Low molecular weight heparins in the cardiac catheterization laboratory

[Enoxaparin vs. non-fractionated heparin in primary angioplasty of acute myocardial infarction]

OBJECTIVE

The objective of this study is to compare the effectiveness of intravenous enoxaparin (ENX) and Non-fractionated Heparin (NFH) in primary angioplasty (PA) of acute myocardial infarction (PA-AMI).

DESIGN

A prospective, observational study.

PATIENTS AND METHODS

A total of 191 patients admitted at the hospital with the diagnosis of Acute Myocardial Infarction (AMI) and treated with primary angioplasty were included. ENX was used in 91 patients (47.6%) and NFH in 100 patients (52.4%). Choice of treatment was based on the operator's opinion. Patients with cardiogenic shock were excluded. The first group received an intravenous bolus of ENX (0.75-1 mg/Kg) and the second one NFH (70-100 u/Kg), depending on whether it was associated with abciximab or not. In-hospital follow-up was performed, evaluating mortality and bleeding complications of both treatments.

RESULTS

In-hospital mortality was 1.1% for the ENX group and 3.3% for NFH one. No significant differences were found in the number of bleeding complications with ENX (4.4%) and NFH (9.0%). There was one subacute thrombosis of stent for the ENX group and 3 thrombosis in the NFH-treated group. No significant differences were found in size of infarction measure with troponin I level (63.1 for ENX and 54.8 for the NFH) or in the left ventricle ejection fraction on hospital discharge (51% for ENX and 49.4% for the NFH).

CONCLUSIONS

Primary angioplasty can be safely sued with the intravenous administration of ENX, no significant differences being found between both treatments in mortality and bleeding complications.

Direct thrombin inhibitors: alternatives to heparin

After more than 70 years of effective clinical use, heparin remains the most common anticoagulant in use and one of the most commonly prescribed drugs to hospitalized patients. However, the biologic variability and immunogenicity limit its utility. With increasing volumes of vascular intervention and an aging population, an increase in the need for anticoagulation can be anticipated. This article reviews current viable options and barriers to the use of heparin.

Comparison of Abciximab Combined With Dalteparin or Unfractionated Heparin in High-Risk Percutaneous Coronary Intervention in Acute Myocardial Infarction Patients

The purpose of this study was to determine the clinical outcomes of abciximab combined with the low molecular weight heparin (LMWH), dalteparin, in high-risk percutaneous coronary intervention (PCI) patients with acute myocardial infarction (AMI). A total of 140 high-risk PCI patients with AMI were divided into 2 groups: unfractionated heparin (UFH) with abciximab (group I: 70 patients, 58.7 +/- 10.5 years), and dalteparin with abciximab (group II: 70 patients, 59.6 +/- 9.8 years). Major adverse cardiac events (MACE) during hospitalization and at 4 years after PCI were examined. Baseline clinical characteristics, laboratory findings, echocardiography parameters, and baseline angiographic characteristics were not different between the 2 groups. The incidence of thrombotic total occlusion lesions was 62.9% in both groups. Procedural success was achieved in 91.4% in group I and 90.0% in group II. Bleeding and hemorrhagic events were not different between the 2 groups. No significant intracranial bleeding was observed in either group. The incidence of in-hospital MACE was 7 (10.0%) in group I and 4 (5.7%) in group II. Four-year clinical follow-up was performed in 97% of the patients. Four years after PCI, death occurred in 6 (8.6%) patients in group I and in 7 (10.0%) in group II. MI occurred in 4 (5.7%) and 4 (5.7%), target vessel revascularization (TVR) in 23 (32.9%) and 16 (22.9%), and bypass surgery in 3 (4.3%) and 1 (1.4%), respectively. Overall, a MACE occurred in 33 (47.1%) patients in group I and in 26 (35.1%) patients in group II (P = 0.23). The long-term clinical outcome with dalteparin combined with abciximab may be comparable to that of UFH plus abciximab in high risk PCI patients with AMI.

