The emerging role of low-molecular-weight heparin and antiplatelet therapies in the cardiac catheterization laboratory

Ranolazine, a new antianginal drug

The increasing and unmet social and economic burden of ischemic heart disease calls for new antianginal therapies. Ranolazine, a new antianginal agent, has a different mode of action from existing therapies, which act by decreasing indices of cardiac work. Ranolazine mainly affects the late sodium current across the membrane of cardiomyocytes, inducing a cascade of electrophysiologic and metabolic effects with the potential to reduce the cardiac ischemic burden without significantly changing blood pressure and heart rate. In clinical trials, ranolazine has been demonstrated to exert antianginal and anti-ischemic effects in chronic angina. It improves exercise performance, and decreases angina frequency and nitroglycerin use. Ranolazine is well tolerated at therapeutic doses. Larger studies are needed to explore the effects on hard end-points of morbidity and mortality.

Preoperative use of enoxaparin increases the risk of postoperative bleeding and re-exploration in cardiac surgery patients

OBJECTIVE

The purpose of this study was to investigate if the preoperative use of new platelet inhibitors and low-molecular-weight heparins may contribute to bleeding after cardiac surgery.

DESIGN

Retrospective data review.

SETTING

University teaching hospital.

PARTICIPANTS

One hundred eleven patients divided in 5 groups.

INTERVENTIONS

Patients were grouped according to preoperative antithrombotic regimen: group 1, control, no agents (n=55); group 2, clopidogrel (n=9); group 3, enoxaparin (n=17); group 4, any GP IIb/IIIa inhibitor (n=14); and group 5, any drug combination (n=15). Data included cumulative mediastinal chest tube drainage, allogeneic blood transfusions, total blood donor exposures, and re-exploration.

MEASUREMENTS AND MAIN RESULTS

Use of any drug (groups 2-5) resulted in greater total blood transfusions and donor exposure (p=0.0003) than control, especially red cells (p=0.002) and platelets (p=0.006). A greater percentage of patients on enoxaparin required mediastinal re-exploration for nonsurgical bleeding versus control (3/17 v 0/55, p=0.001). The use of enoxaparin was associated with significantly higher chest tube output after the first 24 hours postoperatively (p=0.048).

CONCLUSION

Newer antithrombotic agents were associated with greater transfusion rates and total donor exposures. Enoxaparin use was associated with greater overall blood loss and with higher incidence of mediastinal re-exploration. The relative risk-benefit ratio of reduced periprocedure morbidity versus increased bleeding complications has yet to be determined.

Pharmacokinetics and pharmacodynamics of argatroban in combination with a platelet glycoprotein IIB/IIIA receptor antagonist in patients undergoing percutaneous coronary intervention

The pharmacokinetic-pharmacodynamic (PK-PD) relationship of argatroban, administered in combination with a platelet glycoprotein IIb/IIIa receptor antagonist, was characterized in patients undergoing percutaneous coronary intervention (PCI). Plasma argatroban and activated clotting times (ACTs) were assessed periprocedurally in 152 patients administered argatroban (250- or 300-microg/kg bolus, then 15-microg/kg/min infusion) in combination with abciximab or eptifibatide during PCI. The PK and PK-PD models were developed utilizing a sequential population approach in NONMEM. Population PK estimates for clearance, central volume, and peripheral volume were 22.0 L/h, 11.0 L, and 13.0 L, respectively (coefficients of variation [CVs] </= 10%). By covariate analysis, clearance increased linearly with body weight. Plasma argatroban and ACT effect were well described using a sigmoidal E(max) model. For argatroban in combination with platelet glycoprotein IIb/IIIa receptor blockade in patients undergoing PCI, population PK parameters are consistent with values reported for argatroban in healthy subjects. A predictable relationship exists between argatroban concentration and effect in this setting.

The role of enoxaparin in interventional management of patients with acute coronary syndromes

Interventional management strategies involving early angiography and percutaneous coronary intervention (PCI) are increasingly widespread in the management of patients with acute coronary syndromes (ACS). Notwithstanding the benefits of early intervention, there is a significant risk of postprocedural thrombotic complications and a need to optimize antithrombotic regimens for use before and during PCI. It is clear that the current standard therapy with unfractionated heparin (UFH) and aspirin can be improved upon, in terms of both efficacy and safety. The low-molecular-weight heparin(s) (LMWHs) offer pharmacologic and practical advantages over UFH. The LMWH enoxaparin has recently emerged as the anticoagulant of choice for the acute management of ACS. Enoxaparin has also demonstrated sustained benefits over UFH in patients proceeding to PCI, and as a procedural anticoagulant. Combination therapy with enoxaparin and a glycoprotein IIb/IIIa inhibitor may further improve the efficacy and safety of antithrombotic treatment during coronary interventions, as a result of the drugs' complementary mechanisms of action. Early clinical evidence supports the use of enoxaparin in combination with glycoprotein IIb/IIIa inhibitors in high-risk patients with ACS. Ongoing, large-scale, randomized controlled studies will help to clarify the role of enoxaparin in interventional cardiology, either as the primary anticoagulant or as part of a combination regimen, and to define optimal regimens for treatment.

Signs of thrombin generation in pediatric cardiac catheterization with unfractionated heparin bolus or subcutaneous low molecular weight heparin for antithrombotic cover

INTRODUCTION

Thrombosis is one of the most frequent adverse events after cardiac catheterization, which can be reduced by anticoagulation with unfractionated heparin (UFH) in both children and adults. Low molecular weight heparin (LMWH) might possibly offer advantages. Laboratory signs of thrombin generation during pediatric cardiac catheterization, with unfractionated heparin (UFH) bolus or subcutaneous LMWH for thrombosis prophylaxis, were determined in a first step to investigate the potential of LMWH for antithrombotic cover.

