Background/Introduction: Idiopathic pulmonary hypertension (IPAH) is a progressive disease that leads to right ventricular (RV) failure. Patients with Eisenmenger physiology have an improved course by RV unloading and function preservation. To mimic this physiology, reverse Potts shunt has been utilized in patients with severe IPAH. To further protect the pulmonary vasculature bed from left-to-right shunting when pulmonary pressures are subsystemic, a valved pulmonary-to-systemic shunt has been utilized in adolescents and adults which allows for unidirectional right-to-left shunting at the great arterial level. We describe here two pediatric patients who presented with severe IPAH in which this procedure was performed.

Case Description: Patient 1 (P1) was a 5-year-old male with IPAH with workup notable for a pulmonary vascular resistance (PVR) of 24 indexed Wood units. Despite percutaneous atrial septostomy, Bosentan and subcutaneous Treprostinil titration, he had worsening symptoms and moderately decreased right ventricular function. 
Patient 2 (P2) was a 5-year-old female with IPAH with workup notable for a PVR of 18 indexed Wood units and severe right ventricular dysfunction. Despite percutaneous atrial septostomy, sildenafil and intravenous Treprostinil, she had a prolonged hospital course with frequent pulmonary hypertensive crises and inability to wean off inhaled nitric oxide. 

Discussion: Both patients underwent similar procedures with placement of a valved pulmonary-to-systemic shunt via median sternotomy and aortic and bi-caval venous cardiopulmonary bypass. The unidirectional-valved shunt (UVS) was fashioned by sewing a 9mm pulmonary homograft into a 10mm Hemashield graft to prevent late dilation. This graft was anastomosed to the main pulmonary artery and to the underside of the left subclavian artery, just distal to the left subclavian artery. To allow for an additional right-to-left level shunt to maintain cardiac output, a valved atrial septal defect patch was fashioned using autologous pericardium with an 8mm central fenestration with an overlying flap on its left atrial side sutured for two-thirds of its circumference.
P1 post-operative imaging demonstrated right-to-left shunting at both the atrial and great arterial level. P2 post-operative imaging did not demonstrate immediate atrial nor great artery level shunting, but differential saturations have been noted during intercurrent illness and transthoracic echocardiogram has shown shunting through the UVS. Postoperative recovery was uneventful in both patients, and they were both successfully discharged home.
Both patients continue to have elevated PA pressures despite optimization of their medical therapy. P1 developed bidirectional shunting across the UVS one-year post-operatively and P2 developed this six months post-operatively.

Conclusion: Valved unidirectional pulmonary-to-systemic shunt can be used in pediatric patients with supra-systemic IPAH who have recurrent pulmonary hypertension crises. This allows for Eisenmenger physiology with right-to-left shunting at the great artery level when pulmonary artery pressures are suprasystemic and avoids left-to-right shunting during periods when pulmonary artery pressures are subsystemic. With serial follow up, we have noted that these patients have developed bidirectional shunting at the UVS indicating that the homograft valve has become incompetent at an accelerated rate in this location. The clinical profiles of the patients remain reassuring despite the structural valve deterioration, but the long-term clinical implications of this remain to be seen. To our knowledge, these are the youngest patients undergoing this procedure in the literature.  Continued follow-up will be needed to determine durability of this intervention.