Low-molecular-weight heparin vs. unfractionated heparin in percutaneous coronary intervention: A combined analysis

This meta-analysis assessed the rates of the efficacy and safety endpoints with intravenous low-molecular-weight heparin (LMWH) compared with unfractionated heparin (UFH) in patients undergoing percutaneous coronary intervention (PCI). Subcutaneous LMWH has compared favorably with UFH, but limited experience exists with intravenous LMWH for immediate anticoagulation in PCI. The meta-analysis included data from eight randomized trials in which patients received LMWH (n = 1,037) or UFH (n = 978) during PCI. Seven additional nonrandomized studies/registries were analyzed to assess the efficacy and safety of LMWH during PCI. Efficacy endpoints were ischemic events (usually a composite of death, myocardial infarction, and urgent revascularization) and the safety endpoint was bleeding (major, minor, or all bleeding). In the randomized studies, LMWH was comparable with UFH in terms of efficacy (6.2% vs. 7.5%) and major bleeding (0.9% vs. 1.8%). The analysis of pooled data, randomized or not, suggests potential improved efficacy (5.8% vs. 7.6%) and reduced major bleeding (0.6% vs. 1.8%) with LMWH (n = 3,787) compared with UFH (n = 978). During PCI, intravenous LMWH without coagulation monitoring has the potential to be at least as safe and efficacious as intravenous UFH. Further studies of LMWHs in PCI are therefore required.

Interventional cardiovascular pharmacotherapy: current issues

In the last decade, a variety of novel anticoagulant and antiplatelet agents that improve outcomes in patients undergoing percutaneous coronary revascularization have emerged. During the next decade, continued refinements in catheter-based device technology should lead to further increases in the number of interventional procedures. The use of optimal antithrombotic strategies is pivotal in reducing adverse events among patients undergoing percutaneous coronary intervention (PCI). Our purpose is to review the current evidence regarding the efficacy of available adjunctive anticoagulant and antiplatelet agents in treating patients undergoing percutaneous coronary revascularization. It should be borne in mind that patients undergoing PCI in the midst of an acute coronary event require a different level of coagulation and platelet aggregation inhibition than low-risk patients undergoing elective PCI for stable angina pectoris. Similarly, generalizing antithrombotic regimen safety data to a wide spectrum of catheter-based therapeutic devices should be avoided. A level of anticoagulation that is safe and effective for angioplasty and stent placement may not be sufficient for devices with longer intracoronary dwell times such as brachytherapy catheters. In light of current evidence, activated clotting times should be targeted in the 200- to 250-second range during elective PCI and in the 250- to 300-second range when intervening on a higher-risk lesion, such as one with an angiographically visible thrombus or in patients presenting with an acute coronary syndrome (ACS).Low-dose enoxaparin sodium is an attractive antithrombin strategy in PCI because it is intrinsically adjusted for renal function, age, and concomitant glycoprotein (GP) IIb/IIIa antagonist use. Other low-molecular weight heparins have also been studied as adjunctive anticoagulants during cardiac catheterization. For example, in pilot studies, dalteparin sodium was shown to have a good safety profile when used alone or in combination with abciximab during PCI.A wealth of data supports the use of a GP IIb/IIIa antagonist in patients presenting with ACS, especially those with high-risk features such as elevated cardiac markers; the systematic use of GP IIb/IIIa inhibitors in this population is therefore encouraged. Overall, the use of GP IIb/IIIa inhibitors reduces the incidence of thrombotic complications following PCI, is associated with a mortality benefit, but has no impact on the risk of restenosis.

A unique, low dose of intravenous enoxaparin in elective percutaneous coronary intervention

OBJECTIVES

This study was designed to examine a unique and low dose of intravenous enoxaparin in elective percutaneous coronary intervention (PCI) that would be applicable to an unselected population regardless of age, weight, renal function, or use of glycoprotein IIb/IIIa inhibitors.

BACKGROUND

There is limited experience of anticoagulation using intravenous (IV) low-molecular-weight heparin in PCI, which has been obtained with high doses causing elevated anticoagulation levels and delayed sheath withdrawal.

METHODS

A total of 242 consecutive patients undergoing elective PCI were treated with a single IV bolus of enoxaparin (0.5 mg/kg), and 26% of patients (n = 64) also received eptifibatide. Sheaths were removed immediately after the procedure in patients treated with enoxaparin only, and 4 h after the procedure in those also treated with eptifibatide.

RESULTS

A peak anti-Xa >0.5 IU/ml was obtained in 97.5% of the population, and 94.6% of patients had their peak anti-Xa level in the predefined target range of 0.5 to 1.5 IU/ml. Advanced age, renal failure, being overweight, and eptifibatide use did not alter the anticoagulation profile. At one-month follow-up, six patients (2.5%) had died, had a myocardial infarction, or undergone an urgent revascularization; all the patients had an anti-Xa level >0.5 IU/ml during PCI. Patients without an ischemic event and without a creatine kinase rise, but with a detectable troponin release in the next 24 h of PCI (>2 microg/ml, n = 21), had similar anti-Xa levels as those without troponin elevation. There were one major and three minor bleeding events that were not associated with anti-Xa overshoot.

