Fetal Echocardiographic Assessment of Right Ventricular and Tricuspid Valve Function in Hypoplastic Left Heart Syndrome: Correlation with Postnatal Outcomes

Background: Hypoplastic left heart syndrome (HLHS) carries significant morbidity and mortality. Postnatal transthoracic echocardiogram (echo) assessment of right ventricular (RV) and tricuspid valve (TV) function correlates with HLHS outcomes. There are limited reports on the association between RV and TV function in prenatally diagnosed HLHS and postnatal outcomes. This study attempted to correlate fetal-echo (F-echo) parameters of RV and TV function with postnatal transplant-free survival and timing of bidirectional Glenn (BDG) in fetal HLHS patients.

Methods: Imaging and clinical data of fetuses diagnosed with HLHS between February 2014 and September 2020 at our institution were retrospectively reviewed. Initial F-echo measurements of RV myocardial performance index (MPI) and fractional area change (FAC) were measured. The RV shortening fraction (SF), along with the presence, degree of tricuspid regurgitation (TR) and RV size by diastolic short-axis dimension were recorded. Postnatal outcomes including transplant-free survival (survival), hospital length of stay after initial palliation (LOS) and age at BDG were recorded. Early BDG was defined as repair at < 4 months of age. Mann-Whitney U test was used to correlate F-echo measurements and postnatal outcomes.

Results: F-echo was available in 69 subjects; 22 were excluded for pregnancy termination or fetal demise, 9 for genetic syndromes, resulting in 38 subjects. Mean gestational age at initial F-echo was 31w3d +/- 6 days. Eleven were referred to our institution after 30 weeks from regional cardiologists. Mean gestation for first F-echo was adjusted to 23w1d +/- 3 days after late outside cardiology referrals were excluded. Age of subjects at time of review ranged from 7 months to 6.5 years. Eight subjects died and three required transplant (median age at death 2 months; median age at transplant 8 months). F-echo RV MPI was significantly higher (> 0.372 +/- 0.09; p = 0.005) and RV FAC was significantly lower ( < 43% +/- 6.4%; p = 0.016) in HLHS non-survivors versus survivors. RV size and presence of TR were not significantly different. Subjects with initial LOS > 30 days were more likely to have fetal TR (p = < 0.001) and RV dilation (p = 0.019), but no significant RV MPI and FAC difference. No fetal parameters correlated with need for an early Glenn ( < 4 months of age).

Conclusion: F-echo evaluation of RV function using MPI and FAC in HLHS correlates with transplant-free survival. Presence of fetal TR and RV dilation correlate with a longer initial LOS. These findings suggest F-echo parameters of RV and TV function may inform prenatal counseling and expectations of postnatal outcomes for fetal HLHS patients and families.