Are both aspirin and heparin justified as adjuncts to thrombolytic therapy for acute myocardial infarction?

Endogenous tPA levels: A biomarker for discriminating hemorrhagic stroke from ischemic stroke and stroke mimics

OBJECTIVE

Stroke is the leading cause of death and disability. Timely differentiation between ischemic stroke, hemorrhagic stroke, and stroke mimics is critical for tailored treatment and triage. To accelerate the identification of stroke's subtype, we propose to use the levels of circulating tPA as a biomarker.

METHODS

Biostroke is an observational study performed at the Caen Hospital. We quantified tPA levels in 110 patients with ischemic strokes, 30 patients with hemorrhagic strokes, and 67 stroke mimic patients upon their arrival at the emergency. Two logistic regression models were formulated: one with parameters measurable in an ambulance (Model A) and one with parameters measurable at the hospital (Model H). These models were both tested with or without plasma tPA measurements. Our initial assessment involved evaluating the effectiveness of both models in distinguishing between hemorrhagic strokes, ischemic strokes, and stroke mimics within our study cohort.

RESULTS

Plasmatic tPA levels exhibit significant distinctions between hemorrhagic, ischemic, and mimic stroke patients (1.8; 2.5; 2.4 ng/mL, respectively). The inclusion of tPA in model A significantly enhances the classification accuracy of hemorrhagic patients only, increasing identification from 0.67 (95% CI, 0.59 to 0.75) to 0.78 (95% CI, 0.7 to 0.85) (p = 0.0098). Similarly, in model H, classification accuracy of hemorrhagic patients significantly increased with the addition of tPA, rising from 0.75 (95% CI, 0.67 to 0.83) without tPA to 0.86 (95% CI, 0.81 to 0.91) with tPA (p = 0.024).

INTERPRETATIONS

Our findings underscore the valuable role of tPA levels in distinguishing between stroke subtypes.

Self-Administration of Aspirin After Chest Pain for the Prevention of Premature Cardiovascular Mortality in the United States: A Population-Based Analysis

BACKGROUND

Aspirin, an effective, low-cost pharmaceutical, can significantly reduce mortality if used promptly after acute myocardial infarction (AMI). However, many AMI survivors do not receive aspirin within a few hours of symptom onset. Our aim was to quantify the mortality benefit of self-administering aspirin at chest pain onset, considering the increased risk of bleeding and costs associated with widespread use.

METHODS AND RESULTS

We developed a population simulation model to determine the impact of self-administering 325 mg aspirin within 4 hours of severe chest pain onset. We created a synthetic cohort of adults ≥ 40 years old experiencing severe chest pain using 2019 US population estimates, AMI incidence, and sensitivity/specificity of chest pain for AMI. The number of annual deaths delayed was estimated using evidence from a large, randomized trial. We also estimated the years of life saved (YOLS), costs, and cost per YOLS. Initiating aspirin within 4 hours of severe chest pain onset delayed 13 016 (95% CI, 11 643-14 574) deaths annually, after accounting for deaths due to bleeding (963; 926-1003). This translated to an estimated 166 309 YOLS (149391-185 505) at the cost of $643 235 (633 944-653 010) per year, leading to a cost-effectiveness ratio of $3.70 (3.32-4.12) per YOLS.

CONCLUSIONS

For <$4 per YOLS, self-administration of aspirin within 4 hours of severe chest pain onset has the potential to save 13 000 lives per year in the US population. Benefits of reducing deaths post-AMI outweighed the risk of bleeding deaths from aspirin 10 times over.

Heparin Dosing and Postoperative Blood Loss in Patients Taking Aspirin

A large number of patients scheduled to undergo elective coronary artery bypass grafting continue to take aspirin along with other antianginal medication up to the day of surgery. Patients taking aspirin preoperatively are known to bleed more in the postoperative period than those not taking aspirin. This study was undertaken to determine whether the method of heparin administration (protocol-based bolus dose versus an individualized dose) affected postoperative blood loss or requirements of blood and blood products in patients taking aspirin preoperatively. In this prospective study, 300 consecutive patients taking aspirin prior to coronary artery bypass graft surgery were randomly assigned to receive heparin either as a protocol-based bolus of 400 IU·kg−1 (group A) or according to a dose-response curve to obtain an activated coagulation time of 500 seconds on cardiopulmonarybypass (group B). Group B required significantly less heparin (mean 275 IU·kg−1)and less protamine than group A. Postoperative blood loss, requirement of blood and blood products, and time spent on hemostasis in group B was significantly less at 24 hours than group A. We concluded that individualized dosing of heparin using a dose-response curve is preferable to a protocol-based bolus heparin dose in patients taking preoperative aspirin.

Low-Molecular-Weight Heparins in Conjunction with Thrombolysis for ST-Elevation Acute Myocardial Infarction

BACKGROUND

Intravenous unfractionated heparin (UFH) is recommended in ST-elevation acute myocardial infarction (STEMI), following thrombolysis with fibrin-specific agents. Subcutaneous low-molecular-weight heparins (LMWH), previously proven effective in non-ST-elevation acute coronary syndromes, have been recently investigated in the setting of STEMI. We aimed at evaluating the current level of evidence supporting the use of LMWH in STEMI.

