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Platelet reactivity on aspirin, clopidogrel and abciximab in patients with acute coronary syndromes and reduced estimated glomerular filtration rate
Thrombosis Research 125 (2010) 67–71
Contents lists available at ScienceDirect
Thrombosis Research j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / t h r o m r e s
Brief Communication
Platelet reactivity on aspirin, clopidogrel and abciximab in patients with acute coronary syndromes and reduced estimated glomerular filtration rate Łukasz A. Małek a,⁎, Zofia T. Bilińska a, Dariusz Sitkiewicz b, Mariusz Kłopotowski a, Adam Witkowski a, Witold Rużyłło a a b
1st Department of Coronary Artery Disease, Institute of Cardiology, Warsaw, Poland Department of Laboratory Diagnostics, Institute of Cardiology, Warsaw, Poland
a r t i c l e
i n f o
Article history: Received 17 January 2009 Received in revised form 7 March 2009 Accepted 27 March 2009 Available online 13 May 2009 Keywords: antiplatelet drugs estimated glomerular filtration rate acute coronary syndrome platelet reactivity
However, deminished platelet function in renal impairment may be related to lower platelet reactivity in patients with ACS and renal dysfunction in comparison to patients with ACS and normal renal function [5–7]. Confirmation of the above hypothesis would improve our understanding of the potential mechanism behind increased tendency for bleeding in patients with ACS and renal dysfunction. Therefore, the aim of the study was to analyze platelet reactivity in relation to renal function in patients with ACS treated with dual (aspirin and clopidogrel) or triple (aspirin, clopidogrel and abciximab) antiplatelet therapy. Materials and methods
Introduction Antiplatelet drugs are a cornerstone of tretment in patients with acute coronary syndromes leading to significant reduction of recurrent ischemic events [1]. Benefits of antiplatelet therapy may be limited by increased frequency of bleeding incidents [1]. Renal impairment has been established as one of the major risk factors of bleeding in ACS mainly as a cause of coexisting patelet dysfunction [2–3]. Commonly used antiplatelet drugs in ACS such as aspirin, clopidogrel or abciximab are not undergoing renal elimination and therefore are believed to have a safe profile in renal dysfunction [4].
Abbreviations: ACS, acute coronary syndrome; ADPtest, platelet reactivity test with adenosine diphosphate; ASPItest, platelet reactivity test with arachidonic acid; AU, aggregation unit; BMI, body mass index; CABG, coronary artery bypass grafting; CI, confidence interval; CKD, chronic kidney disease; COX-1, cyclooxygenase-1; eGFR, estimated glomerular filtration rate; GP, glycoprotein; Hgb, hemoglobin; Hct, hematocryte; IQR, interquartile range; K/DOQI, acronym of the Kidney Disease Outcomes Quality Initiative; LMWH, low molecular weight heparin; LVEF, left ventricular ejection fraction; MI, myocardial infarction; MVD, multivessel coronary artery disease; OR, odds ratio; PAD, peripheral artery disease; PCI, percutaneous coronary intervention; PLT, platelet count; SD, standard deviation; STE, ST elevation; TIA, transient ischemic attack; TRAPtest, platelet reactivity test with thrombin receptor activating peptide; TXA2, thromboxan A2; UFH, unfractionated heparin. ⁎ Corresponding author. Institute of Cardiology, Alpejska str 42, 04-628 Warsaw, Poland. Tel.: +48 22 34 34 267; fax: +48 22 613 38 19. E-mail address: [email protected] (ŁA. Małek). 0049-3848/$ – see front matter © 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.thromres.2009.03.015
The study was conducted on the group of 92 consecutive patients with ACS treated invasively, of whom 46 received abciximab at the discretion of the interventional cardiologist along with dual antiplatelet therapy with 300 mg loading dose of aspirin and 600 mg loading dose of clopidogrel. The remaining 46 patients received only dual antiplatelet therapy. Renal function was assessed as an estimated glomerular filtration rate with the use of serum creatinine concentration on admission and the Cockroft-Gault formula [8]. Renal dysfunction was classified as eGFRb90 ml/min according to K/DOQI stages of CKD [9]. Platelet reactivity testing was performed in all patients (after 24 hours from admission in the case of dual antiplatelet therapy and in patients on abciximab at the end of infusion) by means of multiple electrode impedance aggregometry (Multiplate®, Dynabyte, Munich, Germany) [10]. The instrument measures the change in impedance between two electrodes as platelets adhere and aggregate in response to specific agonist. Multiplate® continuously records platelet aggregation. The increase of impedance is transformed to arbitrary aggregation units and plotted against time. The most important parameter is the area under the aggregation curve measured as AU*min [11–16]. In all patients whole blood was withdrawn from antecubital venipuncture into a polyethylene tube containing a stabilized direct thrombin inhibitor. Specific agonists were used to detect platelet reactivity dependent on aspirin (arachidonic acid - ASPItest), clopidogrel (adenosine diphosphate – ADPtest), and abciximab (thrombin receptor activating peptide – TRAPtest). In each case platelet reactivity was assessed by means of all used tests giving a total of 276 tests performed. Because abciximab influences results of all three tests patients treated with triple antiplatelet therapy were analyzed as a separate group.
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ŁA. Małek et al. / Thrombosis Research 125 (2010) 67–71
The study was approved by the local Ethics Committee on human research and all patients provided written informed consent.
Table 1 Clinical, medical therapy and laboratory parameters on admission in patients on dual and triple antiplatelet therapy.
