O2050: Pre-fontan Cardiovascular Magnetic Resonance and Hemodynamic Assessment Predicting Postoperative Fontan Outcomes: A Single Center Experience

Background: Many studies have described the utility of cardiovascular magnetic resonance (CMR) and cardiac catheterization measured indices in determining ideal Fontan candidacy as well as predicting early and mid-term postoperative Fontan outcomes. Hence, performing CMR and cardiac catheterization has become the standard of care in many centers across the world. In this study, we describe the role of combined CMR and cardiac catheterization in predicting post-Fontan adverse outcomes.

Methods: All CMR and cardiac catheterization performed as part of the clinical work up before undergoing Fontan palliation between April 2017 and November 2022 were analyzed. Sequences of CMR included (i) balanced 2D steady state free precision cine imaging, (ii) phase contrast imaging to estimate pulmonary and systemic flow (Qp:Qs), (iii) T2 weighted turbo-spin echo sequence to assess the lymphatic system, (iv) 3D-SSFP, and (v) 3D-black blood VISTA. Lymphatic abnormality was classified into grade 1-4 according to Dori et al. Combined indices such as pulmonary vascular resistance (PVRi) was calculated using transpulmonary gradient obtained by pressure catheter and branch pulmonary artery flow by phase contrast CMR. Cardiac catheterization was performed in the MRI suite or the cardiac catheterization laboratory. Surgical details and immediate post-operative outcomes were reviewed. Composite adverse outcome was defined as takedown of Fontan circulation, mechanical circulatory support (MCS), heart transplantation (HT) or death. CMR and hemodynamic parameters were compared between groups with adverse and favorable outcomes.

Results: Of the total 119 pre-Fontan evaluations performed, 81 underwent Fontan palliation. The remaining 38 were deferred due to reasons mentioned in figure 1. Of those who underwent the Fontan palliation with a median (IQR) age of 4.1 (3.4-6.1), composite adverse outcome was achieved in 8 (10%) including Fontan takedown in 1 (12.5%), heart transplant in 1 (12.5%), mechanical circulatory support in 1 (12.5%), and death in 5 (62.5%) during a median (IQR) follow up of 21 (3-32) months. Diagnosis of heterotaxy syndrome (p=0.04), higher pre-fontan PVRi (p=0.03), lower ejection fraction (p=0.07), and moderate-severe (>30%) atrioventricular valve regurgitation (p=0.046) were significantly associated with adverse outcomes. PVRi calculated using transpulmonary gradient from catheterization and Qep from CMR showed statistical significance while PVRi using only catheterization data did not. Patients with grade 4 lymphatic abnormalities did not have a significant association with poor outcomes (p=0.10). However, of the 3 patients with grade 4 lymphatic abnormalities, 2 underwent evaluation for transplant and only 1 underwent Fontan palliation. Other factors such as end-diastolic volume, end-diastolic pressure, maldistribution of pulmonary blood flow, and percent aortopulmonary collateral burden before catheter intervention were not associated with adverse outcomes postoperatively.

Conclusion: Currently, CMR and cardiac catheterization provides comprehensive assessment prior to undergoing Fontan palliation. Diagnosis of heterotaxy, higher pre-operative PVRi, and moderate to severe atrioventricular valve regurgitation were associated with adverse early postoperative Fontan outcomes.