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Abstract

We thank Salih et al for the contribution of their data to this important topic. We did recently compare activated clotting time (ACT) and anti-activated factor X (anti-Xa) activity for monitoring of unfractionated heparin (UFH) therapy in 104 patients with aortic aneurysm undergoing an endovascular procedure at our vascular medical center.1Dieplinger B. Egger M. Luft C. Hinterreiter F. Pernerstorfer T. Haltmayer M. et al.Comparison between activated clotting time and anti-activated factor X activity for the monitoring of unfractionated heparin therapy in patients with aortic aneurysm undergoing an endovascular procedure.J Vasc Surg. 2018; 68: 400-407Abstract Full Text Full Text PDF PubMed Scopus (8) Google Scholar We found a poor agreement between the two methods, and increased peak anti-Xa activity was an independent predictor of periprocedural bleeding but not of increased peak ACT. Our findings suggest that monitoring of UFH therapy with anti-Xa activity during an aortic endograft procedure may reduce total UFH use and possibly even improve outcomes.1Dieplinger B. Egger M. Luft C. Hinterreiter F. Pernerstorfer T. Haltmayer M. et al.Comparison between activated clotting time and anti-activated factor X activity for the monitoring of unfractionated heparin therapy in patients with aortic aneurysm undergoing an endovascular procedure.J Vasc Surg. 2018; 68: 400-407Abstract Full Text Full Text PDF PubMed Scopus (8) Google Scholar Confirming our results, Salih et al also describe a moderate correlation between ACT and anti-Xa activity in 20 patients undergoing a thoracoabdominal endovascular procedure at their institution. Interestingly, they used considerably higher doses of UFH compared with our study. This might be explained by differences in institutional protocols, higher ACT target values, and differences in the procedure's duration. Salih et al reported no major thrombotic or bleeding complications in their cohort, but four patients (20%) received a periprocedural blood transfusion. Unfortunately, no detailed information on estimated blood loss or preprocedural and postprocedural hemoglobin level is given. Therefore, no clear conclusions with respect to the association between ACT and anti-Xa activity with clinical outcomes, such as periprocedural bleeding, can be drawn from their study. Even though we agree with Salih et al that ACT is a bedside test available 24 hours a day in many hospitals, we disagree with their statement that ACT measurement therefore remains more clinically useful than anti-Xa activity to monitor UFH therapy during vascular interventions. In this context, a recent systematic review on the measurement of ACT to monitor UFH therapy during noncardiac arterial procedures clearly demonstrated that there is no robust and concluding evidence on an optimal ACT target range.2Doganer O. Wiersema A.M. Scholtes V. Blankensteijn J.D. Yeung K.K. Jongkind V. No concluding evidence on optimal activated clotting time for non-cardiac arterial procedures.Eur J Vasc Endovasc Surg. 2019 Nov 4; ([Epub ahead of print])PubMed Google Scholar Even more important, there are doubts about the proposed association of ACT with bleeding and thromboembolic complications in patients undergoing noncardiac vascular interventions.2Doganer O. Wiersema A.M. Scholtes V. Blankensteijn J.D. Yeung K.K. Jongkind V. No concluding evidence on optimal activated clotting time for non-cardiac arterial procedures.Eur J Vasc Endovasc Surg. 2019 Nov 4; ([Epub ahead of print])PubMed Google Scholar Many laboratories are now transitioning to monitor actual heparin activity by chromogenic anti-Xa assays, which are considered the reference method for monitoring heparin therapy.3Hirsh J. Raschke R. Heparin and low-molecular-weight heparin: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy.Chest. 2004; 126: 188S-203SAbstract Full Text Full Text PDF PubMed Scopus (840) Google Scholar, 4Rosenberg A.F. Zumberg M. Taylor L. LeClaire A. Harris N. The use of anti-Xa assay to monitor intravenous unfractionated heparin therapy.J Pharm Pract. 2010; 23: 210-216Crossref PubMed Scopus (27) Google Scholar, 5Carroll R. Mansell J. Platton S. Green L. MacCallum P.K. The future of activated clotting time?.Anesth Analg. 2018; 127: e25-e26Crossref PubMed Scopus (2) Google Scholar In line with this, we suggest substituting ACT with anti-Xa activity (with a target range of 0.5-1.0 IU/mL) to monitor UFH therapy during aortic endovascular procedures at vascular medical centers. At our institution, we have anti-Xa activity measurements available in the central laboratory 24 hours a day with an optimized turnaround time from blood draw to result reporting of 20 minutes. We are well aware that this setup is not available in many hospitals. Therefore, a point-of-care device to measure anti-Xa activity in the hybrid endovascular room might be useful for clinical routines. Monitoring of heparin anticoagulation during complex aortic endovascular surgeryJournal of Vascular SurgeryVol. 71Issue 4PreviewThe paper by Dieplinger and colleagues1 in the Journal of Vascular Surgery describes the association between activated clotting time (ACT) and anti-activated factor X (anti-Xa) activity for managing anticoagulation during complex vascular surgery. The authors concluded that anti-Xa activity should be used instead of ACT. We have discussed similar concerns in our high-volume tertiary vascular surgical unit and would like to contribute our data. Full-Text PDF