PURPOSE: Individuals born with defects resulting in a functionally univentricular heart Fontan-type palliation (FP) are prone to physiologic deterioration requiring advanced cardiac therapies. Given limitations to organ availability and long transplant waiting-list times, mechanical circulatory support (MCS) has become an important tool to permit individuals with a single ventricle circulation to either survive to transplant or may be used for destination therapy. The physiologic and clinical impact of MCS in FP patients are undefined. METHODS: Centers participating in the ACTION Learning Network entered data on FP patients that received a VAD at their center, between 1/26/12 and 10/1/2019, in the ACTION Outcomes registry. Additional survey data on physiologic variables will be completed by Nov 2019. RESULTS: Thirty-nine FP patients were reported to the ACTION registry. Limited clinical variables can be found in table 1. MCS types included intracorporeal continuous flow support (25 patients), paracorporeal support (10), total artificial heart (2) and biventricular assist devices (1). Among supported patients, 23 % (9) died while on support, 10 % (4) are currently alive on support, and 67% (26) were transplanted and are alive while none died post-transplant. Major adverse events included major bleeding (17 episodes), driveline infection (n=1) and other neurologic dysfunction (n=1). There was no stroke or pump thrombosis (table 1). MCS implant improved NYHA functional class (12.5% versus 75% NYHA class 1/2) and decreased severe atrioventricular valve regurgitation (47% versus 30%). Complete clinical and hemodynamic data will be available and presented at the ISHLT meeting. CONCLUSION: This is the first multicenter report of FP outcomes post MCS. MCS results in improved functional status and decreased atrioventricular valve regurgitation in FP patients awaiting transplant without adverse post-transplant outcomes and with good on-device survival. MCS for Fontan patients as both destination and bridge to transplant is a reasonable option.