The impact of patient-reported frailty on cardiovascular outcomes in elderly patients after non-ST-acute coronary syndrome.

BACKGROUND: As life expectancy increases, the population of older individuals with coronary artery disease and frailty is growing. We aimed to assess the impact of patient-reported frailty on the treatment and prognosis of elderly early survivors of non-ST-elevation acute coronary syndrome (NSTE-ACS). METHODS: Frailty data were obtained from two prospective trials, POPular Age and the POPular Age Registry, which both assessed elderly NSTE-ACS patients. Frailty was assessed one month after admission with the Groningen Frailty Indicator (GFI) and was defined as a GFI-score of 4 or higher. In these early survivors of NSTE-ACS, we assessed differences in treatment and 1-year outcomes between frail and non-frail patients, considering major adverse cardiovascular events (MACE, including cardiovascular mortality, myocardial infarction, and stroke) and major bleeding. RESULTS: The total study population consisted of 2192 NSTE-ACS patients, aged ≥70 years. The GFI-score was available in 1320 patients (79 ± 5 years, 37% women), of whom 712 (54%) were considered frail. Frail patients were at higher risk for MACE than non-frail patients (9.7% vs. 5.1%, adjusted hazard ratio [HR] 1.57, 95% confidence interval [CI] 1.01-2.43, p = 0.04), but not for major bleeding (3.7% vs. 2.8%, adjusted HR 1.23, 95% CI 0.65-2.32, p = 0.53). Cubic spline analysis showed a gradual increase of the risk for clinical outcomes with higher GFI-scores. CONCLUSIONS: In elderly NSTE-ACS patients who survived 1-month follow-up, patient-reported frailty was independently associated with a higher risk for 1-year MACE, but not with major bleeding. These findings emphasize the importance of frailty screening for risk stratification in elderly NSTE-ACS patients.

Characteristics and outcomes in patients with a prior myocardial infarction treated with extended dual antiplatelet therapy with ticagrelor 60 mg: findings from ALETHEIA, a multi-country observational study.

BACKGROUND: Guidelines recommend extended dual antiplatelet therapy, including ticagrelor 60 mg twice daily, in high-risk post-myocardial infarction (MI) patients who have tolerated 12 months and are not at high bleeding risk. The real-world utilization and bleeding and ischaemic outcomes associated with long-term ticagrelor 60 mg in routine clinical practice have not been well described. METHODS: Register and claims data from the USA (Optum Clinformatics, IBM MarketScan, and Medicare) and Europe (Sweden, Italy, UK, and Germany) were extracted. Patients initiating ticagrelor 60 mg ≥12 months after MI, meeting eligibility criteria for the PEGASUS-TIMI (Prevention of Cardiovascular Events in Patients with Prior Heart Attack Using Ticagrelor Compared to Placebo on a Background of Aspirin - Thrombolysis in Myocardial Infarction 45) 54 trial, were included. The cumulative incidence of the composite of MI, stroke, or all-cause mortality and that of bleeding requiring hospitalization were calculated. Meta-analyses were performed to combine estimates from each source. RESULTS: A total of 7035 patients treated with ticagrelor 60 mg met eligibility criteria. Median age was 67 years and 29% were females; 12% had a history of multiple MIs. The majority (95%) had been treated with ticagrelor 90 mg prior to initiating ticagrelor 60 mg. At 12 months from initiation of ticagrelor 60 mg, the cumulative incidence [95% confidence interval (CI)] of MI, stroke, or mortality was 3.33% (2.73-4.04) and was approximately three-fold the risk of bleeding (0.96%; 0.69-1.33). CONCLUSIONS: This study provides insights into the use of ticagrelor 60 mg in patients with prior MI in clinical practice. Observed event rates for ischaemic events and bleeding generally align with those in the pivotal trials, support the established safety profile of ticagrelor, and highlight the significant residual ischaemic risk in this population.Clinical Trials.gov Registration NCT04568083.

Health economic analysis of ticagrelor in patients with acute coronary syndromes intended for non-invasive therapy.

