Cigarette Smoking Does Not Enhance Clopidogrel Responsiveness After Adjusting VerifyNow P2Y12 Reaction Unit for the Influence of Hemoglobin Level

Investigation of smoking on the antiplatelet response to clopidogrel: Unravelling the smoker's paradox

The intricate relationship between smoking and the effects of the antiplatelet drug clopidogrel has been termed the "smoker's paradox". This paradox details the enhanced efficacy of clopidogrel in smokers compared to non-smokers. This review begins with an exploration of the proposed mechanisms of the smoker's paradox, particularly drawing attention to the induction of cytochrome P450 (CYP) isoenzymes via tobacco smoke, specifically the enzymes CYP1A2 and CYP2C19. Moreover, an investigation of the effects of genetic variability on the smoker's paradox was undertaken from both clinical and molecular perspectives, delving into the effects of ethnicity and genetic polymorphisms. The intriguing role of CYP1A2 genotypes and the response to clopidogrel in smoking and non-smoking populations was examined conferring insight into the individuality rather than universality of the smoker's paradox. CYP1A2 induction is hypothesised to elucidate the potency of smoking in exerting a counteracting effect in those taking clopidogrel who possess CYP2C19 loss of function polymorphisms. Furthermore, we assess the comparative efficacies of clopidogrel and other antiplatelet agents, namely prasugrel and ticagrelor. Studies indicated that prasugrel and ticagrelor provided a more consistent effect and further reduced platelet reactivity compared to clopidogrel within both smoking and non-smoking populations. Personalised dosing was another focus of the review considering patient comorbidities, genetic makeup, and smoking status with the objective of improving the antiplatelet response of those taking clopidogrel. In summation, this review provides insight into multiple areas of research concerning clopidogrel and the smoker's paradox taking into account proposed mechanisms, genetics, other antiplatelet agents, and personalised dosing.

Unfolding the reality of the smoking paradox in a South Asian cohort of patients presenting with ST-elevation acute coronary syndrome undergoing primary percutaneous coronary intervention

Objectives

Smoking is a potent risk factor for coronary artery disease, but there is controversy about its protective nature in terms of prognosis in ST-elevation acute coronary syndrome patients undergoing primary percutaneous coronary intervention. So, the main objective of this study is to unfold this controversy in a South Asian population in terms of clinical angiographic parameters and its in-hospital outcomes.

Methods

In this study, we included 1756 consecutive patients diagnosed with ST-elevation acute coronary syndrome undergoing primary percutaneous coronary intervention. Patients were classified into smokers and non-smokers, and the in-hospital mortality rate was compared. Multivariable logistic regression analysis was performed to evaluate the paradoxical role of smoking.

Results

Smokers were younger (53.78 ± 11.16 years vs 56.43 ± 11.17 years; p < 0.001) and more frequently men (98.7% vs 69.9%; p < 0.001) and had less diabetes (19.6% vs 44.8%; p < 0.001) and hypertension (38.5% vs 64.9%; p < 0.001). Smokers presented less frequently in Killip III (5.6% vs 8.1%; p < 0.001) and Killip IV (2.5% vs 4.8%; p < 0.001). Smokers mostly had single vessel disease (41.7% vs 34.4%; p = 0.013), whereas non-smokers had the multi-vessel disease and frequently presented with total occlusion of the culprit vessel (64.6% vs 58.8%; p = 0.040). Smokers have significantly lesser mortality (1.8% vs 4.3%; p = 0.009) compared to non-smokers with an odds ratio of 0.41 (95% confidence interval (CI): 0.21-0.82, p = 0.011); however, adjusted odds ratio on multivariable analysis was 0.67 (95% CI: 0.31-1.41, p = 0.290).

Conclusions

The paradoxical protective role of smoking is the confounding effect of mainly younger age, less coronary artery disease burden, lower prevalence of diabetes and hypertension, and lower Killip III/IV at presentation.

Association between post-stroke smoking and stroke recurrence in first-ever ischemic stroke survivors: based on a 10-year prospective cohort

BACKGROUND

Whether smoking is a risk factor for ischemic stroke (IS) recurrence in IS survivors is still uncovered, and evidences are sparse. Meanwhile, an add-on effect of clopidogrel was observed in myocardial infarction patients who smoked, but whether the paradox exists in IS patients is still unsolved. The objectives of this study are to explore the association between smoking behavior after index stroke and IS recurrence and to explore whether the paradox exists.

