Andrew Smallwood

Individualised Assessment of Response to Clopidogrel in Patients Presenting with Acute Coronary Syndromes: A Role for Short Thrombelastography?

INTRODUCTION There is considerable interindividual variation in response to the antiplatelet agent clopidogrel. Hyporesponse predicts negative outcomes in patients presenting with a variety of ischemic cardiac conditions and following intracoronary stent placement. Many tests of clopidogrel activity are time consuming and complex. Short thromboelastography (s-TEG) allows rapid measurement of platelet clopidogrel response. AIMS We initiated this study to investigate the utility of s-TEG in assessing the response to clopidogrel in patients presenting with acute coronary syndromes (ACS) and to compare these results with established clopidogrel monitoring techniques. METHODS Patients admitted with unstable angina (UA) or Non ST elevation myocardial infarction (NSTEMI) undergoing coronary angiography were recruited. After routine loading with clopidogrel, all patients were tested with s-TEG and Accumetrics Verify-Now rapid platelet function analyzer (VN-RPFA). We used the modified TEG technique of measuring area under the curve at 15 min (AUC15), which allows a rapid estimation of antiplatelet response. Vasodilator-stimulated phosphoprotein phosphorylation (VASP) was also tested in a subgroup of patients. Clinical follow-up was obtained at 1 year. s-TEG results were correlated with VN-RPFA and VASP findings. RESULTS A total of 49 patients (33 male, mean age 63) were recruited and tested with s-TEG and VN-RPFA and a total of 39 patients were also assessed with VASP. s-TEG readings correlated well with VN-RPFA (r(2)= 0.54, P < 0.0001) and VASP (r(2)= 0.26, P= 0.001). CONCLUSION s-TEG provides timely results which compare to current tests of clopidogrel activity. This technique can also be used to measure a variety of other clotting parameters and as such could develop into a valuable near patient test for the interventional cardiologist.

Near patient anti-platelet response testing over time and gene analysis in patients admitted with acute coronary syndromes

We sought to assess the relationships between platelet reactivity at different time points, CYP2C19*2 and ABCB1 status and clinical outcomes in patients with acute coronary syndromes (ACS). Anti-platelet response to clopidogrel was studied prospectively using the VerifyNow (VN) P2Y12 assay at the time of angiography and at 30 days post procedure in 151 patients admitted with ACS who underwent percutaneous coronary intervention (PCI). Troponin T levels were measured at angiography and 16–24 hour following PCI. DNA was extracted and the presence of CYP2C19*2 allele and ABCB1 polymorphisms were determined. Adverse cardiovascular and cerebral events (ACCE) were assessed at 12 months. High VN P2Y12 response at angiography was associated with a greater peri-procedural rise in troponin T, but not ACCE. However, VN P2Y12 response measured at 30 days was associated with ACCE (p = 0.017). CYP2C19*2 status was associated with higher VN P2Y12 response at angiography (p < 0.0001) and 30 days (p = 0.006) but not ACCE. Near-patient testing for clopidogrel response was associated with subsequent ACCE when performed 30 days following PCI, but not at angiography.

Clopidogrel and proton pump inhibitors: can near patient testing help in the tailoring of dual antiplatelet prescription?

Platelet activation and aggregation are key elements in the pathogenesis of arterial thrombosis, often resulting in an acute coronary syndrome (ACS), as well as being a major cause of complications seen during and after percutaneous coronary intervention (PCI). Antiplatelet agents such as aspirin and the thienopyridine clopidogrel are widely prescribed for the reduction of atherosclerotic events in patients presenting with ACS and myocardial infarction (MI) [1]. Clopidogrel is a prodrug that is converted in the liver to its active metabolite by isoforms of the cytochrome (CYP) P450 enzyme, with CYP2C19 playing a major role [2]. This active metabolite targets and irreversibly binds to the P2Y12 receptor on circulating platelets, thereby preventing its agonist, ADP, from

Vascular endothelial growth factor and hypoxia-inducible factor-1α gene polymorphisms and coronary collateral formation in patients with coronary chronic total occlusions

