Net clinical benefit of extended dual pathway inhibition according to Baseline risk in patients with chronic coronary syndrome: a COMPASS substudy

AIMS

Guidelines recommend extended dual pathway inhibition (DPI) with aspirin and rivaroxaban in patients with chronic coronary syndrome (CCS) at high ischemic risk. The CHADS-P2A2RC score improves risk prediction and enables antithrombotic treatment allocation in these patients. This study evaluated the net clinical benefit of DPI treatment according to baseline risk as classified by the CHADS-P2A2RC score in patients with CCS included in the COMPASS trial.

METHODS

COMPASS patients with CCS (n = 14 670), randomized to aspirin alone or DPI, were stratified according to cardiovascular risk using the CHADS-P2A2RC score. Endpoints were major adverse cardiovascular events (MACE), all-cause death, fatal/critical organ bleeding, and composite adverse events (MACE and bleeding). Net clinical benefit was the 30-month risk difference of MACE and bleeding.

RESULTS

30-month incidences of MACE (7.9% vs 3.9%, HR 2.01, 95% CI 1.83-2.18) and fatal/critical organ bleeding (1.2% vs 0.8%, HR 1.49 [1.06-1.92]) were higher in high-risk (CHADS-P2A2RC ≥ 4) than low/moderate-risk (CHADS-P2A2RC < 4) patients. DPI reduced MACE (low/moderate-risk: HR 0.62 [0.47-0.82]; high-risk: HR 0.82 [0.68-0.99], p for interaction 0.09) and all-cause death (low/moderate-risk: HR 0.65 [0.46-0.91]; high-risk: HR 0.81 [0.65-1.00], p for interaction 0.29), without substantially increasing fatal/critical organ bleeding (low/moderate-risk: HR 1.35 [0.72-2.53]; high-risk: HR 1.18 [0.73-1.90], p for interaction 0.73). DPI provided net clinical benefit of similar magnitude in low/moderate-risk (-1.81% [-3.00 to -0.62]) and high-risk CCS patients (-1.96% [-3.60 to -0.33]).

CONCLUSIONS

As classified by the CHADS-P2A2RC score, low/moderate- and high-risk patients with CCS derived similar net clinical benefit and reduction in all-cause death from DPI treatment.

Antithrombotic treatment for chronic coronary syndrome: Evidence and future perspectives

Background The clinical presentation of coronary artery disease can range from asymptomatic, through stable disease in the form of chronic coronary syndrome, to acute coronary syndrome. Chronic coronary syndrome is a frequent condition, and secondary prevention of ischaemic events is essential. Summary Antithrombotic therapy is a key component of secondary prevention strategies, and it may vary in type and intensity depending on patient characteristics, comorbidities, and revascularisation modalities. Dual antiplatelet therapy is the default strategy in patients with chronic coronary syndrome and recent coronary stent implantation, while antiplatelet monotherapy is commonly prescribed for long-term prevention of cardiovascular events. Oral anticoagulation, in combination with antiplatelet therapy or alone, is used in patients with e.g., concomitant atrial fibrillation or venous thromboembolism. Key messages This review provides an overview of antithrombotic treatment strategies in patients with chronic coronary syndrome. Key messages from current guidelines are conveyed, and we provide future perspectives on long-term antithrombotic strategies.

Antithrombotic treatment beyond one year after percutaneous coronary intervention in patients with atrial fibrillation

Aims

Beyond 1 year after percutaneous coronary intervention (PCI), guidelines recommend anticoagulant monotherapy in patients with atrial fibrillation (AF) rather than dual therapy with an anticoagulant and an antiplatelet drug. The risks and benefits of this strategy, however, remain uncertain. We examined hospitalization for bleeding and ischemic risk beyond 1 year after PCI in patients with AF treated with monotherapy versus dual therapy. Furthermore, among patients treated with monotherapy, we compared direct oral anticoagulant (DOAC) therapy and vitamin K antagonist (VKA) therapy.

Methods and results

We included all patients with AF undergoing first-time PCI between 2003 and 2017 from the Western Denmark Heart Registry and followed them for up to 4 years. Follow-up started 15 months after PCI to enable assessment of medical treatment after 12 months. Using a Cox regression model, we computed weighted hazard ratios (HRw) of hospitalization for bleeding and major adverse cardiac events (MACE). Analyses comparing monotherapy versus dual therapy included 3331 patients, and analyses comparing DOAC versus VKA monotherapy included 1275 patients. Risks of hospitalization for bleeding (HRw 0.90, 95% confidence interval [CI] 0.75–1.09) and MACE (HRw 1.04, 95% CI 0.90–1.19) were similar with monotherapy and dual therapy. Similarly, risks of hospitalization for bleeding (HRw 1.27, 95% CI 0.84–1.92) and MACE (HRw 1.15, 95% CI 0.87–1.50) were equal with DOAC and VKA monotherapy.

Conclusion

Our results support long-term OAC monotherapy beyond 1 year after PCI in patients with atrial fibrillation and suggest that DOAC monotherapy is as safe and effective as VKA monotherapy.

Thirteen-year trends in cardiovascular risk in men and women with chronic coronary syndrome

AIMS

To examine combined and sex-specific temporal changes in risks of adverse cardiovascular events and coronary revascularization in patients with chronic coronary syndrome undergoing coronary angiography.

METHODS AND RESULTS

We included all patients with stable angina pectoris and coronary artery disease examined by coronary angiography in Western Denmark from 2004 to 2016. Patients were stratified by examination year interval: 2004-2006, 2007-2009, 2010-2012, and 2013-2016. Outcomes were 2-year risk of myocardial infarction, ischaemic stroke, cardiac death, and all-cause death estimated by adjusted incidence rate ratios using patients examined in 2004-2006 as reference. A total of 29 471 patients were included, of whom 70% were men. The 2-year risk of myocardial infarction [2.8% vs. 1.9%, adjusted incidence rate ratio 0.65, 95% confidence interval (CI) 0.53-0.81], ischaemic stroke (1.8% vs. 1.1%, adjusted incidence rate ratio 0.48, 95% CI 0.37-0.64), cardiac death (2.1% vs. 0.9%, adjusted incidence rate ratio 0.38, 95% CI 0.29-0.51), and all-cause death (5.0% vs. 3.6%, adjusted incidence rate ratio 0.65, 95% CI 0.55-0.76) decreased from the first examination interval (2004-2006) to the last examination interval (2013-2016). Coronary revascularizations also decreased (percutaneous coronary intervention: 51.6% vs. 42.5%; coronary artery bypass grafting: 24.6% vs. 17.5%). Risk reductions were observed in both men and women, however, women had a lower absolute risk.

CONCLUSION

The risk for adverse cardiovascular events decreased substantially in both men and women with chronic coronary syndrome from 2004 to 2016. These results most likely reflect the cumulative effect of improvements in the management of chronic coronary artery disease.

CHA2 DS2 -VASc impact on risk following percutaneous coronary intervention in atrial fibrillation

AIMS

In 2010, the European Society of Cardiology Guidelines on atrial fibrillation (AF) introduced the CHA₂ DS₂ -VASc score to guide initiation of oral anticoagulation. In patients with AF undergoing percutaneous coronary intervention (PCI), triple therapy with oral anticoagulation and dual antiplatelet therapy was recommended to reduce ischaemic risk. We examined how the CHA₂ DS₂ -VASc score impacted oral anticoagulation use and risks of ischaemic and hospitalized bleeding events in patients with AF undergoing PCI.

METHODS

We included 6,014 patients with AF undergoing first-time PCI in Western Denmark between 2003 and 2017. We divided patients into four groups based on year of PCI and estimated 1-year risks of major adverse cardiac events (MACE) and hospitalization for bleeding.

