Antithrombotic therapy in patients undergoing coronary angioplasty

Unfractionated heparin during elective PCI: fixed dose or weight adjusted?

INTRODUCTION

To assess two different dosing strategies of unfractionated heparin (UFH) during elective percutaneous coronary intervention (PCI).

AIMS

The optimal dose of heparin during elective PCI in patients with stable angina is unknown. Existing guidelines are based on limited data. We interrogated data from the PCI database. Patients with stable angina undergoing planned transradial PCI for uncomplicated single lesions were included. The main endpoint was troponin I release. We compared a fixed heparin dose (3000 U) UFH to a weight-adjusted dose.

RESULTS

Of 698 patients 244 (35.0%) received fixed dose (3000 U) and 454 (65.0%) 70 U/kg weight-adjusted UFH. There was no significant difference in median troponin between the fixed dose and the weight-adjusted groups; 0.17 ng/mL versus 0.14; P= 0.21. The proportion of troponin positive patients was similar in both groups (61.9% in the fixed dose group vs. 58.1%; P= 0.37). There were no deaths or major ischemic events during hospitalization. There was no bleeding requiring transfusion or delaying hospital discharge.

CONCLUSION

In conclusion, this retrospective observational study of elective transradial PCI demonstrated that a reduced, fixed dose of periprocedural heparin was associated with similar postprocedural troponin levels when compared to a standard weight-adjusted regime. Our study further questions the optimal dose of heparin required during elective PCI and suggests a need for further trials.

Bivalirudin versus heparin during coronary angioplasty for unstable or postinfarction angina: Final report reanalysis of the Bivalirudin Angioplasty Study

BACKGROUND

This study was a reanalysis of the Bivalirudin Angioplasty Study, which compared bivalirudin with high-dose heparin during coronary angioplasty for unstable angina.

METHODS

Differences in rates of death, myocardial infarction, or repeat revascularization were compared at 7, 90, and 180 days after angioplasty with intention-to-treat analysis.

RESULTS

The combined end point occurred in 135 of 2161 patients (6.2%) in the bivalirudin group and in 169 of 2151 patients (7.9%) in the heparin group at 7 days (P =.039). Differences persisted between the groups at 90 days (P =.012) and 180 days (P =.153). Bleeding occurred in 76 patients (3.5%) in the bivalirudin group versus 199 (9.3%) in the heparin group (P <.001).

CONCLUSIONS

This analysis supports the hypothesis that bivalirudin reduces ischemic complications and bleeding after angioplasty. Further trials are needed to evaluate bivalirudin versus heparin in conjunction with platelet-glycoprotein IIb/IIIa inhibitors and for coronary stenting.

Ecarin clotting time is sensitive to heparinoids: comparison of two different techniques

Ecarin clotting time (ECT) is currently developed for the specific monitoring of antithrombin drugs, such as hirudin, argatroban, and hirulog. Aqueous reagent and dry chemistry technology have become available for ECT monitoring of antithrombin agents. Currently, many heparinoids and heparinomimetic drugs are being developed. These agents activate heparin cofactor II (HCII) and primarily mediate their effects by inhibiting thrombin. Although the test is specific for antithrombin agents, heparin cofactor II-mediated thrombin inhibitors are capable of prolonging the ECT. In order to study the relative effects of some of these agents, ECT was measured in human plasma supplemented with Pl-88 (a sulfated pentomanose; Progen Industries Limited, Sydney, Australia), aprosulate, pentosan polysulfate, dermatan sulfate, unfractionated heparin (UFH), and recombinant hirudin (r-hirudin). All agents were supplemented to the citrated-pooled plasma prepared from 10 healthy volunteers at a graded dosage of 0 to 100 microg/ml. These techniques gave comparable results for all of the agents used (PI-88, r2 = 0.99; r-hirudin, r2 = 0.98; UFH, r2 = 0.98; dermatan sulfate, r2 = 0.95; aprosulate, r2 = 0.95; pentosan polysulfate, r2 = 0.94). The relative anticoagulant effects of various agents used on ECT varied widely, exhibiting their potency in the following order: r-hirudin = pentosan polysulfate > dermatan sulfate > PI-88 > aprosulate > UFH. The sensitivity of ECT was adjusted by varying the concentration of the ecarin reagent. The results suggest that HCII-mediated inhibition of thrombin can be detected by using ECT reagents.