Introduction: We evaluated the association between two single nucleotide polymorphisms of the vascular endothelial growth factor gene and one of the hypoxia-inducible factor-1α gene and the degree of coronary collateral formation in patients with a coronary chronic total occlusion. Methods: Totally, 98 patients with symptomatic coronary artery disease and a chronic total occlusion observed during coronary angiography were recruited. Genotyping of two vascular endothelial growth factor promoter single nucleotide polymorphisms (−152G>A and −165C>T) and the C1772T single nucleotide polymorphism of hypoxia-inducible factor-1α were performed using polymerase chain reaction and restriction fragment length polymorphism analysis. The presence and extent of collateral vessel filling was scored by blinded observers using the Rentrop grade. Results: We found no association between the vascular endothelial growth factor −152G>A, −165C>T and hypoxia-inducible factor-1α −1772C>T with the presence and filling of coronary collateral vessels. A history of percutaneous coronary intervention and transient ischaemic attack/cerebrovascular accident were associated with the presence of enhanced collateral vessel formation following binary logistic regression analysis. Conclusion: The study findings suggest that coronary collateral formation is not associated with the tested polymorphic variants of vascular endothelial growth factor and hypoxia-inducible factor-1α in patients with symptomatic coronary artery disease and the presence of a chronic total occlusion.

Poor aspirin response in diabetic patients presenting with acute coronary syndromes: Results using a near patient test.

Mortensen et al. have recently published a study describing the impact of the presence of type 2 diabetes mellitus on the anti-platelet effect of aspirin in patients with coronary artery disease (CAD) [1]. Here we describe data relating to the effect of aspirin in patients presenting with high risk acute coronary syndromes (ACS) Platelet activation and aggregation are key elements in the pathogenesis of arterial thrombosis often resulting in an ACS [2,3], as well as being a major cause of complications seen during and after percutaneous coronary intervention (PCI). Aspirin is widely prescribed for the reduction of atherosclerotic events in patients presenting with ACS and myocardial infarction (MI). It is seen as the mainstay of anti-platelet therapy and reduces adverse ischaemic events by 25–30% [4]. It acts by the irreversible acetylation of the enzyme cyclooxygenase, thus preventing the synthesis of thromboxane from arachidonic acid [5]. Diabetes mellitus (DM), and particularly type-2 diabetes mellitus (T2DM), is becoming a global epidemic. Approximately 180 million people are affected worldwide and as many as 300 million are expected to be affected by 2025 [6]. Patients with T2DM have a twoto four-fold increase in the risk of Coronary artery disease (CAD) and patients with DM but without previous MI, carry the same level of risk for subsequent acute coronary events as non-diabetic patients with previousMI [7,8]. Diabetes leads to alterations in platelet turnover [9– 11], aggregation and augmented thromboxane synthesis [12], in addition to impaired endothelial function [13]. Aspirin is therefore an important agent in the treatment of patients with the condition and known coronary disease, however its efficacy, particularly in the setting of a poor metabolic control, is attenuated [14]. A number of putative mechanisms for “aspirin low-responsiveness ” have been postulated including poor compliance [15], drug-drug interactions [16], genetic polymorphisms in genes coding COX-1 [17] and platelet glycoprotein (GP) IIb/IIIa PL haplotypes [18] with the latter being proposed to influence clinical outcome in ACS [19] although this hypothesis has been disputed [20]. In the Mortensen et al. study all patients in the study group presented with stable CAD and all patients in the diabetic group were diagnosed with T2DM. Both platelet activation and aggregation was assessed between the two groups of patients using VerifyNow rapid platelet function analyzer and Multiplate aggregometry, respectively. This study demonstrated that diabetic patients had significantly higher levels of both platelet aggregation and activation compared to non-diabetics when treated with the same dose of aspirin. Subsequent to this we have assessed the impact of DM on aspirin response in diabetic patients admitted to a cardiothoracic centre with a diagnosis of high risk ACS. 269 patients (n=50 diabetic) with ACS (mean age 63±11, females n=85) were enrolled over a twenty-one month period.

Retinal embolic events: frequency and impact following transcatheter aortic valve implantation (TAVI) for aortic stenosis

Objectives Transcatheter aortic valve implantation (TAVI) is an established treatment for patients with severe symptomatic aortic stenosis. It has a cerebrovascular accident rate of about 5% but the effect on retinal embolic events has not been previously reported. This study investigated the occurrence of retinal emboli following TAVI. Methods and analysis In this prospective observational study, 20 patients underwent full ophthalmic examination to assess retinal embolic events prior to TAVI and at 48 hours and 1 month post-TAVI. Results At 48 hours post-TAVI, one patient had a new cotton wool spot in the right eye. At 1 month, another two patients had new retinal emboli events in at least one eye and a fourth patient developed retinal splinter haemorrhages in the right eye. Conclusion Retinal embolic events and new retinal abnormalities following TAVI occurred in 15% and 20% of our cohort, respectively, without any associated retinal damage or significant visual problems. Retinal evaluation may be a useful surrogate test for cerebral embolisation in future studies assessing the utility of new valve prostheses and embolic protection devices

