Bidirectional Glenn Procedure or Hemi-Fontan

The bidirectional Glenn (BDG) and hemi-Fontan are surgical techniques used to create superior cavopulmonary anastomosis, the second stage repair in Fontan completion (see Superior Cavopulmonary Anastomosis). They are performed in patients with an anatomic or functional single ventricle. Whether it is right or left, the single ventricle must, therefore, provide blood supply to the higher resistance systemic circulation and the lower resistance pulmonary circulation until surgical correction is undertaken. The BDG procedure, or hemi-Fontan, helps eliminate volume load on the single ventricle and simplifies the operative procedure at Fontan. Several centers have reported decreased mortality and morbidity of the Fontan procedure in those who have undergone BDG or hemi-Fontan. All patients with a single ventricle must eventually undergo a Fontan procedure to achieve separation of their systemic and pulmonary circulations. A patient with a completed Fontan procedure has systemic venous return diverted to the pulmonary circulation, driven by central venous pressure and affected by intrathoracic pressure changes and systemic ventricular relaxation. As of 2018, there are an estimated 50,000 to 70,000 patients with a Fontan circulation, 40% of these patients older than 18. About 1000 Fontan procedures are performed annually in the United States.