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

Anticoagulant Therapy for Acute Coronary Syndromes

Anticoagulation in conjunction with antiplatelet therapy is central to the management of acute coronary syndromes (ACS). When used effectively it is associated with a reduction in recurrent ischaemic events including myocardial infarction and stent thrombosis as well as a reduction in death. Effective ischaemic risk reduction whilst balancing bleeding risk remains a clinical challenge. This article reviews the current available evidence for anticoagulation in ACS and recommendations from the European Society of Cardiology.

Parenteral anticoagulants in heart disease: Current status and perspectives (Section II)

Anticoagulants are a mainstay of cardiovascular therapy, and parenteral anticoagulants have widespread use in cardiology, especially in acute situations. Parenteral anticoagulants include unfractionated heparin, low-molecular-weight heparins, the synthetic pentasaccharides fondaparinux, idraparinux and idrabiotaparinux, and parenteral direct thrombin inhibitors. The several shortcomings of unfractionated heparin and of low-molecular-weight heparins have prompted the development of the other newer agents. Here we review the mechanisms of action, pharmacological properties and side effects of parenteral anticoagulants used in the management of coronary heart disease treated with or without percutaneous coronary interventions, cardioversion for atrial fibrillation, and prosthetic heart valves and valve repair. Using an evidence-based approach, we describe the results of completed clinical trials, highlight ongoing research with currently available agents, and recommend therapeutic options for specific heart diseases.

High-dose Intravenous Dalteparin Can be Monitored Effectively Using Standard Coagulation Times

The objective of this study was to examine the pharmacokinetics of intravenous dalteparin (Fragmin, Pharmacia-Upjohn, Peapack, NJ) and to assess the accuracy of standard coagulation-based monitoring techniques as an estimate of drug concentration with which to guide dosing. Knowledge of the kinetic behavior of low-molecular-weight heparins (LMWHs) and the possible utility of coagulation times for monitoring may aid in the development of safe and effective dosing algorithms for percutaneous coronary interventions. Twenty normal volunteers were treated at 2-week intervals with each of three intravenous dalteparin doses. Measurement of anti-IIa, anti-Xa, activated partial thromboplastin time (aPTT), activated clotting time (ACT), and low-range ACT was performed at baseline and at seven additional time points over 8 hours. The half-life of intravenous dalteparin is 77 minutes with slight dose-related variation. The aPTT, LR-ACT, and standard ACT are prolonged after dalteparin administration with the increase closely correlated to anti-Xa activity (aPTT, r = 0.85; LR-ACT, r = 0.79). Classification of anticoagulation intensity range using aPTT or LR-ACT in comparison to anti-Xa activity (0.5-0.99, 1.0-1.49, 1.5-2, >2) displays a level of agreement (kappa: aPTT = 0.69, LR-ACT = 0.59) that is comparable to values reported for coagulation time guidance of unfractionated heparin administration. Standard coagulation times are sensitive to the anticoagulant effect of dalteparin with a degree of correlation that suggests their utility for estimating drug concentration during high dose therapy. Trials establishing a relationship between monitoring and clinical efficacy, and the risk/reward of different treatment ranges alone or in combination with GPIIb/IIIa inhibitors and clopidogrel, are necessary.

Anticoagulation in Pregnant Women With Prosthetic Heart Valves

Background: Pregnancy is associated with an increased risk of thrombosis in women with mechanical prosthetic heart valves. Effective anticoagulation is therefore critical in such patients but remains problematic, since oral anticoagulation and both unfractionated and low-molecular-weight heparin may be associated with important fetal and maternal side effects.

Purpose: To review information related to the use of anticoagulation with both warfarin and heparin and reassess the safety and efficacy of these therapies in pregnant women with mechanical prosthetic heart valves.

Data source and selection: A MEDLINE search from 1966 to October 2003 for English and non-English language articles that reported the use of anticoagulation in pregnancy was conducted. Articles were included if they reported use of anticoagulation in pregnancy with emphasis on those that included women with mechanical prosthetic heart valves.

Conclusions: Anticoagulation prophylaxis with both warfarin and heparin (unfractionated heparin and low-molecular-weight heparin) may be associated with important fetal and maternal side effects. Optional regimens for the treatment of low-risk and high-risk patients are proposed to minimize potential complications.