111 The Degree and Time Course of Platelet Inhibition Following the Administration of Oral Antiplatelet Agents in Patients Presenting with ST Elevation MI (STEMI)

Introduction Oral P2Y12 inhibitors have proven clinical efficacy in a variety of cardiological settings. The degree and time course of platelet inhibition using common P2Y12 inhibitors during the acute phase of a myocardial infarction is an under explored area. We aimed to determine the effect of clopidogrel, prasugrel and ticagrelor in the first four hours following loading in patients admitted with STEMI undergoing primary percutaneous coronary intervention (PPCI). Methods A single centre non-randomised study in patients presenting with STEMI. All patients gave informed consent. Enrolled patients were administered a loading dose of aspirin 300mg and then either clopidogrel 600mg, prasugrel 60mg or ticagrelor 180mg prior to percutaneous coronary intervention. Platelet reactivity was measured using a Verify Now assay at 20 minutes post loading, first balloon inflation, 1 and 4 hours post loading. Results are expressed a P2Y12 reaction units (PRU). PRU ≥ 208 indicates poor antiplatelet response. The effect of the three drugs over time were assessed using 2 way ANOVA. P < 0.05 was taken as a significant result. Results A total of 43 STEMI patients were recruited to the study. Refer to Table 1 for baseline characteristics. PRU results for the 3 drugs at 20 minutes, balloon time, 60 minutes and 240 minutes were determined. Mean dose to balloon time was 26.8 + 12.7. At balloon time, 20 minutes and 60 minutes none of the agents achieved a PRU < 208. There was a significant difference over time between clopidogrel and ticagrelor (P = 0.04), clopidogrel and prasugrel P < 0.0001 and no statistical difference was found when ticagrelor was compared with prasugrel over time (Figure 1).Abstract 111 Table 1 Baseline Characteristics Characteristic Clopidogrel (N=13) Prasugrel (N=15) Ticagrelor (N=15) P-value Age (yrs) 78¡À9.7 56¡À12.95 67.3¡À11.59 <0.001 Female 6 3 4 0.302 Diabetes Mellitus 0 4 2 0.127 Hypertension 6 7 7 1 Current Smoker 2 3 4 0.761 Ex Smoker 4 8 4 0.271 Hyperlipidaemia 4 5 3 0.691 Familial History of CAD 6 9 8 0.765 CAD = Coronary Artery DiseaseAbstract 111 Figure 1 The degree and time course of platelet inhibition (expressed as PRU) over time following the administration of clopidogrel, prasugrel or ticagrelor in STEMI patients. PRU = P2Y12 Reactivity Units Conclusion Clopidogrel in the context of STEMI does not provide adequate platelet inhibition as evidenced by PRU > 208 at all data collection time points, Both prasugrel and ticagrelor are superior to clopidogrel resulting in a significant reduction in the degree of platelet reactivity. Although Prasugrel and ticagrelor are comparable in terms of inhibition of platelet activity at 20 minutes, balloon inflation, 1 hour and 4 hours, they still do not achieve the desired levels of platelet inhibition necessary during PPCI as demonstrated by PRU > 208. It is possible that fast acting intravenous antiplatelet agents may have a role to play in achieving adequate platelet inhibition in the context of PPCI.

109 Marked Differences in the Pharmacodynamics of Modern P2Y12 Inhibitors in Patients Undergoing Treatment for ST Segment Elevation MI (STEMI) and Non ST Segment Elevation MI (NSTEMI)

