*Purpose: Direct oral anticoagulants (DOACs) have recently transformed the field of anticoagulation, offering more predictable pharmacokinetic and pharmacodynamic characteristics when compared to traditional warfarin therapy. However, data regarding the use of DOACs in comparison to warfarin in the solid organ transplant population is limited. This is particularly relevant to the heart transplant population due to the high risk of  venothromboembolism  post-transplant and the potential for significant drug interactions with both warfarin and DOACs. 

*Methods: In this study we investigated the use of anticoagulants in post-heart transplant  recipients  and compared bleeding and breakthrough thromboembolic  events in patients receiving either warfarin or DOACs.  This is a single center, retrospective cohort study  including  all adult heart transplant recipients requiring anticoagulation following transplantation between January 1, 2010 and May 31, 2021.

*Results: A total of 51 patients on anticoagulation were identified and reviewed. Out of the 51 patients, 15 (29%) were prescribed warfarin and 36 (71%) were prescribed a DOAC. Apixaban (84%) followed by rivaroxaban (16%) were the most commonly prescribed  DOACs.  The most common indication for anticoagulation was  deep vein thrombosis  (61%); of  these,  15 were classified as upper extremity and 16 were lower extremity.  Bleeding events were observed in 11 patients, 6 of whom were on concurrent antiplatelet therapy with aspirin, including one patient on both aspirin and clopidogrel. Seven out of the 11 patients with bleeding events were also on concurrent fluconazole, a CYP3A4 inhibitor, per institution protocol. Seven of the bleeding events occurred for patients on warfarin and four patients were on a DOAC. Two patients on warfarin and two on a DOAC required blood transfusions. One patient on warfarin and one on a DOAC required administration of fresh frozen plasma for reversal. There were no breakthrough thromboembolism/stroke events in either the patients on warfarin or DOAC therapy.  

*Conclusions: This study demonstrates a trend towards higher prescribing rates of DOAC vs warfarin in our adult heart transplant population. This study also suggests higher bleeding rates in adult heart transplant recipients on warfarin therapy versus those on DOACs. Our findings contribute to the available  literature on the use of DOACs when compared to warfarin in the solid organ transplant population.  

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