Cardiovascular magnetic resonance–derived hemodynamics predict adverse outcomes after Fontan palliation

Background Long-term outcomes following the Fontan procedure remain heterogeneous, and robust imaging-based predictors of adverse events are limited. Patients residing at moderate-altitude may experience additional pulmonary vascular stress; however, the prognostic value of cardiovascular magnetic resonance (CMR)–derived flow parameters in this population are not well defined. Methods We performed a retrospective cohort study of Fontan patients followed at a single moderate-altitude center who were ≥5 years post-Fontan and had undergone comprehensive CMR exams. Demographic, anatomic, and surgical data were collected. CMR-derived variables included indexed ventricular volumes and function, systemic arterial dimensions, and flow indices in the ascending and descending aorta, superior vena cava (SVC), inferior vena cava, and branch pulmonary arteries. The primary composite outcome was death or referral/listing for heart transplantation. Time-to-event analyses from the time of CMR were performed using Kaplan–Meier estimates and Cox proportional hazards regression. Results A total of 182 Fontan patients were included (median age at Fontan 3.2 years [interquartile range (IQR) 2.6–3.9]; median time from Fontan to CMR 10.9 years [IQR 7.7–14.2]). Over a median follow-up of 4.7 years following CMR (IQR 3.1–6.6), 14 patients (7.7%) experienced the primary outcome. In univariable Cox regression, a higher SVC flow index was significantly associated with a lower risk of the primary outcome [hazard ratio [HR] 0.70 per 0.1 L/min/m 2 increase; 95% confidence interval [CI] 0.50–0.92; p = 0.008]. Conclusions In this moderate-altitude Fontan cohort, reduced CMR-derived SVC flow index was significantly associated with the primary outcome. This finding suggests that systemic venous flow merits further investigation as a prognostic marker in the Fontan population.