Background: Congestive heart failure patients have hepatic congestion and abnormal coagulation profiles, increasing perioperative bleeding at time of ventricular assist device implantation. This study examined the impact of the preoperative administration of vitamin K on perioperative blood transfusion requirements., Methods: Retrospectively, 190 patients met inclusion criteria. Patients received no vitamin K (n = 62) or two 10-mg doses of intravenous vitamin K (n = 128) in the 24 hours before assist device implantation. Primary end points included transfusion requirements and reexploration rates for bleeding. Secondary outcomes were pump thrombosis and in-hospital mortality., Results: Baseline characteristics were similar between the 2 groups, with slight differences (not statistically significant) noted in the Interagency Registry for Mechanically Assisted Circulatory Support profile and total bilirubin levels. The only significant difference noted was the year of implantation (P < .001). Blood product usage was significantly lower in the vitamin K group compared to the no vitamin K group (P < .001). Higher rates of reexploration for bleeding (29.7% vs 13.6%, P = .023) and death at hospital discharge (16.2% vs 2.8%, P = .004) were noted for the no vitamin K group compared with the vitamin K group. After adjusting for age, sex, race, body mass index, Interagency Registry for Mechanically Assisted Circulatory Support profile, total bilirubin, surgeon, and year of operation, reexploration rates and death did not achieve statistical significance. No statistically significant difference was observed in stroke and pump thrombosis rates between the 2 groups., Conclusions: Preoperative vitamin K administration may help reduce blood product use without any increased risk for strokes or pump thrombosis., (Copyright © 2020 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.)