Clinical application of enoxaparin

Low-molecular-weight heparins have several important advantages over unfractionated heparin (UFH). Due to a longer plasma half life together with high bioavailability and a linear dose-response relationship, the drugs can be safely and effectively administered in the hospital or ambulatory settings without the need to monitor the anticoagulant effect. Enoxaparin (Lovenox), Aventis Pharma) is a low-molecular-weight heparin which has been studied in a variety of clinical situations. In general surgery the efficacy of enoxaparin to prevent venous thromboembolism is similar to UFH but the tolerability is better. In patients undergoing cancer, orthopedic or vascular surgery the efficacy of enoxaparin is significantly higher with similar rates of bleeding complications. The database for enoxaparin in nonsurgical patients is smaller compared with surgical groups. There is evidence that the efficacy of enoxaparin may be superior to UFH in patients with severe cardiac disease. Efficacy and safety of UFH and enoxaparin are similar for the treatment of deep vein thrombosis. However, enoxaparin can be safely administered by the patients at home which is not possible with UFH. In patients with acute coronary syndromes, enoxaparin has been shown to reduce the rate of deaths and serious cardiac events in comparison with UFH. Furthermore, exonaparin treatment has been shown to be cost-effective, and therefore is the therapy of choice in this setting. In addition, enoxaparin has been shown to be a safe and effective alternative to the combination of UFH and phenprocoumone therapy in patients undergoing electrical cardioversion for atrial fibrillation.

Enoxaparin in acute coronary syndromes

Enoxaparin is a low-molecular-weight heparin (LMWH) derivative that exerts its anticoagulant activity through antithrombin III, an endogenous inhibitor of factor Xa and thrombin IIa. Unlike its unfractionated heparin (UFH) counterparts, enoxaparin has a greater bioavailability, lower incidence of heparin-induced thrombocytopenia and more stable and predictable anticoagulation, allowing fixed dosing without the need for monitoring. These advantages make it an attractive anticoagulant to be used in acute coronary syndrome management. Indeed, several clinical trials and meta-analyses have consistently demonstrated the efficacy of enoxaparin in reducing cardiovascular events and mortality in this population. Although initial clinical trials with enoxaparin during the early conservative approach suggested superior efficacy without differences in safety compared with UFH, emerging data in the current era of early revascularization approach indicate that superior effects of enoxaparin over heparin in reducing clinical events should be balanced against an increase in major hemorrhagic complications. Enoxaparin is a rational alternative to UFH in patients presenting with either unstable angina/non-ST-elevation myocardial infarction or ST-elevation myocardial infarction, with a clinically modest increase in bleeding complications.

Monitoring and Reversal of Anticoagulation and Antiplatelets

Since percutaneous transluminal coronary angioplasty was first described and the breakthrough studies of the role of stents were reported, the evolution in anticoagulation and antiplatelet therapy used during percutaneous coronary intervention (PCI) has reduced periprocedural ischemic events and stent thrombosis. Although greater combinations and doses of anticoagulation with antiplatelets seem to provide the best protection against thrombogenic and embolic events, there is a significant trade-off with a higher risk of major and minor bleeding episodes. This review article expands on each of the commonly used antiplatelet and anticoagulants used at time of PCI, focusing on drug monitoring and reversal.

Risk of bleeding after prehospital administration of high dose tirofiban for ST elevation myocardial infarction

BACKGROUND

In most patients with ST-elevation myocardial infarction (STEMI), antiplatelet drugs are already administrated in the ambulance, before hospital admission. We investigated the safety of prehospital initiation of a high dose of the glycoprotein IIb/IIIa inhibitor tirofiban on top of aspirin, clopidogrel and heparin.

METHODS

It concerns a sub-analysis of the On-TIME 2 trial. 1398 patients were enrolled and 1275 patients (91.2%) had clinical follow up. Non CABG-related bleeding was defined according to the TIMI criteria. Logistic regression was used to determine predictors of 30-day bleeding. The independent association between bleeding and mortality (30-day and 1-year) was evaluated using Cox proportional Hazard models.