RESULTS

The proportion of oral anticoagulation users was 48% in 2003-2006 and 49% in 2006-2010. Following the CHA₂ DS₂ -VASc score implementation, the proportion increased to 59% in 2011-2014 and 77% in 2015-2017. Using 2003-2006 as reference, risks of MACE were similar in 2007-2010 (adjusted relative risk [RR_adj ] 0.99, 95% confidence interval [CI] 0.83-1.18) and 2011-2014 (RR_adj 0.92, 95% CI 0.78-1.09), but declined by 23% in 2015-2017 (RR_adj 0.77, 95% CI 0.65-0.92). Hospitalizations for bleeding did not increase despite wider use of triple therapy.

CONCLUSION

Implementation of the CHA₂ DS₂ -VASc score in the 2010 European guidelines on AF was associated with an increased utilization of oral anticoagulation and triple therapy among AF patients undergoing PCI. These changes were associated with a gradual decline in the risk of MACE, while the risk of hospitalized bleeding remained unchanged.

Effectiveness and Safety of Ticagrelor Implementation in Patients with Acute Coronary Syndrome undergoing Percutaneous Coronary Intervention: A Cohort Study in Western Denmark

Background

Methods

Findings

Interpretation

Dual antithrombotic treatment in chronic coronary syndrome: European Society of Cardiology criteria vs. CHADS-P2A2RC score

AIMS 

According to the 2019 European Society of Cardiology (ESC) guidelines on chronic coronary syndromes (CCS), adding a P2Y12 inhibitor or rivaroxaban to aspirin should be considered in high-risk patients. We estimated the proportion of patients eligible for treatment with the ESC criteria and examined if a recently validated risk score (CHADS-P2A2RC) could improve risk prediction.

METHODS AND RESULTS 

We included 61 338 CCS patients undergoing first-time coronary angiography in Western Denmark (2003-16) and classified them according to the ESC criteria and the CHADS-P2A2RC score. The ESC criteria identified 33.9% as high risk, 53.3% as moderate risk, and 12.8% as low risk. The CHADS-P2A2RC score identified 24.9% as high risk (≥4 points), 48.1% as moderate risk (2-3 points), and 27.0% as low risk (≤1 points). Major adverse cardiovascular events per 100 person-years were 4.8 [95% confidence interval (CI) 4.6-5.0] in patients considered high risk with both schemes, 2.1 (95% CI 2.0-2.2) in patients considered high risk with the ESC but low-to-moderate risk with the CHADS-P2A2RC criteria, 3.8 (95% CI 3.6-4.1) in patients considered low-to-moderate risk with the ESC but high risk with the CHADS-P2A2RC criteria, and 1.5 (95% CI 1.5-1.6) in patients considered low-to-moderate risk with both schemes. The CHADS-P2A2RC score enabled correct downward risk reclassification of 5161 patients (8%) without events, yielding an improved specificity of 9.7%, a loss of sensitivity of 4.4%, and an overall net reclassification index of 0.053.

CONCLUSION 

Based on the 2019 ESC guidelines, dual antithrombotic treatment should be considered in one-third of CCS patients. The CHADS-P2A2RC score improved risk classification and may particularly identify low-risk patients with limited benefit from treatment.

[Menorrhagia during oral anticoagulant therapy]

Menorrhagia is a common complication to oral anticoagulant therapy in premenopausal women. Clinical management of menorrhagia poses a clinical dilemma with the need of weighting bleeding risk against the risk of recurrent thrombosis. In this review, we describe the risk of menorrhagia during oral anticoagulant therapy, with emphasis on the differences between the specific anticoagulant drugs. We critically assess the treatment options for anticoagulant-associated menorrhagia, and we provide a treatment algorithm for the management of anticoagulant-associated menorrhagia.

Insulin-treated versus noninsulin-treated diabetes and risk of ischemic stroke in patients with atrial fibrillation

BACKGROUND

Diabetes mellitus (DM) and atrial fibrillation (AF) are known risk factors for ischemic stroke. Recent data, however, suggest that only insulin-treated DM is a risk factor for ischemic stroke among AF patients.

OBJECTIVES

To evaluate the risk of stroke in patients with insulin and noninsulin treated DM.

METHODS

We included AF patients undergoing coronary angiography in Western Denmark between 2003 and 2016. Patients were categorized as 1) insulin treated DM, 2) noninsulin treated DM, or 3) nonDM patients. The main outcome was ischemic stroke >30 days after CAG.

RESULTS

AF patients (n = 21,223) were included, of whom 17,181 (81%) did not have DM, 2890 (14%) had noninsulin-treated DM and 1152 (5%) had insulin-treated DM. Median follow-up was 5.3 years. Ischemic stroke rates were 0.83 per 100 person-years for nonDM, 1.19 for noninsulin-treated DM and 1.40 for insulin-treated DM. Insulin-treated DM (adjusted hazard ratio (HR_adj) 1.48, 95% CI 1.15-1.91) and noninsulin-treated DM patients (HR_adj 1.30, 95% CI 1.09-1.54) had higher risks of ischemic stroke than nonDM patients. There was no difference between insulin-treated DM and noninsulin-treated DM (HR_adj 1.09, 95% CI 0.82-1.46). Stratification by coronary artery disease yielded comparable risk estimates.

CONCLUSION

In patients with AF, DM increases the risk of ischemic stroke, regardless of treatment.

A Novel Model for Prediction of Thromboembolic and Cardiovascular Events in Patients Without Atrial Fibrillation

Patients without atrial fibrillation (AF) constitute approximately 75% of patients suffering thromboembolism and major adverse cardiovascular events (MACE), but evidence supporting risk stratification in these patients is sparse. We aimed to develop a risk prediction model for identification of patients without AF at high risk of first-time thromboembolic events. We included 72,381 coronary angiography patients without AF and without previous ischemic stroke or transient ischemic attack. The cohort was randomly divided into a derivation cohort (80%, n = 57,680) and a validation cohort (20%, n = 14,701). The primary thromboembolic end point was a composite of ischemic stroke, transient ischemic attack, and systemic embolism. MACE was defined as a composite of cardiac death, myocardial infarction, and ischemic stroke. The final model was compared with 2 validated clinical risk models (CHADS₂ and CHA₂DS₂-VASc). The risk prediction model assigned 1 point to heart failure, hypertension, diabetes mellitus, renal disease, age 65 to 74 years, active smoking, and multivessel obstructive coronary artery disease, and 2 points to age ≥75 years and peripheral artery disease. A C-index of 0.66 (95% CI 0.64 to 0.69) for prediction of the composite thromboembolic end point was found in the validation cohort, which was higher than for CHADS₂ (C-index 0.63 [95% CI 0.60 to 0.67]; p < 0.001) and CHA₂DS₂-VASc (C-index 0.64 [95% CI 0.62 to 0.67]; p = 0.034). The model also predicted MACE (C-index 0.71 [95% CI 0.69 to 0.73]). In conclusion it is possible to identify patients without AF at high risk of first-time thromboembolic events and MACE by use of a simple clinical prediction model.

Comorbidity and risk of venous thromboembolism after hospitalization for first-time myocardial infarction: A population-based cohort study

BACKGROUND

Myocardial infarction (MI) is a risk factor for venous thromboembolism (VTE). Although comorbidities affect MI prognosis, it is unclear whether they affect VTE risk after MI.

OBJECTIVES

We examined the impact of comorbidity on VTE risk after MI.

