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In volume 6, issue 2 of The VAD Journal, we published a paper by Rainess et al. who reported their experience with managing subtherapeutic INRs, mostly in patients with HeartMate II (Thoratec, Pleasanton, CA). Although, the cohort did include some HeartMate 3-supported patients. In their program (Wake Forest University), pharmacists manage anticoagulation according to the institutional protocol, which allows bridging with low molecular weight heparin when INR decreases to less than 1.8. The study is unique because the patients did NOT require interruption of anticoagulation for any purpose. In all instances, the INR decreased because of dietary variations, recent dose changes, skipped doses, medication interactions, etc. Almost half of their patients had a history of hemolysis or pump thrombosis. After analyzing 155 bridging episodes, the authors reported systemic bleeding events in 9% of the patients and localized bleeding in 10%. Importantly, no event resulted in hospitalization or blood transfusion; this rate seems to be excessive considering a relatively minor deviation of INR from the therapeutic range, and it raises a question about an appropriate threshold for bridging initiation.

Studies such as Rainess et al. fill an important knowledge gap. From our standpoint, a 20% risk in bleeding, which includes a 9% risk of systemic bleeding, is a too high price to pay for such a minor decrease in INR. Perhaps tolerating a subtherapeutic INR for a few days would be a safer approach. A specific cutoff of the INR value triggering bridging should be a subject of a randomized study, but setting the bar at 1.8 may represent an excessively aggressive strategy.

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