MATERIALS AND METHODS

Signs of thrombin generation (D-dimer and F1+2), anti-Xa activity and activated clotting time (ACT) were measured in 65 patients with congenital heart disease. A total of 40 patients were treated with a UFH bolus of 100 IU/kg bodyweight and, in 25 children, enoxaparin was subcutaneously administered at a dosage of 1/1.6 mg/kg bodyweight.

RESULTS

The dose to plasma activity of enoxaparin was more consistent than in the UFH group. Only a slight elevation of F1+2 was found in some patients, which was a little higher in the enoxaparin group, but no difference of incidence of increased F1+2 generation was detected between the two groups. D-dimer was elevated in three children after UFH bolus application, but no such effect was observed in any child after LMWH administration.

CONCLUSIONS

Application of LMWH was equally efficacious during pediatric cardiac catheterization than UFH bolus administration, as determined by plasma levels and markers of clotting activation. In contrast to UFH bolus, no further monitoring was necessary after the application of LMWH during cardiac catheterization due to a consistent dose to plasma activity.

Guideline on the management of anticoagulation and antiplatelet therapy for endoscopic procedures

This is one of a series of statements discussing the practice of gastrointestinal endoscopy in common clinical situations. It is intended to aid endoscopists in determining the appropriate use of endoscopic procedures in conjunction with anticoagulation and/or antiplatelet therapy. Guidelines for the appropriate practice of endoscopy are based on critical review of the available data and expert consensus. Controlled clinical studies would be beneficial to clarify some aspects of this statement and revision might be necessary as new data appear. Clinical consideration may justify a course of action at variance from these specific recommendations.

Are activated clotting times helpful in the management of anticoagulation with subcutaneous low-molecular-weight heparin?

BACKGROUND

Enoxaparin has recently been shown to be superior to unfractionated heparin in patients with unstable angina/non-ST-elevation myocardial infarction. Theoretical advantages of low-molecular-weight heparin versus unfractionated heparin include a higher ratio of anti-Xa to anti-IIa activity (3:1 for enoxaparin), a more predictable dose response that precludes the need for frequent monitoring, and the convenience of subcutaneous administration. Both activated partial thromboplastin time and activated clotting time (ACT) are used to monitor anticoagulation with heparin, and ACTs are now standard during percutaneous coronary intervention (PCI) with heparin. At doses of up to 90 mg, subcutaneous enoxaparin leads to a modest dose-related increase in activated partial thromboplastin time, but the effect on ACT is unknown.

METHODS

Thrombolysis In Myocardial Infarction (TIMI) 11A was a multicenter, dose-ranging trial to evaluate the safety and tolerability of subcutaneous enoxaparin in patients with unstable angina/non-ST-elevation myocardial infarction. We obtained peak (mean 4.3 hours after enoxaparin) and trough (mean 11.5 hours after enoxaparin) anti-Xa levels and ACTs for 26 patients in the TIMI 11A trial.

RESULTS

Despite doses of enoxaparin in the range of 89 +/- 19 mg every 12 hours and significant increases in anti-Xa levels even at trough, there was no change in the ACT measured by HemoTec and only a small increase with Hemachron. The correlation of peak Hemachron ACT with peak anti-Xa levels was poor (R = 0.5, P =.08).

CONCLUSIONS

In contrast to heparin, ACTs are not useful for assessment of anticoagulation with subcutaneous enoxaparin and should not be relied on in patients receiving enoxaparin who require acute PCI. Studies to determine the optimal dose, safety, and efficacy of enoxaparin in patients undergoing PCI are underway.

Risk stratification in non-ST segment elevation acute coronary syndromes with special focus on recent guidelines

Patients with unstable angina or non-ST segment elevation (non-Q-wave) myocardial infarction are a heterogeneous group with respect to their risk of developing clinically significant adverse events such as subsequent myocardial infarction and death. Recent guidelines promote risk stratification of these patients, targeting high-risk patients for maximal antithrombotic and antiischemic therapy and low-risk patients for early discharge. We reviewed current and future modalities for risk stratification of patients and the predictive value of these methods in context with available pharmacologic agents. Unfortunately, most of the data identifying a particular pharmacologic regimen as beneficial in high-risk patients are retrospectively derived from large trials. Until prospective studies that use markers to guide therapy are available, clinicians should be familiar with the use of these risk markers and their application to the role of a given management strategy, including pharmacologic therapy.

Low-molecular weight heparins in coronary artery disease

Recently published trials strongly support the use of low-molecular weight heparins in the treatment of unstable coronary syndromes. These agents provide an alternative to heparin that is at least as effective and safe, and does not require intravenous infusions or meticulous monitoring. Although comparative trials are not yet available, the available evidence allows for selection of specific agents in acute management of unstable angina. This review summarizes the current clinical data supporting the use of these agents.

Calming the plaque to delay intervention for 24 hours in acute coronary syndromes

One approach to management of patients with acute coronary syndromes involves use of pharmacologic therapy to passivate plaque for at least 24 hours before interventional procedures are undertaken. This approach is supported by the view that whatever subsequent treatment the patient receives will less likely be complicated. An important factor in revolutionizing treatment for acute coronary syndromes in recent years has been the introduction of potent new antithrombotic and antiplatelet pharmacologic therapies such as low-molecular-weight heparins and glycoprotein IIb/IIIa inhibitors. Incorporation of these newer agents into clinical practice, along with a better understanding of the pathophysiology underlying acute coronary syndromes, has contributed greatly to improved outcomes in these patients. Although the optimal methods for integrating the newer therapies remains to be determined, thus far, they have been shown to lower the risk of acute complications, as well as improve long-term results.