METHODS

A Medline search of the English language literature between January 1995 and December 2005 was performed and randomized clinical trials comparing LMWH to either placebo or UFH in conjunction with thrombolysis were selected.

RESULTS

About 26,800 patients treated with various thrombolytic regimens were included in 12 randomized clinical trials. Dalteparin was superior to placebo on left ventricular thrombosis/arterial thromboembolism, with no significant effect on the early patency rate of the infarct-related artery (IRA). Compared to UFH, dalteparin had no significant effect on clinical events and on the IRA late patency, although less thrombus was present. Enoxaparin was superior to placebo on the medium-term death/reinfarction/angina rate and late IRA patency, and superior also to UFH on in-hospital and medium-term occurrence of death/reinfarction/angina. The effect of enoxaparin on IRA patency rate was not univocal. Compared to placebo, reviparin significantly reduced early and medium-term mortality and reinfarction rates, without a substantial increase in overall stroke rate. As regards safety, bleedings were more frequent than placebo and comparable to UFH in LMWH groups, with the exception of the pre-hospital ASSENT-3 PLUS trial, where in elderly patients, enoxaparin had an incidence of intracranial hemorrhage twice higher than UFH.

CONCLUSIONS

In-hospital subcutaneous administration of dalteparin, enoxaparin or reviparin, as an adjunct to various thrombolytics in STEMI, appears feasible and at least as effective and safe as intravenous UFH. Before LMWH might be recommended, however, some yet unresolved issues (i.e. use in elderly patients, in severe renal insufficiency, in association with glycoprotein IIb/IIIa inhibitors and during interventional procedures), need to be addressed.

Evolving Role of Low-Molecular-Weight Heparins in ST-Elevation Myocardial Infarction

OBJECTIVE:

To review the available literature on the efficacy and safety of low-molecular-weight heparin (LMWH) in the treatment of ST-elevation myocardial infarction (STEMI) in patients treated with fibrinolytic therapy or conservative medical management.

DATA SOURCES:

A MEDLINE search (1966–March 2004) using the key words myocardial infarction, STEMI, LMWH, enoxaparin, and dalteparin identified pertinent articles. The references of these articles were reviewed for additional pertinent references.

STUDY SELECTION AND DATA EXTRACTION:

All human trials of LMWH in STEMI were evaluated. All pertinent studies were included in the review.

DATA SYNTHESIS:

LMWH did not show a benefit in STEMI without fibrinolytic therapy. Enoxaparin is similar to intravenous unfractionated heparin (UFH) in combination with nonspecific fibrinolytic therapy with regard to invasive reperfusion markers and 30-day clinical outcomes. Enoxaparin decreases composite endpoints in combination with fibrin-specific fibrinolytic therapy compared with UFH, primarily through a reduction in the incidence of reinfarction at 30 days. Bleeding rates with LMWH in combination with fibrinolytic agents are not greater than those with UFH.

CONCLUSIONS:

Enoxaparin is a reasonable alternative to UFH in patients with STEMI treated with fibrin-specific fibrinolytic therapy. LMWH in patients managed with nonspecific fibrinolytic therapy or conservative medical treatment does not provide an advantage over standard management. Large clinical trials are ongoing which will provide more definitive recommendations.

Streptokinase-induced platelet activation involves antistreptokinase antibodies and cleavage of protease-activated receptor-1

Streptokinase activates platelets, limiting its effectiveness as a thrombolytic agent. The role of antistreptokinase antibodies and proteases in streptokinase-induced platelet activation was investigated. Streptokinase induced localization of human IgG to the platelet surface, platelet aggregation, and thromboxane A2production. These effects were inhibited by a monoclonal antibody to the platelet Fc receptor, IV.3. The platelet response to streptokinase was also blocked by an antibody directed against the cleavage site of the platelet thrombin receptor, protease-activated receptor-1 (PAR-1), but not by hirudin or an active site thrombin inhibitor, Ro46-6240. In plasma depleted of plasminogen, exogenous wild-type plasminogen, but not an inactive mutant protein, S741A plasminogen, supported platelet aggregation, suggesting that the protease cleaving PAR-1 was streptokinase-plasminogen. Streptokinase-plasminogen cleaved a synthetic peptide corresponding to PAR-1, resulting in generation of PAR-1 tethered ligand sequence and selectively reduced binding of a cleavage-sensitive PAR-1 antibody in intact cells. A combination of streptokinase, plasminogen, and antistreptokinase antibodies activated human erythroleukemic cells and was inhibited by pretreatment with IV.3 or pretreating the cells with the PAR-1 agonist SFLLRN, suggesting Fc receptor and PAR-1 interactions are necessary for cell activation in this system also. Streptokinase-induced platelet activation is dependent on both antistreptokinase-Fc receptor interactions and cleavage of PAR-1.

