Recovery during mid-term mechanical support of fontan circulation in sheep

Total cavopulmonary connection (CPC) has a significant incidence of late failure due to increased systemic venous pressure and low cardiac output. Mechanical support could prevent failure by correcting hemodynamics. We established a model of inferior CPC using an axial flow pump (Thoratec HeartMate II, Thoratec Corp. Pleasanton, CA) in a group of ten 47-57 kg sheep and assessed hemodynamics and metabolism as a potential chronic treatment option for failed Fontan circulation. After pilot studies (n = 7), three animals underwent pump-supported inferior CPC to assess hemodynamic and metabolic responses. Pump inflow was connected to the inferior vena cava (IVC) and outflow to the main pulmonary artery. The IVC was ligated at the right atrium. Hemodynamic and biochemical parameters were recorded over four days. The first seven animals died from pump-related causes (graft kinking, three; pump thrombosis, one) or other causes (GI bleeding, one; suspected stroke, two). The subsequent three animals were electively euthanized on postoperative day four due to IRB requirements. Over the four day postoperative period, pump flow was 3.43 +/- 0.62 L/min and IVC pressure 4.05 +/- 3.21 mm Hg (mean +/- SD). Lactate levels remained normal. Low pressure and high-volume IVC flow was sustained by mechanical support. We will next attempt chronic pump implantation.