Antithrombotics in acute coronary syndromes

Antithrombotic agents are an integral component of the medical regimens and interventional strategies currently recommended to reduce thrombotic complications in patients with acute coronary syndromes (ACS). Despite great advances with these therapies, associated high risks for thrombosis and hemorrhage remain as the result of complex interactions involving patient comorbidities, drug combinations, multifaceted dosing adjustments, and the intricacies of the care environment. As such, the optimal combinations of antithrombotic therapies, their timing, and appropriate targeted subgroups remain the focus of intense research. During the last several years a number of new antithrombotic treatments have been introduced, and new data regarding established therapies have come to light. Although treatment guidelines include the most current available data, subsequent findings can be challenging to integrate. This challenge is compounded by the complexity associated with different efficacy and safety measures and the variability in study populations, presenting syndromes, physician, and patient preferences. In this work we review recent data regarding clinically available antiplatelet and anticoagulation agents used in the treatment of patients with ACS. We address issues including relative efficacy, safety, and timing of therapies with respect to conservative and invasive treatment strategies. In specific cases we will highlight remaining questions and controversies and ongoing trials, which will hopefully shed light in these areas. In addition to reviewing existing agents, we take a look forward at the most promising new antithrombotics currently in late-stage clinical development and their potential role in the context of ACS management.

Relation between aspirin dose, all-cause mortality, and bleeding in patients with recent cerebrovascular or coronary ischemic events (from the BRAVO Trial)

Despite aspirin's established role in the treatment of atherosclerotic vascular disease, considerable controversy exists regarding its most effective dosing strategy. In a retrospective observational study, we examined the relation between prescribed aspirin dose (<162 mg vs > or =162 mg/day aspirin) and clinical outcome in 4,589 placebo-treated patients enrolled in the Blockage of the Glycoprotein IIb/IIIa Receptor to Avoid Vascular Occlusion (BRAVO) trial over a median follow-up of 366 days. Standard Cox regression analysis was employed because propensity analysis was not feasible. Compared with lower aspirin doses, higher doses were associated with lower unadjusted all-cause mortality (2.9 vs 1.6%, respectively; log rank chi-square 8.6, p = 0.0034). Higher aspirin dose remained independently predictive of lower all-cause mortality in a multivariable Cox proportional hazards model (hazard ratio 0.64, 95% confidence interval 0.42 to 0.97, p = 0.037). However, there was no significant difference in the incidence of the composite endpoint death, nonfatal myocardial infarction, or nonfatal stroke (6.1% vs 6.2%, p = 0.74). Higher aspirin dose was a significant independent predictor of any (hazard ratio 1.32, 95% confidence interval 1.12 to 1.55, p = 0.001) but not serious bleeding. In conclusion, our findings suggest that aspirin doses of > or =162 mg/day may be more beneficial than those <162 mg/day at preventing death.

Clinical considerations with the use of antiplatelet therapy in patients undergoing percutaneous coronary intervention

Despite the proven benefits of using antiplatelet therapy in patients undergoing percutaneous coronary intervention (PCI), a number of key questions remain to be answered. In recent years, clopidogrel dosing strategies among such patients have evolved considerably, with newer approaches involving loading doses prior to PCI and increases in the time interval and loading dosage in an effort to overcome variable responsiveness/hyporesponsiveness to platelet inhibition. Further, the role of glycoprotein (GP) IIb/IIIa antagonists in elective stenting continues to be defined, with recent evidence suggesting that most appropriate use of these agents is in high-risk patients with elevated troponin levels. There appears to be a relationship between the use of GP IIb/IIIa antagonists with clopidogrel loading and attenuation of early inflammatory and cardiac marker release. Strategies to minimize the chance of late stent thrombosis in patients who receive drug-eluting stents (DES) are also under intense investigation. Among some patients receiving sirolimus and paclitaxel DES, current standard long-term antiplatelet strategies may be insufficient. Patient nonadherence to treatment and premature discontinuation and underutilization of antiplatelet therapies by physicians remain important clinical problems with potentially dire consequences.

Clopidogrel pre-treatment in stable angina: for all patients > 6 h before elective coronary angiography or only for angiographically selected patients a few minutes before PCI? A randomized multicentre trial PRAGUE-8

AIMS

To compare two different clopidogrel regimens on the outcomes of patients undergoing elective coronary angiography (CAG)+/-ad hoc percutaneous coronary intervention (PCI).

METHODS AND RESULTS

Open-trial randomized 1028 patients with stable angina to group A ('non-selective'-clopidogrel 600 mg > 6 h before CAG; n = 513) or group B ('selective'-clopidogrel 600 mg in the cath-lab after CAG, only in case of PCI; n = 515). Combined primary endpoint was death/periprocedural myocardial infarction (MI)/stroke/re-intervention within 7 days. Secondary endpoints were troponin elevation and bleeding complications. Primary endpoint occurred in 0.8% group A patients vs. 1% group B (P = 0.749; 90% CI for the percentage difference -1.2-0.8). Periprocedural troponin elevation (> 3 x ULN) was detected in 2.6% group A vs. 3.3% group B (P = 0.475; 90% CI -2.5-1.0). Bleeding complications occurred in 3.5% group A patients vs. 1.4% group B (P = 0.025). After adjustment for covariates and factors that may influence the bleeding risk, patients in group A were shown to have more likely bleeding complications when compared with group B (OR = 3.03; 95% CI 1.14-8.10; P = 0.027).

CONCLUSION

High (600 mg) loading dose of clopidogrel before elective CAG increased the risk of minor bleeding complications, while the benefit on periprocedural infarction was not significant. Clopidogrel can be given safely in the catheterization laboratory between CAG and PCI in chronic stable angina patients.