The TIMI 9b and GUSTO IIb Trials and the "Thrombin Hypothesis"

The "thrombin hypothesis" proposes that the clinical outcome of patients with unstable angina or acute myocardial infarction (MI) is related to the degree of thrombin inhibition, with greater inhibition resulting in improved outcome. Two recent trials (TIMI 9b and GUSTO IIb) tried to test this hypothesis by randomizing 15,000 patients with MI or unstable angina to a 3-to-5 day intravenous administration of either the powerful thrombin inhibitor hirudin, or standard heparin. In both studies, after 30 days, there was no significant difference in the rates of death or nonfatal infarction between the 2 treatment arms. More than one reason may explain these findings. In both trials the anticoagulant regimens were carefully tailored to prevent excessive bleeding complications and to achieve a predetermined level of efficacy, as measure by aPTT. It is possible that similar aPTTs and similar bleeding rates will result in similar clinical outcomes, regardless of the anticoagulant agent used. It is also possible that patients already receiving fibrinolytic drugs and aspirin did not derive such additional thrombolytic benefit from anticoagulants to compensate for the increased bleeding risk associated with their use. Finally, thrombin may not always play the crucial role that has been attibuted to it: marked thrombin generation may occur only in subgroups of patients, or as a secondary response to a primary trigger that fails to be antagonized by antithrombin therapy or that re-emerges after stopping treatment. The true role played by anticoagulants in the management of acute coronary syndromes is not clear from TIMI 9b or GUSTO IIb because neither study included a control group not receiving anticoagulants. These trials, however, raise important issues that deserve further investigation: for example, the definition of what drives thrombin generation in patients with acute coronary syndromes and the identification of possible subgroups of patients deriving true clinical benefit from anticoagulant therapy.

Direct Comparison of Aspirin Plus Hirudin, Aspirin Plus Heparin, and Aspirin Alone Among 12,000 Patients with Acute Myocardial Infarction Not Receiving Thrombolysis: Rationale and Design of the First American Study of Infarct Survival (ASIS-1)

While antithrombotic therapy of acute myocardial infarction is clearly beneficial, substantial controversy exists regarding the optimal regimen. In particular, while aspirin alone has proven highly effective in reducing rates of reinfarction, stroke, and death following acute coronary occlusion, heparin has not clearly been shown to have additional benefit when added to aspirin but is associated with increased rates of hemorrhagic stroke and major bleeding. At the same time, available data for newer specific thrombin inhibitors such as hirudin suggest greater benefits than aspirin alone or aspirin plus heparin in terms of maintaining coronary flow, but possibly higher risks of hemorrhagic stroke and major bleeding. Since no completed or ongoing large-scale clinical trial has directly compared aspirin plus hirudin, aspirin plus heparin, and aspirin alone, it is not currently possible to decide which of these three antithrombotic regimens provides the optimal bmefit-to-risk ratio. The First American Study of Infarct Survival (ASIS-1) is directly comparing aspirin alone, aspirin plus heparin, and aspirin plus hirudin among 12,000 patients presenting with signs and symptoms of acute myocardial infarction who are not felt by their responsible physicians to be appropriate candidates for thrombolytic therapy. Such patients comprise almost two thirds of all U.S. subjects presenting with acute myocardial infarction and are a group at substantial risk of death, reinfarction, and stroke. Thus, the ASIS-I trial will provide importantly relevant data regarding the optimal antithrombotic regimen for the majority of patients presenting with acute myocardial infarction. In this manuscript we provide the rationale and design for the First American Study of Infarct Survival (ASIS-1), a randomized, double-blind, placebo-controlled trial directly comparing aspirin alone, aspirin plus intravenous heparin, and aspirin plus intravenous hirudin in the treatment of acute myocardial infarction patients not receiving thrombolytic therapy.

Comparison of enteric-coated aspirin and uncoated aspirin effect on bleeding time

Aspirin therapy is an essential part of the drug regimen for patients with acute myocardial infarction (MI), unstable angina, or after coronary angioplasty and coronary stenting. Recognizing this importance, this study sought to compare the bleeding time in two groups of 10 normal volunteers 4 hr after ingestion of either an enteric-coated aspirin or an uncoated aspirin, assuming that a difference between the two groups could be clinically significant. Defining < or = 8 min as normal, 80% of the uncoated group developed abnormal bleeding times, compared to 10% of the enteric-coated group (P < 0.01). The study demonstrates a significant difference between the two types of aspirin preparations on bleeding times in normal individuals. This strongly suggests that some enteric-coated aspirin preparations may not be as effective as uncoated aspirin in acutely decreasing platelet aggregation. Therefore, uncoated aspirin is recommended in the setting of acute MI, unstable angina, or after percutaneous transluminal coronary angioplasty.

Low molecular weight heparin as an adjunct to thrombolysis for acute myocardial infarction: the FATIMA study. Fraxiparin Anticoagulant Therapy in Myocardial Infarction Study Amsterdam (FATIMA) Study Group

OBJECTIVE

To investigate the feasibility of fixed dose, weight adjusted subcutaneous low molecular weight heparin (LMWH), with monitoring of anti-Xa levels and assessment of coronary patency rates after three to five days, thereby giving an initial indication of its safety and efficacy.

DESIGN

In 30 patients with acute myocardial infarction, LMWH (nadroparine) was given as a body weight adjusted intravenous bolus with thrombolysis (rt-PA infusion) and in weight adjusted subcutaneous doses at six hours, and every 12 hours thereafter for 72 hours. The target range was defined prospectively as 0.35-0.70 anti-factor Xa activity (aXa) units. The aXa level was measured every six hours. Coronary angiography was performed in all patients within five days after the start of thrombolytic treatment to determine patency (TIMI 2 and 3 flow) of the infarct related artery.

