Heparin-induced prolongation of partial thromboplastin time after thrombolysis: relation to coronary artery patency. HART Investigators

High-Risk Non-ST Elevation Acute Coronary Syndrome Outcomes in Patients Treated with Unfractionated Heparin Monitored Using Anti-Xa Concentrations Versus Activated Partial Thromboplastin Time

BACKGROUND

While the activated partial thromboplastin time (aPTT) is the most widely used assay to monitor unfractionated heparin (UFH), providing a general measure of the extent of anticoagulation, it does not reliably correlate with the blood concentration of heparin or its antithrombotic effect. While cost and availability have limited the widespread use of UFH in hospitals, monitoring UFH with heparin levels has been shown to reduce both the number of monitoring tests and the time to a therapeutic range.

OBJECTIVES

To compare outcomes in patients with non-ST elevation acute coronary syndrome (ACS) treated with weight-based UFH monitored with anti-Xa concentrations versus aPTT.

METHODS

A retrospective chart review was completed in patients admitted with high-risk ACS and compared to the UFH arm of the SYNERGY trial. The primary outcome included the clinical endpoint of all-cause death or non-fatal myocardial infarction until time of hospital discharge. Safety endpoints evaluated included incidence of stroke and major bleeding.

RESULTS

The primary endpoint occurred in 6.3% of patients in the study cohort compared to 6.5% of patients in the heparin arm of the SYNERGY trial at 48 hours (P = .006). Bleeding was reduced in the study cohort with a significant decrease in GUSTO severe bleeding (P = .007). Additionally the study cohort had significantly fewer patients with an absolute drop in hemoglobin or hematocrit. Thrombolysis in Myocardial Infarction (TIMI) major and minor bleeding, rate of transfusion, and platelet counts were similar between groups.

CONCLUSIONS

Outcomes for high-risk ACS patients receiving heparin monitored by anti-Xa concentrations are noninferior to heparin monitored by aPTT.

A pilot study on systemic thrombolysis followed by low molecular weight heparin in ischemic stroke

Low molecular weight heparin (LMWH) administered immediately after intravenous thrombolysis (IT) may reduce the risk of arterial re-occlusion. Its benefit, however, may not outweigh the risk of intracranial hemorrhage (ICH). We sought preliminary data regarding safety of this combined therapy in an open-label, non-randomized study. The patients received either a standard anticoagulation (AC) starting 24 h after IT (the standard AC group) or AC with 2850 IU of nadroparin, given every 12 h immediately after IT (the early AC group). Sixty patients received IT treatment: 25 in the standard AC group [mean age 66, median National Institutes of Health Stroke Scale (NIHSS) 13, 64% men] and 35 in the early AC group (mean age 68, median NIHSS 13, 69% men). Symptomatic ICH occurred in one patient (4%) in the standard AC group and three patients (8.6%) in the early AC group [odds ratio (OR) 1.8; 95%CI 0.2-12.8]. At 3 months, nine patients in the standard AC group (36%) and 16 patients in the early AC group (45.7%) achieved a modified Rankin scale 0 or 1 (OR 1.2; 95%CI 0.5-3.2). Our study suggests that treatment with LMWH could be associated with higher odds of ICH, although it may not necessarily lead to a worse outcome. This justifies larger clinical trials.

Antithrombotic therapy for coronary artery disease: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy

