Role of Thromboelastography Platelet Mapping and International Normalized Ratio in Defining "Normocoagulability" During Anticoagulation for Mechanical Circulatory Support Devices: A Pilot Retrospective Study

Abstract

Thromboembolic (TE) events and hemorrhagic complications continue to remain as frequent adverse events and causes of death after mechanical circulatory support device (MCSD) implantation. To counterbalance this postimplant multifactorial hypercoagulable state, antithrombotic therapy given postimplant must be individually tailored to keep patient adequately anticoagulated yet normocoagulable. Prior studies describing different anticoagulation protocols do not define normocoagulability for patients on MCSDs. We evaluated the role of thromboelastography platelet mapping (TEG PM) in defining "normocoagulability" for MCS patients on anticoagulant (warfarin) and antiplatelet agents. Ninety-eight MCSD patients who underwent TEG PM assay at our institution from 2012 to 2014 were included for retrospective analysis. Eleven (11.2%) subjects developed at least one TE event during the study period. Of the 13 TE events, 8 occurred in patients with total artificial heart (TAH). TEG parameters closest to the event or when patient was clinically adequately anticoagulated and corresponding international normalized ratio (INR) were measured. Thromboelastography coagulation index (CI) appears to be the single most statistically significant parameter that can be used to designate a patient as normocoagulable. Based on our results, patients with HeartMate II (HM II) and Heart Ware (HW) devices should be maintained at a CI value of less than or equal to 1.5 whereas patients with TAH devices should be maintained at a CI less than or equal to 1.2. The CI should be correlated with the degree of Vitamin K-dependent coagulation factor inhibition that is achieved using device-specific goal INR ranges. A recent modification, TEG PM assesses the effects of antiplatelet drug. Maximal amplitude arachidonic acid (MA-AA) < 50 and maximal amplitude adenosine diphosphate (MA-ADP) < 50 are desired for normocoagulable state.