International Journal of Cardiology 181 (2015) 413–414
Contents lists available at ScienceDirect
International Journal of Cardiology journal homepage: www.elsevier.com/locate/ijcard
Letter to the editor
Antiplatelet properties of oral anticoagulants Corinne Frère a,b, Marc Laine c, Franck Paganelli c, Françoise Dignat-George b, Laurent Bonello b,c,⁎ a b c
Laboratoire d'Hématologie, Centre Hospitalier Universitaire de Marseille, Hôpital Timone, Assistance Publique-Hôpitaux de Marseille, Marseille, France Vascular Research Center of Marseille, INSERM UMRS-1076, Aix-Marseille Université, Marseille, France Service de Cardiologie, Centre Hospitalier Universitaire de Marseille, Hôpital NORD, Assistance Publique-Hôpitaux de Marseille, Marseille France
a r t i c l e
i n f o
Article history: Received 20 November 2014 Accepted 21 December 2014 Available online 24 December 2014 Keywords: Anticoagulants Thrombosis Bleeding
Until recently, vitamin K antagonists (VKA) were the only oral anticoagulant drugs used in clinical practice for stroke or systemic embolism prevention in patients with non-valvular atrial fibrillation (AF). New oral anticoagulant drugs such as dabigatran etexilate and rivaroxaban have been developed and are currently available as an alternative in this indication. Both drugs were demonstrated to be noninferior to warfarin for the prevention of stroke or systemic embolism in patients with non-valvular AF in the RE-LY and ROCKET trials [1,2]. Their advantages are the consistency of the resulting anticoagulant level and the lack of need of biological follow-up favoring their widespread. While VKA acts by reducing the synthesis of functional clotting factors II, VII, IX and X, dabigatran etexilate acts as a competitive reversible non-peptide antagonist of thrombin, and rivaroxaban as a competitive reversible antagonist of activated factor X (Xa). These new oral anticoagulants (NOAC) result in the inhibition of thrombin generation. Thrombin is a multifunctional enzyme which converts fibrinogen to fibrin, cross-links fibrin monomers via activation of factor XIII, activates protein C and initiates numerous cellular processes including vascular healing. In addition, thrombin activates platelets via its platelet protease-activated receptors (PAR) 1 and 4. By inhibiting thrombin generation, anticoagulants are therefore expected to exert indirect effects on platelet function. Since these anticoagulants act through different mechanisms of action (indirect or direct thrombin inhibition), we hypothesize that they could have differential effects on platelet activation that might in part explain ⁎ Corresponding author at: Département de Cardiologie, Hôpital universitaire Nord de Marseille, Vascular Research Center of Marseille, INSERM UMRS-1076, Aix-Marseille Université Chemin des Bourrely, Marseille 13015, France. E-mail address: [email protected] (L. Bonello).
http://dx.doi.org/10.1016/j.ijcard.2014.12.073 0167-5273/© 2014 Elsevier Ireland Ltd. All rights reserved.
the clinically observed differences between these drugs in terms of bleedings. Forty five patients with non-valvular AF for stroke and systemic embolism prevention as recommended by the guidelines have been prospectively included in our study. Patients were treated for at least one month with anticoagulant and had no antiplatelet agents. Two patients were excluded because of a low platelet count. Fifteen patients were taking VKA, 15 patients dabigatran exilate 150 mg twice daily and 15 patients rivaroxaban 20 mg daily. For patients taking VKA the INR was within the therapeutic range in all patients. Fifty healthy volunteers were also included as controls. The study protocol conforms to the ethical guidelines of the Declaration of Helsinki and was approved by local committees. All subjects gave informed consent to participate in the study. Indirect effects on platelet function were assessed by lighttransmittance aggregometry (LTA). Platelet aggregation was measured in-vitro in recalcified platelet rich plasma (PRP) with a platelet aggregometer according to the manufacturer's instructions (APACT®4004, Elitech, France). Briefly, 200 μl of PRP was incubated in an aggregation cuvette while stirring with a stir bar for 2 min at 37 °C. Platelets were stimulated with ADP (2.5 μM), arachidonic acid (0.5 mg mL−1), epinephrine (0.3 mM), Thrombin Receptor Activating Peptide (TRAP) (50 μM) or ristocetin (1.5 mg mL−1). Aggregation was expressed as the percentage change in LT from baseline with plateletpoor plasma (PPP) as reference. Here, we report data on maximal intensity of platelet aggregation. Statistical