The Glenn

Second-stage palliation: Hemi-Fontan or bidirectional Glenn anastomosis procedure

The hemi-Fontan operation or a bidirectional Glenn anastomosis is typically performed in infants aged 3-10 months to minimize the period of time during which the right ventricle is subject to volume overload. Cardiac catheterization is performed prior to this procedure to evaluate pulmonary vascular resistance, pulmonary artery anatomy, tricuspid valve regurgitation, and right ventricular function.

To perform a bidirectional Glenn procedure, CPB is achieved with neoaortic arch cannulation and separate right-angle IVC and right-angle SVC cannulae. The aortopulmonary shunt is ligated and divided when CPB is initiated. If any stenosis of the pulmonary artery secondary to the prior shunt or patch is present, the stenosis is repaired with patch augmentation. The azygous vein is ligated and divided. The SVC is transected and anastomosed in an end-to-side fashion to the superior aspect of the right pulmonary artery. The cardiac end of the transected SVC is oversewn. Some groups routinely perform the bidirectional Glenn procedure without CPB, with or without an SVC-to–right aorta temporary shunt, during the anastomosis to minimize high cerebrovenous pressures.

The hemi-Fontan procedure has the same physiologic factors as a bidirectional Glenn anastomosis but includes an anastomosis of the pulmonary arteries to an incision in the atriocaval junction. The cavopulmonary connection may be performed under a brief period of deep hypothermic circulatory arrest. Alternatively, cannulation of the IVC and high on the SVC can be used to perform the procedure entirely during CPB.

Whether the procedure is performed under circulatory arrest or during CPB, the remainder of the procedure is the same. The aortopulmonary shunt is divided, and the pulmonary arteries are mobilized from the right to the left upper lobe. The azygous vein is ligated. The right atrium is opened along the superior aspect of the appendage, and a corresponding incision is made transversely along the confluence of the branch pulmonary arteries (see upper left of Media file 4). The posterior aspect of the right arteriotomy is anastomosed to the inferior aspect of the pulmonary arteriotomy (see upper right of Media file 4).

A patch of pulmonary allograft tissue is fashioned to augment the pulmonary arteries. The allograft patch is begun at the left upper lobe, incorporating a separate end-to-side anastomosis for a left SVC, if necessary (see lower portion of Media file 4). A patch is placed within the right atrium, which isolates SVC return into the pulmonary arteries and provides an unobstructed pathway for connection of IVC return during the Fontan procedure (see lower portion of Media file 4). The atrial septal defect is inspected and enlarged, if necessary, which is completed best by cutting back the coronary sinus into the left atrium. Tricuspid valve repair is also performed as needed.

The advantage of the hemi-Fontan is that it shortens the length of time of CPB and dissection required for the completion Fontan procedure, which requires only the removal of the intra-atrial patch and placement of a lateral tunnel in the right atrium from the IVC to the SVC. In addition, routine augmentation of the branch pulmonary arteries helps optimize the anatomy for the completion Fontan procedure.

http://emedicine.medscape.com/article/904137-treatment#Secondstage