Statistical analysis
Parameter
All categorical variables were expressed in terms of frequencies and percentages and continuous variables by means and standard deviations or by medians and interquartile ranges in the presence or absence of normal distribution, respectively. Chi2 test was applied to test for normality of distribution. Categorical variables were compared by either Fisher exact or chi2 test and continuous variables by student t-test or Mann-Whitney test, when appropriate. Correlations were assessed with means of r-Pearson or rho-Spearman tests, when appropriate. Multivariable stepwise logistic regression model including all significant parameters in univariable analysis was used to find independent variables differentiating patients with reduced and normal eGFR. All tests were 2-tailed and p-value b0.05 was considered statistically significant. All statistical analyses were performed with SAS software varsion 8e (SAS Institute, Cary, NC). Because of the lack of previous data we have arbitrary defined a significant difference in platelet aggregation between patients with normal and reduced eGFR as ≥ 30%. Therefore, to achieve at least 80% power of the results with p b 0.05 and 1:1 ratio of patients with and without reduced eGFR, each group (dual or triple antiplatelet therapy) should include at least 40 patients [17].
Clinical Age (±SD) Male sex (%) Hypertension (%) Hyperlipidemia (%) Diabetes (%) BMIN25 kg/m2 (%) Heart failure (%) PAD (%) Prior MI (%) Prior PCI/CABG (%) Prior Stroke or TIA (%) Smoking (%) MI during index hospitalization (%) STE-ACS (%) MVD (%) LVEF % (±SD) Medical therapy Heparin UFH (%) LMWH (%) Dose U/kg (±SD) Acenocumarol (%)
Results
Laboratory findings on admission eGFR ml/min (±SD) 76 ± 39 eGFRb 90 ml/min (%) 23 (50) PLT ths/ml (IQR) 171 (141,212) Hgb g/dl (±SD) 13 ± 1 Hct % (±SD) 39 ± 4
Clinical, medical therapy and laboratory parameters on admission of the two studied groups are compared in Table 1. Patients on dual antiplatelet therapy were older, less frequently diagnosed with STEACS and had a lower eGFR in comparison to those receiving triple antiplatelet therapy. Estimated glomerular filtration rate followed a normal distribution (p = 0.63) and reduced eGFR was present in 49 patients (53%). Numbers and percentages of patients with reduced eGFR according to stages of CKD proposed by K/DOQI were: 43 (47%) in stage I, 21 (23%) in stage II, 24 (26%) in stage III and 4 (4%) in stages IV and V. Platelet reactivity on dual antiplatelet therapy (aspirin and clopidogrel) Reduced eGFR was present in 23 patients (63%) on dual anitplatelet therapy. Correlations between eGFR and platelet reactivity tests in this subgroup of patients are shown on Fig. 1 abc. Comparison of median platelet reactivity in patients with reduced and normal eGFR on aspirin and clopidogrel are demonstrated on Fig. 2a (respectively for eGFR b90 and ≥90 ml/min: ASPItest 166 IQR 115-244 vs. 314 IQR 118-581 AU*min, p = 0.14; ADPtest 149 IQR 93-227 vs. 205 IQR 97-336 AU*min, p = 0.59; TRAPtest 682 IQR 427-950 vs 662 IQR 416-987 AU*min, p = 0.86). Univariable analysis demonstrated that patients with reduced eGFR on dual antiplatelet therapy were older, less likely male, less frequently smokers and had a lower platelet count, hemoglobin concentration and hematocryte on admission in comparison to patients with preserved eGFR. Multivariable analysis showed that age is the only independent factor discriminating patients with reduced and normal eGFR (OR = 1.240, 95%CI 1.102-1.395 for every 1 year increase, p = 0003) in this subgroup of patients. Platelet reactivity on triple anitplatelet therapy (aspirin, clopidogrel, abciximab) Reduced eGFR was present in 20 patients (43%) on triple anitplatelet therapy. Correlations between eGFR and platelet reactivity tests in this subgroup of patients are shown on Fig. 1 def. Comparison of median platelet reactivity in patients with reduced and normal
Dual antiplatelet therapy n = 46
Triple antiplatelet therapy n = 46
p
69 ± 12 30 (65) 33 (51) 30 (65) 11 (24) 16 (35) 6 (13) 6 (13) 11 (24) 8 (17) 3 (6) 14 (30) 39 (85)
61 ± 11 33 (51) 28 (43) 35 (76) 11 (24) 21 (46) 2 (4) 2 (4) 7 (15) 7 (15) 2 (4) 21 (46) 41 (89)
0.002 0.65 0.38 0.36 1.00 0.40 0.27 0.27 0.43 1.00 1.00 0.20 0.76
20 (43) 13 (28) 45 ± 11
46 (100) 9 (20) 49 ± 12
b0.0001 0.46 0.09
40 (87) 7 (15) 100 ± 32 6 (13)
45 (98) 2 (4) 103 ± 28 4 (9)
0.11 0.16 0.64 0.74
96 ± 35 20 (43) 191 (151,223) 13 ± 1 39 ± 4
0.01 0.68 0.72 0.29 0.64
eGFR on aspirin, clopidogrel and abciximab are demonstrated on Fig. 2b (respectively for eGFR b90 and ≥90 ml/: ASPItest 95 IQR 26124 vs. 121 IQR 93-176 AU*min, p = 0.07; ADPtest 50 IQR 2-131 vs. 99 IQR 49-124 AU*min, p = 0.22; TRAPtest 208 IQR 86-331 vs. 380 IQR 253-447 AU*min, p = 0.007). Univariable analysis demonstrated that patients with reduced eGFR on triple antiplatelet therapy were older, less likely male, less frequently diagnosed with MI during index hospitalization, had a lower hemoglobin concentration and hematocryte on admission in comparison to patients with preserved eGFR. Multivariable analysis including all of the above parameters and TRAPtest showed that age and TRAPtest are the only independent factors discriminating patients with reduced and normal eGFR (OR = 0.989 95%CI 0.981-0.998 for every 1 AU*min increase, p = 0.01; OR = 1.320 95%CI 1.120-1.557 for every 1 year increase, p = 0.0009) in this subgroup of patients.
