A high ratio of ADP-TRAP induced platelet aggregation is associated more strongly with increased mortality after coronary stent implantation than high conventional ADP induced aggregation alone

Time from blood draw to multiple electrode aggregometry and association with platelet reactivity

Results from multiple electrode aggregometry (MEA) may vary according to pre-analytic factors. This study aimed to analyze the association of time from blood draw to MEA in patients undergoing percutaneous coronary intervention (PCI). In this observational single-center cohort study, platelet aggregation (aggregation units, U) was quantified by MEA (Multiplate Analyzer) after stimulation with adenosine diphosphate (ADP; final concentration [Fc] 6.4 μM), thrombin receptor activating peptide (TRAP; Fc 32 μM), or arachidonic acid (AA; Fc 0.5 mM) in patients treated with ASA and clopidogrel following PCI. High on-clopidogrel platelet reactivity (HPR) was defined as ADP-induced platelet aggregation ≥ 46 U. The manufacturer recommends performing the analysis within 30-180 min after blood draw. Patients were grouped according to the time from blood draw to MEA: 30-180 min, < 30 min, or > 180 min. Platelet function of 273 patients with coronary artery disease undergoing PCI with dual antiplatelet therapy was analyzed. The median age was 72 years (interquartile range, IQR 62-79) and 179 (66%) were male. Median ADP-, TRAP-, and AA-induced aggregation was 25 (IQR 18-36) U, 79 (IQR 63-96) U, and 12 (IQR 7-18) U, respectively. For those analyzed within 30-180 min from blood draw, no significant correlation of time from blood draw to MEA was observed 1) ADP (r = - 0.04, p = 0.51); 2) TRAP (r = - 0.06, p = 0.32); 3) AA (r = - 0.03, p = 0.67). In patients undergoing percutaneous coronary intervention and treated with dual antiplatelet therapy, the time from blood draw to multiple electrode aggregometry does not correlate with ADP- induced aggregation when the measurement occurred within the recommended time interval of 30-180 min after blood draw.

Clinical Significance of Thrombin Blockade with Low Doses (2.5 mg) of Rivaroxaban in Ischemic Heart Disease Patients

Arterial thrombosis is a result of complex interaction between blood cells, soluble coagulation factors in plasma and vessel wall. Antiplatelet drugs do not always provide the necessary antithrombotic effect of sufficient strength, because their influence does not extend to all three factors involved in this process. Low doses of direct oral inhibitors of thrombin are able to potentiate antithrombotic effect of antiplatelet therapy. The combination of rivaroxaban in a dose of 2.5 mg and standard double antiplatelet therapy turned out to be the most promising for clinical use, since studies with dabigatran and apixaban at the II and III stages of the trials were found to be unsuccessful due to the unacceptably high frequency of bleeding. Studies of the combination of rivaroxaban at a dose of 2.5 mg and standard antiplatelet therapy conducted in previous years among patients with acute myocardial infarction showed a decrease in the frequency of complications of atherothrombosis associated with their ischemic nature, while at the same time there was a slight increase in hemorrhagic complications. In the COMPASS study the combination of rivaroxaban (2.5 mg) plus aspirin reduced the risk of the primary endpoint (myocardial infarction, ischemic stroke, cardiovascular death) more significantly than aspirin alone in patients with stable ischemic heart disease and ischemic brain disease. The pathophysiological rationales for the use of low doses of rivaroxaban when added to dual antiplatelet therapy are considered, and the significance of recent studies in patients with acute coronary syndrome, stable ischemic heart disease and in the prevention of ischemic stroke is discussed.

High platelet reactivity after P2Y12-inhibition in patients with atrial fibrillation and coronary stenting

High platelet reactivity (HPR) after P2Y12-inhibition in patients undergoing coronary stenting is associated with an increased risk for thromboembolic events and coronary death. So far it is not known how HPR affects the clinical outcome of different treatment strategies in patients with atrial fibrillation (AF) undergoing coronary stenting. In this single centre, observational study the antiplatelet effect of P2Y12-inhibitors in AF patients undergoing coronary stenting was investigated using impedance aggregometry. Patients received either dual antiplatelet therapy (DAPT) or triple therapy (TT). HPR was defined as the ratio of ADP-to TRAP-induced aggregation (r-ADP-agg) ≥50 %. Thromboembolic and bleeding events were assessed within the first 30 days after stenting. Out of 910 screened patients 167 patients were available for the present analysis. HPR was found in 5 of 43 (12 %) patients treated with DAPT and in 18 of 124 (15 %) patients treated with TT. In patients receiving TT, HPR was not a risk factor for thromboembolic events compared to patients with adequate response to P2Y12-inhibitors (6 vs. 8 %, p = 0.712). There was a trend for less bleeding events in patients with HPR compared to r-ADP-agg <50 % in the TT group (0 vs. 16 %, p = 0.077). Our data suggest that HPR after P2Y12-antagonism in patients receiving TT due to AF and coronary stenting might protect from bleeding without increasing thromboembolic risk. Future studies will need to investigate if patients with AF receiving coronary stenting benefit from a reduction of antithrombotic therapy.