METHODS

We used nationwide population-based registries to identify first-time hospitalizations for MI and subsequent occurrence of VTE in Denmark (1995-2013). We included a comparison cohort from the general population matched 5:1 with MI patients by sex, age, and comorbidities. We computed 30-day and 1- to 12-month cumulative risks, rates, and hazard ratios of VTE. We also assessed the interaction between MI and comorbidity, defined as excess VTE risk in patients with both MI and comorbidity, by computing interaction contrasts and attributable fractions relating to the interaction.

RESULTS

Thirty-day and 1- to 12-month VTE risks were 0.6% and 0.5% in the MI cohort (n = 160 338) and 0.03% and 0.3% in the comparison cohort (n = 792 384). The 30-day hazard ratio for VTE in the MI cohort was 23 (95% confidence interval, 20-27), which decreased during 1-year follow-up. Thirty days after MI, interactions between MI and comorbidity accounted for 16% and 39% of VTE rates in MI patients with low-to-moderate and high comorbidity, respectively. The interactions were driven primarily by hemiplegia and cancer.

CONCLUSIONS

Thirty-day VTE risk was substantially increased after MI compared with the general population. Although the absolute VTE risk was low, comorbidity substantially increased this risk, especially hemiplegia and cancer. VTE prophylaxis might be indicated in such high-risk patients but warrants further investigation.

Diabetes is not a risk factor for myocardial infarction in patients without coronary artery disease: A study from the Western Denmark Heart Registry

BACKGROUND

Diabetes is considered a risk factor for myocardial infarction. However, we have previously found that diabetes was not a short-term risk factor for myocardial infarction in the absence of obstructive coronary artery disease.

METHODS

We conducted a cohort study of patients undergoing coronary angiography from 2003 to 2012 and followed them by cross-linking Danish health registries. Patients were stratified according to coronary artery disease and diabetes. Endpoints included myocardial infarction, cardiac death, all-cause death and coronary revascularization.

RESULTS

86,202 patients were included in total (diabetes: n = 12,652). Median follow-up was 8.8 years. Using patients with neither coronary artery disease nor diabetes as reference (cumulative myocardial infarction incidence 2.6%), the risk of myocardial infarction was low and not substantially increased for patients with diabetes alone (3.2%; hazard ratio 1.202, 95% confidence interval 0.996-1.451), was increased for patients with coronary artery disease alone (9.3%; hazard ratio 2.75, 95% confidence interval 2.52-3.01) and was highest for patients with both coronary artery disease and diabetes (12.3%; hazard ratio 3.79, 95% confidence interval 3.43-4.20). Similar associations were observed for cardiac death and coronary revascularization.

CONCLUSION

Diabetes patients without coronary artery disease by coronary angiography have a low risk of myocardial infarction, not substantially increased compared to patients with neither coronary artery disease nor diabetes. In the presence of coronary artery disease, however, diabetes increases the risk of myocardial infarction.

The ABO Locus is Associated with Increased Fibrin Network Formation in Patients with Stable Coronary Artery Disease

BACKGROUND

 The ABO locus has been associated with increased risk of myocardial infarction (MI) in patients with coronary artery disease (CAD), but the underlying mechanisms are unknown. As altered fibrin clot structure has been demonstrated to predict MI in CAD patients, we examined the association between the ABO risk variant and fibrin clot properties, and investigated the effects of other CAD-associated risk variants.

METHODS

 We included 773 stable CAD patients. Patients were genotyped for 45 genome-wide CAD risk variants, including rs495828 at the ABO locus. We used a genetic risk score (GRS) for CAD calculated as the weighted sum of the number of risk alleles based on all 45 variants. Fibrin clot properties were evaluated using a turbidimetric assay. We studied clot maximum absorbance, a measure of clot density and fiber thickness, together with clot lysis time, an indicator of fibrinolysis potential.

RESULTS

 The rs495828 risk allele was present in 13.2% of patients and associated with higher clot maximum absorbance (adjusted effect size per risk allele: 1.05 [1.01 - 1.09], p = 0.01) but not with clot lysis time (p = 0.97). The rs12936587 (p = 0.04), rs4773144 (p = 0.02), and rs501120 (p = 0.04) were associated with clot lysis time; however, after Bonferroni correction, no significant associations were found between any of the remaining 44 CAD-associated variants and fibrin clot properties. The GRS was not associated with fibrin clot properties (p-values > 0.05).

CONCLUSION

 The ABO risk allele was associated with a more compact fibrin network in stable CAD patients, which may represent a mechanism for increased MI risk in ABO risk variant carriers.

Diabetes Mellitus Is Associated With Increased Risk of Ischemic Stroke in Patients With and Without Coronary Artery Disease

Background and Purpose- Diabetes mellitus (DM) and non-DM patients without coronary artery disease (CAD) have a similar low risk of myocardial infarction after coronary angiography. The risk of ischemic stroke in DM patients dependent on CAD status is less explored. We examined whether DM patients without CAD have a risk of ischemic stroke similar to that in patients with neither DM nor CAD. Methods- We conducted a cohort study of patients who underwent coronary angiography between 2004 and 2012 in Western Denmark. Patients diagnosed with previous ischemic stroke or transient ischemic attack were excluded. Patients were stratified according to the presence of DM and CAD. Follow-up started 30 days after coronary angiography. We computed event rates and adjusted incidence rate ratios using patients without DM or CAD as reference. We examined the trend between CAD extent and ischemic stroke in patients with DM. Results- A total of 81 909 patients were included. Median follow-up was 3.8 years. Patients with both DM and CAD were at the highest risk of ischemic stroke (1.32 events per 100 person-years; adjusted incidence rate ratio, 2.00 [95% CI, 1.72-2.32]). Patients with CAD alone (0.77 events per 100 person-years; adjusted incidence rate ratio, 1.27 [95% CI, 1.12-1.44]) or DM alone (0.95 events per 100 person-years; adjusted incidence rate ratio, 1.74 [95% CI, 1.42-2.15]) were at intermediate risk, whereas patients with neither DM nor CAD (0.52 events per 100 person-years) were at the lowest risk. Among patients with DM, extent of CAD was further predictive of risk (P_trend<0.001). Conclusions- Not only CAD but also DM are associated with the risk of ischemic stroke after coronary angiography. Their combination further increases the risk of ischemic stroke depending on the extent of CAD.

[Anticoagulant therapy of patients undergoing cardioversion for atrial fibrillation]

Cardioversion of atrial fibrillation entails a risk of thromboembolic events, especially ischaemic stroke. Oral anticoagulation therapy before and after cardioversion is therefore crucial. Assessing ischaemic stroke risk and time of arrhythmia onset is important when deciding on the optimal anticoagulation strategy. For decades, vitamin K antagonists (VKA) have been the primary anticoagulant drugs used in relation to cardioversion, but non-VKA oral anticoagulants may be preferred because of their rapid onset of action and predictable anticoagulant effect without the need for monitoring.

External applicability of the COMPASS trial: the Western Denmark Heart Registry

Aims

In the COMPASS trial, combined aspirin and rivaroxaban treatment reduced ischaemic events in patients with stable coronary artery disease (CAD) or peripheral artery disease (PAD). We estimated the proportion of COMPASS eligible patients among unselected patients undergoing coronary angiography (CAG) and compared outcome rates among COMPASS eligible and non-eligible patients.

