Tetralogy of Fallot or TOF is the most common heart defect in children that occur due to abnormal development of the fetal heart during the first 8 week of pregnancy.  TOF is one of hearth lesions in which the primary defect is an anterior deviation of the infundibular septum. The 4 abnormalities of the heart described by Fallot include the following; pulmonary stenosis, ventricular septal defect( VSD ), overriding aorta, right ventricular hypertrophy

TOF Causes
TOF is one of the conotruncal family of heart lession and may have a genetic link that occurs during development of the fetus. Maternal abuse of alkohol during pregnancy is linked to TOF.

Clinical Manifestations
Often,cyanosis is not present at birth,but with increasing hypertrophy of the right ventrikel infundibulum and patien growth,cyanosis occurs later in the 1st year of life. The skin,lips and mucous membranes inside the mouth and nose take on a noticeably dusky blue color. Only some infants with severe obstruction of the right ventricle outflow turn blue at birth.

Older children with long standing cyanosis who have not undergone surgery may have dusky blue skin,gray sclerae with engorged blood vessels,and marked clubbing of the fingers and toes.

Dspnea occurs on exertion. Growth and development may be delayed in patients with severe untreated TOF, particulary when oxygen saturation is chronically < 70%

DIAGNOSIS
Because of right ventricular hypertrophy,the left anterior hemithorax may bulge anteriorly. In about half the cases,a systolic thrill is felt along the left sternal border in the 3rd an 4th parasternal spaces. Infrequently,a continuous murmur may be audible,especially if prominent collaterals are present.

Rontgenographically- the heart size is normal,elevation of the apex,concavity in the region of the main pulmonary artery, right-sided aortic arch,and diminished pulmonary vascularity

Complications
Brain abscess and bacterial endocarditis are complications of TOF.But, these complication are rare. Heart failure is not a usual feature in patiens with TOF

Treatment & Prognosis
TOF is treated by surgical repair of the defects.

The operation is performed under general anesthesia,and involves of the following:

1. The ventriculas septal defect is closed with a patch
2. The obstructed pathwax between the right ventricle and the pulmonary artery is opened and enlarged with a patch. If the pulmonary valve is small,it may be opened as well or removed

Prognosis
After succesful total correction,patients are generally asymptomatic and are able to lead unrestricted lives. (dr. rendra)