Combined CMR and Catheterization for Pre-Fontan Evaluation: Comparing Metrics and Clinical Correlations

BACKGROUND: Cardiac magnetic resonance imaging (CMR) is increasingly used in combination with cardiac catheterization (Cath) for the pre-Fontan evaluation of children with single ventricle (SV) physiology. The aim of this study was to describe our institutional experience of this combined assessment. METHODS: We conducted a retrospective, single-center study of 57 single-ventricle patients who underwent CMR and Cath under the same anesthesia prior to Fontan completion. CMR and Cath-based pulmonary and systemic blood flow ratio (Qp/Qs) and aortopulmonary collateral (APC) assessments were compared. In addition, we analyzed the association between significant APC burden (>30% of aortic flow) and preoperative hemodynamics, as well as postoperative outcomes, including chest tube duration and hospital length of stay. RESULTS: CMR consistently yielded higher Qp/Qs values compared to Cath, with a mean underestimation of 0.41 by the latter. This difference was strongly correlated with CMR-derived APC burden (p<0.0001). In comparison, Cath-based qualitative assessment of the APC had a poor correlation with the CMR APC burden and Qp/Qs. The CMR APC burden was also associated with increased indexed ventricular volumes and lower ejection fraction (EF). CONCLUSIONS: Combined CMR and Cath provide a comprehensive pre-Fontan assessment, with CMR offering superior quantification of aortopulmonary collateral burden and demonstrating larger Qp/Qs than calculated by Cath methods. These findings support the continued use of integrated imaging modalities for individualized care.