Discussion The main finding of this study is a lower platelet reactivity in relation to abciximab in patients with ACS and reduced eGFR in comparison to those with ACS and preserved eGFR as shown both in univariable and multivariable analysis. Abciximab is a chimeric monoclonal antibody eliminated from platelets in spleen [1]. Contrary to other inhibitors of glycoprotein IIb/ IIIa receptor, which undergo renal elimination such as tirofiban or eptifibatide, abciximab does not require dose adjustment in renal failure [4]. On the other hand it was found that glycoprotein IIb/IIIa receptors in patients on hemodialysis have lower affinity for fibrinogen, which may be caused by conformational change of the receptors [18,19]. Hemodialysis led to improvement of fibrinogen binding by platelets, which suggests existance of putative toxins in patients with uremia. Platelet defect was also seen after incubation of
ŁA. Małek et al. / Thrombosis Research 125 (2010) 67–71
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Fig. 1. a-f. Correletions between platelet reactivity tests and eGFR in patients with ACS on dual antiplatelet therapy (a – ASPItest, b - ADPtest, c – TRAPtest) and triple antiplatelet therapy (d – ASPItest, e – ADPtest, f – TRAPtest).
platelets from healthy volunteers with serum of patients with renal failure before hemodialysis. Decreased binding of fibrinogen to platelets in uremia may lead to impairment of platelet aggregation and subsequently to higher frequency of bleeding. It was also demonstrated that patients with uremia have lower expression of fibrinogen receptors on platelets in comparison to normal controls [20]. Other study showed that patients with uremia have a higher
concentration of fibrinogen fragments, which compete with fibrinogen for binding to an active site of glycoprotein IIb/IIIa receptor [21]. Hemodialysis was related to elimination of fibrinogen fragments from blood. Importanly, studies reporting platelet dysfunction in renal impairment included patients with end-stage renal failure requiring dialysis. Our results demonstrate that platelet function on abciximab may be additionally suppresed in patients with ACS and even mildly or
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Fig. 2. ab. Platelet reactivity in patients with ACS and reduced vs normal eGFR, a – on dual antiplatelet therapy, b – on triple antiplatelet therapy.
moderately reduced eGFR. This phenomenon is not a result of slower drug elimination, but is most likely caused by acquired platelet deficiency. Other findings of this study prove that there are no significant differences in platelet reactivity in patients with ACS and reduced vs normal eGFR in relation to aspirin or clopidogrel. It was disclosed that patients with uremia produce lower amounts of thromboxan A2 both in normal conditions and after administration of arachidonic acid in comparison to healthy controls which is related to functional defect of cyclooxygenese-1, an enzyme blocked by aspirin. Degree of decrease in tromboxan A2 production was parallel to administration of 40 mg of aspirin to healthy subjects [22]. Other study demonstrated that aspirin significantly increases bleeding time in subjects with uremia, but not in normal controls [23]. Our results suggest that observed insignificant difference in platelet reactivity on aspirin in patients with reduced eGFR may be related to dose independent inhibition of tromboxan A2 with does over 30 mg. All patients with ACS in the studied group received pretreatment with 300 mg of aspirin which might have bridged the differences. Experimental studies found that patients with renal failure have decreased secretion of ADP, which competes with clopidogrel for the binding site on platelets [24]. However, this mechanism does not translate into higher platelet inhibition in patients with renal impairment which is confirmed by the results of our study. One of the first papers analyzing the influence of renal dysfunction on platelet response to clopidogrel focused on pharmacokinetics and pharmacodynamics of clopidogrel in patients with moderate and severe renal failure. After eight days of treatment with 75 mg of the drug platelet aggregation in response to ADP, bleeding time and concentration of the active form of clopidogrel and its inactive metabolite in serum and urine were similar in patients with moderate and severe renal impairment. Authors concluded that clopidogrel is a well tolerated antiplatelet drug in patients with renal failure leading to effective platelet inhibition and the dose of the drug does not need
to be adjusted in relation to renal function [25]. Other study found that 14-day clopidogrel administration in patients on hemodialysis causes insignificant difference of platelet aggregation inhibition after stimulation with ADP in comparison to healthy controls. Platelet function was completely regained after 7 days from cessation of treatment in both groups [24]. It is important to discuss why platelet aggregation in patients with ACS and reduced eGFR is lower in relation to abciximab but not to aspirin or clopidogrel. Abciximab is the most potent of the three studied antiplatelet drugs. It inhibits platelet aggregation, which is the last stage of platelet response to various activating factors, while aspirin and clopidogrel reduce platelet activation. Importantly, we have not observed significant