PRENATAL DETECTION OF SEVERE RIGHT-VENTRICULAR OUTFLOW TRACT OBSTRUCTION - PULMONARY STENOSIS AND PULMONARY ATRESIA

We reviewed the prenatal echocardiograms and clinical outcomes of 12 f etuses with severe valvar pulmonary stenosis (six cases) or pulmonary atresia (six cases), to identify in utero echocardiographic features a ssociated with severe right ventricular outflow tract obstruction. The mean age at initial prenatal study was 25 +/- 6 weeks of gestation. T he echocardiographic appearance of the four chamber view, the right ve ntricular outflow tract, and the pulmonary arteries were similar for s evere pulmonary stenosis and pulmonary atresia. The four chamber view was abnormal in all 12 cases. Right atrial dilation, with or without t ricuspid regurgitation, was a common feature of severe pulmonary steno sis (six patients) and pulmonary atresia (four patients). In two fetus es with pulmonary atresia and significant right ventricular hypoplasia , a large atrial septal defect and no obvious right atrial enlargement were seen. Right ventricular hypoplasia was a feature in five fetuses with pulmonary atresia and in five fetuses with a patent pulmonic val ve. All six fetuses with severe pulmonary stenosis and four fetuses wi th pulmonary atresia had right ventricular hypertrophy. Tricuspid regu rgitation was present in five fetuses with severe pulmonary stenosis a nd in two with pulmonary atresia. All of the fetuses with pulmonary at resia had retrograde blood flow in the ductus arteriosus by color flow mapping. Despite the presence of a patent pulmonary valve, three fetu ses with severe pulmonary stenosis had no antegrade blood flow detecte d through the right ventricular outflow tract, and only retrograde duc tal and pulmonary artery flow could be demonstrated. Ratios of the dim ensions of right to left heart structures, including ventricular diame ters and lengths, and diameters of the atrioventricular valve and grea t artery, were not statistically different between the fetuses with at resia and stenosis. Recognition of the echocardiographic features asso ciated with severe right ventricular outflow tract obstruction, partic ularly abnormalities of the four chamber view, should facilitate detec tion of severe pulmonary stenosis and pulmonary atresia on routine fet al screening. However, differentiation between these two conditions an tenatally in the absence of antegrade right ventricular outflow appear s to be unreliable at present.