Over-the-counter analgesics and antipyretics: a critical assessment

BACKGROUND

It is just 100 years since the introduction of aspirin to medicine. Since then, aspirin and its derivatives have been joined by acetaminophen, and the nonsteroidal anti-inflammatory drugs--ibuprofen, naproxen sodium, and ketoprofen--as the only over-the-counter (OTC) agents approved by the US Food and Drug Administration for the short-term treatment of pain, headache, dysmenorrhea, and fever. Recently the prescription use of aspirin has expanded to include a number of antiplatelet indications.

OBJECTIVE

The purpose of this paper is to review critically the history, mechanisms of action, efficacy, and tolerability of OTC analgesic and antipyretic products. Relatively new and potential future indications for these drugs are also discussed.

CONCLUSION

Although all of the OTC analgesic/antipyretic agents seem to share a common mechanism of prostaglandin inhibition, there are important differences in their pharmacology, efficacy, and side-effect profiles. Considering their often-unsupervised use, the risk-benefit ratio of this class of drugs has been extremely favorable. However, when used inappropriately, even these drugs pose significant risks to certain patient populations.

The heparin management test: a new device for monitoring anticoagulation during coronary intervention

Whole blood coagulation analysers are widely used during percutaneous coronary interventions. The precise degree of anticoagulation in patients is important in this setting. The aim of this investigation was to compare the results obtained with ACT (Hemochron) and HMT, the Heparin Management Test (TAS) in patients undergoing percutaneous coronary interventions. Patients (n = 100) were enrolled prospectively. Each patient received 10,000 units of heparin. At the end of the procedure, the mean ACT was 284+/-31 seconds and the mean HMT was 292+/-33 seconds. The correlation between the two methods was highly significant (r = 0.64, p<0.001). The HMT correlates well with ACT values in patients undergoing percutaneous coronary interventions. Its use in the management of these patients should be considered.

Clinical outcomes of bivalirudin for ischemic heart disease

BACKGROUND

Current treatment strategies for percutaneous coronary revascularization and acute coronary syndromes incorporate thrombin inhibition with either unfractionated or fractionated heparin. The peptide bivalirudin (Hirulog) is a direct thrombin inhibitor whose pharmacological properties differ from those of heparin. We conducted a systematic overview (meta-analysis) to assess the effect of bivalirudin on 4 end points: death, myocardial infarction, major hemorrhage, and the composite of death or infarction.

METHODS AND RESULTS

Six trials (5674 patients) represent the randomized, controlled bivalirudin experience, including 4603 patients undergoing elective percutaneous coronary revascularization and 1071 patients with acute coronary syndromes. ORs for the 4 clinical end points were calculated for each trial. Four trials (4973 patients) that compared bivalirudin with heparin were combined with the use of a random-effects model. In these trials, bivalirudin was associated with a significant reduction in the composite of death or infarction (OR 0.73, 95% CI 0.57 to 0.95; P=0.02) at 30 to 50 days, or 14 fewer events per 1000 patients so treated. There also was a significant reduction in major hemorrhage for the same trials (OR 0.41, 95% CI 0. 32 to 0.52; P<0.001, or 58 fewer events per 1000 patients so treated). A similar analysis combined 2 dose-ranging trials (701 patients) that compared therapeutic (activated partial thromboplastin time more than twice the control time) with subtherapeutic bivalirudin anticoagulation (activated partial thromboplastin time less than twice the control time).

CONCLUSIONS

Bivalirudin is at least as effective as heparin, with clearly superior safety. Thus, it provides an unprecedented net clinical benefit over heparin in patients with ischemic heart disease.

Clinical trials in interventional cardiology

Several well-designed, randomized trials and registries have recently been completed in patients undergoing percutaneous coronary intervention (PCI) for the treatment of symptomatic coronary artery disease. These studies have further clarified the value of newer pharmacologic and mechanical approaches to patients with atherosclerotic disease and have resulted in improved clinical outcomes in patients undergoing PCI. As a result, many of the older paradigms of lesion-specific device selection have been revised to include the intricate balance of devices and drugs, tailored to the specific clinical presentation and lesion morphology in patients undergoing PCI. This article reviews several recent clinical trials and discusses their impact on early and late outcomes in patients undergoing PCI for symptomatic coronary artery disease.

