Fetal growth of left‐sided structures and postnatal surgical outcome in borderline left heart varies by cardiac phenotype

ABSTRACT Objectives There are two borderline left‐heart phenotypes in the fetus: (1) severe aortic stenosis (AS), which is associated with a ‘short, fat’, globular left ventricle (LV), LV systolic dysfunction and LV growth arrest; and (2) severe left‐heart hypoplasia (LHH), which is associated with a ‘long, skinny’ LV, laminar flow across hypoplastic mitral and aortic valves and arch hypoplasia. Both phenotypes may be counseled for possible single‐ventricle palliation. We aimed to compare the rates of left‐sided cardiac structure growth and Z‐score change over gestation and to describe the postnatal outcomes associated with these two phenotypes. We hypothesized that the left‐sided structures would grow faster in fetuses with LHH compared to those with AS, and that those with LHH would be more likely to achieve biventricular circulation. Methods This was a retrospective cohort study using data collected in an institutional cardiology database between April 2001 and April 2018. We included fetuses with severe AS or severe LHH, and with at least two fetal echocardiograms. Inclusion criteria for the AS group included: aortic‐annulus Z‐score