METHODS

A prospective cohort of first-ever IS patients was conducted between 2010 and 2019. The prognosis and smoking features of enrolled patients were obtained via telephone follow-up every 3 months. Fine-gray model with interaction terms was applied to measure the relationships between stroke recurrence and smoking behaviors after index stroke and to explore the add-on effect of clopidogrel in smoking patients.

RESULTS

There were 171 (24.26%) recurrences and 129 (18.30%) deaths during follow-up in 705 enrolled IS patients. One hundred forty-six (20.71%) patients smoked after index stroke. The hazard ratios (HRs) and 95% confidence intervals (CIs) of interaction terms between antiplatelet drug and follow-up smoking (smoking status and daily smoking amount) were 1.092 (95% CI: 0.524, 2.276) and 0.985 (95% CI: 0.941, 1.031), respectively. A significantly higher risk of recurrence was observed in patients with a higher daily smoking amount during follow-up (per cigarette), with HR being 1.027 (95% CI: 1.003, 1.052).

CONCLUSIONS

Smoking could elevate the risk of IS recurrence, and IS survivor should be advised to quit or smoke less. Add-on effect of clopidogrel may not exist in smoking strokers taking clopidogrel.

Correlation Between Smoking Paradox and Heart Rhythm Outcomes in Patients With Coronary Artery Disease Receiving Percutaneous Coronary Intervention

BACKGROUND

The effect of smoking on short-term outcomes among patients with acute coronary syndrome (ACS) undergoing percutaneous coronary intervention (PCI) is controversial. However, little is known about the impact of smoking on long-term outcomes in patients with stable coronary artery disease (CAD) who receive PCI.

METHODS

A total of 2,044 patients with stable CAD undergoing PCI were evaluated. They were divided into two groups according to smoking status (current smokers vs. non-smokers). Baseline characteristics, exposed risk factors, angiographic findings, and interventional strategies were assessed to compare the long-term clinical outcomes between groups. Predictors for myocardial infarction (MI), all-cause death, cardiovascular (CV) death, and repeated PCI procedures were also analyzed.

RESULTS

Compared with non-smokers, current smokers were younger and mostly male (both P < 0.01). They also had a lower prevalence of chronic kidney disease (CKD) and diabetes (both P < 0.01). Drugs including a P2Y12 receptor inhibitor of platelets (P2Y12 inhibitor), beta-blockers (BB), and statins were used more frequently in current smokers (P < 0.01, P < 0.01, P = 0.04, respectively). Freedom from all-cause death and CV death was lower in the non-smoker group (P < 0.001, P = 0.003, respectively). After adjustment, logistic regression revealed smoking was a major predictor for all-cause death and repeated PCI procedure [hazard ratio(HR): 1.71 and 1.46, respectively].

CONCLUSIONS

Smoker's paradox extends to long-term outcome in patients with stable CAD undergoing PCI, which is partially explained by differences in baseline characteristics. However, smoking strongly predicted all-cause mortality and repeated PCI procedures in patients with stable CAD undergoing PCI.

Platelet activity with hemoglobin level in patients with hemodialysis: Prospective study

BACKGROUND

VerifyNow (VN; Accumetrics, San Diego, CA) P2Y12 reaction unit (PRU) has an inverse relation with hemoglobin level (Hb). Chronic kidney disease (CKD) is associated with low response to clopidogrel and low Hb. Our aim is to investigate the relation between PRU and Hb, and to assess whether Hb directly affects PRU or not in patients with CKD undergoing hemodialysis (HD).

METHODS

We analyzed the relation between PRU and Hb in 43 HD patients and compared it with a control group of 127 patients with normal renal function. Both groups underwent percutaneous coronary intervention for stable coronary artery disease. We also compared PRU between the 2 groups considering Hb as a confounding factor.

