Preoperative factors affecting mortality in HLHS patients undergoing the Norwood procedure

Hypoplastic left heart syndrome (HLHS) is characterized by hypoplasia of the left heart and outflow tract. The three-stage surgical reconstruction of heart consists of circumventing the underdeveloped left ventricle by connecting right ventricle to systemic circulation and grafting a passive flow conduit which shunts venous blood into pulmonary artery. First stage surgery (Norwood) has the highest mortality among common congenital surgeries (7-19%) followed by a high risk interstage (IS) phase where additional 4-15% of infants die. A retrospective chart review of HLHS patients was conducted at Cook Children's hospital between January 2007 and January 2017. Objective of the study was to identify preoperative risk factors that may lead to premature death during IS. Univariate logistic regression analyses were used to determine whether feeding, intubation, and extracorporeal membrane oxygenation (ECMO) predicted mortality. IS was defined as time following Norwood procedure until Glenn, the second stage of reconstruction. Analysis revealed that receiving Norwood feeding prior to surgery was associated with lower mortality (OR=0.42, CI=0.20-0.90, p= 0.025). Furthermore, intubation prior to surgery (OR=1.73, CI=1.05-2.85, p= 0.03) and pre-operative ECMO (OR=2.83, CI=1.12-7.19, p=0.028) were associated with higher IS mortality. Current findings suggest a positive relationship between pre-operative respiratory interventions and increased rate of post-operative mortality. This relationship suggests that pulmonary status and inability to feed may be the leading prognostic factors in IS infant death. Norwood nutrition and continued respiratory support warrant further studies in order to understand the clinical implications of these findings.