Agreement between Anti-Factor Xa and Activated Partial Thromboplastin Time Measurements in Syncardia Total Artificial Heart Recipients Receiving Postoperative Anticoagulation with Unfractionated Heparin

Abstract

<h3>Purpose</h3> The Activated Partial Thromboplastin Time (aPTT) has been the historical method of choice for anticoagulation monitoring in patients undergoing mechanical circulatory support with intravenous unfractionated heparin (IVUFH). However, the assay is susceptible to interference effects and is being progressively superseded by the anti-Factor Xa (anti-Xa) method. The study aim was to investigate the agreement between aPTT and anti-Xa measurements in patients receiving post-operative anticoagulation with IVUFH following Syncardia Inc. Total Artificial Heart (TAH) implantation. <h3>Methods</h3> A retrospective single arm, single centre analysis of 20 patients who underwent TAH implantation from July 2014 to October 2018 entailed simultaneous determinations of aPTT and anti-Xa. Agreement between these parameters was assessed using a novel statistical approach based on the Bland-Altman method. <h3>Results</h3> In spite of a positive correlation between aPPT and anti-Xa measurements, normal target ranges were poorly aligned: from 5^th to 30^th post-operative day, for anti-Xa values of 0.2 and 0.4 U/mL corresponding APTT values were 51.1 and 64.3 seconds, respectively. Moreover, white blood cell count was associated with a trend towards lower aPTT levels with respect to anti-Xa. Conversely, bilirubin level was significantly associated with an increase in aPTT levels with respect to anti-Xa values. <h3>Conclusion</h3> A novel method developed to investigate the agreement between aPTT and anti-Xa in the peri-operative phase of TAH therapy showed comparatively low levels of anticoagulation (with respect to historical target aPTT range) were not associated with thromboembolic sequalae. Methodology developed for this study is generalisable to other forms of mechanical circulatory support.