RESULTS

In the control group, Hb and PRU showed a significant inverse correlation (correlation coefficient r = -0.340; P < .001), but not in the HD group (correlation coefficient r = -0.099; P = .53). PRU was higher in the HD group than the control group after adjusting for the influence of Hb (299.2 [95% confidence interval: 278.4-316.7] vs 248.7 [95% confidence interval: 227.7-269.0]; P < .001), even after propensity score matching (299.2 [95% confidence interval: 278.4-316.7] vs 241.7 [95% confidence interval: 221.8-262.2]; P < .001).

CONCLUSIONS

PRU was higher regardless of lower Hb in CKD on HD patients than normal renal function patients. Therefore, Hb was not crucial factor to decide PRU in CKD on HD patients in this study.

Smoking and outcomes following guided de-escalation of antiplatelet treatment in acute coronary syndrome patients: a substudy from the randomized TROPICAL-ACS trial

Aims

Prior analyses disclosed variations in antiplatelet drug response and clinical outcomes between smokers and non-smokers, thus the safety and efficacy of any dual antiplatelet therapy (DAPT) de-escalation strategy may differ in relation to smoking status. Hence, we assessed the impact of smoking on clinical outcomes and adenosine diphosphate-induced platelet aggregation following guided de-escalation of DAPT in invasively managed acute coronary syndrome (ACS) patients.

Methods and results

The multicentre TROPICAL-ACS trial randomized 2610 biomarker-positive ACS patients 1:1 to standard treatment with prasugrel for 12 months (control group) or a platelet function testing guided de-escalation of DAPT. Current smokers (n = 1182) showed comparable event rates between study groups [6.6% vs. 6.6%; hazard ratio (HR) 1.0, 95% confidence interval (CI) 0.64–1.56, P &gt; 0.99]. In non-smokers (n = 1428), a guided DAPT de-escalation was associated with a lower 1-year incidence of the primary endpoint [cardiovascular death, myocardial infarction, stroke, or bleeding ≥ Grade 2 according to Bleeding Academic Research Consortium (BARC) criteria] compared with control group patients (7.9% vs. 11.0%; HR 0.71, 95% CI 0.50–0.99, P = 0.048). This reduction was mainly driven by a lower rate of BARC ≥ Grade 2 bleedings (5.2% vs. 7.7%; HR 0.68, 95% CI 0.45–1.03, P = 0.066). There was no significant interaction of smoking status with treatment effects of guided DAPT de-escalation (Pint = 0.23). Adenosine diphosphate-induced platelet aggregation values were higher in current smokers [median 28 U, interquartile range (IQR: 20–40)] vs. non-smoker [median 24 U (16–25), P &lt; 0.0001] in the control group and in current smokers [median 42 U, IQR (27–68)] vs. non-smoker [median 37 U, IQR (25–55), P &lt; 0.001] in the monitoring group.

Conclusion

Guided DAPT de-escalation appears to be equally safe and effective in smokers and non-smokers. Regardless of smoking status and especially for those patients deemed unsuitable for 1 year of potent platelet inhibition this DAPT strategy might be used as an alternative antiplatelet treatment regimen.

Impact of Smoking on Platelet Reactivity and Clinical Outcomes After Percutaneous Coronary Intervention

Background:

Smoking is a potent risk factor for coronary artery disease; however, prior studies describe increased platelet inhibition with clopidogrel among smokers, and some studies report improved outcomes among smokers, a finding described as the smoker’s paradox. This study assessed the relationship between platelet reactivity and clinical outcomes after percutaneous coronary interventions among current smokers and nonsmokers.

Methods:

ADAPT-DES (Assessment of Dual Antiplatelet Therapy With Drug-Eluting Stents) was a prospective, multicenter registry of patients treated with coronary drug-eluting stents. Platelet reactivity was assessed by the VerifyNow point-of-care assay; high on-treatment platelet reactivity (HPR) was defined as P2Y12 reaction units >208. A propensity-adjusted multivariable analysis was performed to determine the relationship between current smoking, platelet reactivity, and subsequent adverse events.

Results:

Among 8582 patients, 22.6% were active smokers at the time of their percutaneous coronary intervention procedure. Current smokers were younger and had fewer comorbidities compared with nonsmokers. Current smokers had lower mean P2Y12 reaction units and lower rates of HPR compared with nonsmokers. Current smokers had similar rates of adverse events compared with nonsmokers. HPR was associated with higher rates of adverse events for both smokers and nonsmokers; however, there was evidence of interaction between smoking status and the effect of HPR. Smokers with HPR had significantly higher rates of stent thrombosis. Adverse event rates were highest among current smokers with HPR.

