Methods: In this study, a total of 97 pediatric patients who were operated due to hypoplastic left heart syndrome and its variants between March 2011 and October 2018 were retrospectively analyzed. Thirty-two of the patients (28 males, 4 females; median age 5 days; range, 1 to 25 days) underwent Norwood Stage I operation (Group N), while the remaining 65 patients (44 males, 21 females; median age 6 days; range, 1 to 55 days) underwent a hybrid procedure (Group H). Both treatment strategies were compared.

Results: The median body weight in Group H was significantly lower and the number of patients with a low birth weight (<2,500 g) was significantly higher than Group N (p=0.002 and 0.004, respectively). The postoperative early mortality rate was similar between the groups. Univariate and multivariate analyses revealed that the need for preoperative mechanical ventilation was a significant factor for mortality (p=0.004 and 0.003, respectively). Syndromic appearance was also a significant factor the multivariate analysis (p=0.03). There was a statistically significant difference between the groups in terms of the inter-stage mortality rates (p=0.0045). Second-stage procedure was performed in 32 patients. The early mortality rate after the Glenn operation was 7.6%. Six patients died after comprehensive Stage II operation. Five patients underwent biventricular repair and 8 patients had third-stage fenestrated extracardiac Fontan operation (Group N, n=7 and Group H, n=1). The Kaplan-Meier survival curve demonstrated that Group N had a higher survival rate at both one and five years than Group H, although the difference was not statistically significant (p=0.15). Subgroup analysis showed that the Norwood procedure with Sano modification had the highest survival rate with 40% at five years.

Conclusion: Our study results show that patients undergoing the Norwood procedure have a more uneventful course of inter-stage period and Stage II and III, despite drawbacks early after Stage I procedure. Based on our experiences, we recommend performing the hybrid intervention in patients with a poor clinical condition and a body weight of <2,500 g.