Tetralogy of Fallot *

Definition

This anomaly consists of four defects,
1) Ventricular septal defect
2) Pulmonary stenosis
3) Right ventricle hypertrophy
4) Overriding aorta
* If an associated ASD is present then the anomaly is referred to as Pentalogy of Fallot.

Pathology

The right ventricular (RV) infundibulum lies anterior to the position of the VSD and is bounded by the anterior and septal walls anteriorly and medially, the posterior wall is in the position of a vertical crista supraventricularis. RV infundibulum is a is a distinctive channel, usually eshibits a significant degree of stenosis, and is the dominant site of pulmonary flow obstruction in TOF. Pulmonary valve is often malformed, usually either bicuspid or unicuspid, the pulmonary trunk is thin walled and narrower. Foramen ovale is frequently patent, collateral branches arise from the aorta to the lungs in all cases when significant pulmonary obstruction is present.
Size of VSD and degree of pulmonary stenosis play a major role in determining the degree of hemodynamic changes. Since VSD is usually large, both ventricles and aorta have essentially the same pressures, and the shunt flow thus depends on the difference between pulmonary and systemic vascular resistance. Left to right shunt is present when systemic resistance is higher than pulmonary resistance. Right to left shunt is present when pulmonary vascular resistance is higher than systemic resistance. Pulmonic stenosis would decrease blood flow to the lungs and, consequently, decrease the amount of oxygen returned to the left heart.

Clinical Manifestations

One of the most common congenital cardiac defects that causes cyanosis. Some infants may be cyanotic at birth, other may have mild cyanosis that progresses over the first year. Anoxic spells occur when the infant's oxygen requirements exceed the supply. Clubbing, squatting, and poor growth may be present. All patients are at risk for emboli, cerebrovascular disease, loss of consciousness, or sudden death. Murmur is present.

Surgical Interventions