OBJECTIVE: To investigate the cost effectiveness of ticagrelor versus clopidogrel in patients with acute coronary syndromes (ACS) in the Platelet Inhibition and Patient Outcomes (PLATO) study who were scheduled for non-invasive management. METHODS: A previously developed cost effectiveness model was used to estimate long-term costs and outcomes for patients scheduled for non-invasive management. Healthcare costs, event rates and health-related quality of life under treatment with either ticagrelor or clopidogrel over 12 months were estimated from the PLATO study. Long-term costs and health outcomes were estimated based on data from PLATO and published literature sources. To investigate the importance of different healthcare cost structures and life expectancy for the results, the analysis was carried out from the perspectives of the Swedish, UK, German and Brazilian public healthcare systems. RESULTS: Ticagrelor was associated with lifetime quality-adjusted life-year (QALY) gains of 0.17 in Sweden, 0.16 in the UK, 0.17 in Germany and 0.13 in Brazil compared with generic clopidogrel, with increased healthcare costs of €467, €551, €739 and €574, respectively. The cost per QALY gained with ticagrelor was €2747, €3395, €4419 and €4471 from a Swedish, UK, German and Brazilian public healthcare system perspective, respectively. Probabilistic sensitivity analyses indicated that the cost per QALY gained with ticagrelor was below conventional threshold values of cost effectiveness with a high probability. CONCLUSIONS: Treatment of patients with ACS scheduled for 12 months' non-invasive management with ticagrelor is associated with a cost per QALY gained below conventional threshold values of cost effectiveness compared with generic clopidogrel. TRIAL REGISTRATION NUMBER: NCT000391872.

Platelet function testing and prediction of procedural bleeding risk.

The essential role of platelets in haemostasis underlies the relationship between platelet function and spontaneous or procedure-related bleeding, which has important prognostic implications. Although not routinely undertaken, platelet function testing offers the potential to tailor antiplatelet therapy for individual patients. However, uncertainties remain about how well platelet function testing may predict haemostasis and guide management of bleeding risk. Studies of aspirin, P2Y12 inhibitors and other antiplatelet drugs clearly demonstrate how inhibition of platelet function increases bleeding risk. More potent antiplatelet drugs are associated with higher bleeding rates, consistent with the levels of platelet inhibition achieved by these drugs. Studies of patients treated with clopidogrel, which is associated with wide inter-individual variation in antiplatelet effect, suggest that platelet function testing may predict bleeding risk related to coronary artery bypass grafting (CABG) surgery and potentially guide the timing of surgery following discontinuation of clopidogrel. Similarly, some studies have demonstrated a relationship between clopidogrel response and bleeding in patients undergoing percutaneous coronary intervention (PCI), although other studies have not supported this. Carriage of the *17 allele of cytochrome P450 2C19, which is associated with gain of function and enhanced response to clopidogrel, seems to be associated with increased bleeding risk, although studies showing lack of apparent effect of loss-of-function alleles provide contradictory evidence. Further large studies are needed to guide best practice in the application of platelet function testing in the clinical management of patients treated with antiplatelet drugs in order to optimise individual care.

Earlier recovery of platelet function after discontinuation of treatment with ticagrelor compared with clopidogrel in patients with high antiplatelet responses.

BACKGROUND: The rate of recovery of platelet function after discontinuation of P2Y(12) inhibitors depends on the reversibility of the antiplatelet effect and the extent of the on-treatment response. P2Y(12) inhibition increases the bleeding risk in patients requiring surgery. OBJECTIVES: To evaluate recovery of platelet function after discontinuation of ticagrelor vs. clopidogrel in stable coronary artery disease (CAD) patients with high levels of platelet inhibition (HPI) during the ONSET/OFFSET study. METHODS: Patients received aspirin 75-100 mg per day and either ticagrelor 90 mg twice-daily or clopidogrel 75 mg daily for 6 weeks. This subanalysis included patients with HPI after the last dose of maintenance therapy, defined as: inhibition of platelet aggregation (IPA) > 75% 4 h post-dose (ADP 20 µm, final extent); < 120 P2Y(12) reaction units 8 h post-dose (VerifyNow P2Y(12) assay); or platelet reactivity index < 50% 8 h post-dose (VASP-P assay). RESULTS: IPA > 75% was observed in 39 out of 47 ticagrelor-treated and 17 out of 44 clopidogrel-treated patients. The rate of offset of IPA over 4-72 h was greater with ticagrelor (IPA %/hour slope: -1.11 vs. -0.67 for clopidogrel; P < 0.0001). Mean IPA was significantly lower with ticagrelor than clopidogrel between 48 and 168 h post-dose (P < 0.01). Similar findings were observed with the other assays. The average time for IPA to decline from 30% to 10% was 50.8 h with ticagrelor vs. 110.4 h with clopidogrel. CONCLUSIONS: In patients with HPI, recovery of platelet function was more rapid after discontinuation of ticagrelor than clopidogrel leading to significantly greater platelet reactivity by 48 h after the last dose in the ticagrelor group.