Methods and results

We applied the COMPASS study criteria on patients undergoing CAG in Western Denmark (2004–11). Both COMPASS eligible and non-eligible patients had CAD/PAD and met no exclusion criteria, but only COMPASS eligible patients met the inclusion criteria. We assessed the COMPASS primary endpoint of cardiovascular death, ischaemic stroke, haemorrhagic stroke, or myocardial infarction (MI). We computed event rates and adjusted incidence rate ratios (aIRRs). Of 80 071 patients undergoing CAG, 27 939 did not have CAD or PAD and were not considered. Of the 52 132 patients remaining, 11 930 were COMPASS eligible. Rates of the primary endpoint were 4.8 (95% confidence interval 4.6–5.0) events per 100 person-years among COMPASS eligible patients and 2.3 (2.2–2.4) among COMPASS non-eligible patients [aIRR 1.7 (1.6–1.9)]. COMPASS eligible patients also had higher risks of cardiovascular death [aIRR 2.5 (2.1–3.0)], ischaemic stroke [aIRR 1.4 (1.2–1.6)], and MI [aIRR 1.9 (1.7–2.1)].

Conclusion

In this all-comers CAG cohort, 15% were eligible for combined aspirin and rivaroxaban treatment. COMPASS eligible patients had up to 2.5-fold higher rates of cardiovascular events than non-eligible patients. The higher incidence of ischaemic events in COMPASS eligible patients highlights an unmet need for additional preventive measures.

The ABO locus is associated with increased platelet aggregation in patients with stable coronary artery disease

BACKGROUND

Genome-wide association studies of patients with coronary artery disease (CAD) suggest that several risk loci increase the risk of CAD and myocardial infarction (MI) equally. In contrast, the ABO locus is stronger associated with MI than with CAD, but the underlying mechanisms are unknown.

PURPOSE

To investigate the association between the ABO risk variant and platelet activation and aggregation. Moreover, to explore the effects of other CAD-associated risk variants.

METHODS

We included 879 stable CAD patients receiving low-dose aspirin. All patients were genotyped for 45 genome-wide significant CAD risk variants, including rs495828 at the ABO locus. A genetic risk score (GRS) was calculated to assess the combined risk of all genetic variants. Serum soluble P-selectin (sP-selectin) and thromboxane B₂ were used as measures of platelet activation, and platelet aggregation was assessed by multiple electrode aggregometry (MEA) using arachidonic acid and collagen as agonists and VerifyNow.

RESULTS

The rs495828 CAD risk allele was associated with higher MEA platelet aggregation; arachidonic acid: 14.9% (6.7-23.7%, p = 0.0002) higher AUC (Area Under aggregation Curve) per risk allele, and collagen: 13.1% (5.8%-20.9%, p = 0.0003). Conversely, sP-selectin levels were 7.5% (3.1%-11.7%, p = 0.001) lower per risk allele. Rs495828 genotypes were not associated with aggregation assessed by VerifyNow (p = 0.30) or S-thromboxane B₂ levels (p = 0.98). None of the remaining variants or the GRS were associated with platelet activation or aggregation.

CONCLUSIONS

The ABO risk allele was associated with increased platelet aggregation as assessed by MEA. This finding may contribute to explain the increased MI risk in ABO risk variant carriers.

Effect of remote ischaemic conditioning on platelet aggregation and platelet turnover

Remote ischaemic conditioning (RIC) is a new beneficial treatment for patients with ST-elevation myocardial infarction. RIC may inhibit thrombus formation and, therefore, we investigated whether RIC affects platelet aggregation and turnover. 30 healthy male volunteers were subjected to intervention on day 1 (sham intervention, no aspirin), day 2 (RIC, no aspirin), and day 16 (RIC, treated 7 days with aspirin 75 mg/day). RIC was performed as four cycles of 5 min interchangeable inflation and deflation using an automated cuff. Blood samples were collected 5 min before, as well as 5 and 45 min after RIC. Platelet aggregation was measured by Multiplate® using collagen (COLtest), adenosine diphosphate (ADPtest), and arachidonic acid (ASPItest) as agonists. Platelet turnover was evaluated by flow cytometry. Serum thromboxane B₂ was determined by ELISA to confirm aspirin compliance. We found no significant change in platelet aggregation at visit 1 (COLtest: p = 0.32; ADPtest: p = 0.24; ASPItest: p = 0.07), visit 2, except for ADP-induced platelet aggregation evaluated 5 min after RIC (COLtest: p = 0.39; ADPtest: p = 0.02; ASPItest: p = 0.39), or visit 3 (COLtest: p = 0.48; ADPtest: p = 0.61; ASPItest: p = 0.90). Platelet turnover was not influenced by RIC, neither on nor off aspirin (all p-values > 0.07). (1) RIC did not affect platelet aggregation in healthy young men. (2) RIC did not affect platelet turnover in healthy young men. (3) Aspirin did not influence the effect of RIC on platelet aggregation and turnover. (4) Future studies exploring the effect of RIC on platelet aggregation and turnover in patients with ischaemic heart disease are warranted.

The influence of low-grade inflammation on platelets in patients with stable coronary artery disease

Inflammation is likely to be involved in all stages of atherosclerosis. Numerous inflammatory biomarkers are currently being studied, and even subtle increases in inflammatory biomarkers have been associated with increased risk of cardiovascular events in patients with coronary artery disease (CAD). Low-grade inflammation may influence both platelet production and platelet activation potentially leading to enhanced platelet aggregation. Thrombopoietin is considered the primary regulator of platelet production, but it likely acts in conjunction with numerous cytokines, of which many have altered levels in CAD. Previous studies have shown that high-sensitive C-reactive protein (CRP) independently predicts increased platelet aggregation in stable CAD patients. Increased levels of CRP, fibrinogen, interleukin-6, stromal cell-derived factor-1, CXC motif ligand 16, macrophage migration inhibitory factor, RANTES, calprotectin, and copeptin have been associated with increased risk of cardiovascular events in CAD patients. Additionally, some of these inflammatory markers have been associated with enhanced platelet activation and aggregation. However, CRP and other inflammatory markers provide only limited additional predictive value to classical risk factors such as smoking, blood pressure, and cholesterol levels. Existing data do not clarify whether inflammation simply accompanies CAD and increased production and aggregation of platelets, or whether a causal relationship exists. In this review, we provide a comprehensive overview of inflammatory markers in stable CAD with particular emphasis on platelet production, activation, and aggregation in CAD patients.

The SH2B3 and KCNK5 loci may be implicated in regulation of platelet count, volume, and maturity

INTRODUCTION

In recent genome-wide association studies, coronary artery disease (CAD) and myocardial infarction (MI) have been linked to a number of genetic variants, but their role in thrombopoiesis is largely unknown.

AIM

We investigated the association between CAD and MI-associated genetic variants and five thrombopoiesis-related indices: platelet count (PC), mean platelet volume (MPV), immature platelet count (IPC), immature platelet fraction (IPF), and serum thrombopoietin (TPO).

METHODS

We genotyped 45 genome-wide significant CAD/MI-markers in 879 stable CAD patients. A genetic risk score was calculated to assess the combined risk associated with all the genetic variants. Platelet indices were analysed using the Sysmex XE-2100 haematology analyser. TPO was measured by ELISA.

RESULTS

Two variants were nominally associated with several indices; for rs10947789 (KCNK5), the adjusted geometric mean was 2% higher for MPV (95% confidence interval: 1-2%, p=0.002), 6% for IPC (0-12%, p=0.033), and 9% for IPF (3-16%, p=0.004) per CAD risk allele. Moreover, an 11% lower TPO (3-19%, p=0.010) was observed. Rs3184504 (SH2B3) was associated with a higher adjusted geometric mean of 3% (1-6%, p=0.003) per CAD risk allele for PC, and an 11% (5-17%, p<0.001) lower TPO. Furthermore, the adjusted IPC was 5% (0-9%, p=0.037) lower per CAD risk allele for PC, whereas IPF levels did not vary across genotypes.