RESULTS

The mean (SEM) aXa level over 72 hours was 0.52 (0.08) U/ml; from 12 hours onwards 88% of all aXa measurements were within the target range. At angiography, a patent infarct related artery was present in 24 of the 30 patients. No major bleeding complications occurred, though minor bleeding complications were observed in two patients.

CONCLUSIONS

This small study indicates that LMWH is feasible as an adjunct to thrombolysis in patients with acute myocardial infarction. The aXa levels were within the target range and patency rates at three to five days were around 80%, with no major bleeding complications.

Use and effectiveness of intravenous heparin therapy for treatment of acute myocardial infarction in the elderly

OBJECTIVES

We sought to determine the use and association with 30-day mortality of intravenous heparin for the treatment of acute myocardial infarction in elderly patients not treated with a reperfusion strategy and without contraindications to anticoagulation.

BACKGROUND

The benefit of using full-dose intravenous heparin for the treatment of acute myocardial infarction in the elderly is not known.

METHODS

We conducted a retrospective cohort study using hospital medical records of all Medicare beneficiaries admitted to the hospital with an acute myocardial infarction in Alabama, Connecticut, Iowa and Wisconsin from June 1992 through February 1993.

RESULTS

Among the 6,935 patients > or = 65 years old who had no absolute chart-documented contraindications to heparin, 3,227 (47%) received early full-dose intravenous heparin therapy. After adjustment for baseline differences in demographic, clinical and treatment factors between patients with and without heparin, the use of heparin (odds ratio 1.02, 95% confidence interval 0.87 to 1.18) was not associated with a significantly better 30-day mortality rate.

CONCLUSIONS

Although intravenous heparin was commonly used for treatment of acute myocardial infarction in the elderly, it was not associated with an improved 30-day mortality rate. Although the findings of this observational study must be interpreted with care, they lead us to question whether the prevalent use of intravenous heparin has therapeutic effectiveness in this population.

Cardiac complications in non-insulin-dependent diabetes mellitus

There is clear evidence of the negative influence of type I or II diabetes non-insulin-dependent diabetes mellitus (NIDDM) on the prevalence, severity, and prognosis of cardiovascular disease. Epidemiologic studies have confirmed the relationship between NIDDM and the occurrence of coronary artery disease (CAD) and cardiac heart failure (CHF). The clinical aspects of NIDDM cardiac complications include a high rate of silent events, which merit an improvement in their diagnosis and treatment. Besides pharmacological therapy, aggressive approaches including percutaneous transluminal coronary angioplasty (PTCA), and coronary surgery should be considered for the treatment of stable angina. IN some subgroups, the benefit of surgery has been proven. Available data indicate that diabetes (both type I and II) is a risk factor for an increase in morbidity and mortality following coronary bypass surgery. These data do not differentiate results between type I and type II diabetes. The indications for surgical revascularization are: three-vessel disease, left main artery stenosis, two-vessel disease including proximal left anterior descending artery stenosis, and two-vessel disease with left ventricular dysfunction. For PTCA, diabetes (type I more than type II) renders the technique more difficult and restenosis more frequent. From the results obtained in the general population and from a few specific studies, it is suspected that, in type II diabetes, PTCA and CABG are superior to conventional medical treatment. However, further specific studies on the beneficial effects of PTCA/CABG over optimal medical therapy are needed, at least in some angiographic conditions. Management of the diabetic patient with acute myocardial infarction is for the most part similar to the nondiabetic patient, with certain special considerations. Treatment includes thrombolytic therapy, invasive management, surgery, PTCA, beta blocker use, and aspirin use. Finally, diabetes mellitus is a cause of systolic and diastolic function, leading to clinical signs of CHF. Conventional medical therapy also applies to cardiac failure complicating diabetes. Medical therapy includes as the first line diuretics and angiotensin-converting enzyme inhibitors. We conclude that cardiac care can be improved in diabetic patients. For the time being, the first step is to improve the detection of coronary artery disease. As serious events are more likely to occur in the diabetic population, it would be easier (shorter studies and less patients) to demonstrate the benefit of a selected therapy. Further studies are therefore required. In the meantime, special efforts can be made: (1) prevent the development of coronary artery disease. Preventive measures aimed at the control of risk factors at the individual level must be optimal. What should be promoted is a more global approach to the patient, taking into account all parts of the risk factor profile, in order to amplify the reduction in risk and in cardiovascular morbidity and mortality. (2) When CAD is confirmed: the goal is to prevent all major cardiac events: unstable angina, myocardial infarction, sudden death, and CHF secondary to silent ischemic events. This can be achieved through the improvement of the accuracy of noninvasive diagnostic procedures, taking into account the cost of these procedures and the absence of pain perception in diabetic patients.

Clinical effects of anticoagulant therapy in suspected acute myocardial infarction: systematic overview of randomised trials

OBJECTIVES

Most randomised trials of anticoagulant therapy for suspected acute myocardial infarction have been small and, in some, aspirin and fibrinolytic therapy were not used routinely. A systematic overview (meta-analysis) of their results is needed, in particular to assess the clinical effects of adding heparin to aspirin.

