1002-83 In Utero Pulmonary Outflow Obstruction: Natural History and Predictors of Postnatal Severity

We reviewed prenatal and postnatal echocardiograms of fetuses with pulmonary stenosis (PS, n=14) and pulmonary atresia (PAtr, n=5), to elucidate the antenatal natural history of PS and PAtr and identify predictors of severe postnatal disease. Fifteen were serially studied in utero (age at first study 24±4wks). Fetuses with PS were divided into severe and mild groups according to whether they were (9) or were not (4) ductus-dependent at birth, respectively. Measurements of RV short and long-axis, tricuspid valve, main and branch pulmonary artery (PA) and pulmonary valve dimensions were converted to Z-scores based on age-adjusted normal fetal data. At the initial exam, main and branch PA and pulmonary valve Z-scores were larger in fetuses with mild PS than in those with severe PS or PAtr (p≤0.01). On serial followup, however, growth rates of right heart structures did not differ for mild PS versus severe PS and PAtr groups. Ductal flow in utero was antegrade in systole in all with mild PS, but was either bidirectional (5 severe PS) or retrograde only (4 severe PS, all PAtr) in the severe PS and PAtr groups. Initial RV outflow gradients by Doppler did not differ between the mild and severe PS groups with antegrade PA flow (mean 26±12mmHg). Pulmonary insufficiency was a consistent feature in fetuses with mild PS, but was not present in the severe PS or PAtr groups. By color Doppler, 3/4 with mild PS had mild tricuspid regurgitation, whereas mild or moderate tricuspid regurgitation was found in 9/9 with severe PS and 4/5 with PAtr. When severe PS and PAtr groups were compared, there was no significant difference in initial Z-scores or growth rates of right heart structures between the groups. Tricuspid regurgitation severity and initial RV pressure by the tricuspid regurgitation jet (mean 71±21mmHg) also did not differ between the severe PS and PAtr groups. On serial followup in 6/8 with severe RV outflow obstruction (1 PAtr, 7 severe PS), the RV pressure increased by 18–47mmHg. In 3/6 serially studied fetuses with antegrade PA flow (2 severe PS, 1 mild PS), the RV outflow gradient increased later in gestation. There was no change in the severity of tricuspid or pulmonary regurgitation during followup in any fetus. The severity of PS may be differentiated in utero by the direction of ductal flow, the presence of pulmonary insufficiency, severity of tricuspid insufficiency and the size of the pulmonary valve and PAs. In the absence of antegrade PA flow, severe PS may be difficult to distinguish from PAtr antenatally