CONCLUSION

As a novel finding, our study suggests a role for KCNK5 in the regulation of platelet size and maturity. Furthermore, our findings confirm an association between the SH2B3-locus and platelet count.

Reduced Antiplatelet Effect of Aspirin Does Not Predict Cardiovascular Events in Patients With Stable Coronary Artery Disease

Background

Increased platelet aggregation during antiplatelet therapy may predict cardiovascular events in patients with coronary artery disease. The majority of these patients receive aspirin monotherapy. We aimed to investigate whether high platelet‐aggregation levels predict cardiovascular events in stable coronary artery disease patients treated with aspirin.

Methods and Results

We included 900 stable coronary artery disease patients with either previous myocardial infarction, type 2 diabetes mellitus, or both. All patients received single antithrombotic therapy with 75 mg aspirin daily. Platelet aggregation was evaluated 1 hour after aspirin intake using the VerifyNow Aspirin Assay (Accriva Diagnostics) and Multiplate Analyzer (Roche; agonists: arachidonic acid and collagen). Adherence to aspirin was confirmed by serum thromboxane B₂. The primary end point was the composite of nonfatal myocardial infarction, ischemic stroke, and cardiovascular death. At 3‐year follow‐up, 78 primary end points were registered. The primary end point did not occur more frequently in patients with high platelet‐aggregation levels (first versus fourth quartile) assessed by VerifyNow (hazard ratio: 0.5 [95% CI, 0.3–1.1], P=0.08) or Multiplate using arachidonic acid (hazard ratio: 1.0 [95% CI, 0.5–2.1], P=0.92) or collagen (hazard ratio: 1.4 [95% CI, 0.7–2.8], P=0.38). Similar results were found for the composite secondary end point (nonfatal myocardial infarction, ischemic stroke, stent thrombosis, and all‐cause death) and the single end points. Thromboxane B₂ levels did not predict any end points. Renal insufficiency was the only clinical risk factor predicting the primary and secondary end points.

Conclusions

This study is the largest to investigate platelet aggregation in stable coronary artery disease patients receiving aspirin as single antithrombotic therapy. We found that high platelet‐aggregation levels did not predict cardiovascular events.

Coronary artery disease-associated genetic variants and biomarkers of inflammation

INTRODUCTION

Genetic constitution and inflammation both contribute to development of coronary artery disease (CAD). Several CAD-associated single-nucleotide polymorphisms (SNPs) have recently been identified, but their functions are largely unknown. We investigated the associations between CAD-associated SNPs and five CAD-related inflammatory biomarkers.

METHODS

We genotyped 45 CAD-associated SNPs in 701 stable CAD patients in whom levels of high-sensitivity C-reactive protein (hsRCP), interleukin-6, calprotectin, fibrinogen and complement component 3 levels had previously been measured. A genetic risk score was calculated to assess the combined risk associated with all the genetic variants. A multiple linear regression model was used to assess associations between the genetic risk score, single SNPs, and the five inflammatory biomarkers.

RESULTS

The minor allele (G) (CAD risk allele) of rs2075650 (TOMM40/APOE) was associated with lower levels of high-sensitivity C-reactive protein (effect per risk allele: -0.37 mg/l [95%CI -0.56 to -0.18 mg/l]). The inflammatory markers tested showed no association with the remaining 44 SNPs or with the genetic risk score.

CONCLUSIONS

In stable CAD patients, the risk allele of a common CAD-associated marker at the TOMM40/APOE locus was associated with lower hsCRP levels. No other genetic variants or the combined effect of all variants were associated with the five inflammatory biomarkers.

Thrombopoietin and platelet aggregation in patients with stable coronary artery disease

Thrombopoietin (TPO) may facilitate platelet activation and aggregation. However, data on the impact of TPO on platelet aggregation in patients with stable coronary artery disease (CAD) are scarce. We aimed to investigate associations between TPO and platelet aggregation and activation in patients with stable coronary artery disease (CAD). We studied 900 stable CAD patients. Serum TPO was assessed by ELISA. Platelet aggregation was evaluated using the Multiplate Analyzer (agonists: arachidonic acid [AA] and collagen) and the VerifyNow Aspirin Assay. Platelet activation was evaluated by soluble (s)P-selectin. Cyclooxygenase-1 inhibition was evaluated by serum thromboxane B₂ (TXB₂). We found that TPO correlated weakly with platelet aggregation evaluated by Multiplate using AA (r = -0.09, p = 0.01) and collagen as agonists (r = -0.03, p = 0.43) and by VerifyNow (r = 0.07, p = 0.03). We found no correlation between TPO and sP-selectin (r = -0.01, p = 0.70). Independent predictors of AA-induced platelet aggregation by Multiplate included high levels of sP-selectin and serum TXB₂, high platelet count, increasing age and body mass index, female sex, and active smoking. Independent predictors of TPO included low AA-induced platelet aggregation by Multiplate, high levels of hs-CRP, active smoking, and high platelet aggregation evaluated by VerifyNow. In conclusion, TPO levels did not correlate with platelet activation and only weak associations were found between TPO and platelet aggregation, suggesting that TPO did not substantially facilitate platelet aggregation in stable CAD patients.

A genetic risk score predicts cardiovascular events in patients with stable coronary artery disease

BACKGROUND

Genetic risk scores (GRSs) may predict cardiovascular risk in community-based populations. However, studies investigating the association with recurrent cardiovascular events in patients with established coronary artery disease (CAD) are conflicting.

METHODS

We genotyped 879 patients with high-risk stable CAD and created a GRS based on 45 single nucleotide polymorphisms previously reported to be associated with CAD in genome-wide association studies. Patients were categorised into high or low GRS according to the median GRS and followed for recurrent cardiovascular events using national Danish registries. The primary endpoint was a composite of myocardial infarction, coronary revascularisation, and cardiovascular death.

RESULTS

Median (interquartile range) follow-up time was 2.8 (2.4-3.8)years. The cumulative incidence proportions of the primary endpoint at 1 and 3years were 6.4% and 11.5% in high-GRS patients vs. 2.5% and 7.3% in low-GRS patients. The corresponding relative risks were 2.56 (95% confidence interval (CI) 1.29-5.07), and 1.57 (95% CI 1.02-2.44). The adjusted hazard ratio (HR) of the primary endpoint was 1.50 (95% CI 1.00-2.25). The most pronounced effect of a high GRS was observed on coronary revascularisations (adjusted HR 2.10 [95% CI 1.08-4.07]). Risks of cardiovascular death (adjusted HR 1.07 [95% CI 0.46-2.48]) and all-cause death (adjusted HR 1.15 [95% CI 0.65-2.03]) were unaffected.

CONCLUSIONS

A GRS predicts recurrent cardiovascular events in high-risk stable CAD patients. The observed effect was mainly driven by coronary revascularisations.

[The stratified H-index makes scientific impact transparent]

The H-index is widely used to quantify and standardize researchers' scientific impact. However, the H-index does not account for the fact that co-authors rarely contribute equally to a paper. Accordingly, we propose the use of a stratified H-index to measure scientific impact. The stratified H-index supplements the conventional H-index with three separate H-indices: one for first authorships, one for second authorships and one for last authorships. The stratified H-index takes scientific output, quality and individual author contribution into account.

Preadmission use of selective serotonin reuptake inhibitors and short-term mortality in diabetic patients hospitalized due to stroke

BACKGROUND

Patients with diabetes have an increased risk of stroke with a poor prognosis. Moreover, diabetic patients are at increased risk of depression and therefore likely to use selective serotonin reuptake inhibitors (SSRIs). We examined whether preadmission SSRI use was associated with increased mortality in diabetic patients hospitalized due to stroke.

