Tetralogy of fallot

[Dianne]

In tetralogy of Fallot, four specific heart defects occur together.

This condition includes four heart defects that can lead to the circulation of oxygen-poor blood.
Symptoms include mild to severe cyanosis (a bluish discoloration of the skin), life-threatening attacks, and a heart murmur (a sound created by turbulent blood flow through narrowed or leaking heart valves or through abnormal heart structures).
The diagnosis is suspected based on a characteristic murmur and cyanosis and is confirmed based on the results of echocardiography.
Surgery is required to correct the defect.

(See also Overview of Heart Defects.)
The four heart defects are

A narrowing of the outflow passage from the right side of the heart
A large ventricular septal defect
Displacement of the aorta that allows oxygen-poor blood to flow directly from the right ventricle to the aorta (causing a right-to-left shunt), which is also called overriding aorta
A thickening of the wall of the right ventricle

In infants with tetralogy of Fallot, the narrowed passage from the right ventricle restricts blood flow to the lungs. The restricted blood flow causes the oxygen-poor blood in the right ventricle to pass through the septal defect to the left ventricle and into the aorta (right-to-left shunt). The more oxygen-poor blood (which is blue) that flows to the body, the bluer the body appears.
Infants with severe or complete blockage of blood flow from the right side of the heart may depend on having an open ductus arteriosus for survival. The ductus arteriosus is a blood vessel in the fetus that connects the two great arteries leaving the heart, the pulmonary artery and the aorta (see Normal Fetal Circulation). After birth, the ductus arteriosus is no longer needed and usually closes within the first days of life. However, if the ductus stays open after birth in infants with severe tetralogy, some blood from the aorta can flow back into the lungs through the open ductus and thus pick up oxygen.

[Monty]

Tetralogy of Fallot consists of 4 features: a large ventricular septal defect, right ventricular outflow tract obstruction, pulmonic valve stenosis, right ventricular hypertrophy, and over-riding of the aorta. Symptoms include cyanosis, dyspnea with feeding, poor growth, and hypercyanotic tet spells (sudden, potentially lethal episodes of severe cyanosis). A harsh systolic murmur at the left upper sternal border with a single 2nd heart sound (S2) is common. Diagnosis is by echocardiography. Definitive treatment is surgical repair.
(See also Overview of Congenital Cardiovascular Anomalies.)
Tetralogy of Fallot (see figure Tetralogy of Fallot) accounts for 7 to 10% of congenital heart anomalies. Associated anomalies include right aortic arch (25%), abnormal coronary artery anatomy (5 to 10%), stenosis of the pulmonary artery branches, presence of aorticopulmonary collateral vessels, patent ductus arteriosus, complete atrioventricular septal defect, atrial septal defect, additional muscular ventricular septal defects (VSDs), and aortic valve regurgitation.