This chapter about antithrombotic therapy for coronary artery disease (CAD) is part of the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy: Evidence Based Guidelines. Grade 1 recommendations are strong and indicate that the benefits do, or do not, outweigh risks, burden, and costs. Grade 2 suggests that individual patients' values may lead to different choices (for a full understanding of the grading see Guyatt et al, CHEST 2004; 126:179S-187S). Among the key recommendations in this chapter are the following: For patients presenting with non-ST-segment elevation (NSTE) acute coronary syndrome (ACS), we recommend immediate and then daily oral aspirin (Grade 1A). For patients with an aspirin allergy, we recommend immediate treatment with clopidogrel, 300-mg bolus po, followed by 75 mg/d indefinitely (Grade 1A). In all NSTE ACS patients in whom diagnostic catheterization will be delayed or when coronary bypass surgery will not occur until > 5 days, we recommend clopidogrel as bolus therapy (300 mg), followed by 75 mg/d for 9 to 12 months in addition to aspirin (Grade 1A). In NSTE ACS patients in whom angiography will take place within 24 h, we suggest beginning clopidogrel after the coronary anatomy has been determined (Grade 2A). For patients who have received clopidogrel and are scheduled for coronary bypass surgery, we recommend discontinuing clopidogrel for 5 days prior to the scheduled surgery (Grade 2A). In moderate- to high-risk patients presenting with NSTE ACS, we recommend either eptifibatide or tirofiban for initial (early) treatment in addition to treatment with aspirin and heparin (Grade 1A). For the acute treatment of NSTE ACS, we recommend low molecular weight heparins over unfractionated heparin (UFH) [Grade 1B] and UFH over no heparin therapy use with antiplatelet therapies (Grade 1A). We recommend against the direct thrombin inhibitors as routine initial antithrombin therapy (Grade 1B). For patients after myocardial infarction, after ACS, and with stable CAD, we recommend aspirin in doses from 75 to 325 mg as initial therapy and in doses of 75 to 162 mg as indefinite therapy (Grade 1A). For patients with contraindications to aspirin, we recommend long-term clopidogrel (Grade 1A). For primary prevention in patients with at least moderate risk for a coronary event, we recommend aspirin, 75 to 162 mg/d, over either no antithrombotic therapy or vitamin K antagonist (VKA) [Grade 2A]; for patients at particularly high risk of events in whom the international normalized ratio (INR) can be monitored without difficulty, we suggest low-dose VKA (target INR, 1.5) [Grade 2A].

The determinants of activated partial thromboplastin time, relation of activated partial thromboplastin time to clinical outcomes, and optimal dosing regimens for heparin treated patients with acute coronary syndromes: a review of GUSTO-IIb

CONTEXT

Unfractionated heparin remains widely utilized in the treatment of acute coronary syndromes (ACS). However, limited data exist on optimal dosing and range of activated partial thromboplastin time (aPTT) in this setting. A large trial of thrombolysis for acute myocardial infarction has reported an association between longer aPTTs and adverse outcomes.

OBJECTIVES

Estimate the optimal heparin-dosing regimen in achieving early therapeutic aPTTs (50 to 75 seconds) and determine the association of aPTT and death, reinfarction, and bleeding in population with ACS.

DESIGN

Subgroup analysis within a randomized, controlled trial of 5861 patients given unfractionated heparin who had aPTTs at 6, 12, or 24 hours, with outcome analyses by weight categories.

SETTING

In 373 hospitals in 13 countries from May 1994 to October 1995.

PATIENTS

A total of 12142 patients admitted for ACS, stratified by the presence (n = 4131) or absence (n = 8011) of ST-segment elevation, and randomized to 72 hours of unfractionated heparin.

RESULTS

In a simulated weight-adjusted model, based on retrospective grouping by weight, a simulated dose of 60-U/kg bolus and 12-U/kg/h infusion resulted in the highest proportion of therapeutic aPTTs. After adjustment for baseline variables, longer 12-hour aPTT was associated with the composite of 30-day death or reinfarction in patients not treated with thrombolytic therapy (odds ratio, 1.10; 95% CI, 1.00 to 1.22; P = 0.047). Longer aPTT at 6 hours was associated with increased moderate or severe bleeding for the entire cohort. There was also a significant, nonlinear correlation of the 12-hour aPTT with moderate or severe bleeding in thrombolysis-treated patients.

CONCLUSIONS

For ACS patients who are treated with heparin, aPTT is highly associated with body weight. Longer aPTT within the first 12 hours is associated with adverse outcomes in ACS. Heparin dosing for ACS should be weight based.

Heparin dosing and outcome in acute coronary syndromes: the GUSTO-IIb experience. Global Use of Strategies to Open Occluded Coronary Arteries

BACKGROUND

This study analyzed relationships among heparin dosage, patient characteristics, and 30-day outcome because optimal unfractionated-heparin dosing in acute coronary syndromes remains uncertain.

METHODS

Patients (n = 5335) randomized to heparin therapy in the Global Use of Strategies to Open Occluded Coronary Arteries (GUSTO) IIb trial were studied. The heparin dose was adjusted to a target activated partial thromboplastin time (aPTT) and normalized for the patient's weight. Mortality and cardiac (re)infarction within 30 days and their association with patient characteristics and heparin dosing were evaluated.

RESULTS

The lowest mortality rate appeared with a heparin dose of approximately 14 U/kg/h or an aPTT of approximately 70 seconds. Heparin dosing was a significant predictor of outcome after adjusting for presenting coronary syndrome; a trend remained after adjusting for other baseline differences. This association was lost when adjusted for the aPTT result. Patients who died early appeared to have lower heparin dosing than those with later mortality (P =.012). Heparin "resistance" with relatively high heparin dosages and low aPTT values did not increase the risk for adverse outcome.

