Please advise what is the difference between a bi-directional gleen and a hemi fontan procedure?

Very similar: Both connect svc (large vein bringing blood back to heart from upper body) to pulmonary arteries to provide blood flow to lungs. In the glenn, svc is disconnected from right atrium ; connected to the pas. In the hemi-fontan, svc stays connected to the RA but patch-closed so flow still only goes to the pas. Same physiology, but sets up slightly different approach for next surgery in staged repair.