METHODS

Population-based medical databases were used to identify all first-time stroke-related hospitalizations and subsequent mortality in diabetic patients in Denmark between 2004 and 2012 (n = 12 620). Based on redeemed prescriptions, SSRI use was categorized as current (new or long term), former or nonuse, and absolute 30-day mortality and mortality rate ratios (MRRs) were computed using Cox regression controlling for confounding factors.

RESULTS

Amongst SSRI nonusers, 30-day stroke mortality was 15.8% (10.4% for ischaemic stroke, 41.8% for intracerebral haemorrhage and 27.3% for subarachnoid haemorrhage). Amongst current SSRI users, 30-day stroke mortality was 23.3% (17.1% for ischaemic stroke, 50.7% for intracerebral haemorrhage and 28.6% for subarachnoid haemorrhage). Current SSRI use was associated with increased 30-day stroke mortality compared with nonuse [adjusted MRR 1.3, 95% confidence interval (CI) 1.1-1.5], with the highest risk observed amongst new users (MRR 1.5, 95% CI 1.2-1.8). Overall stroke mortality was driven by increased mortality due to ischaemic stroke, with adjusted MRRs of 1.3 (95% CI 1.1-1.7) for current users and 1.7 (95% CI 1.2-2.4) for new users. Propensity score-matched results were similar and robust across subgroups.

CONCLUSION

In patients with diabetes, preadmission SSRI use was associated with increased mortality following ischaemic stroke, compared with nonuse.

Aspirin in coronary artery disease: an appraisal of functions and limitations

Aspirin (acetylsalicylic acid) is an antiplatelet drug used to treat and prevent coronary artery disease. Aspirin is used more frequently than any other drug in the world, however it does not inhibit platelet function equally well in all patients. The risk of platelet-dependent cardiovascular events is increased in patients, in whom aspirin inhibits platelet function suboptimally. Platelet inhibition with aspirin can be evaluated by use of modern whole blood platelet function tests. The overall aim of this dissertation was to identify and describe functions and limitations of aspirin. We used whole blood platelet aggregometry (Multiplate® Analyzer and VerifyNow® Aspirin) as the primary measure of platelet function. To identify biological mechanisms explaining our findings we also measured a number of biological markers, including markers of cyclooxygenase-1 activity, platelet activation, and platelet turnover. All participants (except healthy individuals in study 1) were treated with non-enteric coated aspirin 75 mg once daily during study participation and received no other drugs affecting platelet function. We used serum TXB2 measurements to verify that all patients were adherent to aspirin. In study 1, we investigated the association between platelet aggregometry results and platelet count, red blood cell count, and white blood cell count. The study population consisted of 417 aspirin-treated patients with stable coronary artery disease and 21 drug-naïve healthy individuals. We found consistent associations between aggregation and platelet count, red blood cell count, and white blood cell count. In particular, platelet count was an independent predictor of platelet aggregation, although generally associations were rather weak. In study 2, we focused on patients previously suffering definite stent thrombosis because these patients may be at a prothrombotic state. We compared levels of platelet aggregation and platelet turnover in 39 patients with previous definite stent thrombosis with levels in 78 patients with stable coronary artery disease. We found that patients with previous definite stent thrombosis displayed increased platelet aggregation and had a tendency towards increased platelet turnover. In study 3, we investigated if the antiplatelet effect of aspirin is sustained through the standard 24-hour dosing interval. We included 50 patients with previous definite stent thrombosis, 100 patients with stable coronary artery disease, and 50 healthy individuals. We found that platelet aggregation increased significantly through the 24-hour dosing interval, and so did cyclooxygenase-1 activity and platelet activation. The increase in platelet aggregation did not differ between groups, but patients with previous definite stent thrombosis had higher levels of platelet turnover indices and thrombopoietin. In study 4, we addressed an ongoing debate concerning potential interactions between antiplatelet drugs and proton pump inhibitors. In patients with coronary artery disease, we investigated if the antiplatelet effect of aspirin was reduced in 54 patients treated with aspirin and a proton pump inhibitor compared to 364 patients treated with aspirin only. We found increased levels of platelet aggregation and platelet activation in patients treated with aspirin and a proton pump inhibitor.

Reduced Effect of Aspirin and Clopidogrel Following Hybrid Coronary Revascularization

OBJECTIVE

Reduced effect of antiplatelet therapy following coronary artery bypass grafting is associated with reduced graft patency. We sought to evaluate the impact of hybrid coronary revascularization on the effect of aspirin and clopidogrel and whether high baseline platelet aggregation, high postoperative levels of platelet turnover, and acute-phase response may contribute to the effect.

METHODS

We prospectively studied platelet aggregation (VerifyNow and Multiplate Analyzer), platelet turnover (immature platelets, mean platelet volume, and thrombopoietin), and acute-phase reactants (C-reactive protein, von Willebrand factor, and coagulation factor VIII) in 40 patients undergoing elective hybrid coronary revascularization (off-pump surgical revascularization through J-hemisternotomy followed by percutaneous coronary intervention [PCI]). Preoperative blood samples on- and off-aspirin were compared with blood samples obtained postoperatively, following PCI when dual antiplatelet therapy had been initiated and at 1-year follow-up.

RESULTS

The antiplatelet effect of aspirin was significantly reduced in the early postoperative period as measured by VerifyNow Aspirin but not by Multiplate ASPI test. The antiplatelet effect of clopidogrel was significantly reduced following PCI as measured by VerifyNow P2Y12 and Multiplate ADP test. The level of baseline aggregation did not predict the antiplatelet effect of aspirin or clopidogrel, and no association was found between platelet aggregation and postoperative platelet turnover or acute-phase reaction.

CONCLUSIONS

A transient reduction in the antiplatelet effect of aspirin and clopidogrel was observed after hybrid coronary revascularization despite limited surgical trauma and off-pump technique. Neither baseline platelet aggregation nor postoperatively increased platelet turnover and acute-phase response could explain this finding. ClinicalTrials.gov identifier, NCT02293928.

Genetic determinants of on-aspirin platelet reactivity: focus on the influence of PEAR1

Background

Platelet aggregation during aspirin treatment displays considerable inter-individual variability. A genetic etiology likely exists, but it remains unclear to what extent genetic polymorphisms determine platelet aggregation in aspirin-treated individuals.

Aim

To identify platelet-related single nucleotide polymorphisms (SNPs) influencing platelet aggregation during aspirin treatment. Furthermore, we explored to what extent changes in cyclooxygenase-1 activity and platelet activation may explain such influence.

Methods

We included 985 Danish patients with stable coronary artery disease treated with aspirin 75 mg/day mono antiplatelet therapy. Patients were genotyped for 16 common SNPs in platelet-related genes using standard PCR-based methods (TaqMan). Platelet aggregation was evaluated by whole blood platelet aggregometry employing Multiplate Analyzer (agonists: arachidonic acid and collagen) and VerifyNow Aspirin. Serum thromboxane B₂ was measured to confirm aspirin adherence and was used as a marker of cyclooxygenase-1 activity. Soluble P-selectin was used as marker of platelet activation. Platelet aggregation, cyclooxygenase-1 activity, and platelet activation were compared across genotypes in adjusted analyses.

Results

The A-allele of the rs12041331 SNP in the platelet endothelial aggregation receptor-1 (PEAR1) gene was associated with reduced platelet aggregation and increased platelet activation, but not with cyclooxygenase-1 activity. Platelet aggregation was unaffected by the other SNPs analyzed.

Conclusion

A common genetic variant in PEAR1 (rs12041331) reproducibly influenced platelet aggregation in aspirin-treated patients with coronary artery disease. The exact biological mechanism remains elusive, but the effect of this polymorphism may be related to changes in platelet activation. Furthermore, 14 SNPs previously suggested to influence aspirin efficacy were not associated with on-aspirin platelet aggregation.

