7 Tetralogy of Fallot
In classic TOF with pulmonary stenosis, delivery should be at term in a tertiary care center because there is no perfect antenatal indicator of the degree of pulmonary outflow obstruction at birth, the risk of cyanotic spells, and the need for full postnatal evaluation.
a. Palliation: In infants with severe RV outflow obstruction and cyanosis or uncontrollable hypoxic spells in whom corrective surgery cannot be performed, palliation in the form of a modified Blalock–Taussig shunt may be created using a Gortex tube to anastomose the subclavian artery or brachiocephalic artery and the ipsilateral pulmonary artery.
7. Branch pulmonary artery stenosis (diagnosed by cardiac magnetic resonance imaging [MRI] and lung isotope scan) can require postoperative balloon angioplasty with stent placement or surgical repair. The aim is to normalize blood flow to both lungs, thus reducing the RV systolic pressure. These additional procedures carry a risk of morbidity and mortality.
3. Postnatal echocardiography confirmed the diagnosis of TOF with large subpulmonary VSD with posterior deviation of the outlet septum causing valvar and subvalvar pulmonary stenosis. The pulmonary arteries were of good size, with a transpulmonary Doppler velocity of 4.5 m/s (Fig. 7-3).
5. In view of the baby’s anatomy and the current degree of cyanosis, prostaglandin E1 (PGE1) infusion was not started. It was decided to let the ductus arteriosus start to close and then decide based on the degree of cyanosis.
6. The baby maintained a pulse oximeter saturation of 85% to 90% and was feeding well, so he was discharged home and followed monthly at the cardiology outpatient clinic. The mother was made aware of the possibility of cyanotic spells.
b. TOF is one of the more commonly encountered forms of heart disease in the fetus, and in one series it is the third most commonly identified form of structural heart disease. This could be due to the very common occurrence of aneuploidy and extracardiac structural pathology rather than recognition of the pathology at routine obstetrics assessment.
c. Classic TOF can be missed if echocardiographic examination of the fetal heart is confined to the four-chamber view, because an abnormal four-chamber view is rarely observed in this condition. One might see an abnormal four-chamber view in tetralogy with absent pulmonary valve, with mitral valve obstruction, or with restrictive VSD, all of which are less common than the classic form of TOF.