Conclusions:

Current smoking was associated with lower P2Y12 reaction units and lower rates of HPR on average; however, the combination of current smoking and HPR was associated with high rates of stent thrombosis.

Clinical Trial Registration:

URL: https://www.clinicaltrials.gov . Unique identifier: NCT00638794.

Effects of cigarette smoking on older chinese men treated with clopidogrel monotherapy or aspirin monotherapy: a prospective study

We investigated the comparative effects of smoking status on outcomes in older Chinese men receiving aspirin or clopidogrel monotherapy. This was a prospective observational study of outcomes in 668 men aged ≥ 60 years undergoing annual health examination in the Chinese People's Liberation Army General Hospital from March-April 2017. All patients received regular treatment with aspirin or clopidogrel. Platelet aggregation and phenotyping for rs762551 were measured in all patients. We recorded all major adverse cardiovascular and cerebrovascular events; namely, all-cause death, myocardial infarction, stroke, transient ischemic attack, and unstable angina. In the clopidogrel subgroup, homozygous carriers (AA) of the CYP1A2*1F gene (rs762551, 163C>A) appeared more frequently in smokers than in nonsmokers (45.6% vs 32.7%, p = .035). Adenosine diphosphate-induced platelet aggregation using light transmittance aggregometry was lower in smokers compared with nonsmokers (44.97 ± 20.05% vs 51.98 ± 19.38%, respectively; p = .0018). Smokers (n = 103) had a decreased risk of major adverse cardiovascular and cerebrovascular events, compared with nonsmokers [n = 159; hazard ratio, 0.466; 95% confidence interval: 0.262-0.829, p = .008]. In the aspirin subgroup, AA-induced platelet aggregation showed no significant difference regarding smoking vs nonsmoking status (30.90 ± 32.21 vs 29.78 ± 31.47, respectively; p = .771). However, we saw a significant increase in adverse clinical events in the smoking group (n = 148) compared with the nonsmoking group (n = 258; hazard ratio = 1.907, 95% confidence interval: 1.128-3.225; p = .016). In older Chinese men, active smokers benefitted from clopidogrel therapy compared with aspirin. Long-term cigarette smoking may contribute to increased variations in CYP1A2*1F, but the variations do not fully explain the smoking paradox.

Clinical outcomes and predictive model of platelet reactivity to clopidogrel after acute ischemic vascular events

BACKGROUND

High on-treatment platelet reactivity (HTPR) has been suggested as a risk factor for patients with ischemic vascular disease. We explored a predictive model of platelet reactivity to clopidogrel and the relationship with clinical outcomes.

METHODS

A total of 441 patients were included. Platelet reactivity was measured by light transmittance aggregometry after receiving dual antiplatelet therapy. HTPR was defined by the consensus cutoff of maximal platelet aggregation >46% by light transmittance aggregometry. CYP2C19 loss-of-function polymorphisms were identified by DNA microarray analysis. The data were compared by binary logistic regression to find the risk factors. The primary endpoint was major adverse clinical events (MACEs), and patients were followed for a median time of 29 months. Survival curves were constructed with Kaplan-Meier estimates and compared by log-rank tests between the patients with HTPR and non-HTPR.

RESULTS

The rate of HTPR was 17.2%. Logistic regression identified the following predictors of HTPR: age, therapy regimen, body mass index, diabetes history, CYP2C192, or CYP2C193 variant. The area under the curve of receiver operating characteristic for the HTPR predictive model was 0.793 (95% confidence interval: 0.738-0.848). Kaplan-Meier analysis showed that patients with HTPR had a higher incidence of MACE than those with non-HTPR (21.1% vs. 9.9%; χ = 7.572, P = 0.010).

CONCLUSIONS

Our results suggest that advanced age, higher body mass index, treatment with regular dual antiplatelet therapy, diabetes, and CYP2C192 or CYP2C193 carriers are significantly associated with HTPR to clopidogrel. The predictive model of HTPR has useful discrimination and good calibration and may predict long-term MACE.