CONCLUSIONS

Low-dose (0.5 mg/kg) IV enoxaparin allows a prespecified target level of anticoagulation (anti-Xa >0.5 IU/ml) in the vast majority of patients undergoing PCI, appears to be safe and effective, allows immediate sheath removal when used alone, and does not require dose adjustment when used with eptifibatide.

Unfractionated versus fractionated heparin for percutaneous coronary intervention

Since the advent of percutaneous coronary intervention (PCI), intravenous unfractionated heparin has been the primary antithrombotic therapy to prevent periprocedural ischemic complications. As compared with unfractionated heparin, low molecular weight heparins (LMWHs) have a greater bioavailability and a more predictable therapeutic response. In several recent studies of patients undergoing PCI, LMWHs have been shown to be as safe and effective as unfractionated heparin; given their better pharmacokinetic profile and the lack of need for coagulation monitoring, they have the potential to replace unfractionated heparin during coronary interventions. This article reviews the current status of anticoagulation therapy with unfractionated heparin and LMWHs in the cardiac catheterization laboratory.

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.

Percutaneous coronary intervention after subcutaneous enoxaparin pretreatment in patients with unstable angina pectoris

BACKGROUND

Subcutaneous low-molecular-weight (LMW) heparins can effectively replace unfractionated heparin in patients with unstable angina or non-Q-wave myocardial infarction. However, the optimal anticoagulation strategy for these patients when they require cardiac catheterization is still unclear. Therefore, we evaluated a new and simple strategy of anticoagulation in these patients.

METHODS AND RESULTS

A total of 451 consecutive patients with unstable angina/non-Q-wave myocardial infarction were treated for at least 48 hours with subcutaneous injections of enoxaparin (1 mg [100 IU]/kg every 12 hours, cycled at 6 AM and 6 PM). Of this unselected population, 293 patients (65%) underwent a coronary angiography within 8 hours of the morning LMW heparin injection, followed by immediate percutaneous coronary intervention (PCI) in 132 patients (28%). PCI was performed without any additional bolus of unfractionated/LMW heparin and without coagulation monitoring. Anti-Xa activity at the time of catheterization was 0.98+/-0.03 IU/mL, was >0.5 IU/mL in 97.6% of patients, and did not relate to the LMW heparin injection-to-catheterization time. There were no in-hospital abrupt closures or urgent revascularizations after PCI. The death/myocardial infarction rate at 30 days was 3.0% in the PCI group (n=132) but 6.2% in the whole population (n=451) and 10.8% in the patients not undergoing catheterization (n=158). The 30-day major bleeding rate was 0.8% in the PCI group, which was comparable to that of patients without catheterization (1.3%).

CONCLUSIONS

PCI within 8 hours of the last enoxaparin subcutaneous injection seems to be safe and effective. The safety of subcutaneous LMW heparin in combination with platelet glycoprotein IIb/IIIa blockade awaits further study.

The role of low-molecular-weight heparins in arterial diseases: optimizing antithrombotic therapy

On the basis of current evidence, all patients with acute coronary syndromes should receive optimized medical therapy, whether or not they ultimately undergo an invasive revascularization procedure, to improve both clinical outcomes and cost effectiveness. While standard aspirin and unfractionated heparin (UFH) have improved short-term outcomes, they do not eliminate the risk of recurrent ischemic episodes. The recent introduction of platelet fibrinogen receptor antagonists and low-molecular-weight heparins (LMWHs) has offered an opportunity to develop more aggressive antithrombotic regimens. The LMWHs have been thoroughly evaluated in unstable angina and non-Q wave myocardial infarction (UA/NQMI), and have demonstrated improved efficacy compared to standard UFH, without an increase in major complications caused by bleeding. Experience has also been gathered using LMWHs in other arterial diseases (such as pregnant patients with prosthetic heart valves) and as an adjunctive therapy with thrombolytics for acute myocardial infarction. Lastly, studies are currently underway evaluating LMWHs in patients with atrial fibrillation.

Low-molecular-weight heparin in patients with non-ST-segment elevation acute coronary syndrome: role in the emergency department

Intravenous unfractionated heparin (UFH) has been shown to be an effective therapy in reducing the risk of death or myocardial infarction in patients with unstable angina. Low molecular weight heparins demonstrate improved pharmacologic and pharmacokinetic properties relative to standard heparin, and these advantages have been translated into similar or even greater clinical efficacy in several large-scale clinical trials evaluating their use. The simple mode of administration and lack of dependency on anticoagulation monitoring make low-molecular-weight heparins an extremely attractive option in the treatment of patients with acute ischemic coronary syndromes presenting without persistent ST-segment elevation.