The Ratio of ADP- to TRAP-Induced Platelet Aggregation Quantifies P2Y12-Dependent Platelet Inhibition Independently of the Platelet Count

OBJECTIVE

This study aimed to assess the association of clinical factors with P2Y12-dependent platelet inhibition as monitored by the ratio of ADP- to TRAP-induced platelet aggregation and conventional ADP-induced aggregation, respectively.

BACKGROUND

Controversial findings to identify and overcome high platelet reactivity (HPR) after coronary stent-implantation and to improve clinical outcome by tailored anti-platelet therapy exist. Monitoring anti-platelet therapy ex vivo underlies several confounding parameters causing that ex vivo platelet aggregation might not reflect in vivo platelet inhibition.

METHODS

In a single centre observational study, multiple electrode aggregometry was performed in whole blood of patients after recent coronary stent-implantation. Relative ADP-induced aggregation (r-ADP-agg) was defined as the ratio of ADP- to TRAP- induced aggregation reflecting the individual degree of P2Y12-mediated platelet reactivity.

RESULTS

Platelet aggregation was assessed in 359 patients. Means (± SD) of TRAP-, ADP-induced aggregation and r-ADP-agg were 794 ± 239 AU*min, 297 ± 153 AU*min and 37 ± 14%, respectively. While ADP- and TRAP-induced platelet aggregation correlated significantly with platelet count (ADP: r = 0.302; p<0.001; TRAP: r = 0.509 p<0.001), r-ADP-agg values did not (r = -0.003; p = 0.960). These findings were unaltered in multivariate analyses adjusting for a range of factors potentially influencing platelet aggregation. The presence of an acute coronary syndrome and body weight were found to correlate with both ADP-induced platelet aggregation and r-ADP-agg.

CONCLUSION

The ratio of ADP- to TRAP-induced platelet aggregation quantifies P2Y12-dependent platelet inhibition independently of the platelet count in contrast to conventional ADP-induced aggregation. Furthermore, r-ADP-agg was associated with the presence of an acute coronary syndrome and body weight as well as ADP-induced aggregation. Thus, the r-ADP-agg is a more valid reflecting platelet aggregation and potentially prognosis after coronary stent-implantation in P2Y12-mediated HPR than conventional ADP-induced platelet aggregation.

Morphine interaction with prasugrel: a double-blind, cross-over trial in healthy volunteers

Background

Morphine decreases the concentrations and effects of clopidogrel, which could lead to treatment failure in myocardial infarction.

Objectives

To clarify whether more potent P2Y₁₂-inhibitors may provide an effective alternative, we examined drug–drug interactions between morphine and prasugrel.

Methods

Twelve healthy volunteers received 60 mg prasugrel with placebo or 5 mg morphine intravenously in a randomized, double-blind, placebo-controlled, cross-over trial. Pharmacokinetics were determined by liquid chromatography tandem mass spectrometry, and prasugrel effects were measured by platelet function tests.

Results

Morphine neither diminished total drug exposure (AUC), which was the primary endpoint, nor significantly delayed drug absorption of prasugrel. However, morphine reduced maximal plasma concentrations (C_max) of prasugrel active metabolite by 31 % (p = 0.019). Morphine slightly, but not significantly, delayed the onset of maximal inhibition of platelet plug formation under high shear rates (30 vs. 20 min). Whole blood aggregation was not influenced.

Conclusions

Although morphine significantly decreases the maximal plasma concentrations of prasugrel active metabolite, it does not diminish its effects on platelets to a clinically relevant degree in healthy volunteers. However, it should be considered that the observed decrease in C_max of prasugrel active metabolite caused by morphine co-administration may gain relevance in STEMI patients.

Clinical Trial Registration: NCT01369186, EUDRA-CT#: 2010-023761-22.

[Antiplatelet therapy after acute coronary syndrome. Therapeutic strategies and treatment duration]

Besides percutaneous coronary interventions, antiplatelet drugs are of overwhelming importance for patients with acute coronary syndrome (ACS). For ACS patients, the guidelines recommend treatment with acetylsalicylic acid and a P2Y12 receptor antagonist. The third generation P2Y12 receptor antagonists prasugrel and ticagrelor provide stronger platelet inhibition than clopidogrel and improve the clinical outcome in patients with ACS; however, it is still under discussion which P2Y12 antagonist fits best to which subgroup of ACS patients. This article summarizes current guidelines and antiplatelet treatment strategies for patients with non-ST-segment elevation (NSTE) ACS or ST-segment elevation myocardial infarction (STEMI). The information is mainly based on the recently published guidelines of the European Society of Cardiology on myocardial revascularization.