Potentiation of clopidogrel active metabolite formation by rifampicin leads to greater P2Y12 receptor blockade and inhibition of platelet aggregation after clopidogrel.

BACKGROUND: The thienopyridine P2Y(12) receptor antagonist clopidogrel reduces the risk of arterial thrombosis and individual pharmacodynamic responses to clopidogrel are believed to reflect the levels of active metabolite (AM) generated. Rifampicin increases the inhibitory effect of clopidogrel on platelet aggregation (PA). We studied the response to clopidogrel before and during administration of rifampicin in order to study the relationship between individual AM levels and P2Y(12) blockade. METHODS: Healthy volunteers received a 600-mg loading dose of clopidogrel followed by 75 mg daily for 7 days and, after a washout period and treatment with rifampicin [300 mg twice a day (b.i.d.)], received the same regimen of clopidogrel. Clopidogrel AM levels were determined over 4 h after the clopidogrel loading dose and unblocked P2Y(12) receptor number was assessed using a (33) P-2MeSADP binding assay. PA was measured by optical aggregometry with ADP and TRAP. RESULTS: Rifampicin enhanced clopidogrel AM production [area-under-the-curve (AUC): clopidogrel 89±22 ng h mL(-1) , clopidogrel+rifampicin 335±86 ng h mL(-1) , P<0.0001], and P2Y(12) blockade (unblocked receptors: clopidogrel 48±24, clopidogrel+rifampicin 4±2, P<0.0001) and reduced PA (5 µmol L(-1) ADP: clopidogrel 20±4, clopidogrel+rifampicin 5±2, P<0.01). Increasing numbers of unblocked receptors were required for an aggregation response with a decreasing concentration of ADP. PA induced by ADP 2 µmol L(-1) was particularly sensitive to low levels of receptor blockade. CONCLUSION: Potentiation of clopidogrel AM production by rifampicin leads to greater P2Y(12) blockade and consequently greater inhibition of PA. PA responses to low concentrations of ADP are more sensitive to P2Y(12) blockade.

Bleeding risk with AZD6140, a reversible P2Y12 receptor antagonist, vs. clopidogrel in patients undergoing coronary artery bypass grafting in the DISPERSE2 trial.

AZD6140, the first reversible oral P2Y(12) receptor antagonist, exhibits greater and more consistent inhibition of platelet aggregation than the irreversible thienopyridine clopidogrel. As a result of its reversible effect, AZD6140 may pose less risk for bleeding when antiplatelet treatment cannot be stopped at least 5 days before coronary artery bypass graft (CABG) surgery or other invasive procedures. The Dose conflrmation Study assessing anti-Platelet Effects of AZD6140 vs. clopidogRel in NSTEMI (DISPERSE2) trial showed overall comparable bleeding rates with antiplatelet treatment with AZD6140 90 mg twice daily or 180 mg twice daily vs. clopidogrel 75 mg once daily in 984 patients with non-ST-elevation acute coronary syndromes. A post hoc exploratory analysis of bleeding outcomes in the subset of 84 patients undergoing CABG in DISPERSE2 suggests reduced risk for total bleeding (41% and 58% vs. 62%), all major bleeding (38% and 50% vs. 62%), and life-threatening bleeding (22% and 38% vs. 54%) with AZD6140 90 mg (n = 32) and 180 mg (n = 26) vs. clopidogrel (n = 26) respectively. Trends suggested that major bleeding rates were reduced with AZD6140 (combined groups) vs. clopidogrel when treatment was stopped < or = 5 days prior to surgery (39% vs. 63%, p = 0.15) but not when treatment was stopped > 5 days before surgery (50% vs. 60%). This observation is consistent with the reversible binding of AZD6140 to the P2Y(12) receptor. Further prospective studies are planned to assess the relationship between this potential clinical benefit of AZD6140 and the reversibility of its antiplatelet effects.

