Summary of Objectives The MOMENTUM 3 trial has demonstrated superiority of the centrifugal HeartMate 3 (HM3) device to the mechanical bearing axial HeartMate II (HMII) continuous-flow cardiac pump, in patients with advanced heart failure refractory to medical management. In this final analysis of the full trial cohort, we evaluate the net burden of hemocompatibility related adverse events between the two LVAS in the long-term and identified risk factors associated with the development of hemocompatibility related adverse events (HRAE's). Methods MOMENTUM 3 is a randomized controlled trial of the HM3 pump versus the HMII pump, irrespective of intended goal of support. This large adaptive trial is designed to have 3 prespecified end points of which the short term (n=294, 6-months) and long-term (n=366, 2-years) primary end points have been reported; we now present this analysis from the full of all 1028 randomized patients. To assess the aggregate of HRAEs, we evaluate the endpoint of 2-year survival free of any non-surgical bleeding, thromboembolic event, pump thrombosis or any neurological event. The net burden of HRAEs will be assessed using a previously defined and validated severity tiered hemocompatibility score, which separates clinical events into four escalating tiers of severity to derive a total score for HRAE events encountered during the entire experience for each patient to death, transplantation or study end. Furthermore, we will identify risk factors for the development of HRAEs. The analysis will be performed with the full cohort of MOMENTUM 3: n=1028 patients. The last patient completed 2 years of follow-up in August 2018; the data lock will be accomplished in November 2018 and final results will be analyzed and available by March 2019. Endpoints This will be the first comprehensive analysis of the long-term outcomes for an aggregate hemocompatibility related adverse endpoint and tiered severity score to evaluate the net burden of bleeding and thrombotic complications experienced by patients treated with either the HM3 or HMII LVAS in the pivotal MOMENTUM 3 trial. (Funded by Abbott; MOMENTUM 3 ClinicalTrials.gov number, NCT02224755.)