DESIGN

Computer aided searches, scrutiny of reference lists, and inquiry of investigators and companies were used to identify potentially eligible studies. On central review, 26 studies were found to involve unconfounded randomised comparisons of anticoagulant therapy versus control in suspected acute myocardial infarction. Additional information on study design and outcome was sought by correspondence with study investigators.

SUBJECTS

Patients with suspected acute myocardial infarction.

INTERVENTIONS

No routine aspirin was used among about 5000 patients in 21 trials (including half of one small trial) that assessed heparin alone or heparin plus oral anticoagulants, and aspirin was used routinely among 68,000 patients in six trials (including the other half of one small trial) that assessed the addition of intravenous or high dose subcutaneous heparin.

MAIN OUTCOME MEASUREMENTS

Death, reinfarction, stroke, pulmonary embolism, and major bleeds (average follow up of about 10 days).

RESULTS

In the absence of aspirin, anticoagulant therapy reduced mortality by 25% (SD 8%; 95% confidence interval 10% to 38%; 2P = 0.002), representing 35 (11) fewer deaths per 1000. There were also 10 (4) fewer strokes per 1000 (2P = 0.01), 19 (5) fewer pulmonary emboli per 1000 (2P < 0.001), and non-significantly fewer reinfarctions, with about 13 (5) extra major bleeds per 1000 (2P = 0.01). Similar sized effects were seen with the different anticoagulant regimens studied. In the presence of aspirin, however, heparin reduced mortality by only 6% (SD 3%; 0% to 10%; 2P = 0.03), representing just 5 (2) fewer deaths per 1000. There were 3 (1.3) fewer reinfarctions per 1000 (2P = 0.04) and 1 (0.5) fewer pulmonary emboli per 1000 (2P = 0.01), but there was a small non-significant excess of stroke and a definite excess of 3 (1) major bleeds per 1000 (2P < 0.0001).

CONCLUSIONS

The clinical evidence from randomised trials dose not justify the routine addition of either intravenous or subcutaneous heparin to aspirin in the treatment of acute myocardial infarction (irrespective of whether any type of fibrinolytic therapy is used).

Hirudin in acute myocardial infarction. Thrombolysis and Thrombin Inhibition in Myocardial Infarction (TIMI) 9B trial

BACKGROUND

The TIMI 9 trial evaluated whether the direct antithrombin hirudin is more effective than an indirect-acting antithrombin, heparin, as adjunctive therapy for thrombolysis in myocardial infarction.

METHODS AND RESULTS

Patients (n = 3002) with acute myocardial infarction were treated with aspirin and either accelerated-dose tissue plasminogen activator (TPA) or streptokinase. They were randomized within 12 hours of symptoms to receive either intravenous heparin (5000 U bolus followed by infusion of 1000 U/h) or hirudin (0.1 mg/kg bolus followed by infusion of 0.1 mg/ kg per hour). The infusions of both antithrombins were titrated to a target activated partial thromboplastin time (aPTT) of 55 to 85 seconds and were administered for 96 hours. Patients randomized to hirudin were significantly more likely to have an aPTT measurement in the target range (P < .0001). The primary end point (death, recurrent nonfatal myocardial infarction, or development of severe congestive heart failure or cardiogenic shock by 30 days) occurred in 11.9% of the 1491 patients in the heparin group and 12.9% of the 1511 patients in the hirudin group (P = NS). Subgroup analyses did not reveal any profile of patients who benefited more from one of the antithrombins. The rate of major hemorrhage was similar in the heparin (5.3%) and hirudin (4.6%) groups; intracranial hemorrhage occurred in 0.9% of the heparin and 0.4% of the hirudin patients.

CONCLUSIONS

Heparin and hirudin have an equal effect as adjunctive therapy to TPA and streptokinase in preventing unsatisfactory outcome in patients with acute myocardial infarction. Similar rates of major bleeding were observed for patients in the heparin and hirudin groups.

Acute myocardial infarction treatments in 58 Italian hospitals: a drug utilization survey

OBJECTIVES

To provide an updated and comprehensive profile of therapeutic practice in the management of acute myocardial infarction (AMI) in a sample of Italian hospitals, and to test the possible role of a network of hospital pharmacists in providing drug utilization data.

DESIGN

Prospective drug utilization survey. Participating pharmacists collected information on patients consecutively admitted to the hospital with a suspected AMI. The form reproduced those adopted in the Gruppo Italiano per lo Studio della Sopravvivenza nell'Infarto miocardico trials.

SETTING

Fifty-eight general hospitals in Italy belonging to the National Health Service, 6 of which are teaching hospitals. Thirty-four hospitals recruited patients from a coronary care unit, 10 from intensive monitoring beds in cardiology wards, and 14 from an intensive care unit.

PARTICIPANTS

The study population consisted of patients consecutively admitted with a suspected AMI from May 31 through July 5, 1993.

MAIN OUTCOME MEASURES

The management of AMI in terms of the use of drugs and nonpharmacologic treatments is described.