The impact of smoking on mortality after acute ST-segment elevation myocardial infarction treated with primary percutaneous coronary intervention: a retrospective cohort outcome study at 3 years

The "smoker's paradox", where smokers have improved survival post-myocardial infarction, was predominantly observed in the thrombolytic era. However, evidence for the smoker's paradox in the current era of PCI therapy is both limited and inconsistent. We aimed to examine the effect of smoking status on survival in unselected ST-elevation myocardial infarction (STEMI) patients managed by primary percutaneous coronary intervention (PCI). Data were collected for all patients with acute STEMI undergoing primary PCI at The South Yorkshire Cardiothoracic Centre, UK over a 5-year period between 2009 and 2014. Differences in survival by smoking status were assessed before and after adjustment for differences in baseline variables using a Kaplan-Meier curve and a Cox regression analysis, respectively. A total of 3133 STEMI patients were included in the study. After adjustment for differences in baseline variables, smoking was associated with a significantly increased mortality (hazard ratio 1.35 (95% CI 1.04-1.74)) compared to never smokers after 3 years. The risk for ex-smokers (hazard ratio 0.99 (0.76-1.28)) was similar to never smokers. There were no significant differences in survival by smoking status at 30 days and 1 year. In this large registry of STEMI patients managed by primary PCI, smokers had a significantly higher 3-year mortality than non-smokers. This study is the first to not only dispel the existence of the smoker's paradox, but to highlight a high-risk subgroup who may warrant tailored secondary prevention treatment, including smoking cessation.

The effect of smoking on residual platelet reactivity to clopidogrel: a systematic review and meta-analysis

Cigarette smoking is an important cardiovascular risk factor, causing morbidity and mortality. There are many original studies on the impact of smoking, but its influence on platelet ADP-P2Y12 receptor inhibitors lack consistency. Thus, we conducted a systematic review and meta-analysis of already existing data/studies to further explore this issue. PubMed, Web of science, EMBASE, Clinical Trials, and the Cochrane Library were searched from inception to March 2018. Studies investigating the residual platelet reactivity categorized by smoking status and patients treated with platelet ADP-P2Y12 receptor inhibitors qualified the inclusion criteria. The primary outcome was P2Y12 reaction unit (PRU) value measured by VerifyNow P2Y12 assay, compared with different smoking status in ADP-P2Y12 receptor inhibitors treatment groups. Secondary outcome was post-treatment with 5 μmol/L ADP-inhibition of platelet aggregation (ADP-IPA) measured by light transmittance aggregometry (LTA). Of the 4954 citations retrieved, 12 studies involving 16 296 patients with acute coronary syndrome and/or stent deployment using platelet ADP-P2Y12 receptor inhibitors were included for meta-analysis. Pooled analysis revealed that PRU values of current smokers were 25.70 lower than nonsmokers (95% CI -38.81 to -12.60, p = 0.0001), getting better effects of antiplatelet treatment. In the smoking extent subgroup analysis, patients smoking >10 cigarettes/day shown about 46.49 lower of PRU values than patients smoking <10 cigarettes/day (p < 0.00001). Racial subgroup analyses found that smokers had increased platelet inhibition in the Caucasian population. Further, pooled analysis of ADP-IPA values for 1658 patients from five studies showed a significantly lower residual platelet reactivity in current smokers compared to that in nonsmokers (MD = -4.19; 95% CI -6.55 to -1.83; p = 0.0005). This systematic review and meta-analysis suggested that smokers have increased platelet inhibition and lower aggregation in response to clopidogrel than nonsmokers. These residual platelet reactivity observations may help to explain differential clinical outcomes in smokers vs. nonsmokers in large scale clinical trials.

Neutrophil extracellular traps in thrombi retrieved during interventional treatment of ischemic arterial diseases

INTRODUCTION

The ultrastructure and cellular composition of thrombi has a profound effect on the outcome of acute ischemic stroke (AIS), coronary (CAD) and peripheral artery disease (PAD). Activated neutrophils release a web-like structure composed mainly of DNA and citrullinated histones, called neutrophil extracellular traps (NET) that modify the stability and lysability of fibrin. Here, we investigated the NET-related structural features of thrombi retrieved from different arterial localizations and their interrelations with routinely available clinical data.