analysis was conducted using the GraphPad Prism 5.0 software (GraphPad Software, Inc). A p b 0.05 was considered as significant. Patients with non-valvular AF treated with VKAs exhibited lower maximal intensities of platelet aggregation than healthy volunteers when induced by ADP (p = 0.027), arachidonic acid (p = 0.0286) and epinephrine (p = 0.0187) whereas no difference was observed between healthy volunteers and patients treated with dabigatran or rivaroxaban (p no significant) (Fig. 1). Regarding TRAP or ristocetin induced aggregation no difference was observed between healthy volunteers and patients treated with VKAs (Fig. 1) but patients treated with dabigatran or rivaroxaban exhibited significantly higher levels of platelet activity (Fig. 1). Our results suggest that oral anticoagulant exerts differential effects on platelet function. Lower intensities of platelet-induced aggregation were indeed observed in patients treated with VKA compared to healthy volunteers and patients treated with NOAC suggesting a lower degree of platelet receptor activities during long-term anticoagulation with VKA but not with NOAC. Interestingly, TRAP-induced platelet aggregation,
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C. Frère et al. / International Journal of Cardiology 181 (2015) 413–414
Fig. 1. Maximal intensity of platelet aggregation in healthy volunteers and patients with atrial fibrillation taking vitamin K antagonists, dabigatran or rivaroxaban. Platelet aggregation was induced with ADP 2.5 μM (A), arachidonic acid 0.5 mg mL−1 (B), epinephrine 0.3 mM (C), or TRAP 50 μM (D) or ristocetin 1.25 mg mL−1 (E). Mean ± sem; n = 15 for each group; ***p b 0.001; **p b 0.01; *p b 0.05; ns: not significant.
expected to by-pass any direct or indirect effect on thrombin, and ristocetin-induced platelet aggregation testing platelet adhesion but not platelet reactivity were not found to be lower in patients taking VKAs. In the RE-LY trial, a significantly lower incidence of major bleeding was observed in patients treated with dabigatran versus warfarin, while in the ROCKET trial, critical, fatal and intracranial bleeding occurred less frequently with rivaroxaban than with warfarin. Our results suggest that the more pronounced antiplatelet effects of warfarin could in part explain this difference in bleedings. In addition, the present results may be of clinical importance. In fact following the results of the WOEST trial which suggested a clinical benefit of clopidogrel + VKA compared to triple therapy with the addition of aspirin in PCI patients the most recent guidelines of the ESC advocate either the use of VKAs or NOACs with clopidogrel in high-bleeding risk patients [3,4]. Given the differences observed on platelet function between VKA and NOAC the use of the first one may be associated with an increase risk of bleedings whereas the use of the latest may be associated with an increase risk of platelet mediated events such as stent thrombosis. Conflict of interest The authors report no relationships that could be construed as a conflict of interest.
References [1] S.J. Connolly, M.D. Ezekowitz, S. Yusuf, J. Eikelboom, J. Oldgren, A. Parekh, J. Pogue, P.A. Reilly, E. Themeles, J. Varrone, S. Wang, M. Alings, D. Xavier, J. Zhu, R. Diaz, B.S. Lewis, H. Darius, H.C. Diener, C.D. Joyner, L. Wallentin, RE-LY Steering Committee and Investigators, Dabigatran versus warfarin in patients with atrial fibrillation, N. Engl. J. Med. 361 (2009) 1139–1151. [2] M.R. Patel, K.W. Mahaffey, J. Garg, G. Pan, D.E. Singer, W. Hacke, G. Breithardt, J.L. Halperin, G.J. Hankey, J.P. Piccini, R.C. Becker, C.C. Nessel, J.F. Paolini, S.D. Berkowitz, K.A. Fox, R.M. Califf, ROCKET AF Investigators, Rivaroxaban versus warfarin in nonvalvular atrial fibrillation, N. Engl. J. Med. 365 (2011) 883–891. [3] W.J. Dewilde, T. Oirbans, F.W. Verheugt, J.C. Kelder, B.J. De Smet, J.P. Herrman, T. Adriaenssens, M. Vrolix, A.A. Heestermans, M.M. Vis, J.G. Tijsen, A.W. van 't Hof, J.M. ten Berg, WOEST study investigators, Use of clopidogrel with or without aspirin in patients taking oral anticoagulant therapy and undergoing percutaneous coronary intervention: an open-label, randomised, controlled trial, Lancet 381 (2013) 1107–1115. [4] 2014 ESC/EACTS Guidelines on myocardial revascularization: The Task Force on Myocardial Revascularization of the European Society of Cardiology (ESC) and the European Association for Cardio-Thoracic Surgery (EACTS) Developed with the special contribution of the European Association of Percutaneous Cardiovascular Interventions (EAPCI), Eur. Heart J. 35 (2014) 2541–2619.