CONCLUSIONS

There is a defined, dose-associated benefit of unfractionated heparin in acute coronary syndromes similar to that seen previously in thrombolytic-treated infarctions. Heparin therapy is complicated by its complex biologic interactions and relatively crude measures of its effect. Better measures of heparin effectiveness and strategies need to be developed with either better antithrombin agents or adjunctive therapies such as antiplatelet regimens to treat patients who require benefits beyond that supplied by unfractionated heparin.

The ineffectiveness of a non-weight based heparin regimen in achieving therapeutic activated partial thromboplastin time (aPTT) in acute coronary syndrome

Although low molecular weight heparin (LMWH) is increasingly being used in the treatment of acute coronary syndrome (ACS), unfractionated intravenous (IV) heparin infusion is still widely used in Australian hospitals for the treatment of ACS. This paper evaluates the effectiveness of a non-weight based heparin regimen in achieving a therapeutic activated partial thromboplastin time (aPTT) within 24 hours of IV heparin commencement. A sequential retrospective chart review of 99 medical records of ACS patients in a district hospital in south western Sydney, Australia, was performed. These patients were prescribed IV heparin and did not receive thrombolytic or warfarin therapy. Only 35 per cent reached a therapeutic aPTT level within 24 hours of commencement of IV heparin therapy. Comparison of therapeutic aPTT and non-therapeutic aPTT groups revealed that body weight was the only factor that was significantly different in the two groups. Patients who reached the therapeutic aPTT threshold within 24 hours weighed significantly less (mean body weight: 70.3 kg versus 80.3 kg) than those who did not reach the therapeutic threshold within 24 hours of heparin commencement (t = 3.80, d.f. = 86, p < 0.001). Given that a significant proportion of patients who require IV heparin therapy exceed the 70 kg body weight, the findings from this study suggest that a non-weight based heparin regimen is ineffective in the rapid achievement of therapeutic aPTT.

Issues Regarding the Use of Heparin Following Streptokinase Therapy

The success of thrombolytic therapy is dependent upon the balance of fibrinolytic activity and procoagulant activity. Streptokinase produces fibrin degradation products that have anticoagulant effects and may potentially protect against reocclusion. However, streptokinase also activates platelets and thrombin, and the prothrombotic effects may be more marked than after administration of recombinant tissue plasminogen activator (rt-PA). Administration of high-dose, delayed subcutaneous heparin after streptokinase and aspirin has been shown to have some benefits and some risks. The benefits and risks of adding intravenous heparin to aspirin and streptokinase have not been clearly defined.

Hirudin in Acute Myocardial Infarction

The central role of thrombosis in the pathogenesis of acute myocardial infarction has led to intense interest in developing more effective thrombolytic-antithrombotic regimens. Hirudin is 65 amino acid polypeptide that binds in a 1:1 relationship with thrombin, thereby inhibiting the final step in the coagulation cascade. Hirudin has several potential advantages over the current antithrombin agent heparin: It is a direct inhibitor that does not require a cofactor, it has no known inhibitors that would attentuate its anticoagulant effects, and it can inhibit clot-bound thrombin, thereby achieving an antithrombotic effect at the site of potential rethrombosis. Initial clinical trials have shown promising results: Hirudin, as compared with heparin, provided a more consistent level of anticoagulation, as gauged by the activated partial thromboplastin time. As an adjunct to thrombolytic therapy in acute myocardial infarction, hirudin improved indices of coronary reperfusion and patency. Initial results with clinical end points, including death or myocardial infarction, also have shown favorable results for hirudin compared with heparin. In the first phases of the larger phase III trials, the rate of hemorrhagic events, including intracranial hemorrhage, was higher than expected in both the hirudin and heparin arms, indicating that a safety ceiling had been reached. The TIMI 9B and GUSTO IIb trials are using lower doses of intravenous hirudin and heparin, which should allow testing of the "thrombin hypothesis": that more potent inhibition of thrombin will translate into improved clinical outcome for patients with acute MI.