PATIENTS AND METHODS

Thrombi extracted from AIS (n = 78), CAD (n = 66) or PAD (n = 64) patients were processed for scanning electron microscopy, (immune)stained for fibrin, citrullinated histone H3 (cH3) and extracellular DNA. Fibrin fiber diameter, cellular components, DNA and cH3 were measured and analyzed in relation to clinical parameters.

RESULTS

DNA was least present in AIS thrombi showing a 2.5-fold lower DNA/fibrin ratio than PAD, whereas cH3 antigen was unvaryingly present at all locations. The NET content of thrombi correlated parabolically with systemic inflammatory markers and positively with patients' age. The median platelet content was lower in PAD (2.2%) than in either AIS (3.9%) or CAD (3.1%) and thrombi from smokers contained less platelets than non-smokers. Fibrin fibers were significantly thicker in male patients with CAD (median fiber diameter 76.3 nm) compared to AIS (64.1 nm) or PAD (62.1 nm) and their diameter correlated parabolically with systemic inflammatory markers.

CONCLUSIONS

The observed NET-related variations in thrombus structure shed light on novel determinants of thrombus stability that eventually affect both the spontaneous progress and therapeutic outcome of ischemic arterial diseases.

Comparison of factors affecting platelet reactivity in various platelet function tests

Previous studies have reported that various factors affect ADP-induced platelet reactivity during clopidogrel therapy. The aim of this study was to determine whether clinical and laboratory variables for platelet reactivity during dual antiplatelet therapy (DAPT) are dependent on the assay used. We enrolled 904 patients receiving DAPT following coronary intervention. Platelet reactivity was measured using three methods: the VerifyNow P2Y12 assay, multiple electrode aggregometry (MEA) ADP assay, and the light transmittance aggregometry (LTA) ADP assay at 24-48 h following coronary intervention. The VerifyNow results demonstrated a significant inverse correlation with hematocrit value (r = -0.268, p < 0.0001); however, MEA results had no such correlation with hematocrit (r = 0.044, p = 0.188). There was a positive correlation between the MEA results and platelet count (r = 0.255, p < 0.0001). LTA was weakly influenced by hematocrit (r = -0.064, p = 0.057) and platelet count (r = 0.069, p = 0.040). Gender (odds ratio 1.53, 95% CI 1.10-2.14, p = 0.013) and hematocrit (odds ratio 0.91,95% CI 0.88-0.94, p < 0.0001) were the independent variables for HPR by VerifyNow. Smoking (odds ratio 0.38, 95% CI 0.16-0.94, p = 0.036) and platelet count (odds ratio 1.01, 95% CI 1.00-1.01, p < 0.0001) were independent factors for HPR when using the MEA assay, whereas platelet count (odds ratio 1.00, 95% CI 1.00-1.01, p = 0.006) was identified as the only independent variable for HPR when using LTA. The incidence of HPR and the influencing variables involved are dependent on the platelet function test used.

Cigarette smoking reduces platelet reactivity independently of clopidogrel treatment in patients with non-ST elevation acute coronary syndromes

Smokers receiving clopidogrel show a lower residual platelet reactivity than non-smokers, a phenomenon generally ascribed to smoking-induced increased production of clopidogrel active metabolite, but also associated with the high hemoglobin levels of smokers, which decreases platelet reactivity in tests that measure platelet function in whole blood. We evaluated the impact of cigarette smoking and of hemoglobin levels on platelet reactivity index (PRI) measured by the vasodilator-stimulated phosphoprotein phosphorylation (VASP-P) assay in whole blood samples from patients with non-ST elevation acute coronary syndrome (NSTE-ACS) undergoing percutaneous coronary interventions, both before and after clopidogrel administration. PRI was measured in 718 clopidogrel-naïve NSTE-ACS patients, both before and 1 month after treatment with clopidogrel (75 mg daily). Smokers (n = 347, 48%) had significantly lower mean PRI levels at both baseline (57.7 ± 24.1 vs. 64.8 ± 19.8, p < 0.001) and 1 month (43.4 ± 20.3% vs. 46.8 ± 18.0%, p = 0.017) than non-smokers. After adjusting for potential confounders (age, sex, diabetes, chronic kidney disease, Syntax score>15), the β coefficient of smoke on PRI was -8.51 [-11.90 to -5.11, p < 0.001] at baseline and -3.41 [-6.30 to -0.51, p = 0.02] after 1 month. Hemoglobin was higher in smokers (13.8 ± 1.5 g/dL) than non-smokers (13.1 ± 1.7 g/dL, p < 0.001), but was not significantly correlated with PRI both at baseline (Rho = 0.02, p = 0.60) and at 1 month (Rho = 0.01, p = 0.80). Our analysis confirms that clopidogrel-treated smokers have lower platelet reactivity, measured by the VASP-P assay, compared to clopidogrel-treated non-smokers. However, smokers had lower platelet reactivity already before receiving clopidogrel treatment, suggesting that smoke affects platelet reactivity independently of its potential effect on the pharmacokinetics of clopidogrel. Our data also indicate that such an effect is not mediated by increased hemoglobin levels.