Platelet P2Y(12) receptor influences the vessel wall response to arterial injury and thrombosis.

BACKGROUND: Platelets are believed to play an important role in atherogenesis and the vessel response to vascular injury. The P2Y(12) receptor (P2Y(12)) plays a central role in amplifying platelet aggregation, dense granule and alpha-granule secretion, P-selectin expression, microparticle formation, and procoagulant membrane changes, regardless of the activating stimulus. We hypothesized that P2Y(12) deficiency might reduce the vessel wall response to vascular injury as well as thrombosis in murine vascular injury models. METHODS AND RESULTS: P2Y(12)-deficient (-/-) mice and littermate controls (+/+) were bred on a C57 BL/6 background. In vivo murine models of arterial injury were employed alone and in combination with bone marrow transplantation to investigate the role of P2Y(12) in the vessel wall response to arterial injury and thrombosis. At 21 days after ferric chloride injury, neointima formation in P2Y(12)(-/-) arteries was significantly less than that observed in control strain arteries (P<0.025). In agreement with this, the intima-media ratio was significantly greater in femoral wire-injured arteries from P2Y(12)(+/+) compared with P2Y(12)(-/-) animals (P<0.05). Bone marrow transplantation was used to examine the importance of vessel wall P2Y(12) versus platelet P2Y(12). Analysis of arterial sections from chimeric animals at 21 days after injury revealed a smaller intima-media ratio in -/- to +/+ animals than in the positive (+/+ to +/+) control group (P<0.01). CONCLUSIONS: These data demonstrate a role for platelet P2Y(12) in the vessel wall response to arterial injury and thrombosis. This illustrates the manner in which platelets may contribute to atherogenesis and restenosis.

PAR-1 genotype influences platelet aggregation and procoagulant responses in patients with coronary artery disease prior to and during clopidogrel therapy.

Genetic variations of the protease-activated receptor-1 (PAR-1) have been associated with platelet receptor density and linked to thrombin receptor-activating peptide (TRAP)-induced phenotypes of platelet aggregation and P-selectin expression. We investigated whether the PAR-1 intervening sequence-14 A>T dimorphism influences platelet procoagulant activity. We also determined whether the P2Y12 antagonist clopidogrel could offset any observed functional polymorphism of the PAR-1 receptor by inhibiting P2Y12-mediated amplification of TRAP-induced responses. We studied 54 patients listed for elective percutaneous coronary intervention assessing TRAP-induced platelet aggregation and markers of procoagulant activity. Platelet responses were measured at baseline, 4 h post clopidogrel 300 mg, and 10 and 28 days following clopidogrel 75 mg daily. Each patient was genotyped for the PAR-1 intervening sequence-14 A/T dimorphism. Increased platelet aggregation and procoagulant responses were observed with PAR-1 A allele homozygotes. Clopidogrel significantly inhibited these platelet responses regardless of PAR-1 genotype, but did not offset the hyper-reactivity associated with the A/A homozygotes. We conclude that a common sequence variation within the PAR-1 gene influences TRAP-induced platelet procoagulant activity as well as aggregation. Higher platelet reactivity associated with PAR-1 IVSn-14 A allele homozygotes persists despite clopidogrel therapy. These individuals may be at higher risk of thromboembolic events and may require additional anti-platelet medication.

Antiplatelet therapy in cardiovascular disease.

Platelet activation and aggregation are considered to be central to arterial thrombus formation. Antiplatelet therapy is therefore important for both the treatment and prevention of cardiovascular disease. Aspirin, the most widely used antiplatelet agent, inhibits platelet cyclo-oxygenase and the conversion of arachidonic acid to the potent platelet agonist thromboxane A(2) but does not prevent platelet activation occurring via various signalling pathways that are independent of thromboxane A(2) release. Therefore a number of other compounds have been developed to complement aspirin's beneficial effect. These include the thienopyridines (clopidogrel and ticlopidine), dipyridamole, and the alpha(IIb)beta(3) (glycoprotein IIb/IIIa) receptor inhibitors.