Clinical Trial Registration

ClinicalTrials.gov NCT01383304

Social and Psychological Predictors of Initial Cigarette Smoking Experience: A Survey in Male College Students

Knowledge about social and psychological risk factors for initial cigarette smoking experience (ICSE) is sparse. The present study aimed to estimate the prevalence of ICSE and to examine the psychological and social factors related to ICSE. In a cross-sectional survey, 1,511 male college students were recruited using multistage sampling techniques from four universities located within the city of Ilam, Iran. Self-administered multiple-choice questionnaires were distributed to students from March to June 2013. Risk factors for ICSE were evaluated using logistic regression models. Participants were 22.3 ± 2.4 years of age. ICSE prevalence was 30.6%. In multivariable adjusted analysis, risk taking behavior (odds ratio [OR] = 1.61; 95% confidence interval [CI] = 1.11-2.33), perceived peer smoking prevalence (OR = 2.48; 95% CI = 1.03-5.97), positive thoughts about smoking (OR = 1.06; 95% CI = 1.02-1.10), high self-efficacy (OR = 0.95, 95% CI [0.93, 0.98]), presence in smokers' gathering (OR = 4.45; 95% CI = 2.88-6.81), comity of smokers (OR = 2.56; 95% CI = 1.66, 3.92), very hard access to cigarettes (OR = 2.20; 95% CI = 1.16-4.16), close friends' medium reaction toward smoking (OR = 1.38; 95% CI = 1.02-1.88), and sporting activity (OR = 0.74; 95% CI = 0.56-0.98) were significantly associated with ICSE. This study identified that a combination of psychological and social variables account for up to 78% of the probability of ICSE. The most important protective factor against ICSE was physical activity, whereas the most important risk factor for ICSE was frequent gathering in the presence of smokers.

Rapid evaluation of platelet function using the Multiplate® Analyzer

Rapid evaluation of platelet function may be advantageous in the setting of surgical and interventional procedures to tailor treatment of ongoing bleeding. We investigated if platelet function testing performed with the Multiplate® Analyzer (Roche Diagnostics, Mannheim, Germany) only 5 minutes after blood sampling yields reliable test results compared to analyses performed 30 minutes after sampling as currently recommended. We included 48 patients with type II diabetes and stable coronary artery disease treated with aspirin 75 mg daily and 50 healthy individuals not taking any medications. Platelet aggregometry by the Multiplate® Analyzer was performed 5 and 30 minutes after blood sampling using arachidonic acid (1.0 mM), collagen (3.2 µg/ml) and adenosine diphosphate (ADP; 6.5 µM) as agonists. Compliance with aspirin was verified by serum thromboxane B2 measurements. Aggregation levels assessed 5 minutes after blood sampling correlated strongly with those assessed after 30 minutes irrespective of the agonist used (r-values 0.75-0.89, p values <0.0001). Aggregation levels were 4-8% lower and displayed a larger standard deviation when measured 5 minutes after sampling, compared to 30 minutes after sampling. Weak, but significant correlations were observed between platelet aggregation and platelet count (r-values = 0.28-0.39; p values <0.01). The currently recommended 30-minute standing time can be omitted, when platelet aggregation is measured using the Multiplate® Analyzer. Platelet aggregation measured 5 minutes after blood sampling correlates strongly with aggregation measured 30 minutes after sampling, but yields slightly lower aggregation levels. The Multiplate® Analyzer enables rapid on-site evaluation of platelet function.

[Oral antiplatelet agents can still be used along with proton pump inhibitors in spite of drug interactions]

Acetylsalicylic acid and P2Y12-receptor antagonists are antiplatelet agents widely used in the treatment and secondary prevention of cardiovascular disease. Since upper gastrointestinal bleeding is common during antiplatelet treatment, many patients are also treated with a proton pump inhibitor. In recent years it has been heavily discussed if proton pump inhibitors may attenuate the cardiovascular protection achieved with oral antiplatelet agents. Pharmacodynamic studies have suggested important drug interactions, but clinical studies have failed to confirm any clinical impact.

Pharmacogenomics in cardiovascular disease: focus on aspirin and ADP receptor antagonists

Antiplatelet agents like aspirin and adenosine diphosphate receptor antagonists are effective in reducing recurrent ischemic events. Considerable inter-individual variability in the platelet inhibition obtained with these drugs has initiated a search for explanatory mechanisms and ways to improve treatment. In recent years, numerous genetic polymorphisms have been linked with reduced platelet inhibition and lack of clinical efficacy of antiplatelet drugs, particularly clopidogrel and aspirin. Consequently, attempts to adjust antiplatelet treatment according to genotype have been made, but the clinical benefit has been modest in studies performed so far. The progress in genome science over the last decade and the declining cost of sequencing technologies hold the promise of enabling genetically tailored antiplatelet therapy. However, more evidence is needed to clarify which polymorphisms may serve as targets to improve treatment. The present review outlines the panel of polymorphisms affecting the benefit of aspirin and adenosine diphosphate receptor antagonists, including novel and ongoing studies evaluating whether genotyping may be beneficial in tailoring antiplatelet therapy.

Interindividual variability in the efficacy of oral antiplatelet drugs: definitions, mechanisms and clinical importance

The modern era of antiplatelet therapy was founded by large clinical trials demonstrating the benefit of aspirin and clopidogrel in the treatment and prevention of acute coronary syndromes. The concept of antiplatelet drug "resistance" emerged during the 1990s with studies revealing considerable residual platelet aggregation in some patients despite aspirin treatment. In the wake of these reports, larger studies established an association between high on-treatment platelet reactivity and thrombotic events. The possible mechanisms explaining this phenomenon are manifold and reflect the complexity of platelet function, thrombus formation and cardiovascular disease. Some mechanisms apply to both drugs, while others apply only to one of them. In recent years, efforts have been made to translate this information into an improved clinical outcome by modifying antiplatelet drug regimens. Several studies investigated measurements of on-treatment platelet reactivity, but large clinical trials have failed to demonstrate substantial clinical benefit of individually tailored antiplatelet therapy according to platelet function tests. This article provides an integrated review of interindividual variability in the efficacy of aspirin and clopidogrel with particular emphasis on possible effect-modifying mechanisms and clinical implications.

Platelet function testing in atherothrombotic disease

Platelet function testing was introduced more than a century ago with the invention of bleeding time; a test which has now been replaced by more accurate methods. Light transmittance aggregometry is traditionally regarded as the gold standard for evaluating platelet function. However, lately the position of light transmittance aggregometry has been challenged by a panel of new instruments. Aspirin and P2Y12-inhibitors are antiplatelet drugs used for secondary prevention of cardiovascular disease. However, an increasing recognition of the fact that not all patients respond adequately to these agents has prompted a focus on individualising antiplatelet treatment. Platelet function testing enables the detection of patients with high on-treatment platelet reactivity and facilitates individually tailored antiplatelet therapy, yet platelet function tests have still not been adopted into routine clinical practice. The present review outlines key milestones of the development of platelet function testing and provides an up-to-date overview of currently available tests and important studies evaluating their strengths and limitations in a clinical context.

Gastrointestinal events with clopidogrel: a nationwide population-based cohort study

BACKGROUND

Clopidogrel prevents cardiovascular events, but has been linked with adverse gastrointestinal (GI) complications, particularly bleeding events.

OBJECTIVE

We aimed to investigate the risk of adverse GI events in patients treated with clopidogrel.

DESIGN

A nationwide population-based cohort study based on linkage of three administrative registries in Denmark.

