PM1028: Move the Cannulas! Right Ventricular Mechanical Support After Transplant Using Pulmonary Arterial to Left Atrial ECMO

Introduction: Right ventricular (RV) dysfunction is a post-operative complication in patients after cardiac transplantation, especially those with elevated pulmonary vascular resistance (PVR). In severe RV failure refractory to medical support, mechanical circulatory support (MCS) has been used as a bridge to recovery, with mixed outcomes. We describe a patient with trisomy 21 and failed single ventricle palliation, who, after heart transplant, developed severe RV failure. We herein describe a unique post-heart transplant RV MCS support strategy.

Case Description: An 18-month-old, 10.3 kg male, with trisomy 21 and severely unbalanced right dominant atrioventricular septal defect with a hypoplastic aortic arch previously had a Hybrid palliation with a patent ductus arteriosus stent, and bilateral branch pulmonary artery banding as a newborn. At 6 months, despite medical optimization with pulmonary vasodilator therapies, diagnostic catheterization measured elevated pulmonary arterial (PA) pressures and transpulmonary gradient PVR of 5.47Uxm2 and he was not deemed a candidate for a second stage palliation. He was ultimately listed for heart transplantation. He eventually underwent an uneventful orthotopic heart transplant. Despite pre-emptive medical therapies, he developed acute RV failure within several hours post-transplant, requiring escalation to extracorporeal membrane oxygenation (ECMO) support via right atrium to left atrium (LA) cannulation to allow normal loading conditions for the left ventricle. His RV remained hypertensive and dysfunctional so on post-operative day (POD)4 he was converted to a main pulmonary artery (PA) to LA cannulation to reduce RV afterload directly. The unloaded RV function normalized quickly. Over the next two weeks, the PA-to-LA ECMO flow was weaned and ultimately the centrifugal pump in the ECMO circuit was able to be removed entirely on POD22. Oxygenator flows suggested most flow was through the pulmonary vascular bed and on POD23 he was decannulated in the catheterization laboratory with 50% systemic RV pressure with good RV function. He was discharged home on POD39.

Discussion: RV failure is a possible cause of early graft failure which has high morbidity and mortality following heart transplant. Failure of medical therapy requires escalation to MCS. We describe a novel cannulation strategy to provide a reliable way to 1) dramatically reduce RV afterload directly, 2) provide an opportunity for physiologic weaning/training of the RV to a higher vascular resistance, and 3) maintain normal LV coupling and loading conditions during support. This strategy also avoids ventriculotomy in a freshly transplanted organ.

Conclusion: Pediatric patients with elevated PVR can successfully undergo heart transplantation and be supported post-operatively to survival. MCS can be used effectively to treat patients with early graft dysfunction after transplant and novel cannulation strategies may play a role in improving survival of these patients.