differences in platelet function dependent on TRAP in patients on dual antiplatelet therapy, but only after administration of abciximab. It shows that platelet dysfunction in patients with mildly or moderately reduced eGFR may become elucidated only in the setting of most potent antiplatelet treatment. Our study has several limitations. Because all of the studied patients received pre-hospital treatment with loading doses of aspirin and clopidogrel it was impossible to assess baseline platelet reactivity (without antiplatelet drugs on board). Logistic reasons (admission of patients during off-hours and short time between blood sampling and testing) enabled the performance of platelet reactivity testing with TRAP before abciximab administration. It may be also speculated that platelet reactivity on abciximab may be influenced by fibrinogen concentration which is a ligand for GP IIb/IIIa receptor. Although renal dysfunction is related to protein loss, we have evaluated patients with acute coronary syndromes, and it was shown that fibrinogen is increased in this setting in comparison to healthy controls [26]. Besides, most of the studies report on increased fibrinogen concentration in plasma even in patients on hemodialysis which may be related to its up-regulated synthesis and no loss in urine [27]. In conclusion, we have demonstrated that platelet reactivity is lower in patients with ACS and reduced eGFR in comparison to patients with ACS and preserved eGFR in relation to abciximab, but not to aspirin or clopidogrel. We suggest that the main reason of our findings may be an impaired GP IIb/IIIa receptor performance in patients with reduced eGFR. Conflict of interest statement None Acknowledgements The study was supported with internal grant 2.44/VII/2008 of the Institute of Cardiology, Warsaw, Poland. References [1] Patrono C, Bachmann F, Baigent C, Bode C, De Caterina R, Charbonnier B, et al. European Society of Cardiology. Expert consensus document on the use of antiplatelet agents. The task force on the use of antiplatelet agents in patients with atherosclerotic cardiovascular disease of the European society of cardiology. Eur Heart J 2004;25:166–81. [2] Moscucci M, Fox KA, Cannon CP, Klein W, López-Sendón J, Montalescot G, et al. Predictors of major bleeding in acute coronary syndromes: the Global Registry of Acute Coronary Events (GRACE). Eur Heart J 2003;24:1815–23. [3] Attallah N, Yassine L, Fisher K, Yee J. Risk of bleeding and restenosis among chronic kidney disease patients undergoing percutaneous coronary intervention. Clin Nephrol 2005;64:412–8. [4] Task Force for Diagnosis and Treatment of Non-ST-Segment Elevation Acute Coronary Syndromes of European Society of Cardiology, Bassand JP, Hamm CW, Ardissino D, Boersma E, Budaj A, et al. Guidelines for the diagnosis and treatment of non-STsegment elevation acute coronary syndromes. Eur Heart J 2007;28:1598–660. [5] Sohal AS, Gangji AS, Crowther MA, Treleaven D. Uremic bleeding: pathophysiology and clinical risk factors. Thromb Res 2006;118:417–22. [6] Noris M, Benigni A, Boccardo P, Gotti E, Benfenati E, Aiello S, et al. Enhanced nitric oxide synthesis in uremia: implications for platelet dysfunction and dialysis hypotension. Kidney Int 1993;44:445–50.
ŁA. Małek et al. / Thrombosis Research 125 (2010) 67–71 [7] Noris M, Remuzzi G. Uremic bleeding: closing the circle after 30 years of controversies? Blood 1999;94:2569–74. [8] Cockcroft DW, Gault MH. Prediction of creatinine clearance from serum creatinine. Nephron 1976;16:31–41. [9] National Kidney Foundation. K/DOQI clinical practice guidelines for chronic kidney disease: evaluation, classification, and stratification. Am J Kidney Dis 2002;39: S1–S266. [10] Toth O, Calatzis A, Penz S, Losonczy H, Siess W. Multiple electrode aggregometry: a new device to measure platelet aggregation in whole blood. Thromb Haemost 2006;96:781–8. [11] Mueller T, Dieplinger B, Poelz W, Haltmayer M. Utility of the PFA-100 Instrument and the Novel Multiplate Analyzer for the Assessment of Aspirin and Clopidogrel Effects on Platelet Function in Patients With Cardiovascular Disease. Clin Appl Thromb Hemost 2009;15(6):652–9. [12] Sibbing D, Braun S, Jawansky S, Vogt W, Mehilli J, Schömig A, et al. Assessment of ADP-induced platelet aggregation with light transmission aggregometry and multiple electrode platelet aggregometry before and after clopidogrel treatment. Thromb Haemost 2008;99:121–6. [13] Sibbing D, Busch G, Braun S, Jawansky S, Schömig A, Kastrati A, et al. Impact of bivalirudin or unfractionated heparin on platelet aggregation in patients pretreated with 600 mg clopidogrel undergoing elective percutaneous coronary intervention. Eur Heart J 2008;29:1504–9. [14] Gorlinger K, Jambor C, Dirkmann D, Dusse F, Hanke A, Adamzik M, et al. [Platelet Function Analysis with Point-of-Care Methods.]. Herz 2008;33:297–305. [15] Skoric B, Milicic D, Lovric D, Gornik I, Skoric KN, Sertic J. Initial patency of the infarct-related artery in patients with acute ST elevation myocardial infarction is related to platelet response to aspirin. Int J Cardiol 2008 [Electronic publication ahead of print]. [16] Mueller T, Dieplinger B, Poelz W, Calatzis A, Haltmayer M. Utility of whole blood impedance aggregometry for the assessment of clopidogrel action using the novel Multiplate analyzer–comparison with two flow cytometric methods. Thromb Res 2007;121:249–58.