PARTICIPANTS

All individuals who redeemed at least one prescription of clopidogrel from 1996 to 2008 were included as exposed subjects (n = 77,503). For each exposed subject, three matched controls were randomly selected from the background population (n = 232,510).

ANALYSES

Follow-up began on January 1, 1996, and was censored on December 31, 2007, or if patients emigrated or died. The study endpoint was the occurrence of any gastritis, GI ulcer or bleeding. Analyses were adjusted for comorbidity and medication.

RESULTS

Regardless of dose, adjusted odds ratios associating clopidogrel use with the study endpoint were statistically significant and followed a dose-response pattern. The crude absolute risk of GI events were: never users: 2.2 %; <0.1 defined daily dose (DDD) of clopidogrel per day: 7.1 %; 0.1-0.39 DDD: 6.0 %; 0.4-0.79 DDD: 5.7 %; ≥0.80 DDD: 4.4 %. Adjusted odds ratios were: <0.1 DDD: 1.34, 95 % CI: 1.26-1.42; 0.1-0.39 DDD: 1.58, 95 % CI: 1.48-1.68; 0.4-0.79 DDD: 1.91, 95 % CI: 1.77-2.06; ≥0.80 DDD: 1.77, 95 % CI: 1.66-1.89, all p-values < 0.01. Depending on the dose, numbers needed to harm ranged from 58 to 33 patients receiving 12 months of clopidogrel treatment.

CONCLUSIONS

The well-known cardioprotective effect of clopidogrel must be carefully weighed against an increased risk of GI events.

Combining aspirin and proton pump inhibitors: for whom the warning bell tolls?

Aspirin and clopidogrel are well-known antiplatelet agents that are widely used across the spectrum of cardio- and cerebrovascular disease. Upper gastrointestinal complications, including ulcer and bleeding, are relatively common during antiplatelet treatment and, therefore, many patients are also treated with a proton pump inhibitor (PPI). PPIs exert gastroprotection by raising intragastric pH. In recent years, it has been heavily discussed whether PPIs may reduce the cardiovascular protection by aspirin and, even more so, clopidogrel. Initially, pharmacodynamic and pharmacokinetic studies suggested a considerable drug interaction between PPIs and clopidogrel, and subsequent clinical studies were conducted to evaluate the clinical impact of this interaction. More recently, it has been reported that PPIs may also attenuate the antiplatelet effect of aspirin. This is particularly interesting, because a fixed combination of aspirin and a PPI (esomeprazole) has been developed and is currently under approval. Given the large number of patients taking aspirin and PPIs, even a small attenuation of the antiplatelet effect of aspirin may have substantial clinical impact. The present editorial summarizes current evidence on this drug interaction and discusses potential clinical implications.

Contemporary use of glycoprotein IIb/IIIa inhibitors

Platelet glycoprotein IIb/IIIa inhibitors (GPI) are antithrombotic agents preventing the binding of fibrinogen to GP IIb/IIIa receptors. Thus, GPI interfere with interplatelet bridging mediated by fibrinogen. Currently, three generic GPI with different antithrombotic properties are available for intravenous administration: abciximab, eptifibatide, and tirofiban. The development of oral GPI was abandoned, whereas intravenous GPI were introduced in various clinical settings during the 1990s, yielding substantial benefit in the treatment of acute coronary syndromes, particularly during percutaneous coronary interventions. Results of the many randomised trials evidenced the efficacy of this drug class, though these trials were conducted prior to the emergence of modern oral antiplatelet therapy with efficient P2Y(12) inhibitors. Subsequent trials failed to consolidate the strongly favourable impression of GPI, and indications for their use have been more restricted in recent years. Nonetheless, GPI may still be beneficial during coronary interventions among high-risk patients including acute ST-elevation and non-ST-elevation myocardial infarctions, particularly in the absence of adequate pretreatment with oral antiplatelet drugs or when direct thrombin inhibitors are not utilised. Intracoronary GPI administration has been suggested as adjunctive therapy during primary percutaneous coronary intervention, and the results of larger ongoing trials are expected to elucidate its clinical potential. The present review outlines the key milestones of GPI development and provides an up-to-date overview of the clinical applicability of these drugs in the era of refined coronary stenting, potent antithrombotic drugs, and novel thrombin inhibiting agents.

The epidemiology of herpes zoster in 226 children with acute lymphoblastic leukemia

BACKGROUND

Herpes zoster (HZ) is rare in healthy children, but may occur frequently and take a complicated course in children receiving chemotherapy. We determined the morbidity related to HZ in children with acute lymphoblastic leukaemia (ALL).

PROCEDURE

Medical records of 226 children diagnosed with ALL were reviewed. Of these, 160 were seropositive at the time of diagnosis. HZ eruptions during primary chemotherapy, during therapy for relapse and following bone marrow transplantation (BMT) were registered.

RESULTS

A total of 90 eruptions were recorded: 63 first-time attacks and 27 recurrent episodes among 14 children. All eruptions were treated with acyclovir (ACV) and in 60% it was given intravenously. Cutaneous dissemination occurred in 11 cases, post herpetic neuralgia in five, visceral dissemination in none. During primary chemotherapy 47 children (29%) had HZ. The eruption rate was significantly higher in children on high risk protocols compared to children on standard/intermediate risk protocols (0.36 vs. 0.07/0.09 per year) and was related to intensity of chemotherapy. During therapy for relapse 7 of 29 (24%) had a total of 13 eruptions. Following BMT 9 of 26 (35%) had a total of 10 eruptions.

CONCLUSION

Almost one third of the seropositive children had HZ during primary chemotherapy. Of those treated on high risk protocols more than half had one or more eruptions during the course of treatment. The risk of complicated HZ is small, but prolonged intensive chemotherapy can lead to considerable morbidity from repeated eruptions. Attempts to improve immunity by vaccination after attaining remission seem warranted.

Platelet aggregation is dependent on platelet count in patients with coronary artery disease

INTRODUCTION

Platelet function testing in whole blood is widely used to evaluate the effect of antiplatelet agents, but it is not known whether results are affected by whole blood parameters. This study investigated the importance of platelet count, haematocrit, red blood cells (RBC), and white blood cells in whole blood platelet aggregometry.

MATERIALS AND METHODS

We included 417 patients with coronary artery disease on aspirin mono-therapy and 21 aspirin-naïve healthy individuals. Blood sampling was performed one hour after aspirin ingestion. The antiplatelet effect of aspirin was evaluated using the VerifyNow® Aspirin assay and multiple electrode aggregometry (MEA, Multiplate®) induced by collagen (1.0 μg/mL) and arachidonic acid (1.0 or 0.75 mmol/L). Measurements of whole blood parameters were performed to evaluate the three major cell lines in circulating blood.

RESULTS

In patients, platelet count correlated significantly with platelet aggregation (MEA(collagen), p<0.0001; MEA(arachidonic acid), p<0.0001; VerifyNow®, p=0.03). Haematocrit and RBC correlated inversely with MEA induced by collagen (p(haematocrit)<0.001; p(RBC)=0.07) and with VerifyNow® (p(haematocrit)<0.0001; p(RBC)<0.0001), but not with MEA induced by arachidonic acid (p(haematocrit)=1; p(RBC)=0.87). White blood cells correlated significantly with platelet aggregation (MEA(collagen), p<0.001; MEA(arachidonic acid), p<0.0001; VerifyNow®, p=0.05). Similar associations were observed in aspirin-naïve healthy individuals.

CONCLUSIONS

Whole blood aggregometry is dependent on all major cell lines in whole blood. Importantly, platelet aggregation is significantly associated with platelet count even within the normal range.