Introduction Current pharmacodynamic (PD) data suggest reduced antiplatelet effect in ST-Elevation myocardial infarction (STEMI) of prasugrel and ticagrelor. We sought to investigate the early PD effect of prasugrel and ticagrelor administered in two patient groups: those admitted with STEMI and a cohort admitted with NSTEMI/unstable angina (UA). Methods P2Y12 inhibitor naïve patients presenting with STEMI or NSTEMI/UA were assessed for inclusion. All patients provided informed consent. All received aspirin (300mg) and loading dose of either prasugrel (60mg) or ticagrelor (180mg) in a non-randomised fashion. Platelet reactivity was measured using VerifyNow assay at 20 min, 1 and 4 h post loading. Results are expressed a P2Y12 reaction units (PRU). PRU≥208 indicates a sub optimal antiplatelet response. PRU over time was tested between groups using 2 way ANOVA, P < 0.05 was considered significant. Results A total of 58 patients were enrolled (30 STEMI, and 28 NSTEMI/UA Table 1).Abstract 109 Table 1 Baseline characteristics Characteristic STEMI (N=30) NSTEMI (N=28) P-value Age (yrs) 59.94 ± 12.68 61.61 ± 11 0.595 Female 7 3 0.301 Diabetes Mellitus 6 12 0.089 Hypertension 14 13 1 Current Smoker 7 4 0.508 Ex-Smoker 12 11 1 Hyperlipidaemia 8 16 0.032 Familial History of CAD 17 15 1 CAD = Coronary Artery Disease Results are shown in Fig 1. In the STEMI patients there was little effect of either agent at 20 min post loading (prasugrel PRU 247 + 48.8, ticagrelor PRU 256 + 50.8) with a limited effect at 1 h and persisting attenuated results at 4 h. In the NSTEMI group however there was a marked and rapid antiplatelet effect of both agents at all time points. Over time there was a significant difference between the effect of both prasugrel ( P < 0.001) and ticagrelor ( P < 0.001) in STEMI patients vs NSTEMI patients. There was no significant difference in the effect of ticagrelor vs prasugrel over time in either STEMI or NSTEMI/UA.Abstract 109 Figure 1 The degree of inhibition of platelet reactivity (expressed as PRU) over time following the administration of prasugrel (A) and ticagrelor (B) in STEMI and NSTEMI patients. PRU = P2Y12 reactivity units Conclusion Prasugrel and ticagrelor in the context of STEMI do not provide adequate P2Y12 inhibition at reperfusion and the first hour post loading when compared to patients with NSTEMI/UA.

042 Individualised assessment of response to clopidogrel in patients presenting with acute coronary syndromes: a role for short thromboelastography?

Introduction Many centres already use the thrombelastograph (TEG) Haemostasis Analyser to monitor whole blood clotting parameters following cardiothoracic and other surgical procedures. Our group has modified this technique (short TEG, sTEG), to allow the rapid identification of aspirin and clopidogrel hypo-responsiveness. We sought to validate the sTEG area under curve (AUC)15 parameter, in patients admitted with acute coronary syndromes (ACS) by comparing sTEG with the VerifyNow (VN) analyser, and vasodilator-stimulated phosphoprotein (VASP) assay. Methods Forty-nine patients admitted with ACS and planned for angiography were studied. All had either ECG changes of ischaemia and/or a raised Troponin I. Aspirin and clopidgrel loading were as per contemporary UK practice. Whole blood samples were collected after sheath insertion. The sTEG AUC15 in response to ADP was calculated using a specially developed software programme. Samples were also analysed using the VN (Accumetrics, California, USA) system as per the manufacturers` instructions and VASP assay was performed within 12 h of sampling using a commercial system. The clinical endpoint was adverse clinical events (ACE) at 12 months (death, myocardial infarction (MI), repeat revascularisation (RR), stroke or unplanned cardiovascular hospitalisation (UCH). Results Of the 49 patients investigated (mean age 63 (39–87), 16 female) successful readings were obtained for sTEG, VN P2Y12 and VASP in 47, 49 and 39 subjects respectively. The mean sTEG AUC15 was 742.1±295.6 mm/min, mean VN platelet response units (PRU) was 235.3±105, and mean VASP platelet reactivity index (PRI) 49.3±20.6%. These three variables were normally distributed. sTEG AUC15 correlated with VN PRU r2=0.54, p<0.0001 (Abstract 42 Figure 1a), with a weaker, but significant correlation seen with VASP PRI r2=0.26, p=0.001 (Abstract 42 Figure 1b). Previous studies have estimated a clinically relevant clopidogrel response cut off point VN PRU of 240. In our study, individuals with a PRU ≥240 had significantly greater mean AUC15 compared to those with <240 (911±195, n=29 vs 493±238, n=19, p=<0.0001) (Abstract 42 Figure 2a). sTEG AUC15, using a cut off of 800 mm/min (Abstract 42 Figure 2b) and VN PRU using a cut off of 240 predicted ACE at 1 year (p<0.02). During the follow up period there were 5 (10%) ACE (1 MI, 1 RR, and 3 UCH). Abstract 42 Figure 1 VN, VerifyNow; PRU, platelet response units; VASP, vasodilator-stimulated phosphoprotein; PRI, platelet reactivity index; AUC, area under curve; ADP, adenosine diphosphate. Abstract 42 Figure 2 sTEG, short TEG; AUC, area under curve; PRU, platelet response units. Conclusions This study demonstrates that sTEG, a simple, time responsive technique correlates with VN and VASP methods, and in the studied group identified a cohort of patients with ACE at 1 year. However, further large scale trials of this technique are required to verify this finding.