An echocardiographic study of tetralogy of Fallot in the fetus and infant

Objective: To document the echocardiographic features of tetralogy of Fallot during fetal and postnatal life. Correlation of echocardiographic findings with the requirement for early intervention prior to definitive repair. Design: Retrospective observational study. Setting: A tertiary fetal cardiology unit. Patients: Fetuses with a diagnosis of tetralogy of Fallot identified from a prospective database between 1 January 1999 and 31 October 2002. Main measures of outcome: Growth of aorta and pulmonary trunk during fetal and postnatal life. Doppler assessment of the great arteries both prenatally and postnatally. Clinical outcome to definitive repair. Results: We identified 25 fetuses with tetralogy of Fallot, 23 having a pulmonary valvar diameter below the normal range at some point during gestation. The ratio of the diameter of the aortic to the pulmonary valve was abnormal in all cases. The pulmonary arterial Doppler velocity was within the normal range in six fetuses at presentation, and elevated in the remainder. In two fetuses, the right ventricular outflow tract was patent during fetal life, but had become atretic at birth. Both of these fetuses had reversal of flow in the arterial duct at presentation during fetal life. In 2 fetuses in whom we showed poor growth of the pulmonary trunk in late gestation, it was necessary to intervene early. The Doppler velocity across the pulmonary valve during fetal life did not differentiate between babies who required early intervention and those who were repaired electively. There was a marked increase in pulmonary arterial Doppler velocity following birth, which became more elevated with age. Of 18 liveborn infants, 17 have survived, with 2 having balloon dilation of the right ventricular outflow tract, and 3 insertion of a Blalock-Taussig shunt prior to definitive repair. Conclusions: In tetralogy of Fallot, features of pulmonary valvar hypoplasia and obstruction are evident during fetal life. Progression of obstruction in the right ventricular outflow tract was observed during fetal life as well as postnatally. Reversal of flow in the arterial duct, and failure of growth of the pulmonary trunk, predicted the need for early surgery to maintain pulmonary blood flow. Parents should be counselled about the possibility of emergency intervention being required after birth. Affected fetuses should be delivered at units with experience of managing the cyanosed newborn.