RESULTS

Bleeding (major or minor) was observed in 47 patients (3.7%), with only 13 patients (1%) with major bleeding. The strongest independent determinants of bleeding were age (OR 1.05, 95% CI 1.01-1.08, p=0.011), Killip class >1 at admission (OR 2.5, 95% CI 1.2-5.3, p=0.020) and intra aortic balloon pump (IABP) use (OR 4.2, 95% CI 1.6-11.1, p=0.003). High dose tirofiban was not an independent predictor of bleeding (OR 1.7, 95% CI 0.9-3.2, p=0.116). Bleeding was associated with an increased risk of 30-day mortality (HR 5.5, 95% CI 1.6-7.8, p<0.001) and one-year mortality (HR 3.2, 95% CI 1.4-7.2, p=0.005).

CONCLUSION

Prehospital use of high dose tirofiban is safe and associated with a low risk of bleeding. Age, Killip class >1, IABP use, but not high dose tirofiban are independent determinants of bleeding in STEMI patients. Bleeding is independently associated with 30-day and 1-year mortality.

Anticoagulation in the management of non-ST-segment elevation acute coronary syndrome

There are currently over 1 million patients admitted to hospitals in the United States with the diagnosis of non-ST-segment elevation acute coronary syndrome (NSTE ACS). Due to the significant morbidity and mortality associated with NSTE ACS, appropriate use of the numerous medications employed is critical in ensuring optimal outcomes. Because atherosclerotic plaque rupture and thrombus formation are the central pathophysiologic process in patients with NSTE ACS, it is important to utilize effective and safe combinations of antiplatelet and anticoagulant drug therapy. There are a number of different anticoagulant agents available for use in patients with NSTE ACS, but it is essential to have an in-depth knowledge of the setting in which these agents have been investigated, what current consensus guidelines recommend, as well as an appreciation for the treatment approach and philosophy of the institution for management of patients with NSTE ACS. In this review manuscript, the reader will find an evaluation of the current guidelines concerning the use of anticoagulant therapy in patients with NSTE ACS, as well as a detailed examination of the literature with critical analysis on issues that should be considered when deciding on the appropriate implementation of anticoagulant therapy in protocols for NSTE ACS patients.

Intravenous enoxaparin versus unfractionated heparin in unselected patients undergoing percutaneous coronary interventions: the Zurich enoxaparin versus unfractionated heparin in PCI study (ZEUS)

AIMS

To evaluate the efficacy and safety of intravenous enoxaparin as an alternative to unfractionated heparin (UFH) as antithrombotic therapy in unselected patients undergoing percutaneous coronary intervention (PCI).

METHODS AND RESULTS

Eight hundred and seventy-six (876) consecutive eligible patients undergoing PCI were prospectively randomised to either intravenous enoxaparin 0.75 mg/kg or dose-adjusted UFH in this open-label study that was prematurely stopped due to slow recruitment. Randomisation was stratified on elective PCI or PCI for acute coronary syndrome (ACS). The primary endpoint was a combination of death, myocardial infarction, unplanned target vessel revascularisation and major bleeding at 30 days. Secondary endpoint was a composite of major and minor bleeding and thrombocytopenia < 50x109. The primary endpoint of intravenous enoxaparin did not differ from those of UFH (5.5% vs. 7.0%, p=ns) whereas safety endpoints were reduced with enoxaparin compared to UFH (9.9% vs. 20.0%, p<0.001). Among 229 (26%) patients presenting with ACS, the incidence of both, the primary and secondary endpoints, was lower with enoxaparin as compared to UFH (1.8% vs. 12.9% and 14.2% vs. 31%, p<0.001 and p=0.003, respectively).

CONCLUSIONS

Due to the premature halting of the study and the low event rate, these data are observational only, and no definite conclusion could be made concerning efficacy and safety of intravenous enoxaparin as an alternative to UFH in unselected patients undergoing PCI.

A randomized, partially blinded, multicenter, active-controlled, dose-ranging study assessing the safety, efficacy, and pharmacodynamics of the REG1 anticoagulation system in patients with acute coronary syndromes: design and rationale of the RADAR Phase IIb trial

