Methods: We retrospectively analyzed all consecutive infants undergoing Norwood palliation for HLHS at a single institution over the past 5 years (2007-2012). SGA was defined as birth weight <10thpercentile. We evaluated the effects of weight for gestational age and gender on hospital and ICU length of stay (LOS), ventilation days, RV function, tricuspid regurgitation (TR) and the use of afterload reduction following Norwood palliation. Student’s t-test was used to compare continuous variables while Fisher’s exact test was used for categorical outcomes.
Results: A total of 67 infants (41 males) underwent Norwood palliation of which 8 (5 males) did not survive to hospital discharge (12% mortality). Of the survivors, 7 infants (4 males) were SGA (12%). Compared to infants with appropriate weight for gestational age (AGA), SGA infants had similar age at repair, bypass time and cross clamp time but endured significantly longer ICU LOS (40 vs. 17 days, p<0.01) with a trend towards longer hospital LOS (44 vs. 28 days, p=0.10) and more days intubated (19.6 vs. 13.4 days, p=0.23). SGA infants had a higher incidence of reduced systolic RV function on routine discharge echo (29% vs. 14%, p=0.30) but similar rates of >mild TR (14% vs. 16%, p=1.00) and a similar likelihood of being discharged on afterload reduction (43% vs. 39%, p=1.00). Subgroup analysis of SGA infants by gender, however, revealed that none of the female SGA infants had abnormal RV function, > mild TR or were discharged on afterload reduction, whereas in the SGA males 50% had abnormal RV function, 25% had > mild TR and 75% were discharged on afterload reduction. BW and gestational age were similar amongst the SGA gender subgroups.
Conclusion: In SGA infants with HLHS, males have decreased RV performance compared to females following Norwood palliation. Compared to AGA infants, SGA infants of both genders endure significantly longer ICU LOS but the myocardial pathology is skewed toward males. The same gender disparity is not present in the AGA group. We speculate that the adverse myocardial response to cardiopulmonary bypass in male SGA infants may result from differences in epigenetic regulation and expression of genes associated with cardiac remodeling and metabolism.