Contents lists available at ScienceDirect
International Journal of Cardiology journal homepage: www.elsevier.com/locate/ijcard
Letter to the editor
Antiplatelet properties of oral anticoagulants Corinne Frère a,b, Marc Laine c, Franck Paganelli c, Françoise Dignat-George b, Laurent Bonello b,c,⁎ a b c
Laboratoire d'Hématologie, Centre Hospitalier Universitaire de Marseille, Hôpital Timone, Assistance Publique-Hôpitaux de Marseille, Marseille, France Vascular Research Center of Marseille, INSERM UMRS-1076, Aix-Marseille Université, Marseille, France Service de Cardiologie, Centre Hospitalier Universitaire de Marseille, Hôpital NORD, Assistance Publique-Hôpitaux de Marseille, Marseille France
a r t i c l e
i n f o
Article history: Received 20 November 2014 Accepted 21 December 2014 Available online 24 December 2014 Keywords: Anticoagulants Thrombosis Bleeding
Until recently, vitamin K antagonists (VKA) were the only oral anticoagulant drugs used in clinical practice for stroke or systemic embolism prevention in patients with non-valvular atrial fibrillation (AF). New oral anticoagulant drugs such as dabigatran etexilate and rivaroxaban have been developed and are currently available as an alternative in this indication. Both drugs were demonstrated to be noninferior to warfarin for the prevention of stroke or systemic embolism in patients with non-valvular AF in the RE-LY and ROCKET trials [1,2]. Their advantages are the consistency of the resulting anticoagulant level and the lack of need of biological follow-up favoring their widespread. While VKA acts by reducing the synthesis of functional clotting factors II, VII, IX and X, dabigatran etexilate acts as a competitive reversible non-peptide antagonist of thrombin, and rivaroxaban as a competitive reversible antagonist of activated factor X (Xa). These new oral anticoagulants (NOAC) result in the inhibition of thrombin generation. Thrombin is a multifunctional enzyme which converts fibrinogen to fibrin, cross-links fibrin monomers via activation of factor XIII, activates protein C and initiates numerous cellular processes including vascular healing. In addition, thrombin activates platelets via its platelet protease-activated receptors (PAR) 1 and 4. By inhibiting thrombin generation, anticoagulants are therefore expected to exert indirect effects on platelet function. Since these anticoagulants act through different mechanisms of action (indirect or direct thrombin inhibition), we hypothesize that they could have differential effects on platelet activation that might in part explain ⁎ Corresponding author at: Département de Cardiologie, Hôpital universitaire Nord de Marseille, Vascular Research Center of Marseille, INSERM UMRS-1076, Aix-Marseille Université Chemin des Bourrely, Marseille 13015, France. E-mail address: [email protected] (L. Bonello).
http://dx.doi.org/10.1016/j.ijcard.2014.12.073 0167-5273/© 2014 Elsevier Ireland Ltd. All rights reserved.
the clinically observed differences between these drugs in terms of bleedings. Forty five patients with non-valvular AF for stroke and systemic embolism prevention as recommended by the guidelines have been prospectively included in our study. Patients were treated for at least one month with anticoagulant and had no antiplatelet agents. Two patients were excluded because of a low platelet count. Fifteen patients were taking VKA, 15 patients dabigatran exilate 150 mg twice daily and 15 patients rivaroxaban 20 mg daily. For patients taking VKA the INR was within the therapeutic range in all patients. Fifty healthy volunteers were also included as controls. The study protocol conforms to the ethical guidelines of the Declaration of Helsinki and was approved by local committees. All subjects gave informed consent to participate in the study. Indirect effects on platelet function were assessed by lighttransmittance aggregometry (LTA). Platelet aggregation was measured in-vitro in recalcified platelet rich plasma (PRP) with a platelet aggregometer according to the manufacturer's instructions (APACT®4004, Elitech, France). Briefly, 200 μl of PRP was incubated in an aggregation cuvette while stirring with a stir bar for 2 min at 37 °C. Platelets were stimulated with ADP (2.5 μM), arachidonic acid (0.5 mg mL−1), epinephrine (0.3 mM), Thrombin Receptor Activating Peptide (TRAP) (50 μM) or ristocetin (1.5 mg mL−1). Aggregation was expressed as the percentage change in LT from baseline with plateletpoor plasma (PPP) as reference. Here, we report data on maximal intensity of platelet aggregation. Statistical analysis was conducted using