Anticoagulants are the cornerstone of current acute coronary syndrome (ACS) therapy; however, anticoagulation regimens that aggressively reduce ischemic events are almost uniformly associated with more bleeding. REG1, an anticoagulation system, consists of RB006 (pegnivacogin), an RNA oligonucleotide factor IXa inhibitor, and RB007 (anivamersen), its complementary controlling agent. Phase I and IIa studies defined predictable relationships between doses of RB006, RB007, and degree of antifactor IX activity. The efficacy and safety of REG1 for the treatment of patients with ACS managed invasively and the safety of reversing RB006 with RB007 after cardiac catheterization are unknown. Randomized, partially-blinded, multicenter, active-controlled, dose-ranging study assessing the safety, efficacy, and pharmacodynamics of the REG1 anticoagulation system compared to unfractionated heparin or low molecular heparin in subjects with acute coronary syndrome (RADAR) is designed to assess both the efficacy of the anticoagulant RB006 and the safety of a range of levels of RB006 reversal with RB007. The objectives of RADAR are (1) to determine the safety of a range of levels of RB006 reversal with RB007 after catheterization, (2) to confirm whether a dose of 1 mg/kg RB006 results in near-complete inhibition of factor IXa in patients with ACS, and (3) to assess the efficacy of RB006 as an anticoagulant in patients with ACS undergoing percutaneous coronary intervention.

Enoxaparin 0.3 mg/kg IV supplement for patients transitioning to PCI after subcutaneous enoxaparin therapy for NSTE ACS: a subgroup analysis from the SYNERGY trial

OBJECTIVE

To explore clinical and bleeding outcomes in patients enrolled in the SYNERGY trial who had percutaneous coronary intervention (PCI) based on adherence to the dosing regimens of enoxaparin mandated by the protocol.

BACKGROUND

In SYNERGY, 4,687 patients underwent PCI during index hospitalization. Patients in the subcutaneous (sc) enoxaparin group were to be given an 0.3 mg/kg IV bolus immediately before PCI if balloon inflation occurred > or = 8 hr after their last sc dose of enoxaparin.

METHODS

The incidence of the 1 degrees efficacy end point (death/myocardial infarction [MI] post PCI and through 30 days), and the rates of post-PCI in-hospital TIMI major and GUSTO severe bleeding were compared between patients randomized to unfractionated heparin (UFH) and those randomized to sc enoxaparin who did or did not receive a supplemental IV bolus of enoxaparin in accord with protocol-mandates.

RESULTS

A total of 4,687 patients had PCI; 2,323 were assigned sc enoxaparin and 1,332 received protocol-mandated IV enoxaparin bolus, while 215 enoxaparin patients received inappropriate IV therapy (either receiving IV enoxaparin before the 8-hr protocol time or not receiving the IV enoxaparin as directed after 8 hr). Death or MI occurring post PCI through 30-day follow-up tended to be lower in the enoxaparin patients who were treated according to protocol than in those who were not (12.3% vs. 14.4%; adjusted P = 0.25), as was TIMI major bleeding (3.0% vs. 4.7%, adjusted P = 0.08).

CONCLUSION

These exploratory analyses show that patients in SYNERGY who received the protocol-mandated supplemental IV bolus of 0.3 mg/kg enoxaparin before PCI performed 8-12 hr after their last sc enoxaparin dose tended to have improved outcomes compared with those who did not. Strategies to ensure adherence to dosing guidelines of enoxaparin during PCI should be considered.

Day 1 care in patients with non-ST-segment elevation myocardial infarction

In 2007, the American College of Cardiology/American Heart Association and the European Society of Cardiology updated their guidelines for the management of patients with non-ST-segment elevation myocardial infarction (NSTEMI). Based on evidence from recent clinical studies, both 2007 guidelines recommend early risk stratification, administration of appropriate pharmacologic therapy, and selective use of percutaneous coronary intervention in order to reduce morbidity and mortality in these patients. In this article, we focus on management of patients with NSTEMI during the first 24 h of presentation and present a clinical scenario to illustrate the current guidelines-based management strategy.

Selecting the optimal antithrombotic regimen for patients with acute coronary syndromes undergoing percutaneous coronary intervention

The wide variety of anticoagulant and antiplatelet agents available for clinical use has made choosing the optimal antithrombotic regimen for patients with acute coronary syndromes undergoing percutaneous coronary intervention a complex task. While there is no single best regimen, from a risk-benefit ratio standpoint, particular regimens may be considered optimal for different patients. We review the mechanisms of action for the commonly prescribed antithrombotic medications, summarize pertinent data from randomized trials on their use in acute coronary syndromes, and provide an algorithm (incorporating data from these trials as well as risk assessment instruments) that will help guide the decision-making process.