RESULTS

Of the 676 patients recruited for the study, 47.8% received thrombolytic therapy; alteplase was the preferred agent (55.4% of treated patients). The use of thrombolytic therapy varied significantly according to different demographic and clinical parameters such as age, sex, delay from the onset of symptoms to admission, and Killip scale class. During the first day of hospitalization 63.9% of patients received aspirin, 83.3% received nitrates, 24.8% received beta-blockers, and 77.1% received heparin therapy.

CONCLUSIONS

Thrombolytic therapy was prescribed in a higher percentage of patients than is reported in the US, but lower than that reported in large trials. That a low percentage of patients who experienced a long delay between the onset of symptoms and admission as well as elderly patients received thrombolytic therapy reflects the lower expectations of clinicians for these subgroups of patients. A low proportion of patients received aspirin therapy. This study showed that in Italy an institutional network of hospital pharmacists could be interested observers of therapeutic practice, but further training is needed before high-quality data can be collected.

Contemporary use of and future roles for heparin in antithrombotic therapy

Although heparin therapy is an established component of the prevention and treatment of thromboembolic disease, recent advances have resulted in improvements in the clinical use of this agent. Studies have shown that weight-based dosing influences significantly both the time to reach a therapeutic intensity of anticoagulation and the incidence of thromboembolic recurrence. It is now considered the standard of care. A growing understanding of the variability among activated partial thromboplastin time (aPTT) reagents and the influence of these differences on aPTT outcomes has led to the use of reagent-specific therapeutic ranges for heparin monitoring. Many practitioners now choose to adjust the therapeutic range to correspond to heparin serum concentrations of 0.2-0.4 U/mL rather than the more common practice of prolonging aPTT to 1.5-2.5 times the mean normal aPTT. Pharmaceutical companies have developed low molecular weight heparins to minimize adverse effects associated with unfractionated heparin. More specific thrombin inhibitors are also under investigation with the aim of improving clinical outcomes in coronary syndromes now treated with heparin. Low molecular weight heparins or specific thrombin inhibitors are unlikely to replace unfractionated heparin in the near future. Therefore, optimum dosing and appropriate monitoring of heparin are critically important in the management of thromboembolic disease.

Contemporary management of acute myocardial infarction

Acute myocardial infarction, the leading cause of death in western society, has been the focus of more randomized clinical trial effort over the past decade than any other area of medicine. As a result of this worldwide effort, involving hundreds of thousands of patients with myocardial infarction, data have accumulated showing substantially lower mortality of acute myocardial infarction with simple interventions such as i.v. thrombolytic therapy, aspirin, beta-blockers, and angiotensin-converting enzyme inhibitors. Emergency coronary angioplasty appears to be a suitable alternative to i.v. thrombolytic therapy in skilled centers. Several previously recommended therapies (routine i.v. lidocaine, calcium channel blockers, magnesium, nitrates) have not been proved to be life-saving. Whether routine coronary arteriography should be employed after myocardial infarction remains controversial, but it is generally accepted that patients with evidence of residual ischemia after infarction, either spontaneous or provoked by stress testing, should undergo prophylactic coronary revascularization.

Thrombolysis with recombinant unglycosylated single-chain urokinase-type plasminogen activator (saruplase) in acute myocardial infarction: influence of heparin on early patency rate (LIMITS study). Liquemin in Myocardial Infarction During Thrombolysis With Saruplase

OBJECTIVES

The Liquemin in Myocardial Infarction During Thrombolysis With Saruplase (LIMITS) study was instituted to evaluate and characterize the effect of a prethrombolytic heparin bolus (5,000 IU) on the efficacy and safety of saruplase in patients with acute myocardial infarction.

BACKGROUND

Heparin has been used after thrombolytic therapy for acute myocardial infarction to prevent reocclusion of the infarct-related artery.

METHODS

The study was designed as a randomized, parallel-group, double-blind, multicenter trial. Patients were treated within 6 h of onset of symptoms with either a bolus of 5,000 IU of heparin (Liquemin) (n = 56, HSH group) or placebo (n = 62, PSH group) before thrombolytic treatment with saruplase given as a 20-mg bolus followed by an infusion of 60 mg over 60 min. Thirty minutes after completion of thrombolysis, an intravenous heparin infusion was administered for 5 days. Before coronary angiography was performed at 6 to 12 h after start of lysis, an additional bolus of 5,000 IU heparin was given to all patients. End points studied were patency of the infarct-related artery, changes in the hemostatic system and bleeding complications.

RESULTS

In the HSH group (heparin-saruplase-heparin), 78.6% of patients had an open infarct-related vessel (Thrombolysis in Myocardial Infarction [TIMI] flow grade 2 or 3) compared with 56.5% in the PSH group (placebo-saruplase-heparin) (intention-to-treat analysis, p = 0.01). No significant difference was observed between the two groups with regard to changes in fibrinogen and fibrin/fibrinogen degradation products. A total of eight bleeding complications (14.3%) were observed in the HSH group and five (8.1%) in the PSH group; no cerebrovascular event occurred, and no allergic reaction was reported. A total of 12 patients died during the hospital stay, 3 in the HSH group (5.4%) and 9 in the PSH group (14.5%).

