varying degrees is the common symptom.
  • Echocardiogram can diagnose this condition. The diagnosis is based on the results of an echocardiogram.
  • Surgical correction is the treatment for tetralogy of Fallot.

A large opening in the ventricular septum (septal defect), along with the aorta displaced in such a way that the deoxygenated blood passes directly into the aorta from the infant’s right ventricle, results in right to left shunting of the blood. The right ventricular wall is thickened, and the flow of blood from the right ventricle into the pulmonary artery is restricted by the narrowing of the passage. All these four faults occur together in Fallot Tetralogy.

Infants who have Fallot tetralogy may have shortness of breath because of the decreased flow of blood from the right ventricle to the lungs. The pressure in the right ventricle increases as more blood gets collected there, and it causes this deoxygenated blood to pass into the left ventricle through the defect in the septum. This is termed as right-to left shunt. Cyanosis ranging from mild to severe is the usual symptom in infants. Sometimes, a potentially fatal condition called “tet” spells or hypercyanosis may suddenly develop in some infants, triggered by an activity such as a strained bowel movement or a bout of crying. Extreme shortness of breath develops, and the child may become unconscious. When a heart murmur indicates this condition, echocardiography is done to confirm it.

When a hypercyanotic spell occurs in an infant, oxygen should be administered immediately. A beta- blocker like propranolol and the drug morphine may quickly relieve symptoms. A knee-chest position may make breathing easier for the infant.  It may be beneficial to administer phenylephrine or intravenous fluids to elevate resistance to the blood flow to the body. propranolol may be prescribed by the doctor to prevent future attacks too, till the infant undergoes surgery to correct the faults. In some infants, a condition called pulmonary atresia may be present in which the blood flow from right ventricle is completely blocked. They survive only if the ductus arteriosus remains open, hence alprostadil, a prostaglandin drug which helps keep it open, is given to them.

All infants who have Fallot Tetralogy require surgical correction of the faults, but how early they should undergo surgery depends on the severity of the symptoms. If the infant has severe symptoms which appear frequently, surgical correction is done as early as possible. When symptoms are mild, surgery is delayed till the infant is slightly older. A minimally invasive procedure called balloon valvulotomy may be done to maintain the blood flow to the lungs in the meantime. A balloon-tipped catheter threaded into the heart through a vein enlarges the valve opening by inflating the balloon. During surgery, the defect in the ventricular septum is repaired, and the pulmonary valve and the narrow passage out of the right ventricle are enlarged. Abnormal channels connecting pulmonary artery to the aorta are also blocked.

Watch This Video about Tetralogy of Fallot:

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Yasser Elnahas

MD, PHD, Professor Of CardioVascular Surgery
Dr. Yasser Elnahas, Is an associate Professor of Cardiovascular Surgery. Dr. Elnahas was trained as a fellow At Texas Heart Institute And Mayo Clinic Foundation.Dr. Elnahas is dedicated to educating the general public about different disease conditions and simplifying the medical knowledge in an easy to understand terminology.

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