Potent bivalent thrombin inhibitors: replacement of the scissile peptide bond at P(1)-P(1)' with arginyl ketomethylene isosteres

We have designed highly potent synthetic bivalent thrombin inhibitors, which consist of an active site blocking segment, a fibrinogen recognition exosite blocking segment, and a linker connecting these segments. The bivalent inhibitors bind to the active site and the fibrinogen recognition exosite simultaneously. As a result, the inhibitors showed much higher affinity for thrombin than the individual blocking segments. Various arginyl ketomethylene isosteres ArgPsi[CO-CH(2)-X]P(1)' were incorporated into the bivalent inhibitors as P(1)-P(1)' segment to eliminate the scissile bond. The P(1)' residue is a natural or unnatural amino acid; specifically, the incorporation of mercaptoacetic acid exhibited superiority in synthesis and affinity for thrombin. Inhibitor 16, (D-cyclohexylalanine)-Pro-ArgPsi[CO-CH(2)-S]Gly-(Gly)(4)-Asp-Tyr-G lu- Pro-Ile-Pro-Glu-Glu-Tyr-cyclohexylalanine-(D-Glu)-OH, showed the lowest K(i) value of 3.5 +/- 0.5 x 10(-13) M, which is comparable to that (K(i) = 2.3 x 10(-13) M) of recombinant hirudin. Consequently we successfully reduced the size of the inhibitor from approximately 7 kDa of recombinant hirudin to approximately 2 kDa without losing the affinity.

Combined use of Orgaran and Reopro during coronary angioplasty in patients unable to receive heparin

Orgaran, a heparinoid, has been used successfully in patients with heparin-induced thrombocytopenia. We report three cases in which Orgaran was combined with the glycoprotein IIbIIa receptor antagonist Reopro during coronary angioplasty. Orgaran was given as a single intravenous bolus of 1500 anti-factor Xa units. No ischemic or hemorrhagic complications occurred during or following the procedure.

Comparison of activated clotting times to heparin management test for adequacy of heparin anticoagulation in percutaneous transluminal coronary angioplasty

The aim of this study was to compare the activated clotting time (ACT) obtained with the Hemochron device and the Heparin Management Test (HMT) on a new automated whole-blood coagulometer, the Thrombolytic Assessment System, in patients undergoing angioplasty. Fifty patients undergoing balloon angioplasty were prospectively enrolled. The mean ACT after a 10,000 unit bolus of heparin was 283 +/- 39 sec at the end of the procedure. The mean HMT after 10,000 units of heparin was 286 +/- 31 sec at the end of the procedure in the same patients. The correlation between the two methods was significant (r = 0.6; P < 0.01). The HMT appears to correlate well with standard values obtained with the Hemochron ACT monitor in patients undergoing percutaneous transluminal coronary angioplasty.

A randomized comparison of bivalirudin and heparin in patients undergoing coronary angioplasty for postinfarction angina. Hirulog Angioplasty Study Investigators

The outcome of coronary angioplasty performed for unstable angina is determined, in part, by the acuteness and severity of the clinical presentation. The risk of abrupt vessel closure is increased in patients with postinfarction angina. The Hirulog Angioplasty Study compared the efficacy and safety of bivalirudin with weight-adjusted heparin in patients undergoing percutaneous transluminal coronary angioplasty (PTCA) for unstable or postinfarction angina. We report the results of the intent-to-treat analysis using adjudicated data for the prespecified group of 741 patients who underwent angioplasty within 2 weeks of documented myocardial infarction. Patients received either bivalirudin or heparin immediately before angioplasty. The primary efficacy endpoint was procedural failure defined as abrupt vessel closure, death, myocardial infarction, or revascularization during hospitalization. Bivalirudin significantly (p = 0.004) decreased the incidence of procedural failure compared with heparin (5.1% vs 10.8%, odds ratio 0.45; 95% CI 0.25-0.79). The improved efficacy of bivalirudin was replicated for each individual clinical endpoint. The incidence of major bleeding was significantly (p = 0.001) lower in bivalirudin-treated patients compared with heparin-treated patients (2.4% vs 11.8%, respectively). The benefits observed with bivalirudin are of similar magnitude as those reported for platelet glycoprotein (GP) IIb/IIIa inhibitors, such as abciximab. Bivalirudin may be a more effective foundation anticoagulant than heparin in patients undergoing coronary angioplasty for postinfarction angina.

