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Tetralogy of Fallot Pulmonary Stenosis Pulmonary Atresia Tricuspid Atresia Ebstein's Anomaly

Tetralogy of Fallot

  • The "Tetralogy of Fallot defect" consists of a combination of a tetrad of lesions consisting of: (1) stenosis of the pulmonary artery infundibulum; (2) a ventriculoseptal defect; (3) an overriding of the aortic root and valve; and (4) right ventricular hypertrophy.
  • Tetralogy of Fallot has its developmental origins in a defective neural crest cell migration, which results in abnormal conotruncal formation. The four anatomic manifestation result from the anterior malalignment of the infundibular septum. It is the most common cyanotic heart defect with an incidence of 3.26 per 10,000 live births (Keane).
  • Physiology: Patients will present with cyanosis, known as "blue babies", which is secondary to a greater degree of pulmonary and infundibular stenosis. This results in increased right to left shunting of blood across the ventricular septal defect
    • The volume of this shunt and thus, degree of cyanosis, is directly proportional to the severity of outflow obstruction. Shunting may also occur at the atrial level if there is an atrial septal defect or patent foramen ovale.
    • In cases of Tetralogy of Fallot with pulmonary atresia, all pulmonary flow is derived from systemic-to-pulmonary communications (i.e. aortopulmonary collaterals, bronchial arteries, patent ductus arteriosus) which results in mixing of arterial and venous blood supplies. These left-to-right shunt communications place an increased volume load on the left ventricle which can lead to pulmonary hypertension.
    • Tetralogy of Fallot with an absent or significantly defective pulmonary valve (abnormal leaflets) leads to pulmonary regurgitation and thus, a volume load on right ventricle and central pulmonary arteries. The right ventricle stroke volume increases to compensate for the volume load which leads to dilation of these arteries.
    • The physiology of Tetralogy of Fallot with common atrioventricular canal is largely the same as tetralogy alone; however, in the case where the atrioventricular valve is insufficient, there may be increased volume load to one or both ventricles.
  • Infants with this defect will be variably cyanotic after birth, most often with only mild to moderate cyanosis; some may even be asymptomatic. Cyanosis typically increases in times of distress and with crying and hyperapnea. These hypercyanotic spells are a hallmark of Tetralogy of Fallot and are self-aggravating whereby worsening hypoxemia exacerbates distress which then increases cyanosis. These episodes may often terminate in loss of consciousness and rarely, convulsions and permanent neurological sequelae.
  • Management
    • The current recommendation for age of surgical repair is approximately 3 months: i.e., for infants born at full term and with uncomplicated anatomy. Repair during early infancy can restore normal circulation and minimizes long-term risks associated with right ventricular hypertension and cyanosis.
    • Management of recurrent hypercyanotic spells that occur before surgery is urgent so to prevent neurologic sequelae and/or even death. This may be done with supplemental oxygen and the administrations of IV fluids; i.e., to increase intravascular blood volume and pulmonary blood flow. Medications such as morphine and propranolol have also been given to relieve distress and block beta adrenergic receptors, respectively.