Cardiac MRI in patients with Fontan circulation: assessing risk factors for adverse outcomes.

Background: Cardiac magnetic resonance (CMR) imaging provides critical insight into the prognosis of Fontan patients, enhancing our understanding of their long-term outcomes. This study aimed to investigate the prognostic role of CMR in a carefully selected cohort of Fontan patients with the highest initial likelihood of survival.

Methods: This retrospective nationwide cohort study included 148 Fontan patients who underwent post-Fontan CMR imaging in Finland between 2017 and 2023. The primary endpoint was death or listing for heart transplant. The secondary endpoint was myocardial fibrosis determined by native T1 mapping measured by CMR.

Results: The median time from the Fontan procedure to CMR examination was 10.8 years, with a median post-CMR follow-up of 2.55 years. Six patients (4.1%) reached the primary endpoint. Significant haemodynamic risk factors for the primary endpoint included worse global longitudinal strain (p=0.03), worse global circumferential strain (p<0.001) and reduced ejection fraction (p=0.04). Notably, patients with decreased myocardial function showed higher native T1-mapping values. Additional clinical risk factors that were associated with the primary endpoint included arrhythmias (p=0.01), protein-losing enteropathy (p=0.01), New York Heart Association functional class ≥2 (p<0.001) and liver cirrhosis (p=0.01).

Conclusions: CMR provides critical insights into long-term outcomes in Fontan patients. In our prioritised cohort, characterised by an initially high likelihood of survival, the observed risks of adverse outcomes corroborate findings from higher mortality cohorts. This underscores the importance of myocardial function and native myocardial T1 mapping in risk assessment, reaffirming CMR's role in effective risk stratification for this population.