High-Dose Clopidogrel Loading in Percutaneous Coronary Intervention

Effects of glycoprotein IIb/IIIa inhibitors in patients undergoing percutaneous coronary intervention after pretreatment with clopidogrel: a meta-analysis of randomized trials

Glycoprotein (Gp) IIb/IIIa inhibitors reduce morbidity and mortality in patients undergoing percutaneous coronary intervention (PCI) when added to aspirin and heparin. However, the benefits of Gp IIb/IIIa inhibition in patients pretreated with clopidogrel are less clear. We conducted a meta-analysis to determine the efficacy and safety of adding a Gp IIb/IIIa inhibitor to clopidogrel, aspirin, and heparin before PCI. Five trials were identified via electronic searches of the MEDLINE and Cochrane Central Register of Controlled Trials databases. The studies randomized a total of 5303 patients; 2654 received a Gp IIb/IIIa inhibitor. Two trials examined patients with acute coronary syndromes and 3 examined patients undergoing elective PCI. Loading doses of clopidogrel ranged from 375 to 600 mg. Follow-up ranged from 30 days to 1 year.Gp IIb/IIIa inhibition did not reduce the endpoints of death, myocardial infarction (MI), or target vessel revascularization (odds ratio [OR] = 0.84; 95% confidence interval [CI] = 0.58-1.22, P = 0.35 for death; OR = 0.86; 95% CI = 0.69-1.08, P = 0.19 for MI; and OR = 0.96; 95% CI = 0.81-1.15, P = 0.68 for target vessel revascularization). Analyses restricted to acute coronary syndromes trials yielded similar results (OR = 0.70; 95% CI = 0.33-1.48, P = 0.35 for death; OR = 0.78; 95% CI = 0.59-1.03, P = 0.08 for MI). Gp IIb/IIIa inhibition increased major and minor bleeding (OR = 1.35; 95% CI = 1.04-1.75, P = 0.02) driven by use of abciximab. There was no evidence of heterogeneity in the analyses.

Clopidogrel resistance: role of body mass and concomitant medications

INTRODUCTION

Platelets have a central role in the development of arterial thrombosis and subsequent cardiovascular events. An appreciation of this has made antiplatelet therapy the cornerstone of cardiovascular disease management. Recent studies have described the phenomenon of clopidogrel resistance but the possible mechanisms are still unclear.

PATIENTS AND METHODS

The aim of this study was to compare the characteristics (risk profile, previous diseases, medications, hemorheological variables and plasma von Willebrand factor and soluble P-selectin levels) of patients in whom clopidogrel provided effective platelet inhibition with those in whom clopidogrel was not effective in providing platelet inhibition. 157 patients with chronic cardio- and cerebrovascular diseases (83 males, mean age 61+/-11 yrs, 74 females, 63+/-13 yrs) taking 75 mg clopidogrel daily (not combined with aspirin) were included in the study.

RESULTS

Compared with clopidogrel-resistant patients (35 patients (22%), patients who demonstrated effective clopidogrel inhibition had a significantly lower BMI (26.1 vs. 28.8 kg/m2, p<0.05). Patients with ineffective platelet aggregation were significantly more likely to be taking benzodiazepines (25% vs. 10%) and selective serotonin reuptake inhibitors (28% vs. 12%) (p<0.05). After an adjustment to the risk factors and medications BMI (OR 2.62; 95% CI: 1.71 to 3.6; p<0.01), benzodiazepines (OR 5.83; 95% CI: 2.53 to 7.1; p<0.05) and SSRIs (OR 5.22; 95% CI: 2.46 to 6.83; p<0.05) remained independently associated with CLP resistance. There was no significant difference in the rheological parameters and in the plasma levels of adhesive molecules between the two examined groups.

CONCLUSION

The background of ineffective clopidogrel medication is complex. Drug interactions may play a role on clopidogrel bioavailability, on the other hand, the significant difference in BMI between the two examined groups suggests that clopidogrel therapy should be weight-adjusted.

Determination of Clopidogrel Resistance by Whole Blood Platelet Aggregometry and Inhibitors of the P2Y12 Receptor

Background: Inhibition of platelet aggregation by clopidogrel may be insufficient in up to 30% of users. These nonresponders carry an increased risk of cardiovascular events. We reported here a simple assay to study clopidogrel responsiveness.

Methods: Electrical impedance aggregometry was performed in diluted whole blood in the presence of 5 and 20 μmol/L ADP. Some samples were incubated with 0.1 mmol/L methyl-S-adenosine monophosphate (MeSAMP), a P2Y12 receptor blocker, to maximize inhibition of aggregation before aggregometry. To validate the assay, we analyzed 6-min impedance in 21 healthy probands and 244 patients with coronary artery disease (CAD).

Results: At 5 μmol/L ADP, the imprecision of the assay was 11%. Mean (SD) impedance of the healthy cohort was 12.2 (2.2) Ω. The mean − 3 SD was used to define the cutoff for clopidogrel responsiveness: responders and nonresponders exhibited a 6-min impedance ≤5 Ω and &gt;5 Ω, respectively. Samples from nonresponders were incubated with MeSAMP and analyzed again to distinguish pharmacokinetic and pharmacodynamic types of resistance. Sixteen percent of CAD patients were classified as nonresponders (38 and 2 cases of pharmacokinetic and pharmacodynamic resistance, respectively). Female sex was strongly associated with clopidogrel resistance (P = 0.0002, Fisher exact test). A higher clopidogrel loading dose (P = 0.0353, Mann–Whitney U-test) was given to responders (median, 450 mg) than nonresponders (median, 300 mg). Age and cardiovascular diagnosis showed no significant associations.

Conclusions: Impedance aggregometry using 5 μmol/L ADP is a useful tool for studying clopidogrel responsiveness. MeSAMP allows characterization of responsiveness “on treatment” and may be useful for optimizing clopidogrel dosing.

Clopidogrel: cardiologists' panacea or neurologists' headache?

Clopidogrel (Plavix) is a potent platelet inhibitor that has been demonstrated to be significantly more effective than aspirin for the prevention of atherothrombotic events in patients with established atherosclerotic disease in the Clopidogrel versus Aspirin in Patients at Risk of Ischemic Events (CAPRIE) study. Furthermore, the benefit of clopidogrel compared with placebo in patients with acute coronary syndromes, as well as those undergoing percutaneous coronary intervention receiving a standard therapy including aspirin, has been largely demonstrated by the Clopidogrel in Unstable angina to prevent Recurrent Events (CURE), Clopidogrel for the Reduction of Events During Observation (CREDO), CLopidogrel as Adjunctive ReperfusIon TherapY-Thrombolysis In Myocardial Infarction (CLARITY-TIMI)28, and Clopidogrel and Metoprolol in Myocardial Infarction Trial/Secon Chinese Cardiac Study (COMMIT/CCS-2) trials. However, in the Management of Atherothrombosis with Clopidogrel in High-risk patients with recent transient ischemic attack or ischemic stroke (MATCH) trial, there was no clinical benefit of adding aspirin versus placebo to a standard therapy of clopidogrel in patients with cerebrovascular disease. The implications of these findings, as well as future perspectives from upcoming trials, shall be discussed herein.