IN-UTERO PULMONARY-ARTERY AND AORTIC GROWTH AND POTENTIAL FOR PROGRESSION OF PULMONARY OUTFLOW TRACT OBSTRUCTION IN TETRALOGY OF FALLOT

Objectives. This study was designed to define patterns of pulmonary ar tery and aortic growth in fetuses with tetralogy of Fallot and to dete rmine the potential for in utero progression of right ventricular outf low tract obstruction. Background. Despite an abundance of reports doc umenting the prenatal diagnosis of tetralogy of Fallot, there is littl e information about its course in utero. Methods. Pulmonary artery and ascending aortic diameters were measured from prenatal and postnatal echocardiograms of 16 fetuses with tetralogy of Fallot, initially stud ied at 23.6 +/- 6.0 (mean +/- SD) weeks of gestation. Fetuses were cla ssified retrospectively as having mild and severe tetralogy of Fallot according to whether the pulmonary artery circulation was (severe, n = 5) or was not (mild, n = 11) ductus arteriosus dependent at birth. Re sults. Initial main pulmonary artery diameter was small for gestationa l age in 9 fetuses, large in 2 and normal in 5 compared with data from 57 gestational age-adjusted normal fetal studies; it was significantl y smaller in the group with severe tetralogy of Fallot (p = 0.05). The initial main pulmonary artery/aortic diameter ratio was also smaller for the group with severe tetralogy of Fallot (0.50 +/- 0.15 vs. 0.73 +/- 0.14 in the group with mild tetralogy of Fallot, p = 0.01). Initia l aortic and branch pulmonary artery diameters tended to be normal or near normal for age. In eight fetuses serially studied, main and branc h pulmonary artery growth was normal or reduced during prenatal follow -np, Pulmonary artery growth was most reduced in two fetuses in the gr oup with severe tetralogy of Fallot, resulting in pulmonary artery hyp oplasia at birth, Two fetuses with valvular pulmonaly atresia at birth had previously shown anterograde pulmonary outflow in midgestation, s uggesting progression of pulmonaly outflow obstruction. Conclusions. T he postnatal spectrum of pulmonary artery size in tetralogy of Fallot can be attributed to variable patterns of growth in utero. Main pulmon ary artery size, main pulmonary artery/aortic diameter ratio and patte rn of pulmonary artery growth may be predictive of the severity of pos tnatal pulmonary outflow obstruction. Pulmonary atresia can develop in utero in some fetuses with tetralogy of Fallot.