The Role Of Platelet Hyperreactivity In Venous Thromboembolism After Total Knee Arthroplasty In Elderly Population Without Pharmacologic Prophylaxis: A Single-Center Study

Introduction While it is suggested that platelet hyperreactivity plays a role in the arterial thrombi, its link with venous thromboembolism (VTE) is not well defined. Aggregometry using low concentrations of agonists is proposed as a reliable method to detect hyperreactivity. The aim of this study was to examine whether platelet hyperreactivity affects the development of VTE after total knee arthroplasty (TKA). Methods Total 150 elderly patients without VTE history were enrolled. Mechanical prophylaxis was used for VTE after TKA. We performed platelet aggregation using Chrono-log (Chrono-log Corporation, USA) in the presence of low concentrations of ADP (1.0 mu mol/L) and epinephrine (0.4, 1.0 mu mol/L), and measured maximal aggregation (%). Results At 0.4 mu mol/L epinephrine, 69.3%, 15.3%, and 15.3% displayed low (<40%), moderate (40-60%), and high (>60%) levels of aggregation, respectively. The proportion of high level of aggregation was 36.7%, 30.7% at 1.0 mu mol/L of epinephrine and ADP, respectively. The incidence of VTE was higher in the moderate/high aggregation group (10/46, 21.7%) than in the low aggregation group (1/104, 1.0%) at 0.4 mu mol/L epinephrine (P < 0.0001). In predicting postoperative VTE, sensitivity and specificity of >= 40% aggregation at 0.4 mu mol/L epinephrine were 90.9% and 74.1%. Higher mean platelet volume and lower volume of blood loss were seen in the high aggregation group than in the low aggregation group. Conclusion Aggregation response to 0.4 mu mol/L epinephrine is an optimal assay to classify platelet activity. Platelet hyperreactivity may increase the risk of postoperative VTE in an elderly population, and can be an indication of pharmacologic prophylaxis.