Effects of P2Y(1) and P2Y(12) receptor antagonists on platelet aggregation induced by different agonists in human whole blood.

ADP plays a major role in the amplification of platelet aggregation induced by other platelet agonists. ADP initiates platelet activation via the P2Y(1) receptor and amplifies platelet activation via the P2Y(12) receptor. Using the selective P2Y(1) receptor antagonist A2P5P and the selective P2Y(12) receptor antagonist AR-C69931MX, we assessed the relative contributions of P2Y(1) receptor and P2Y(12) receptor activation to platelet aggregation in hirudin-anticoagulated whole blood induced by PAF, 5HT, epinephrine, TRAP, streptokinase, U46619 and collagen. The effects of aspirin were assessed concurrently. A2P5P and AR-C69931MX variably inhibited aggregation induced by most of the agonists studied, whereas aspirin only inhibited aggregation induced by streptokinase and collagen. In some experiments, A2P5P and AR-C69931MX yielded additive inhibition of aggregation. All three antagonists interacted synergistically to inhibit collagen-induced aggregation. These studies demonstrate that P2Y(1) receptor activation plays a significant role in amplifying aggregation induced by agonists other than ADP, in addition to the established roles of P2Y(12) receptor activation and thromboxane A(2) synthesis.

The P2Y12 receptor as a therapeutic target in cardiovascular disease.

Coronary thrombosis complicating rupture of atherosclerotic plaque is the predominant cause of acute coronary syndromes and platelets play a crucial role in this thrombus formation. Whilst aspirin has been successful in reducing cardiovascular morbidity and mortality, appreciation of its limited antiplatelet effects has stimulated the search for more effective antiplatelet agents. The thienopyridines, ticlopidine and clopidogrel, act, via metabolites, on the platelet ADP receptor subtype now designated P2Y(12 )(formerly P(2T), P2T (AC), P2Y (ADP) or P2Y(cyc)) and these agents have proven clinical efficacy. Analogues of the natural P2Y(12) receptor antagonist ATP have been developed that act directly on the receptor and have a rapid onset of action. One such antagonist, AR-C69931MX, is being developed for clinical use. AR-C69931MX is a potent antagonist of ADPinduced platelet activation, aggregation and secretion and also antagonises platelet responses, including procoagulant activity, induced by all other agonists in view of the central role of the P2Y(12) receptor in amplifying platelet responses. Phase II studies of intravenous AR-C69931MX in patients with acute coronary syndromes show that this agent has a rapid onset of action, rapidly achieving steady-state inhibition of platelet aggregation, with a half-life of only a few minutes. AR-C69931MX appears to be safe and well tolerated as adjunctive therapy in these patients, and more effective inhibition of platelet function is achieved than with clopidogrel. Orally active ATP analogues are also being developed that may be more effective than clopidogrel. Limitations of platelet glycoprotein IIb/IIIa antagonists leave scope for development of alternative antiplatelet agents.

Open multicentre study of the P2T receptor antagonist AR-C69931MX assessing safety, tolerability and activity in patients with acute coronary syndromes.

Platelet aggregation is the central process in the pathophysiology of acute coronary syndromes. ADP contributes to thrombosis by activating platelets, and AR-C69931MX is a specific antagonist of this process acting at the P2T receptor. At 5 hospitals, 39 patients with unstable angina or non-Q wave myocardial infarction, who were receiving aspirin and heparin, were administered intravenous AR-C69931MX with stepped dose increments over 3 h to a plateau of either 2 microg/kg/min for 21 h (Part 1; n = 12) or up to 69 h (Part 2; n = 13) or 4 microg/kg/min for up to 69 h (Part 3: n = 14). Safety parameters, platelet aggregation (PA) induced by ADP 3 micromol/L (impedance aggregometry), bleeding time (BT) and plasma concentrations of AR-C69931XX were assessed. AR-C69931MX was well tolerated. 33 patients completed the study. There were no deaths at 30 days and no serious adverse events attributed to AR-C69931MX. Trivial bleeding (56%) was common. At 24 h, mean inhibition of PA was 96.0 +/- 8.6, 94.9 +/- 14.4 and 98.7 +/- 2.1% and BT was 9.5 +/- 8.4, 14.0 +/- 9.7 and 16.0 +/- 11.1 min for Parts 1, 2 and 3 respectively. At 1 h post-infusion, mean inhibition of PA was 36.2 +/- 39.2, 20.7 +/- 25.9 and 40.7 +/- 36.7% respectively. 90% patients had a plasma half-life for AR-C69931XX of <9 min. In conclusion, AR-C69931MX is a potent, short-acting platelet ADP receptor antagonist suitable for further studies as an antithrombotic agent.

