LEFT-HEART OBSTRUCTIVE LESIONS AND LEFT-VENTRICULAR GROWTH IN THE MIDTRIMESTER FETUS - A LONGITUDINAL-STUDY

Background Isolated case reports that suggest the potential for develo pment of left heart hypoplasia late in gestation provide the only info rmation about the in utero natural history of left heart obstructive l esions. Methods and Results We reviewed the prenatal and postnatal ech ocardiograms of 21 fetuses with left heart obstructive lesions, includ ing 15 with serial antenatal study, to elucidate the antenatal natural history of this spectrum of disease and to identify features indicati ve of postnatal disease severity. Ventricular, atrioventricular valve, and great artery dimensions were measured and growth curves were deve loped with comparisons to data from 47 normal fetuses. Fetuses were di vided into groups according to whether postnatally the left heart was capable (group 1, n=10) or incapable (group 2, n=7) of supporting the systemic circulation in the presence of a patent aortic valve. Group 3 (n=4) included fetuses with aortic atresia. At the initial examinatio n (21.7+/-3.4 weeks' gestation), left heart dimensions were normal or reduced, with the most diminutive measurements in group 3. Three fetus es in group 2 and most in group 1 had normal initial left heart dimens ions. Subsequent growth of left heart structures either paralleled nor mal growth or was reduced, the latter resulting in the development or progression of left heart hypoplasia. All left heart dimensions grew m ore slowly in group 2 and group 3 than in group 1 (P<.05). Other prena tal features observed only in groups 2 and 3 included reversed (n=10) or bidirectional (n=1) foramen ovale flow and retrograde distal arch f low (n=9). Initial midtrimester mitral valve and ascending aorta z sco res and the growth rates of all left heart structures correlated stron gly with postnatal left ventricular end-diastolic dimension (P=.0007 t o .03; r=.57 to .82) and could be additional indicators of postnatal d isease severity. One group 1 fetus developed severe aortic stenosis la te in gestation. Conclusions The potential for the in utero developmen t or progression in severity of left heart obstruction and hypoplasia in left heart obstructive lesions necessitates serial prenatal study i n affected fetuses carried to term.