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[17] Dupont WD, Plummer Jr WD. Power and sample size calculations. A review and computer program. Control Clin Trials 1990;11:116–28. [18] Gawaz MP, Dobos G, Spath M, Schollmeyer P, Gurland HJ, Mujais SK. Impaired function of platelet membrane glycoprotein IIb-IIIa in end-stage renal disease. J Am Soc Nephrol 1994;5:36–46. [19] Benigni A, Boccardo P, Galbusera M, Monteagudo J, De Marco L, Remuzzi G, et al. Reversible activation defect of the platelet glycoprotein IIb-IIIa complex in patients with uremia. Am J Kidney Dis 1993;22:668–76. [20] Walkowiak B, Pawlowska Z, Michalak E, Cierniewski CS. Expression of fibrinogen receptors on platelets of uremic patients is correlated with the content of GPIIb and plasma level of creatinine. Thromb Haemost 1994;71:164–8. [21] Thekkedath UR, Chirananthavat T, Leypoldt JK, Cheung AK, Mohammad SF. Elevated fibrinogen fragment levels in uremic plasma inhibit platelet function and expression of glycoprotein IIb-IIIa. Am J Hematol 2006;81:915–26. [22] Remuzzi G, Benigni A, Dodesini P, Schieppati A, Livio M, De Gaetano G, et al. Reduced platelet thromboxane formation in uremia. Evidence for a functional cyclooxygenase defect. J Clin Invest 1983;71:762–8. [23] Livio M, Benigni A, Vigano G, Mecca G, Remuzzi G. Moderate doses of aspirin and risk of bleeding in renal failure. Lancet 1986;1:414–6. [24] Kaufman JS, Fiore L, Hasbargen JA, O'Connor TZ, Perdriset G. A pharmacodynamic study of clopidogrel in chronic hemodialysis patients. J Thromb Thrombolysis 2000;10:127–31. [25] Deray G, Bagnis C, Brouard R, Necciari J, Leenhardt AF, Raymond F, et al. Clopidogrel activities in patients with renal function impairment. Clin Drug Investig 1998;16:319–28. [26] Itakura H, Sobel BE, Boothroyd D, Leung LL, Iribarren C, Go AS, et al. Do plasma biomarkers of coagulation and fibrinolysis differ between patients who have experienced an acute myocardial infarction versus stable exertional angina? Am Heart J 2007;154:1059–64. [27] Prinsen BH, Rabelink TJ, Beutler JJ, Kaysen GA, De Boer J, Boer WH, et al. Increased albumin and fibrinogen synthesis rate in patients with chronic renal failure. Kidney Int 2003;64:1495–504.
Contents lists available at ScienceDirect
Thrombosis Research j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / t h r o m r e s
Brief Communication
Platelet reactivity on aspirin, clopidogrel and abciximab in patients with acute coronary syndromes and reduced estimated glomerular filtration rate Łukasz A. Małek a,⁎, Zofia T. Bilińska a, Dariusz Sitkiewicz b, Mariusz Kłopotowski a, Adam Witkowski a, Witold Rużyłło a a b
1st Department of Coronary Artery Disease, Institute of Cardiology, Warsaw, Poland Department of Laboratory Diagnostics, Institute of Cardiology, Warsaw, Poland
a r t i c l e
i n f o
Article history: Received 17 January 2009 Received in revised form 7 March 2009 Accepted 27 March 2009 Available online 13 May 2009 Keywords: antiplatelet drugs estimated glomerular filtration rate acute coronary syndrome platelet reactivity
However, deminished platelet function in renal impairment may be related to lower platelet reactivity in patients with ACS and renal dysfunction in comparison to patients with ACS and normal renal function [5–7]. Confirmation of the above hypothesis would improve our understanding of the potential mechanism behind increased tendency for bleeding in patients with ACS and renal dysfunction. Therefore, the aim of the study was to analyze platelet reactivity in relation to renal function in patients with ACS treated with dual (aspirin and clopidogrel) or triple (aspirin, clopidogrel and abciximab) antiplatelet therapy. Materials and methods
Introduction Antiplatelet drugs are a cornerstone of tretment in patients with acute coronary syndromes leading to significant reduction of recurrent ischemic events [1]. Benefits of antiplatelet therapy may be limited by increased frequency of bleeding incidents [1]. Renal impairment has been established as one of the major risk factors of bleeding in ACS mainly as a cause of coexisting patelet dysfunction [2–3]. Commonly used antiplatelet drugs in ACS such as aspirin, clopidogrel or abciximab are not undergoing renal elimination and therefore are believed to have a safe profile in renal dysfunction [4].