Double-Dose Versus Standard-Dose Clopidogrel According to Smoking Status Among Patients With Acute Coronary Syndromes Undergoing Percutaneous Coronary Intervention

Background

Prior Studies have suggested better outcomes in smokers compared with nonsmokers receiving clopidogrel (“smoker's paradox”). The impact of a more intensive clopidogrel regimen on ischemic and bleeding risks in smokers with acute coronary syndromes requiring percutaneous coronary interventions remains unclear.

Methods and Results

We analyzed 17 263 acute coronary syndrome patients undergoing percutaneous coronary intervention from the CURRENT‐OASIS 7 (Clopidogrel and Aspirin Optimal Dose Usage to Reduce Recurrent Events—Seventh Organization to Assess Strategies in Ischemic Symptoms) trial, which compared double‐dose (600 mg day 1;150 mg days 2–7; then 75 mg daily) versus standard‐dose (300 mg day 1; then 75 mg daily) clopidogrel in acute coronary syndrome patients. The primary outcome was cardiovascular death, myocardial infarction, or stroke at 30 days. Interactions between treatment allocation and smoking status (current smokers versus nonsmokers) were evaluated. Overall, 6394 patients (37.0%) were current smokers. For the comparison of double‐ versus standard‐dose clopidogrel, there were significant interactions in smokers and nonsmokers for the primary outcome (P=0.031) and major bleeding (P=0.002). Double‐ versus standard‐dose clopidogrel reduced the primary outcome among smokers by 34% (hazard ratio [HR] 0.66, 95% confidence interval [CI], 0.50–0.87, P=0.003), whereas in nonsmokers, there was no apparent benefit (HR 0.96, 95% CI, 0.80–1.14, P=0.61). For major bleeding, there was no difference between the groups in smokers (HR 0.77, 95% CI, 0.48–1.24, P=0.28), whereas in nonsmokers, the double‐dose clopidogrel regimen increased bleeding (HR 1.89, 95% CI, 1.37–2.60, P<0.0001). Double‐dose clopidogrel reduced the incidence of definite stent thrombosis in smokers (HR 0.41, 95% CI, 0.24–0.71) and nonsmokers (HR 0.63, 95% CI, 0.42–0.93; P for interaction=0.19).

Conclusions

In smokers, a double‐dose clopidogrel regimen reduced major cardiovascular events and stent thrombosis after percutaneous coronary intervention, with no increase in major bleeding. This suggests that clopidogrel dosing in patients with acute coronary syndromes should be personalized, taking into consideration both ischemic and bleeding risk.

Clinical Trial Registration

URL: https://www.clinicaltrials.gov. Unique identifier: NCT00335452.

Haplotype of platelet receptor P2RY12 gene is associated with residual clopidogrel on-treatment platelet reactivity

OBJECTIVE

To investigate a possible association between common variations of the P2RY12 and the residual clopidogrel on-treatment platelet reactivity after adjusting for the influence of CYP2C19 tested by thromboelastography (TEG).

METHODS

One hundred and eighty patients with acute coronary syndrome (ACS) treated with clopidogrel and aspirin were included and platelet function was assessed by TEG. Five selected P2RY12 single nucleotide polymorphisms (SNPs; rs6798347, rs6787801, rs6801273, rs6785930, and rs2046934), which cover the common variations in the P2RY12 gene and its regulatory regions, and three CYP2C19 SNPs (^*2,^*3,^*17) were genotyped and possible haplotypes were analyzed.

