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Study Objective: Little is known about the association between tacrolimus time in therapeutic range (TTR) within the guideline‐recommended targets and heart transplant (HT) patient outcomes. This study evaluated the association of early tacrolimus TTR with rejection and other clinical outcomes during an extended follow‐up after HT. Design: This was a single‐center retrospective cohort study. Setting: The study was conducted at Michigan Medicine (1/1/2006–12/31/2017). Patients: HT recipients ≥18 years of age were included. Measurement: The primary end point was the effect of tacrolimus TTR on time to rejection over the entire follow‐up period. Main Results: A total of 137 patients were included with a median follow‐up of 53 months. Based on the median TTR of 58%, the patients were divided into the low tacrolimus TTR (n = 68) and high tacrolimus TTR (n = 69) cohort. The high tacrolimus TTR was associated with a significantly lower risk of rejection compared to the low tacrolimus TTR cohort (hazard ratio [HR] 0.63, 95% confidence interval [CI] 0.41–0.98; p = 0.04). A post hoc analysis revealed associations between rejection and TTR when high and low TTR groups were created at different levels. TTR <30% was associated with a 7‐fold higher risk of rejection (HR 7.56; 95% CI 1.76–37.6; p < 0.01) and TTR >75% was associated with a 77% lower risk of rejection (HR 0.23; 95% CI 0.08–0.627; p < 0.01). Conclusions: Patients in the higher tacrolimus TTR cohort had a lower risk of rejection. We observed correlations between higher risk of rejection with TTR <30% and lower risk of rejection with TTR >75%. Future studies should focus on validating the optimal TTR cutoff while also exploring a cutoff to delineate high‐risk patients for which early interventions to improve tacrolimus TTR may be beneficial. [ABSTRACT FROM AUTHOR]

Abstract: Patients with a mechanical mitral valve have an increased risk of thrombosis, and guidelines recommend a higher international normalized ratio goal for vitamin K antagonists-based anticoagulation. Guidelines provide recommendations for bridging with unfractionated heparin; however, there is no clear guidance on the heparin infusion intensity that should be used. This study was a retrospective, single-center, cohort study of patients aged ≥18 years or older with a mechanical mitral valve admitted from June 2019 to September 2022 who were maintained on a singular heparin infusion intensity nomogram for at least 48 hours. The patients were stratified into either a low- or a high-intensity heparin infusion nomogram. The exclusion criteria included non-nomogram heparin infusions and patients within 30 days of valve implantation. The primary outcome of this study was a composite of all bleeding events (major, clinically significant nonmajor, and minor bleeding). The secondary outcomes included bleeding events, analyzed individually, and thrombotic events. Seven total bleeding events were observed between the 2 groups, with 1 minor bleeding event in the low-intensity group and 6 bleeding events in the high-intensity group. One thrombotic event occurred in the high-intensity group. No statistically significant differences were found between the primary and secondary outcomes. Future studies are necessary to guide heparin infusion intensity selection in patients with mechanical mitral valves., Competing Interests: The authors report no conflicts of interest., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

Competing Interests: Disclosures: All relevant financial relationships have been mitigated. Disclosures can be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=A22-0012.