Abbreviations: ACS, acute coronary syndrome; ADPtest, platelet reactivity test with adenosine diphosphate; ASPItest, platelet reactivity test with arachidonic acid; AU, aggregation unit; BMI, body mass index; CABG, coronary artery bypass grafting; CI, confidence interval; CKD, chronic kidney disease; COX-1, cyclooxygenase-1; eGFR, estimated glomerular filtration rate; GP, glycoprotein; Hgb, hemoglobin; Hct, hematocryte; IQR, interquartile range; K/DOQI, acronym of the Kidney Disease Outcomes Quality Initiative; LMWH, low molecular weight heparin; LVEF, left ventricular ejection fraction; MI, myocardial infarction; MVD, multivessel coronary artery disease; OR, odds ratio; PAD, peripheral artery disease; PCI, percutaneous coronary intervention; PLT, platelet count; SD, standard deviation; STE, ST elevation; TIA, transient ischemic attack; TRAPtest, platelet reactivity test with thrombin receptor activating peptide; TXA2, thromboxan A2; UFH, unfractionated heparin. ⁎ Corresponding author. Institute of Cardiology, Alpejska str 42, 04-628 Warsaw, Poland. Tel.: +48 22 34 34 267; fax: +48 22 613 38 19. E-mail address: [email protected] (ŁA. Małek). 0049-3848/$ – see front matter © 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.thromres.2009.03.015
The study was conducted on the group of 92 consecutive patients with ACS treated invasively, of whom 46 received abciximab at the discretion of the interventional cardiologist along with dual antiplatelet therapy with 300 mg loading dose of aspirin and 600 mg loading dose of clopidogrel. The remaining 46 patients received only dual antiplatelet therapy. Renal function was assessed as an estimated glomerular filtration rate with the use of serum creatinine concentration on admission and the Cockroft-Gault formula [8]. Renal dysfunction was classified as eGFRb90 ml/min according to K/DOQI stages of CKD [9]. Platelet reactivity testing was performed in all patients (after 24 hours from admission in the case of dual antiplatelet therapy and in patients on abciximab at the end of infusion) by means of multiple electrode impedance aggregometry (Multiplate®, Dynabyte, Munich, Germany) [10]. The instrument measures the change in impedance between two electrodes as platelets adhere and aggregate in response to specific agonist. Multiplate® continuously records platelet aggregation. The increase of impedance is transformed to arbitrary aggregation units and plotted against time. The most important parameter is the area under the aggregation curve measured as AU*min [11–16]. In all patients whole blood was withdrawn from antecubital venipuncture into a polyethylene tube containing a stabilized direct thrombin inhibitor. Specific agonists were used to detect platelet reactivity dependent on aspirin (arachidonic acid - ASPItest), clopidogrel (adenosine diphosphate – ADPtest), and abciximab (thrombin receptor activating peptide – TRAPtest). In each case platelet reactivity was assessed by means of all used tests giving a total of 276 tests performed. Because abciximab influences results of all three tests patients treated with triple antiplatelet therapy were analyzed as a separate group.
68
ŁA. Małek et al. / Thrombosis Research 125 (2010) 67–71
The study was approved by the local Ethics Committee on human research and all patients provided written informed consent.
Table 1 Clinical, medical therapy and laboratory parameters on admission in patients on dual and triple antiplatelet therapy.
Statistical analysis
Parameter
All categorical variables were expressed in terms of frequencies and percentages and continuous variables by means and standard deviations or by medians and interquartile ranges in the presence or absence of normal distribution, respectively. Chi2 test was applied to test for normality of distribution. Categorical variables were compared by either Fisher exact or chi2 test and continuous variables by student t-test or Mann-Whitney test, when appropriate. Correlations were assessed with means of r-Pearson or rho-Spearman tests, when appropriate. Multivariable stepwise logistic regression model including all significant parameters in univariable analysis was used to find independent variables differentiating patients with reduced and normal eGFR. All tests were 2-tailed and p-value b0.05 was considered statistically significant. All statistical analyses were performed with SAS software varsion 8e (SAS Institute, Cary, NC). Because of the lack of previous data we have arbitrary defined a significant difference in platelet aggregation between patients with normal and reduced eGFR as ≥ 30%. Therefore, to achieve at least 80% power of the results with p b 0.05 and 1:1 ratio of patients with and without reduced eGFR, each group (dual or triple antiplatelet therapy) should include at least 40 patients [17].
Clinical Age (±SD) Male sex (%) Hypertension (%) Hyperlipidemia (%) Diabetes (%) BMIN25 kg/m2 (%) Heart failure (%) PAD (%) Prior MI (%) Prior PCI/CABG (%) Prior Stroke or TIA (%) Smoking (%) MI during index hospitalization (%) STE-ACS (%) MVD (%) LVEF % (±SD) Medical therapy Heparin UFH (%) LMWH (%) Dose U/kg (±SD) Acenocumarol (%)
Results
Laboratory findings on admission eGFR ml/min (±SD) 76 ± 39 eGFRb 90 ml/min (%) 23 (50) PLT ths/ml (IQR) 171 (141,212) Hgb g/dl (±SD) 13 ± 1 Hct % (±SD) 39 ± 4
