Left ventricular remodelling in outflow tract obstructive lesions during fetal life

Left ventricular (LV) remodelling in prenatally diagnosed LV outflow tract obstructive lesions such as aortic stenosis and aortic coarctation is important for prenatal counselling and postnatal management. The purpose of this study was to document the spectrum and the progression of different LV remodelling patterns and to identify prenatal markers of hypoplastic left heart syndrome (HLHS).

We studied 29 fetuses with LV outflow tract obstruction: 13 with isolated aortic stenosis, 14 with isolated aortic coarctation and two with combined aortic stenosis and aortic coarctation. Echocardiographic evaluation was performed 4 and 8 weeks after the first observation and at birth.

None of the fetuses had HLHS (LV end-diastolic diameter z score higher than -2) at first prenatal echocardiography (24.5 + or - 3.6 weeks). Fetuses were divided into two groups: group A (n = 25) with a LV end-diastolic volume at birth > 20 ml/m(2); group B (n = 4) with a LV end-diastolic volume at birth < 20 ml/m(2) (LV hypoplasia). At first echocardiographic evaluation, the two groups showed a significantly different aorta to pulmonary ratio (0.44 + or - 0.08 vs. 0.86 + or - 0.14; P < 0.001); other LV echocardiographic features were not significantly different. The growth of the mitral (0.10 + or - 0.02 vs. 0.43 + or - 0.28 mm/week; P < 0.02) and aortic annulus (0.08 + or - 0.01 vs. 0.26 + or - 0.14 mm/week; P < 0.05) was significantly slower in group B.

Our data suggest that LV outflow tract obstruction can progressively evolve in HLHS during pregnancy. A smaller aorta to pulmonary ratio was the only significant difference at initial echocardiographic evaluation in the two groups. Moreover, serial echocardiographic examinations are necessary to recognize fetuses at risk for HLHS caused by a subnormal growth rate of the mitral and aortic annulus.