Left Heart Obstructive Lesions and Left Ventricular Growth in the Midtrimester Fetus

BACKGROUND: Isolated case reports that suggest the potential for development of left heart hypoplasia late in gestation provide the only information about the in utero natural history of left heart obstructive lesions. METHODS AND RESULTS: We reviewed the prenatal and postnatal echocardiograms of 21 fetuses with left heart obstructive lesions, including 15 with serial antenatal study, to elucidate the antenatal natural history of this spectrum of disease and to identify features indicative of postnatal disease severity. Ventricular, atrioventricular valve, and great artery dimensions were measured and growth curves were developed with comparisons to data from 47 normal fetuses. Fetuses were divided 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 examination (21.7 +/- 3.4 weeks' gestation), left heart dimensions were normal or reduced, with the most diminutive measurements in group 3. Three fetuses in group 2 and most in group 1 had normal initial left heart dimensions. Subsequent growth of left heart structures either paralleled normal growth or was reduced, the latter resulting in the development or progression of left heart hypoplasia. All left heart dimensions grew more slowly in group 2 and group 3 than in group 1 (P < .05). Other prenatal features observed only in groups 2 and 3 included reversed (n = 10) or bidirectional (n = 1) foramen ovale flow and retrograde distal arch flow (n = 9). Initial midtrimester mitral valve and ascending aorta z scores and the growth rates of all left heart structures correlated strongly with postnatal left ventricular end-diastolic dimension (P = .0007 to .03, r = .57 to .82) and could be additional indicators of postnatal disease severity. One group 1 fetus developed severe aortic stenosis late in gestation. CONCLUSIONS: The potential for the in utero development or progression in severity of left heart obstruction and hypoplasia in left heart obstructive lesions necessitates serial prenatal study in affected fetuses carried to term.