RESULTS

The high on-treatment platelet reactivity (HTPR) prevalence defined by a platelet inhibition rate <30% by TEG in adenosine diphosphate (ADP)-channel was 69 (38.33%). Six common haplotypes were inferred from four of the selected P2RY12 SNPs (denoted H₀ to H₅) according to the linkage disequilibrium R square (except for rs2046934). Haplotype H₁ showed a significantly lower incidence of HTPR than the reference haplotype (H₀) in the total study population while haplotypes H₁ and H₂ showed significantly lower incidences of HTPR than H₀ in the nonsmoker subgroup after adjusting for CYP2C19 effects and demographic characteristics. rs2046934 (T744C) did not show any significant association with HTPR.

CONCLUSIONS

The combination of common P2RY12 variations including regulatory regions rather than rs2046934 (T744C) that related to pharmacodynamics of clopidogrel in patients with ACS was independently associated with residual on-clopidogrel platelet reactivity. This is apart from the established association of the CYP2C19. This association seemed more important in the subgroup defined by smoking.

A laboratory association between hemoglobin and VerifyNow P2Y12 reaction unit: A systematic review and meta-analysis

BACKGROUND

VerifyNow P2Y12 assay is used widely to evaluate residual platelet reactivity in patients taking P2Y12 receptor antagonists. However, a laboratory association between VerifyNow P2Y12 reaction unit (PRU) and hemoglobin, which might lead to wrong interpretation of the data, is reported. We performed these systematic review and meta-analysis to clearly define the relationship between PRU and hemoglobin and to elucidate whether the relationship, if any, is a true biological association or is just a laboratory error.

METHODS

Through a comprehensive electronic and manual search, 10 studies were selected for the cohort level meta-analysis. Among 10 studies, we were able to retrieve the raw data of 5 studies, and a patient-level meta-analysis was performed. Potential publication bias was searched by funnel plot analysis and was actively adjusted, if present, by trim and fill method.

RESULTS

The pooled analysis revealed a significant inverse correlation between PRU and hemoglobin (r=-0.349; P<.001; 10 studies with 4,793 patients). VerifyNow P2Y12 base unit, which reflects off-drug platelet reactivity, was also inversely correlated with hemoglobin (r=-0.526; P<.001; 8 studies with 4,395 patients). % Inhibition (r=0.081; P=.059; 6 studies with 3,832 patients) and ΔPRU (r=-0.037; P=.188; 5 studies with 3,521 patients) were not associated with hemoglobin. A significant inverse association between PRU and hemoglobin was also observed in the patient-level meta-analysis (3,533 patients pooled from 5 studies; r=-0.335; P<.001). Light transmission aggregometry (r=0.160; P=.072; 4 studies with 1,144 patients) and multiple electrode platelet aggregometry (r=-0.029; P=.394; 3 studies with 7,645 patients) showed no significant association with hemoglobin.

CONCLUSIONS

A significant inverse association was observed between PRU and hemoglobin which is likely to be a laboratory error. Clinicians should be aware that this association might lead to wrong interpretation of the data.

Pharmacokinetic and Pharmacodynamic Responses to Clopidogrel: Evidences and Perspectives

Clopidogrel has significantly reduced the incidence of recurrent atherothrombotic events in patients with acute coronary syndrome (ACS) and in those undergoing percutaneous coronary intervention (PCI). However, recurrence events still remain, which may be partly due to inadequate platelet inhibition by standard clopidogrel therapy. Genetic polymorphisms involved in clopidogrel’s absorption, metabolism, and the P2Y12 receptor may interfere with its antiplatelet activity. Recent evidence indicated that epigenetic modification may also affect clopidogrel response. In addition, non-genetic factors such as demographics, disease complications, and drug-drug interactions can impair the antiplatelet effect of clopidogrel. The identification of factors contributing to the variation in clopidogrel response is needed to improve platelet inhibition and to reduce risk for cardiovascular events. This review encompasses the most recent updates on factors influencing pharmacokinetic and pharmacodynamic responses to clopidogrel.