Abstract 4367274: Invasive Hemodynamic and MRI Predictors of High Risk Lymphatic Subtype T2-Weighted Pre-Fontan MRI and Associated Clinical Outcomes

Background: Lymphatic subtype (LS) 4, as identified on T2-weighted cardiac MRI (CMR), is associated with higher rates of Fontan failure. Pre-Fontan factors predictive of LS are incompletely defined. Prior analysis of our cohort revealed that demographic and clinical factors were not predictive, though moderate or greater atrioventricular valve regurgitation (AVVR) on echocardiogram was associated with higher risk LS. We aim to identify hemodynamic and CMR correlates of high risk LS. Hypothesis: Patients with high-risk lymphatic subtypes would have less favorable hemodynamic measurements by cardiac catheterization and clinical outcomes compared to lower-risk counterparts. Methods: Single-center retrospective cohort study of patients who had pre-Fontan CMR from 2017-2021. Demographic, clinical, echocardiographic, MRI, and catheterization data was collected from birth to one year after Fontan or until death or heart transplant for patients who did not undergo Fontan. Two groups were defined: standard risk (LS 1, 2, or 3 without history of chylothorax) and high risk (LS 3 with history of chylothorax, or 4). Results: There were 171 patients who had CMR within 1 year prior to Fontan, of which 23 had high risk LS. By cardiac catheterization, compared to standard risk patients, high risk patients had a higher Qp:Qs (1.2 vs 1.05, p=0.01), left pulmonary artery pressure (LPAp) (11mmHg vs 10mmHg, p=0.04), and ventricular end diastolic pressure (EDP) (8mmHg vs 7mmHg). AVVR, ejection fraction, aortopulmonary collateral burden, and pulmonary artery dimensions by MRI did not differ by groups. High risk patients had worse outcomes: lower rates of Fontan completion (75% vs 96%, p<0.01), higher rate of death pre-Fontan (9.5% vs 1.3%, p=0.02), and longer length of stay after Fontan surgery (14 days vs 9 days, p=0.01). There was no difference in days alive and out of hospital (DAOH), readmission days, or ICU readmission days 1 year post-operative between the two groups. There was no difference in death within 3 years after Fontan and one standard risk patient underwent a heart transplant within 3 years of Fontan (p=0.01). Conclusions: Pre-Fontan LPAp and EDP by cardiac catheterization were associated with high risk LS. Patients with high risk LS had worse Fontan outcomes, with lower rates of Fontan completion, longer length of stay post-Fontan, and higher rates of death pre-Fontan with no difference between DAOH, readmission or ICU readmission days.