Fetal growth of left-sided structures and postnatal surgical outcomes in the "borderline" left heart varies by cardiac phenotype.

OBJECTIVES Two "borderline" left heart phenotypes are evident in the fetus: 1) severe aortic stenosis (AS), which is associated with a globular left ventricle (LV), systolic LV dysfunction, and LV growth arrest, and 2) 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 left sided structure growth and Z-score change over gestation by phenotype. Secondarily we aimed to describe the postnatal outcomes of these two cohorts. We hypothesized that the left sided structures would grow at a faster rate in the LHH group compared to AS, and that the LHH group would be more likely to undergo biventricular repair. METHODS A retrospective cohort study was conducted using an institutional cardiology database from 4/2001 to 4/2018. Fetuses with severe AS and those with severe LHH, with at least 2 fetal echocardiograms, were included. Inclusion criteria for AS were: aortic annulus Z-score <-2.0, severe AS, depressed LV function, retrograde systolic flow in the arch, and endocardial fibroelastosis. Inclusion criteria for LHH were: aortic annulus Z-score <-2.0, hypoplastic but apex forming LV, normal LV function, and retrograde systolic flow in the aortic arch. Exclusion criteria included abnormal cardiac connections, other forms of structural congenital heart disease, cardiomyopathy, history of fetal aortic valvuloplasty, and participation in a maternal hyperoxygenation study. Measurements and respective Z-scores for aortic annulus, mitral valve annulus, LV long and short axis dimensions, along with aortic arch measurements were collected longitudinally for each fetus and plotted over time for both cohorts. Mean slopes over gestation were compared between the groups for change in dimension and Z-scores using generalized linear regression accounting for repeated measures. A subanalysis was performed matching the groups by aortic annulus z-score and gestational age and comparing growth of left-sided structures over time. RESULTS A total of 53 fetuses with 158 echocardiograms were included. There were 20 fetuses in the AS cohort (38%) with 65 echocardiograms, and 33 fetuses in the LHH cohort (62%) with 93 echocardiograms. On the first fetal echocardiogram LHH fetuses had a later gestational age and larger aortic annulus diameter. The median measurements were: LHH annulus 0.32 cm± 0.08 versus AS 0.20 cm ±0.06 p< 0.001); LHH z-score -3.1 ± 0.67 versus AS -4.6 ± 1.34, p<0.001. The mean rate of aortic annulus growth was faster in the LHH group compared to the AS group (LHH 0.15 ± 0.01 mm/week versus AS 0.07 ±0.01 mm/week, p<0.001. The LHH group did have a decrease in the Z-score over time, but at a slower rate than the AS group (LHH -0.04 ± 0.02/week versus AS -0.13 ± 0.02/week, p<0.001). A similar pattern was seen for the mitral valve and LV dimensions. A subanalysis was performed that included 6 AS and 6 LHH fetuses matched by initial aortic valve z-score and gestational age due to the significant differences in these two variables between the original cohorts. The subanalysis demonstrated the same findings, with the LHH group z scores decreasing at a slower rate than the AS group. There were a total of 52 live births. 15 (75%) of the infants in the AS cohort underwent single ventricle palliation, 2 (10%) underwent biventricular repair, and 3 (15%) died prior to any interventions. In the LHH cohort, 3 (9.4%) underwent single ventricle palliation, 28 (87.5%) achieved biventricular circulation, and 1 (3.1%) died prior to intervention. CONCLUSIONS The left sided cardiac structures grow at a faster rate in fetuses with severe LHH than in fetuses with severe AS, and the Z-scores decrease at a slower rate in fetuses with severe LHH than those with severe AS. A majority of infants in the LHH group did not undergo single ventricle palliation. This information can be useful in counselling expectant families on the expected growth potential of the aortic valve, mitral valve, and LV depending on the cardiac phenotype. This article is protected by copyright. All rights reserved.