Clinical, medical therapy and laboratory parameters on admission of the two studied groups are compared in Table 1. Patients on dual antiplatelet therapy were older, less frequently diagnosed with STEACS and had a lower eGFR in comparison to those receiving triple antiplatelet therapy. Estimated glomerular filtration rate followed a normal distribution (p = 0.63) and reduced eGFR was present in 49 patients (53%). Numbers and percentages of patients with reduced eGFR according to stages of CKD proposed by K/DOQI were: 43 (47%) in stage I, 21 (23%) in stage II, 24 (26%) in stage III and 4 (4%) in stages IV and V. Platelet reactivity on dual antiplatelet therapy (aspirin and clopidogrel) Reduced eGFR was present in 23 patients (63%) on dual anitplatelet therapy. Correlations between eGFR and platelet reactivity tests in this subgroup of patients are shown on Fig. 1 abc. Comparison of median platelet reactivity in patients with reduced and normal eGFR on aspirin and clopidogrel are demonstrated on Fig. 2a (respectively for eGFR b90 and ≥90 ml/min: ASPItest 166 IQR 115-244 vs. 314 IQR 118-581 AU*min, p = 0.14; ADPtest 149 IQR 93-227 vs. 205 IQR 97-336 AU*min, p = 0.59; TRAPtest 682 IQR 427-950 vs 662 IQR 416-987 AU*min, p = 0.86). Univariable analysis demonstrated that patients with reduced eGFR on dual antiplatelet therapy were older, less likely male, less frequently smokers and had a lower platelet count, hemoglobin concentration and hematocryte on admission in comparison to patients with preserved eGFR. Multivariable analysis showed that age is the only independent factor discriminating patients with reduced and normal eGFR (OR = 1.240, 95%CI 1.102-1.395 for every 1 year increase, p = 0003) in this subgroup of patients. Platelet reactivity on triple anitplatelet therapy (aspirin, clopidogrel, abciximab) Reduced eGFR was present in 20 patients (43%) on triple anitplatelet therapy. Correlations between eGFR and platelet reactivity tests in this subgroup of patients are shown on Fig. 1 def. Comparison of median platelet reactivity in patients with reduced and normal
Dual antiplatelet therapy n = 46
Triple antiplatelet therapy n = 46
p
69 ± 12 30 (65) 33 (51) 30 (65) 11 (24) 16 (35) 6 (13) 6 (13) 11 (24) 8 (17) 3 (6) 14 (30) 39 (85)
61 ± 11 33 (51) 28 (43) 35 (76) 11 (24) 21 (46) 2 (4) 2 (4) 7 (15) 7 (15) 2 (4) 21 (46) 41 (89)
0.002 0.65 0.38 0.36 1.00 0.40 0.27 0.27 0.43 1.00 1.00 0.20 0.76
20 (43) 13 (28) 45 ± 11
46 (100) 9 (20) 49 ± 12
b0.0001 0.46 0.09
40 (87) 7 (15) 100 ± 32 6 (13)
45 (98) 2 (4) 103 ± 28 4 (9)
0.11 0.16 0.64 0.74
96 ± 35 20 (43) 191 (151,223) 13 ± 1 39 ± 4
0.01 0.68 0.72 0.29 0.64
eGFR on aspirin, clopidogrel and abciximab are demonstrated on Fig. 2b (respectively for eGFR b90 and ≥90 ml/: ASPItest 95 IQR 26124 vs. 121 IQR 93-176 AU*min, p = 0.07; ADPtest 50 IQR 2-131 vs. 99 IQR 49-124 AU*min, p = 0.22; TRAPtest 208 IQR 86-331 vs. 380 IQR 253-447 AU*min, p = 0.007). Univariable analysis demonstrated that patients with reduced eGFR on triple antiplatelet therapy were older, less likely male, less frequently diagnosed with MI during index hospitalization, had a lower hemoglobin concentration and hematocryte on admission in comparison to patients with preserved eGFR. Multivariable analysis including all of the above parameters and TRAPtest showed that age and TRAPtest are the only independent factors discriminating patients with reduced and normal eGFR (OR = 0.989 95%CI 0.981-0.998 for every 1 AU*min increase, p = 0.01; OR = 1.320 95%CI 1.120-1.557 for every 1 year increase, p = 0.0009) in this subgroup of patients.
Discussion The main finding of this study is a lower platelet reactivity in relation to abciximab in patients with ACS and reduced eGFR in comparison to those with ACS and preserved eGFR as shown both in univariable and multivariable analysis. Abciximab is a chimeric monoclonal antibody eliminated from platelets in spleen [1]. Contrary to other inhibitors of glycoprotein IIb/ IIIa receptor, which undergo renal elimination such as tirofiban or eptifibatide, abciximab does not require dose adjustment in renal failure [4]. On the other hand it was found that glycoprotein IIb/IIIa receptors in patients on hemodialysis have lower affinity for fibrinogen, which may be caused by conformational change of the receptors [18,19]. Hemodialysis led to improvement of fibrinogen binding by platelets, which suggests existance of putative toxins in patients with uremia. Platelet defect was also seen after incubation of
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Fig. 1. a-f. Correletions between platelet reactivity tests and eGFR in patients with ACS on dual antiplatelet therapy (a – ASPItest, b - ADPtest, c – TRAPtest) and triple antiplatelet therapy (d – ASPItest, e – ADPtest, f – TRAPtest).
platelets from healthy volunteers with serum of patients with renal failure before hemodialysis. Decreased binding of fibrinogen to platelets in uremia may lead to impairment of platelet aggregation and subsequently to higher frequency of bleeding. It was also demonstrated that patients with uremia have lower expression of fibrinogen receptors on platelets in comparison to normal controls [20]. Other study showed that patients with uremia have a higher
concentration of fibrinogen fragments, which compete with fibrinogen for binding to an active site of glycoprotein IIb/IIIa receptor [21]. Hemodialysis was related to elimination of fibrinogen fragments from blood. Importanly, studies reporting platelet dysfunction in renal impairment included patients with end-stage renal failure requiring dialysis. Our results demonstrate that platelet function on abciximab may be additionally suppresed in patients with ACS and even mildly or
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Fig. 2. ab. Platelet reactivity in patients with ACS and reduced vs normal eGFR, a – on dual antiplatelet therapy, b – on triple antiplatelet therapy.
