Does Low-Intensity Anticoagulation Using Vitamin K Antagonists Correlate with Factor X Activity Inpatients Implanted with the HeartMate 3 Pump? A Validation Analysis of the MAGENTUM 1 Study

Purpose The MAGENTUM 1 Trial targeted an INR of 1.50-1.90 in patients implanted with HeartMate 3 (HM3) pump. Anticoagulation was maintained in the low intensity range with high efficiency (INR 1.50-1.90, TTR, 75.2 ± 8.6% n=15 patients). None developed thromboembolic events. Factor X activity (FXa) has been suggested as a biologically relevant pharmacodynamic surrogate measure of anticoagulation intensity. We sought to correlate suppression of FXa in MAGENTUM 1 patients to demonstrate the effect of low intensity anticoagulation in HM3 patients. Methods Samples for chromogenic factor X (CFX) assays (Hyphen BioMed) were obtained simultaneously with INR values at routine intervals and stored for batch analysis and not made available to the investigators. Normal reference range for the CFX assay is 71-97%. INR was correlated with CFX; median values and interquartile ranges were determined for INR values >1.50, 1.50-1.90 and Results The correlation of INR range with CFX is shown in Figure 1A. The median CFX value for INR range 1.50-1.90 was 40%. When the INRs were above 1.90 the median CFX value was 30%, when the INRs were below 1.50 the median CFX was 53%. Conclusion We demonstrate that a measured INR range of 1.50-1.90 pharmacodynamically corresponds to less suppression of FX activity than at an INR >1.90 but greater than with INR