Thrombosis and Hemostasis in Cardiology: Review of Pathophysiology and Clinical Practice (Part II)

The adverse consequences of thrombosis are per haps nowhere more evident than in clinical cardiology. Throm bosis and hemostasis are primary issues in the management of patients with atrial fibrillation, prosthetic heart valves, severe left ventricular dysfunction, and coronary artery disease. Clini cal trials have defined a crucial role for anticoagulation with warfarin in patients with atrial fibrillation to reduce the inci dence of stroke. Anticoagulation with warfarin and aspirin in combination offers significant protection from systemic emboli in patients with mechanical prosthetic valves, without a sub stantial increased risk of hemorrhage. The risk of systemic emboli may also be reduced by anticoagulation in patients with severe left ventricular dysfunction. Disturbance of the normal balance of hemostasis is a major factor in the pathophysiology of coronary artery disease. Antiplatelet therapy, antithrombin agents, anticoagulants, and fibrinolytic agents have been used to prevent and treat acute coronary thrombosis and to prevent reocclusion following thrombolysis and interventional therapy. Guidelines are presented for antithrombotic therapy in the prac tice of clinical cardiology. Key Words: Thrombosis— Cardiology—Coronary artery disease—Atrial fibrillation— Valvular heart disease.

Low-molecular-weight heparins for acute coronary syndromes

OBJECTIVE

To review published literature regarding the use of low-molecular-weight heparins (LMWHs) for the acute coronary syndromes of unstable angina and acute myocardial infarction (MI).

METHODS

A MEDLINE search (January 1986-August 1997) was performed to identify all pertinent articles. Selected references from these articles and abstracts of recent clinical trials were also included.

DISCUSSION

LMWHs have several distinct advantages over standard unfractionated heparin (UFH). These advantages include convenient once- or twice-daily standardized administration without the need for activated partial thromboplastin time monitoring. While the use of LMWHs as prophylaxis and treatment of venous thromboembolism is fairly well-established, the use of LMWHs for treating acute myocardial ischemia is evolving. Published studies and abstracts have shown LMWHs to be as effective as or more effective than UFH in preventing death, myocardial infarction, and recurrent ischemia in patients with unstable angina or acute MI. The comparative incidence of bleeding between LMWHs and UFH is controversial, with some studies reporting lower or similar rates of bleeding with LMWHs, while one study demonstrated a higher bleeding rate than with UFH. The cost-effectiveness of using LMWHs over UFH for acute coronary syndromes also remains to be established.

CONCLUSIONS

LMWHs appear to be as effective as, and potentially more effective than, UFH in preventing complications of acute coronary syndromes. However, further studies are needed to better define the comparative bleeding risks of LMWHs and UFH. This, plus the lack of published peer-reviewed trial results and pharmaco-economic analyses, preclude the recommendation of routinely using LMWHs for treating unstable angina and acute MI at this time.

Thrombosis and Hemostasis in Cardiology: Review of Pathophysiology and Clinical Practice (Part I)

The adverse consequences of thrombosis are per haps nowhere more evident than in clinical cardiology. Throm bosis and hemostasis are primary issues in the management of patients with atrial fibrillation, prosthetic heart valves, severe left ventricular dysfunction, and coronary artery disease. Clini cal trials have defined a crucial role for anticoagulation with warfarin in patients with atrial fibrillation to reduce the inci dence of stroke. Anticoagulation with warfarin and aspirin in combination offers significant protection from systemic emboli in patients with mechanical prosthetic valves, without a sub stantial increased risk of hemorrhage. The risk of systemic emboli may also be reduced by anticoagulation in patients with severe left ventricular dysfunction. Disturbance of the normal balance of hemostasis is a major factor in the pathophysiology of coronary artery disease. Antiplatelet therapy, antithrombin agents, anticoagulants, and fibrinolytic agents have been used to prevent and treat acute coronary thrombosis and to prevent reocclusion following thrombolysis and interventional therapy. Guidelines are presented for antithrombotic therapy in the prac tice of clinical cardiology.