moderately reduced eGFR. This phenomenon is not a result of slower drug elimination, but is most likely caused by acquired platelet deficiency. Other findings of this study prove that there are no significant differences in platelet reactivity in patients with ACS and reduced vs normal eGFR in relation to aspirin or clopidogrel. It was disclosed that patients with uremia produce lower amounts of thromboxan A2 both in normal conditions and after administration of arachidonic acid in comparison to healthy controls which is related to functional defect of cyclooxygenese-1, an enzyme blocked by aspirin. Degree of decrease in tromboxan A2 production was parallel to administration of 40 mg of aspirin to healthy subjects [22]. Other study demonstrated that aspirin significantly increases bleeding time in subjects with uremia, but not in normal controls [23]. Our results suggest that observed insignificant difference in platelet reactivity on aspirin in patients with reduced eGFR may be related to dose independent inhibition of tromboxan A2 with does over 30 mg. All patients with ACS in the studied group received pretreatment with 300 mg of aspirin which might have bridged the differences. Experimental studies found that patients with renal failure have decreased secretion of ADP, which competes with clopidogrel for the binding site on platelets [24]. However, this mechanism does not translate into higher platelet inhibition in patients with renal impairment which is confirmed by the results of our study. One of the first papers analyzing the influence of renal dysfunction on platelet response to clopidogrel focused on pharmacokinetics and pharmacodynamics of clopidogrel in patients with moderate and severe renal failure. After eight days of treatment with 75 mg of the drug platelet aggregation in response to ADP, bleeding time and concentration of the active form of clopidogrel and its inactive metabolite in serum and urine were similar in patients with moderate and severe renal impairment. Authors concluded that clopidogrel is a well tolerated antiplatelet drug in patients with renal failure leading to effective platelet inhibition and the dose of the drug does not need
to be adjusted in relation to renal function [25]. Other study found that 14-day clopidogrel administration in patients on hemodialysis causes insignificant difference of platelet aggregation inhibition after stimulation with ADP in comparison to healthy controls. Platelet function was completely regained after 7 days from cessation of treatment in both groups [24]. It is important to discuss why platelet aggregation in patients with ACS and reduced eGFR is lower in relation to abciximab but not to aspirin or clopidogrel. Abciximab is the most potent of the three studied antiplatelet drugs. It inhibits platelet aggregation, which is the last stage of platelet response to various activating factors, while aspirin and clopidogrel reduce platelet activation. Importantly, we have not observed significant differences in platelet function dependent on TRAP in patients on dual antiplatelet therapy, but only after administration of abciximab. It shows that platelet dysfunction in patients with mildly or moderately reduced eGFR may become elucidated only in the setting of most potent antiplatelet treatment. Our study has several limitations. Because all of the studied patients received pre-hospital treatment with loading doses of aspirin and clopidogrel it was impossible to assess baseline platelet reactivity (without antiplatelet drugs on board). Logistic reasons (admission of patients during off-hours and short time between blood sampling and testing) enabled the performance of platelet reactivity testing with TRAP before abciximab administration. It may be also speculated that platelet reactivity on abciximab may be influenced by fibrinogen concentration which is a ligand for GP IIb/IIIa receptor. Although renal dysfunction is related to protein loss, we have evaluated patients with acute coronary syndromes, and it was shown that fibrinogen is increased in this setting in comparison to healthy controls [26]. Besides, most of the studies report on increased fibrinogen concentration in plasma even in patients on hemodialysis which may be related to its up-regulated synthesis and no loss in urine [27]. In conclusion, we have demonstrated that platelet reactivity is lower in patients with ACS and reduced eGFR in comparison to patients with ACS and preserved eGFR in relation to abciximab, but not to aspirin or clopidogrel. We suggest that the main reason of our findings may be an impaired GP IIb/IIIa receptor performance in patients with reduced eGFR. Conflict of interest statement None Acknowledgements The study was supported with internal grant 2.44/VII/2008 of the Institute of Cardiology, Warsaw, Poland. References [1] Patrono C, Bachmann F, Baigent C, Bode C, De Caterina R, Charbonnier B, et al. European Society of Cardiology. Expert consensus document on the use of antiplatelet agents. The task force on the use of antiplatelet agents in patients with atherosclerotic cardiovascular disease of the European society of cardiology. Eur Heart J 2004;25:166–81. [2] Moscucci M, Fox KA, Cannon CP, Klein W, López-Sendón J, Montalescot G, et al. Predictors of major bleeding in acute coronary syndromes: the Global Registry of Acute Coronary Events (GRACE). Eur Heart J 2003;24:1815–23. [3] Attallah N, Yassine L, Fisher K, Yee J. Risk of bleeding and restenosis among chronic kidney disease patients undergoing percutaneous coronary intervention. Clin Nephrol 2005;64:412–8. [4] Task Force for Diagnosis and Treatment of Non-ST-Segment Elevation Acute Coronary Syndromes of European Society of Cardiology, Bassand JP, Hamm CW, Ardissino D, Boersma E, Budaj A, et al. Guidelines for the diagnosis and treatment of non-STsegment elevation acute coronary syndromes. Eur Heart J 2007;28:1598–660. [5] Sohal AS, Gangji AS, Crowther MA, Treleaven D. Uremic bleeding: pathophysiology and clinical risk factors. Thromb Res 2006;118:417–22. [6] Noris M, Benigni A, Boccardo P, Gotti E, Benfenati E, Aiello S, et al. Enhanced nitric oxide synthesis in uremia: implications for platelet dysfunction and dialysis hypotension. Kidney Int 1993;44:445–50.
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