Adding intravenous unfractionated heparin to standard enoxaparin causes excessive anticoagulation not detected by activated clotting time: results of the STACK-on to ENOXaparin (STACKENOX) study

BACKGROUND

The STACKENOX study assessed the cumulative anticoagulation effect of administering stack-on intravenous unfractionated heparin (UFH) to subjects already receiving enoxaparin.

METHODS

Seventy-two healthy subjects aged 40 to 60 years received subcutaneous enoxaparin (1 mg/kg every 12 hours) for 2.5 days (steady state) and were randomized to receive a 70 IU/kg intravenous UFH bolus 4, 6, or 10 hours after the final enoxaparin dose. Anticoagulation levels were assessed in subjects receiving enoxaparin alone and after the UFH bolus by monitoring activated clotting time (ACT), anti-Xa and anti-IIa activities, and thrombin generation (endogenous thrombin potential [ETP]).

RESULTS

After the final enoxaparin dose, ETP levels decreased by 40%; anti-Xa and anti-IIa activities increased, as expected; and ACT levels did not indicate any anticoagulation effect. Stack-on UFH at 4, 6, or 10 hours after the last enoxaparin dose significantly increased anti-Xa and anti-IIa activities (P < .0001) to well above accepted therapeutic levels and resulted in total inhibition of thrombin generation for > or =2 hours; ACT levels remained within the range commonly observed in subjects receiving UFH.

CONCLUSIONS

The administration of stack-on UFH to subjects already receiving recommended enoxaparin dosing may result in over-anticoagulation, and should be avoided. Activated clotting time assessment did not detect the over-anticoagulation resulting from co-administration of enoxaparin and UFH.

Switch from abciximab to eptifibatide during percutaneous coronary intervention

BACKGROUND

Treatment with glycoprotein (GP) IIb/IIIa inhibitors during percutaneous coronary intervention (PCI) reduce ischemic complications and improve outcome. Of the GPIIb/IIIa inhibitors abciximab is better documented than eptifibatide, but the former is more expensive. The aim of this study was to monitor a switch from abciximab to eptifibatide with respect to clinical outcome up to six months after PCI.

METHODS

All consecutive patients that six months before and six months after a switch from abciximab to eptifibatide received GPIIb/IIIa inhibitors during and after de novo PCIs were followed for six months with respect to clinical outcome.

RESULTS

310 patients received abciximab and 350 eptifibatide. Baseline characteristics were similar in the two groups. 55% of the patients underwent PCI for acute ST-elevation myocardial infarction and 41% for unstable coronary artery disease. There were trends for lower mortality among abciximab-treated than among the eptifibatide-treated patients during in-hospital stay (0.6% vs 2.0%:NS) as well as during the six month follow up (2.3% vs 3.7%:NS). The combined endpoint of death, myocardial infarction, stroke, repeated revascularisation and serious bleeding occurred in 14.9% in the abciximab group vs 16.8% in the eptifibatide group (NS).

CONCLUSION

The study could not demonstrate any significant deterioration of clinical results after a switch from abciximab to eptifibatide as routine GPIIb/IIIa inhibition during PCI. With respect to the limited number of patients a clinical significant difference between the two GPIIb/IIIa inhibitors cannot, however, be excluded.

Enoxaparin in patients with primary percutaneous coronary intervention for acute ST segment elevation myocardial infarction

The inhibition of thrombin plays a key role as adjunct therapy in the management of patients with primary percutaneous coronary intervention for ST elevation myocardial infarction. Enoxaparin provides a more predictable and constant level of anticoagulation compared with the current standard unfractionated heparin. The available data from smaller studies and prospective registries suggest that enoxaparin is associated with a reduction in the rate of death and nonfatal reinfarction after primary percutaneous coronary intervention without an increase in bleeding complications. Thus, a large randomized trial is warranted to further evaluate the role of enoxaparin in these patients.

Anticoagulants in coronary artery disease

Anticoagulant therapy for acute coronary syndromes is becoming more complex as newer agents are added to unfractionated heparin and warfarin. The anticoagulants used in current clinical practice are low molecular weight heparins, direct thrombin inhibitors, and heparinoids. Properties of and recent clinical trial data regarding these newer anticoagulants are reviewed in reference to current American College of Cardiology/American Heart Association guidelines.