Is lidocaine infiltration during femoral sheath removal really necessary?

OBJECTIVES

To compare the effectiveness of intravenous morphine sulfate to intravenous morphine sulfate plus 1% lidocaine infiltration in pain management associated with femoral sheath removal, and to evaluate pain intensity and associated complications during femoral sheath removal in patients with heart disease receiving interventional treatment.

DESIGN

Descriptive, correlational, case-control study.

SETTING

Mid-metropolitan, university-affiliated, tertiary care medical center.

SAMPLE

Fifty patients with heart disease, who had no known allergies to morphine or lidocaine and who had not had an acute myocardial infarction, admitted to the cardiovascular intervention unit.

MEASURES

Vertical visual analogue scale, short-form McGill Pain Questionnaire, and demographic tool for complications.

RESULTS

No significant differences in pain intensity, sensation, affect, and total scores were found between the analgesic regimens. Six (12%) patients had vasovagal reactions develop, but no statistical differences were found between pain intensity scores and associated complications.

CONCLUSION

Morphine sulfate does appear effective in controlling pain associated with femoral sheath removal. The benefit of lidocaine infiltration during this procedure is questionable.

Controversies in Antithrombotic Therapy in Cardiovascular Diseases

Antithrombotic treatment became an important point in human medical treatment. Dicoumarols, heparin, aspi rin, and more recently, direct antithrombins and platelet glyco protein IIb/IIIa receptor blockers are the most frequent medi cations used as antithrombotics. The role of these drugs in the treatment of cardiovascular diseases remains controversial. Low-dose aspirin (80-100 mg/day) should be used for second ary prevention in patients with a history of coronary disease. Primary prevention in patients with no risk factors is not rec ommended. Studies using oral anticoagulant therapy indicated that long-term therapy achieves substantial benefit in arterial complications in patient survivors of myocardial infarction. Combined therapy of aspirin and a higher dose of oral antico agulant than that used in the CARS trial seem necessary after myocardial infarction, and further studies should be under taken. In the treatment of unstable angina, the combined use of aspirin and unfractioned heparin (UFH) is widely accepted. Low molecular weight heparin (LMWH) was also proposed for the treatment of these patients, but the beneficial effect of LMWH over UFH is a matter of discussion, and more prospec tive studies with different LMWHs should be undertaken be fore reaching a definitive answer. The use of hirudin needs additional studies because its superiority over heparin is un- proved. The initial clinical experience with blockers/inhibitors of platelet glycoprotein IIb/IIIa receptors has been promising, although some increase of bleeding was reported. According to published trials on the use of antiplatelet drugs and antithrom botic therapy in the prevention of acute closure after PTCA or after stent implantation, antithrombotic therapy decreased the incidence of abrupt closure or reocclusion at 30 days postan gioplasty, but neither antiplatelet agents nor other pharmaco logical agents have been shown to reduce significantly the rate of restenosis. Finally, oral anticoagulant in a target INR of 2.0 to 3.0 together with aspirin 100 mg/day provide good protec tion from thromboembolism and diminish the rate of minor bleeding complications in patients with cardiac valve replace ment.

Introduction to coronary artery stents and their pharmacotherapeutic management

OBJECTIVE

To provide an introduction to coronary artery stents and their pharmacologic management, including anticoagulant therapy and newer antiplatelet regimens.

DATA SOURCES

A MEDLINE and current journal search of relevant articles that evaluated coronary stent success rates and anticoagulation or antiplatelet regimens.

STUDY SELECTION

Data from the use of primarily the Palmaz-Schatz stent were included. Studies using vitamin K antagonists that are not commercially available in the US were excluded unless they compared an antiplatelet regimen with anticoagulation using the international normalized ratio (INR).

