Creation of a bidirectional shunt reduces the amount of blood volume that the heart needs to pump at the time of surgical repair with the Fontan procedure.

[1] The aim of the bidirectional Glenn shunt is to improve oxygenation and reduce the load on the single functioning ventricle while the patient is prepared for definitive surgical correction through separation of the pulmonary and systemic circuits.

[4] The circulation of a patient after BDG shunt placement requires adequate systemic venous return to support pulmonary blood flow.

Right-side dominant circulation, elevated pulmonary vascular resistance, and prolonged operative and recovery time are the major factors that increase the risk of complications and failure.

[6] Prolonged cardiopulmonary bypass time, elevated central venous pressure (CVP) or pulmonary arterial pressure, and specific malformations including unbalanced atrioventricular septal defect or surgical history of total anomalous pulmonary venous connection repair were established as risk factors for worse outcomes.

[7][8][9][10] In the bidirectional Glenn shunt procedure, the surgical aim is to control pulmonary blood flow and volume load on the heart.

This modified circulatory system is established by detaching the superior vena cava from the right atrium and connecting the cranial part of the SVC to the pulmonary arteries (shunt).

As a result, the venous blood from the upper body enters the SVC and perfuses the pulmonary circulation as a low-pressure circuit, similar to a two-ventricle circulatory system.

Extracorporeal membrane oxygenation (ECMO) may be used post-operatively as a temporary measure in cases of cardiac dysfunction or severe pulmonary hypertension.

[17] The Glenn group at Yale worked on several strategies to create anastomoses between the superior or inferior vena cavae to the right or main pulmonary arteries.

These results showed a low survival rate in these canines, and further demonstrated the basis of many surgical complications including pleural effusions, ascites, and thrombosis.