CONCLUSIONS

In acute myocardial infarction, the administration of a heparin bolus before thrombolytic therapy with saruplase is associated with a significantly higher patency at angiography 6 to 12 h after the start of thrombolysis without any appreciable increase in risk of bleeding.

Antithrombotic therapy for acute myocardial infarction

Antithrombotic therapy is clearly beneficial in the treatment of acute myocardial infarction, but the optimal regimen is controversial. Treatment with aspirin leads to substantial and significant reductions in rates of mortality, reinfarction and stroke in patients with acute myocardial infarction, and the benefits are additive with those of thrombolytic therapy. It is unclear whether heparin confers additional net benefits over aspirin alone. In patients receiving aspirin and thrombolytic therapy, there is no mortality benefit from adding delayed subcutaneous heparin, no consistent patency benefit from adding immediate intravenous heparin and no reduction in mortality from adding immediate intravenous heparin, at least for patients treated with streptokinase. However, heparin is consistently associated with increased rates of intracranial and other serious bleeding events when used with both aspirin and thrombolytic therapy. Existing data support the need for further large-scale trials of current and newer antithrombotic regimens in acute myocardial infarction to assess the balance of benefits and risks of these regimens compared with that for aspirin alone. In patients not receiving thrombolytic therapy, randomized trial data are currently insufficient to adequately compare the benefits and risks of adding heparin to aspirin alone. The First American Study of Infarct Survival (ASIS-1) will directly compare the balance of risks and benefits of aspirin alone, aspirin plus intravenous heparin and aspirin plus intravenous hirudin in patients with acute myocardial infarction not receiving thrombolytic therapy.

Role of thrombosis in atherosclerosis and its complications

The endothelium is intact but activated and dysfunctioning during the early phase of atherogenesis. Owing to increased endothelial permeability, many blood-derived components, including hemostatic factors, are present in early as well as advanced atherosclerotic lesions. Insudated fibrin(ogen) and related degradation products and thrombin could contribute to atherogenesis by their chemotactic (attracting monocytes/macrophages) and mitogenic (stimulating cell proliferation) properties. All key cells in plaque may express thrombin receptors, indicating that thrombin may play a role in the genesis of uncomplicated atherosclerosis by mediating inflammatory and proliferative processes. Later, endothelial denudation with platelet adherence occurs over mature plaques. Then, incorporation of microthrombi and probably platelet/thrombus-derived growth factors are critical for the progressive growth of the smooth muscle cell-related plaque component. Besides transendothelial influx and incorporation of mural thrombi, blood products in atherosclerotic plaques may originate from hemorrhage through a ruptured plaque surface or from fragile newly formed vessels (neovascularization) frequently found at the base of advanced plaques. Rupture-related plaque progression due to luminal thrombosis and/or plaque hemorrhage is the most important mechanism underlying the unpredictable rapid progression of coronary lesions responsible for acute coronary syndromes. Both platelets and fibrin play a role in the dynamic thrombotic response to plaque rupture.(ABSTRACT TRUNCATED AT 250 WORDS)

Failure of fixed dose intravenous heparin to suppress increases in thrombin activity after coronary thrombolysis with streptokinase

OBJECTIVES

This study was designed to define the extent of inhibition of thrombin activity achieved with conjunctive fixed dose intravenous sodium heparin compared with fixed dose subcutaneous calcium heparin in patients receiving intravenous streptokinase for acute myocardial infarction.

BACKGROUND

The role of heparin therapy during coronary thrombolysis with streptokinase is controversial, in part because the efficacy of different conjunctive heparin regimens in inhibiting early increases of thrombin activity is not known.

METHODS

Twenty-eight patients treated with 1.5 million U of streptokinase and 165 mg of aspirin for acute myocardial infarction were randomly assigned to receive fixed dose subcutaneous heparin therapy (12,500 U every 12 h delayed until 4 h after the end of streptokinase therapy [n = 14]) or fixed dose intravenous heparin (5,000-U bolus followed by 1,000-U/h infusion [n = 14]). Anticoagulation was assessed with serial measurements of activated partial thromboplastin time, and thrombin activity by measuring fibrinopeptide A and thrombin-antithrombin III complex levels. Plasma concentrations of creatine kinase (CK) MM isoforms were measured for 3 h to determine recanalization (increase in activity > 0.18%/min).

RESULTS

Recanalization occurred in 27%, 64% and 79% of patients given subcutaneous heparin versus 43%, 76% and 86% of those given intravenous heparin at 1, 2 and 3 h, respectively (p = 0.6). Concentrations of fibrinopeptide A (mean +/- SEM) at 1 h were higher in patients without (n = 5) than in those with (n = 23) CK-MM isoform criteria for recanalization (76.4 +/- 25.7 vs. 25.2 +/- 5.2 nmol/liter, p = 0.02), and at 1, 2 and 3 h were significantly lower with fixed dose intravenous heparin (18.4 +/- 4.8 vs. 46.7 +/- 10.2 nmol/liter at 1 h, p = 0.004) than without heparin. After fixed dose subcutaneous heparin at 4 h, fibrinopeptide A levels were similar in both groups despite lower activated partial thromboplastin times in patients who received fixed dose subcutaneous heparin. However, fibrinopeptide A was not consistently suppressed in either group (fixed dose subcutaneous heparin 8.7 +/- 1.8 nmol/liter vs. fixed dose intravenous heparin 11.8 +/- 5.2 nmol/liter) at 48 h (p = 0.4). No significant changes in the concentration of thrombin-antithrombin III complexes were found between the two groups.