Low-molecular-weight heparins : mechanisms, trials, and role in contemporary interventional medicine

The clinical spectrum of acute coronary syndromes (ACS) encompasses unstable angina, non-ST-elevation, and ST-elevation myocardial infarction (STEMI). Within an atherosclerotic plaque, disruption of the endothelium can lead to exposure of tissue factor, with platelet adhesion, activation and aggregation, along with activation of the coagulation cascade, culminating in thrombin formation and the development of a cross-linked fibrin clot at the site of injury. Therapy aimed at blocking thrombin formation is now an integral part of the current cardiovascular guidelines in the treatment of ACS. Although unfractionated heparin (UFH) has been the mainstay of antithrombin therapy in the past, it has numerous clinical and biochemical limitations, including substantial protein binding (leading to inconsistent bioavailability), a need for frequent monitoring and adjustment, unreliable and variable degrees of anticoagulation, significant platelet activation, risk of heparin-induced thrombocytopenia, and the inability to block clot bound thrombin. With all of these limitations of UFH, low-molecular-weight heparins (LMWHs) have emerged as attractive alternatives. This review discusses the mechanism of action of LMWHs, and summarizes available literature concerning the use of LMWHs in a variety of clinical settings. Included in this review is an analysis of both current and prior data showing LMWH is as effective as UFH in the conservative and invasive management of patients with ACS. As well, very recent data are evaluated showing the safety and efficacy of LMWHs used in patients transitioning to the cardiac catheterization laboratory, and in those patients undergoing elective or urgent percutaneous coronary intervention (PCI). We also appraise the literature, along with the very recent studies investigating the use of LMWHs as adjunctive therapy to fibrinolytics in patients with STEMI. Finally, we set forth real-world conclusions concerning the use of LMWHs in contemporary interventional practice, including elective PCI and the treatment of ischemic coronary artery disease in the context of rapid invasive management of ACS.

AFFECT: a prospective, open-label, multicenter trial to evaluate the feasibility and safety of a short-term treatment with subcutaneous certoparin in patients with persistent non-valvular atrial fibrillation

BACKGROUND

Patients with persistent atrial fibrillation (AF) scheduled for electrical cardioversion need immediate anticoagulation. Unfractionated heparin (UFH) is often used for early anticoagulation in these patients before oral anticoagulation becomes effective. However, dose adjustment is required to achieve a two- to three-fold prolongation of the activated partial thromboplastin. Low molecular weight heparins, given in body weight-adjusted or independent fixed dosage, require less laboratory monitoring and are also effective within hours of first dosing. They seem to be an attractive alternative to UFH. Previous evidence has shown that these drugs are safe and effective in this indication.

PATIENTS AND METHODS

In this prospective, open-label, multicenter pilot study, 203 patients were enrolled with persistent non-valvular AF scheduled for electrical cardioversion. Patients received a fixed dose of 8000 U anti-Xa certoparin twice daily starting immediately after enrolment and before cardioversion was performed. Patients with AF > 48 h underwent transoesophageal echocardiography (TEE) before cardioversion to exclude intra-atrial thrombi. After cardioversion, overlapping oral anticoagulation was started. Treatment with certoparin was stopped only after two consecutive days with INR values >2.

OBJECTIVES

The objective was to document the feasibility and safety of a short-term treatment with a fixed, body weight-independent certoparin regimen (2 x 8000 U anti-Xa).

RESULTS

Out of 203 patients enrolled, 200 received at least one dose of certoparin and were included in the analysis (safety population). Median treatment duration with certoparin was 7 days. Bleedings were observed in 8 patients (4.0%) and were classified as major (1.5%) or minor (2.5%). Cerebral ischemia was reported for 1 patient (0.5%). One patient showed mild thrombocytopenia (0.5%). There were no reports of venous thromboembolism or death during the treatment period.

CONCLUSION

Certoparin administered at 8000 U anti-Xa twice daily independent of body weight was safe and appeared to be effective in patients with non-valvular AF undergoing electrical cardioversion. Its ease of use and the possibility of treatment on an outpatient basis make it an attractive option for early anticoagulation in AF.

