Test occlusion of Fontan fenestration:
Criteria for decision making in one old publication - Bridges ND, et al. JACC 1995;25:1712-17.
Mean RA pressure > 18 mmHg
AV difference of saturation increased by > 33%
RA saturation < 40%.
In patients with unfavorable outcome (2 yr follow-up after fenestration closure); systemic venous pressure increased more than 40% and systemic venous saturation decreased more than 23%.
There are other criteria in other publications.