the GraphPad Prism 5.0 software (GraphPad Software, Inc). A p b 0.05 was considered as significant. Patients with non-valvular AF treated with VKAs exhibited lower maximal intensities of platelet aggregation than healthy volunteers when induced by ADP (p = 0.027), arachidonic acid (p = 0.0286) and epinephrine (p = 0.0187) whereas no difference was observed between healthy volunteers and patients treated with dabigatran or rivaroxaban (p no significant) (Fig. 1). Regarding TRAP or ristocetin induced aggregation no difference was observed between healthy volunteers and patients treated with VKAs (Fig. 1) but patients treated with dabigatran or rivaroxaban exhibited significantly higher levels of platelet activity (Fig. 1). Our results suggest that oral anticoagulant exerts differential effects on platelet function. Lower intensities of platelet-induced aggregation were indeed observed in patients treated with VKA compared to healthy volunteers and patients treated with NOAC suggesting a lower degree of platelet receptor activities during long-term anticoagulation with VKA but not with NOAC. Interestingly, TRAP-induced platelet aggregation,
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C. Frère et al. / International Journal of Cardiology 181 (2015) 413–414
Fig. 1. Maximal intensity of platelet aggregation in healthy volunteers and patients with atrial fibrillation taking vitamin K antagonists, dabigatran or rivaroxaban. Platelet aggregation was induced with ADP 2.5 μM (A), arachidonic acid 0.5 mg mL−1 (B), epinephrine 0.3 mM (C), or TRAP 50 μM (D) or ristocetin 1.25 mg mL−1 (E). Mean ± sem; n = 15 for each group; ***p b 0.001; **p b 0.01; *p b 0.05; ns: not significant.
expected to by-pass any direct or indirect effect on thrombin, and ristocetin-induced platelet aggregation testing platelet adhesion but not platelet reactivity were not found to be lower in patients taking VKAs. In the RE-LY trial, a significantly lower incidence of major bleeding was observed in patients treated with dabigatran versus warfarin, while in the ROCKET trial, critical, fatal and intracranial bleeding occurred less frequently with rivaroxaban than with warfarin. Our results suggest that the more pronounced antiplatelet effects of warfarin could in part explain this difference in bleedings. In addition, the present results may be of clinical importance. In fact following the results of the WOEST trial which suggested a clinical benefit of clopidogrel + VKA compared to triple therapy with the addition of aspirin in PCI patients the most recent guidelines of the ESC advocate either the use of VKAs or NOACs with clopidogrel in high-bleeding risk patients [3,4]. Given the differences observed on platelet function between VKA and NOAC the use of the first one may be associated with an increase risk of bleedings whereas the use of the latest may be associated with an increase risk of platelet mediated events such as stent thrombosis. Conflict of interest The authors report no relationships that could be construed as a conflict of interest.
References [1] S.J. Connolly, M.D. Ezekowitz, S. Yusuf, J. Eikelboom, J. Oldgren, A. Parekh, J. Pogue, P.A. Reilly, E. Themeles, J. Varrone, S. Wang, M. Alings, D. Xavier, J. Zhu, R. Diaz, B.S. Lewis, H. Darius, H.C. Diener, C.D. Joyner, L. Wallentin, RE-LY Steering Committee and Investigators, Dabigatran versus warfarin in patients with atrial fibrillation, N. Engl. J. Med. 361 (2009) 1139–1151. [2] M.R. Patel, K.W. Mahaffey, J. Garg, G. Pan, D.E. Singer, W. Hacke, G. Breithardt, J.L. Halperin, G.J. Hankey, J.P. Piccini, R.C. Becker, C.C. Nessel, J.F. Paolini, S.D. Berkowitz, K.A. Fox, R.M. Califf, ROCKET AF Investigators, Rivaroxaban versus warfarin in nonvalvular atrial fibrillation, N. Engl. J. Med. 365 (2011) 883–891. [3] W.J. Dewilde, T. Oirbans, F.W. Verheugt, J.C. Kelder, B.J. De Smet, J.P. Herrman, T. Adriaenssens, M. Vrolix, A.A. Heestermans, M.M. Vis, J.G. Tijsen, A.W. van 't Hof, J.M. ten Berg, WOEST study investigators, Use of clopidogrel with or without aspirin in patients taking oral anticoagulant therapy and undergoing percutaneous coronary intervention: an open-label, randomised, controlled trial, Lancet 381 (2013) 1107–1115. [4] 2014 ESC/EACTS Guidelines on myocardial revascularization: The Task Force on Myocardial Revascularization of the European Society of Cardiology (ESC) and the European Association for Cardio-Thoracic Surgery (EACTS) Developed with the special contribution of the European Association of Percutaneous Cardiovascular Interventions (EAPCI), Eur. Heart J. 35 (2014) 2541–2619.
