A substantial number of patients experiences late Fontan circulation failure. Previous concepts of Fontan failure implicate increasing pulmonary vascular resistance (PVR) as a key contributor to late circulatory failure. However, data to support this assumption are sparse. We sought to characterize hemodynamic findings in adult failing Fontan patients.

We performed a bicentric retrospective cohort study in adult Fontan patients, identifying patients with Fontan failure. Patients were divided into systolic dysfunction (rEF) when ejection fraction (EF)<40%, diastolic dysfunction (pEF) when EF≥40% with systemic ventricular end-diastolic pressure≥12mmHg or elevated BNP level (>200pg/mL) and pulmonary hypertension (PH) when indexed pulmonary vascular resistance were elevated (≥2 WU*m²). Hemodynamic, echocardiographic, and clinical data were recorded.

Between 2000 and 2021, 55 adult patients were diagnosed with failing Fontan. Median age at diagnosis was 27 years (interquartile range (IQR), 22–30.7) i.e., 18.0 years [12.0–23.0] after Fontan surgery. The main hemodynamic cause of failing Fontan was the dysfunction of the systemic ventricle in 25 patients (45%), including 15 rEF and 10 pEF without additional hemodynamic lesions. PH was diagnosed in 6 (11%) patients and was isolated in 4 of them. Nine patients (16%) exhibited significant valvular dysfunction and 6 (11%) conduit stenosis. During a median FU of 5 years [1.25–12], Fontan failure-associated morbidity (33/55; 60%) and mortality (6/55, 11%) were substantial regardless of underlying hemodynamic lesions.

Dysfunction of the systemic ventricle, systolic and/or diastolic, is frequent feature in late Fontan failure in adults, while increases in PVR were rarely observed. The intricate interplay between hemodynamic compromises in Fontan failure deserves further research to optimize treatment strategies and outcome.