Non?ST segment elevation acute coronary syndromes: Treatment guidelines for the nurse practitioner

PURPOSE

To increase awareness among nurse practitioners (NPs) of the American College of Cardiology (ACC)/American Heart Association (AHA) 2002 guideline update for the diagnosis and treatment of acute coronary syndrome, and for secondary prevention in patients with unstable angina (UA) and non-ST segment elevation myocardial infarction (NSTEMI).

DATA SOURCES

ACC/AHA 2002 guideline update for the management of patients with UA and NSTEMI, ACC/AHA guidelines for patients with coronary and other atherosclerotic vascular disease, 2006 update, selected research and clinical articles.

CONCLUSIONS

Recent research has shown that patients with UA/NSTEMI benefit from the routine, long-term use of dual antiplatelet therapy with aspirin and clopidogrel. In suitable patients, outcome is also improved by adoption of an early invasive strategy combined with aggressive medical therapy.

IMPLICATIONS FOR PRACTICE

Familiarity with the patient as well as current management recommendations can improve clinical outcomes for patients with UA/NSTEMI. Thus, NPs can play a pivotal role in the management of coronary disease, both during and following an acute ischemic event.

Pharmacological antithrombotic adjuncts to percutaneous coronary intervention

Stent thrombosis is the major cause of early adverse events during percutaneous coronary intervention. Its incidence has fallen considerably in recent years, principally due to the introduction of effective antithrombotic therapies. The selection of an appropriate antithrombotic regimen is critical in achieving a balance between reducing ischaemic events and minimising bleeding complications in patients undergoing percutaneous coronary intervention. In this article, evidence for the role of antiplatelet and anticoagulant therapies is discussed, including the thienopyridines, glycoprotein IIb/IIIa receptor antagonists, direct thrombin inhibitors and pentasaccharides.

Development of a dosage strategy in patients receiving enoxaparin by continuous intravenous infusion using modelling and simulation

AIM

To develop an appropriate dosing strategy for continuous intravenous infusions (CII) of enoxaparin by minimizing the percentage of steady-state anti-Xa concentration (C(ss)) outside the therapeutic range of 0.5-1.2 IU ml(-1).

METHODS

A nonlinear mixed effects model was developed with NONMEM for 48 adult patients who received CII of enoxaparin with infusion durations that ranged from 8 to 894 h at rates between 100 and 1600 IU h(-1). Three hundred and sixty-three anti-Xa concentration measurements were available from patients who received CII. These were combined with 309 anti-Xa concentrations from 35 patients who received subcutaneous enoxaparin. The effects of age, body size, height, sex, creatinine clearance (CrCL) and patient location [intensive care unit (ICU) or general medical unit] on pharmacokinetic (PK) parameters were evaluated. Monte Carlo simulations were used to (i) evaluate covariate effects on C(ss) and (ii) compare the impact of different infusion rates on predicted C(ss). The best dose was selected based on the highest probability that the C(ss) achieved would lie within the therapeutic range.

RESULTS

A two-compartment linear model with additive and proportional residual error for general medical unit patients and only a proportional error for patients in ICU provided the best description of the data. Both CrCL and weight were found to affect significantly clearance and volume of distribution of the central compartment, respectively. Simulations suggested that the best doses for patients in the ICU setting were 50 IU kg(-1) per 12 h (4.2 IU kg(-1) h(-1)) if CrCL < 30 ml min(-1); 60 IU kg(-1) per 12 h (5.0 IU kg(-1) h(-1)) if CrCL was 30-50 ml min(-1); and 70 IU kg(-1) per 12 h (5.8 IU kg(-1) h(-1)) if CrCL > 50 ml min(-1). The best doses for patients in the general medical unit were 60 IU kg(-1) per 12 h (5.0 IU kg(-1) h(-1)) if CrCL < 30 ml min(-1); 70 IU kg(-1) per 12 h (5.8 IU kg(-1) h(-1)) if CrCL was 30-50 ml min(-1); and 100 IU kg(-1) per 12 h (8.3 IU kg(-1) h(-1)) if CrCL > 50 ml min(-1). These best doses were selected based on providing the lowest equal probability of either being above or below the therapeutic range and the highest probability that the C(ss) achieved would lie within the therapeutic range.

CONCLUSIONS

The dose of enoxaparin should be individualized to the patients' renal function and weight. There is some evidence to support slightly lower doses of CII enoxaparin in patients in the ICU setting.