The central role of the P(2T) receptor in amplification of human platelet activation, aggregation, secretion and procoagulant activity.

Adenosine diphosphate (ADP) is an important platelet agonist and ADP released from platelet dense granules amplifies responses to other agonists. There are three known subtypes of ADP receptor on platelets: P2X(1), P2Y(1) and P(2T) receptors. Sustained ADP-induced aggregation requires co-activation of P2Y(1) and P(2T) receptors. AR-C69931MX, a selective P(2T) receptor antagonist and novel antithrombotic agent, was studied to characterize further the function of the P(2T) receptor. The roles of the P2Y(1) receptor and thromboxane A(2) were assessed using the selective P2Y(1) antagonist A2P5P and aspirin respectively. Aggregation was measured by whole blood single-platelet counting and platelet-rich plasma turbidimetry, using hirudin anticoagulation. Dense granule release was estimated using ([14)C]-5-hydroxytryptamine (HT)-labelled platelets. Ca(2+) mobilization, P-selectin expression, Annexin V binding and microparticle formation were determined by flow cytometry. P(2T) receptor activation amplified ADP-induced aggregation initiated by the P2Y(1) receptor, as well as amplifying aggregation, secretion and procoagulant responses induced by other agonists, including U46619, thrombin receptor-activating peptide (TRAP) and collagen, independent of thromboxane A(2) synthesis, which played a more peripheral role. P(2T) receptor activation sustained elevated cytosolic Ca(2+) induced by other pathways. These studies indicate that the P(2T) receptor plays a central role in amplifying platelet responses and demonstrate the clinical potential of P(2T) receptor antagonists.

A whole blood assay of inhibition of platelet aggregation by glycoprotein IIb/IIIa antagonists: comparison with other aggregation methodologies.

We have used a whole blood single-platelet counting assay (WB-SPC) that is sensitive to microaggregation for monitoring GPIIb/IIIa antagonists and have compared this with other methodologies. In vitro effects of the GPIIb/IIIa antagonist fradafiban on ADP-induced platelet aggregation were determined using WBSPC and PRP turbidimetry, comparing citrate and hirudin anticoagulation. Fradafiban was a more potent inhibitor of aggregation assessed by PRP turbidimetry compared to WBSPC. Citrate showed only a trend towards enhancing fradafiban potency (p = 0.087). Citrated blood from 8 patients with unstable angina, randomised to receive oral lefradafiban (the oral prodrug of fradafiban) or placebo, was studied before and during treatment using WBSPC, PRP turbidimetry, impedance aggregometry and Rapid Platelet Function Assay (RPFA, Accumetrics). RPFA, PRP turbidimetry and WBSPC measurements correlated well. Impedance aggregometry responses were oversensitive to GPIIb/IIIa blockade. WBSPC was most discriminating at high levels of inhibition and offered a rapid means of monitoring GPIIb/IIIa antagonist effect within the therapeutic range of inhibition.

Laboratory investigation of platelet function.

Advancement in the understanding of the mechanisms of platelet activation and the development of new techniques for studying platelet function have created the challenge of a wide range of options for investigating patients with suspected platelet disorders and for studying the effects of anti-platelet drugs. Novel classes of anti-platelet drug, such as adenosine diphosphate (ADP) receptor and glycoprotein IIb/IIIa receptor antagonists, are being developed and introduced into routine clinical practice. This review presents an overview of current techniques for laboratory investigation of platelet function in the light of these recent advances.