The effect of pulmonary circulation hemodynamics on right ventricular unloading via the bidirectional Glenn shunt: implications for congenitally corrected transposition repair.

The bidirectional Glenn shunt has been successfully applied as an adjunct to ventricular septal defect closure and pulmonary valvulotomy to treat congenitally corrected transposition of the great arteries (ccTGA). The purpose of this study was to examine the volume and pressure unloading effects of the bidirectional Glenn shunt on the hypertrophied pulmonary ventricle in a canine model of ccTGA. Five beagles underwent survival surgery to band the pulmonary artery. Three months later, a polytetrafluoroethylene graft was anastomosed to the superior vena cava and right pulmonary artery. The graft or superior vena cava was clamped to create the normal or bidirectional Glenn circulation, and hemodynamic data were recorded. The bidirectional Glenn shunt significantly reduced right ventricular volume loading and stroke work. Dogs with normal pre-bidirectional Glenn cardiac outputs had greatly reduced right ventricular volumes and pressures with the bidirectional Glenn shunt. Dogs with pre-bidirectional Glenn right ventricular dysfunction had moderate volume but no pressure decreases with the bidirectional Glenn shunt owing to improved left ventricular output. In these dogs it is likely that the decreased level of pressure and volume unloading is because of a concomitant improvement in left ventricular output post-bidirectional Glenn shunt placement. The bidirectional Glenn shunt is effective at unloading the right ventricle in a canine model of ccTGA.