Abstract 4144701: Characterizing Pulmonary Artery Growth in Single Ventricle Patients Palliated through Fontan Procedure

Introduction: Pulmonary artery (PA) size influences risks for complications in patients with Fontan physiology. Optimal strategies to augment PA growth over the course of single ventricle surgical palliations are not well understood. Hypothesis: In single ventricle surgical palliations, PA growth will be concentrated in periods of pulsatile blood flow. Aim: Describe PA growth through early childhood in patients with Fontan palliation. Methods: Retrospective, single-center study of Fontan patients between 1998-2022. Absolute PA diameters (right+left PA) and Nakata index (NI) were measured by angiogram and growth compared at three intervals: pre-Glenn, pre-Fontan, and 5yrs post-Fontan. Post-Glenn, pulsatile blood flow was defined as native antegrade flow (with or without PA band) or systemic shunt (surgical or ductal stent). Multivariable linear regression assessed predictors of PA size 5yrs post-Fontan. Results: In 195 patients, hypoplastic left heart syndrome was most common (60/195, 32%). Passive PA flow at Glenn occurred in 164/195(84%). Median age at Fontan was 38 (33,46) months. Absolute PA size increased during both pre-Glenn to pre-Fontan interval (p<0.001) and pre-Fontan to 5yrs post-Fontan interval (p<0.001), but relative growth by NI decreased after Glenn (p<0.001) with no further change post-Fontan (p=0.29). Overall PA and LPA growth velocity was significantly higher in pulsatile than passive Glenn patients (2.0 mm/yr [1.3, 2.7] v 0.7 mm/yr [0.1, 1.7], p=0.01 and 1.0 mm/yr [0.5, 1.5] v 0.2 mm/yr [-0.4, 0.5], p=0.009 respectively, Figure 1). In multivariable analysis, post-Fontan PA size was significantly associated with pre-Fontan size (0.3 mm/mm [0.1, 0.6], p=0.02) but not cardiac diagnosis (p=0.67), initial Stage I surgical type (p=0.10), or use of stent angioplasty (p=0.28). Conclusions: Through single ventricle surgical palliations, absolute PA size increases, while growth velocity remains stable after Glenn. Post-Fontan PA size is primarily driven by pre-Fontan PA size suggesting importance of efforts to improve PA growth during Glenn period. Maintaining pulsatile flow during Glenn represents a viable strategy to augment PA growth and preferentially improve left PA growth through Fontan.