Labyrinthine cor triatriatum sinister in fetal hypoplastic left heart syndrome is associated with poor outcomes.

Objectives: A subset of hypoplastic-left-heart-syndrome (HLHS) fetuses have a complex cor-triatriatum sinister that we named "labyrinthine-cor (L-cor)". We sought to determine the prevalence of L-cor in HLHS fetuses and hypothesized that it is associated with increased mortality.

Methods: This single-center retrospective cohort study included all HLHS fetuses from January 2010-December 2020. Fetuses with other hypoplastic-left-heart variants, inadequate images, lack of follow-up and fetal atrial-septal interventions were excluded. RAS was defined as the ratio of pulmonary-vein forward-to-reverse velocity-time-integral (VTI) ≤ 5 and severe-RAS defined as VTI-ratio <3. Kaplan-Meier survival-analysis was performed for the primary outcome of transplant-free survival for 62 weeks after gestational-age of 30 weeks (∼1 year).

Results: Of the 156 consecutive fetuses with HLHS, 11 (7.7%) had L-cor and 8/11 (72.7%) of these had RAS. When compared to HLHS-RAS without L-cor, fetuses with HLHS-RAS and L-cor were less likely to survive to 28 days (87% vs. 62.5%, p = 0.017) and to 1 year (69.6% vs. 25%, p = 0.029). When comparing by survival analysis, fetuses with severe-RAS with L-cor had lower survival compared severe-RAS without L-cor (p = 0.020).

Conclusion: L-cor in fetal HLHS is associated with increased mortality. Recognition of this finding is important for prognostication and atrial-septal-intervention planning.