CONCLUSIONS

Fixed dose intravenous heparin attenuates increases in fibrinopeptide A early after streptokinase. Subsequent fixed dose intravenous and subcutaneous heparin have similar effects but are relatively ineffective in suppressing thrombin activity, suggesting a role for more potent antithrombin agents during coronary thrombolysis with streptokinase.

Treatment of myocardial infarction in the United States (1990 to 1993). Observations from the National Registry of Myocardial Infarction

BACKGROUND

Multiple clinical trials have provided guidelines for the treatment of myocardial infarction, but there is little documentation as to how consistently their recommendations are being implemented in clinical practice.

METHODS AND RESULTS

Demographic, procedural, and outcome data from patients with acute myocardial infarction were collected at 1073 US hospitals collaborating in the National Registry of Myocardial Infarction during 1990 through 1993. Registry hospitals composed 14.4% of all US hospitals and were more likely to have a coronary care unit and invasive cardiac facilities than nonregistry US hospitals. Among 240,989 patients with myocardial infarction enrolled, 84,477 (35.1%) received thrombolytic therapy. Thrombolytic recipients were younger, more likely to be male, presented sooner after onset of symptoms, and were more likely to have localizing ECG changes. Among the 60,430 patients treated with recombinant tissue-type plasminogen activator (rTPA), 23.2% received it in the coronary care unit rather than in the emergency department. Elapsed time from hospital presentation to starting rTPA averaged 99 minutes (median, 57 minutes). Among patients receiving thrombolytic therapy, concomitant pharmacotherapy included intravenous heparin (96.9%), aspirin (84.0%), intravenous nitroglycerin (76.0%), oral beta-blockers (36.3%), calcium channel blockers (29.5%), and intravenous beta-blockers (17.4%). Invasive procedures in thrombolytic recipients included coronary arteriography (70.7%), angioplasty (30.3%), and bypass surgery (13.3%). Trend analyses from 1990 to 1993 suggest that the time from hospital evaluation to initiating thrombolytic therapy is shortening, usage of aspirin and beta-blockers is increasing, and usage of calcium channel blockers is decreasing.

CONCLUSIONS

This large registry experience suggests that management of myocardial infarction in the United States does not yet conform to many of the recent clinical trial recommendations. Thrombolytic therapy is underused, particularly in the elderly and late presenters. Although emerging trends toward more appropriate treatment are evident, hospital delay time in initiating thrombolytic therapy remains long, aspirin and beta-blockers appear to be underused, and calcium channel blockers and invasive procedures appear to be overused.

Maximizing benefits of therapies in acute myocardial infarction

Major advances in the management of acute myocardial infarction have been achieved by a combination of careful experimental work and development of effective pharmacologic and interventional strategies in conjunction with the conduct of large, reliable randomized trials. Current trials indicate that a combination of thrombolytic therapy, aspirin, and intravenous followed by oral beta blockers reduces mortality. There are a number of additional promising interventions, such as intravenous magnesium, nitrates, and the newer antithrombin agents. However, before these agents are used widely in clinical practice, clear proof of benefit and adequate safety should be available from the ongoing randomized trials. Following discharge from the hospital, long-term therapy with aspirin and beta blockers should be considered in all patients. In patients with heart failure and low ejection fraction, angiotensin-converting enzyme (ACE) inhibitors have been shown to reduce mortality, reinfarction, and the need for further hospitalizations for heart failure. Therefore, these therapies, in conjunction with risk factor modification (cessation of cigarette smoking, treatment of hypercholesterolemia, treatment of hypertension), should be considered in all appropriate patients. A number of new strategies for the prevention of atherosclerosis and its complications are currently being evaluated in prospective randomized trials. These include the natural antioxidant vitamins, estrogen replacement therapy, tamoxifen therapy, and ACE inhibitors in patients without evidence of heart failure or left ventricular dysfunction.

Antiplatelet therapy and risk of stroke

Antiplatelet therapy, especially with aspirin, reduces the risks of occlusive vascular disease, including ischemic stroke. In an overview of 25 trials of antiplatelet therapy in patients with prior cardiovascular disease, antiplatelet treatment reduced subsequent nonfatal stroke by 27% (P = 0.0001), nonfatal myocardial infarction by 32% (P = 0.0001), and all vascular deaths by 15% (P = 0.0003), with no evidence that other antiplatelet agents were more effective than aspirin, or that higher aspirin doses (900 to 1500 mg daily) were more effective than 300 mg, the lowest daily dose tested. If begun during the acute phase of myocardial infarction, aspirin reduces nonfatal stroke by 46% (P < 0.01) and vascular deaths by 23% (P < 0.00001) after 5 weeks. In primary prevention, currently available data are inconclusive regarding the effect of aspirin therapy on stroke. However, any potential benefit on ischemic stroke must be weighed against the possibility that aspirin could increase the risk of the less common, but clinically more severe, strokes of hemorrhagic etiology.