DATA SYNTHESIS

Limitations with percutaneous transluminal coronary angioplasty (PTCA), such as ischemic complications and restenosis, have led to the advent of intracoronary stenting. However, the placement of a stent within the coronary artery lumen is associated with a risk of thrombotic events. Despite current postprocedural anticoagulation and antiplatelet regimens, thrombosis occurs at rates ranging from 0.6% to 21%. When anticoagulation is deemed appropriate, it should be used for 1-2 months and the INR should be maintained between 2 and 3.5. Anticoagulation appears to have no effect on the development of restenosis, but has been shown to cause significant hemorrhagic events in 5-13.5% of patients. Newer data continue to define the subsets of patients who may be managed with antiplatelet agents alone. Combinations of aspirin and ticlopidine or aspirin alone may be used to manage patients who fulfill the following criteria: optimal stent placement, high-pressure inflation, and adequate coronary size.

CONCLUSIONS

Coronary artery stenting is a novel approach for the management of coronary artery disease, but is associated with the complication of stent thrombosis. Anticoagulation reduces the risk of stent thrombosis, but is associated with bleeding risk. Selected patients may be successfully managed with antiplatelet agents only. More data are needed to better define the optimal antithrombotic regimen.

Thrombosis, antithrombotic agents, and the antithrombotic approach in cardiac disease

To develop a rational approach to antithrombotic therapy, in cardiac disease, a sound understanding is required (1) of the hemostatic processes leading to thrombosis, (2) of the various antithrombotic agents, and (3) of the relative risks of thrombosis and thromboembolism in the various cardiac disease entities. With the understanding of pathogenesis and risk of thrombus formation, a rational approach to the use of antiplatelet and anticoagulant agents can be formulated. Those at high risk of thrombus formation should generally receive a high degree of antithrombotics and, depending on the pathophysiology of the thrombus, may benefit from the concomitant use of antiplatelet and anticoagulant agents. Those with a medium risk of thrombus formation may benefit with the use of an antiplatelet agent alone or anticoagulants alone. Patients at low risk of thrombus formation should not receive antithrombotics. Such rational approach to antithrombotic therapy serves as the basis of this article.

Antithrombotic Therapy for Percutaneous Transluminal Coronary Angioplasty

The use of adjunctive pharmacologic therapy in the setting of coronary angioplasty has evolved in recent years with the introduction of new antithrombotics and better understanding of the pharmacologic properties of the drugs. This manuscript reviews the various antithrombotic agents currently in use and their impact on the outcomes of patients receiving them.

Anti-platelet drugs: do they affect megakaryocytes?

Anti-platelet drugs are used in clinical medicine to prevent thromboembolic complications of cardiovascular diseases. Among anti-platelet drugs, very little is known of their possible effects on megakaryocytes. ASA is the only compound for which it has clearly been demonstrated that its mechanism of action involves acetylation of the Ser 529 residue in cyclo-oxygenase in platelets and megakaryocytes. Because megakaryocytes possess membrane receptors for ADP, the thienopyridine metabolites of ticlopidine and clopidogrel may modify these receptors as in platelets and hence prevent ADP binding and further activation. Megakaryocytes also have GPIIb-IIIa receptors for the adhesive protein fibrinogen and may be accessible in vivo to GPIIb-IIIa antagonists such as the monoclonal antibody abciximab. Drugs such as heparin or the phosphodiesterase inhibitor anagrelide can either inhibit or stimulate megakaryocytopoiesis and platelet production, while cytokines such as thrombopoietin affect megakaryocytopoiesis, platelet production and platelet function by potentiating the activation of platelets by other agonists.

Contemporary stent designs: technical considerations, complications, role of intravascular ultrasound, and anticoagulation therapy

A number of studies have shown the benefits of stent placement over balloon angioplasty for the treatment of focal, native coronary artery, and saphenous vein graft disease. Although the number of stent designs available for clinical use has increased dramatically, the late clinical benefit of stenting over balloon angioplasty has yet to be shown in diffuse disease, complex bifurcation stenoses, or smaller (2.5-mm) vessels, each of which may require unique stent designs and adjunct therapies not currently available or extensively studied. The purposes of this review are to discuss the various stent designs currently available for clinical use, outline the known complications associated with these stents, assess the contribution of intravascular ultrasound, and describe current antiplatelet and antithrombotic therapy used after stent use.