Improved Anticoagulation with a Weight-Adjusted Heparin Nomogram in Patients with Acute Coronary Syndromes: A Randomized Trial

The optimal heparin dosing schedule to achieve rapid and therapeutic anticoagulation has not been established. The objective of this study is to determine whether an intravenous heparin dosing nomogram based on body weight achieves adequate anticoagulation more rapidly than a standard-care nomogram. Sixty-four patients requiring intravenous heparin treatment for acute coronary syndromes, but who did not receive thrombolytic therapy, were randomized to a standard-care nomogram in which heparin was given as a 5000 unit IV bolus followed by 1000 U/hr, or a weight-adjusted nomogram in which heparin was given as an 80 U/kg IV bolus and 18 U/kg/hr. Activated partial thromboplastin time (APTT) values were checked at 6, 12, 18, 24, and 48 hours and adjusted either by 100-200 U/hr (standard-care nomogram) or by 2-4 U/kg/hr (weight-based nomogram). Activated partial thromboplastin times were measured using a widely generalizable laboratory method. The primary goal was to achieve and maintain the APTT between 60 and 90 seconds. The median APTT values were higher in the weight-adjusted group compared with the standard-care group at 6, 12, 18, 24, and 48 hours: 150 versus 83 (p = 0.001), 100 versus 79 (p = 0.09), 66 versus 61 (p = 0.005), 63 versus 56 (p = 0.09), and 64 versus 56 (p = 0.11). At 18 hours only 11% of patients in the weight-adjusted group had an APTT <61 compared with 26% in the standard-care nomogram (p = 0.007). No major bleeding complications were noted in either group. A weight-adjusted heparin nomogram offers improved anticoagulation in the first 24 hours after heparin initiation compared with a standard-care nomogram in patients with acute coronary artery syndromes.

Improving the Efficacy and Stability of Coronary Reperfusion Following Thrombolysis: Exploring the Thrombin Hypothesis

A major assumption in the treatment of patients with acute myocardial infarction (MI) implies that the speed of coronary arterial reperfusion correlates directly with the overall extent of myocardial salvage, and that the extent of mycardial salvage, in turn, determines the absolute reduction in patient mortality. While a growing experience has made it clear that myocardial salvage-independent (time-independent) mechanisms of benefit also exist, few would argue with the hypothesis that the greatest benefit derived from coronary thrombolysis occurs with early (time-dependent) treatment. Thus, improvements in the efficacy of reperfusion and the stability of reperfusion are likely to have considerable impact on patient outcome.

Activated partial thromboplastin time (aPTT) monitoring to achieve therapeutic anticoagulation before and after introducing a nomogram for adjunctive heparin treatment with thrombolytic therapy for acute myocardial infarction

In patients with acute myocardial infarction (AMI) receiving thrombolytic therapy and i.v. unfractionated heparin, anticoagulant levels are frequently outside the target range. We evaluated the effects on anticoagulant levels before (group A) and after (group B) the introduction of a heparin nomogram in consecutive AMI-patients, receiving thrombolytic therapy and adjunctive heparin treatment. The target activated partial thromboplastin time (aPTT) was defined as 60-90 s. During the first 72 h after admission, the total number of aPTTs within the target range and the time taken to achieve the range were compared. The incidence of bleeding complications was assessed. Group A consisted of 56 and group B of 55 patients. The number of patients within the target range at 72 h (44 versus 51; chi2=4.51; P=0.034) was significantly higher in group B. No difference was found between total aPTTs within the target range (26% in group A versus 30% in group B; P=ns). Bleeding complications were slightly less in group B (7 versus in group A versus 2 patients in group B; P=ns). We concluded that the introduction of a nomogram resulted in significantly more patients with aPTTs within the target range. However, a substantial number of aPTTs before and after introduction of the nomogram were outside the target range. Moreover, this retrospective study shows that previously acquired prospective data (which showed a marked improvement of anticoagulation using a heparin nomogram) are not necessarily reproduced in the real life clinical setting.

Use of bedside activated partial thromboplastin time monitor to adjust heparin dosing after thrombolysis for acute myocardial infarction: results of GUSTO-I. Global Utilization of Streptokinase and TPA for Occluded Coronary Arteries

BACKGROUND

The safety and efficacy of bedside monitors of activated partial thromboplastin time (aPTT) have not been examined in a large population receiving intravenous heparin after thrombolytic treatment for acute myocardial infarction. We compared outcomes among patients monitored with these devices versus standard monitoring methods.

METHODS AND RESULTS

Investigators chose the bedside device (n = 1713 patients) or their standard method (n = 26,162) for all aPTT measurements at their sites. Clinical outcomes at 30 days, 1-year mortality rate, and aPTT levels at 6, 12, and 24 hours were compared. Bedside-monitored patients had significantly less moderate/severe bleeding (10% vs 12%, P < .01), fewer transfusions (7% vs 11%, P < .001), and a smaller decrease in hematocrit (5.5% vs 6.7%, P < .001) but significantly more recurrent ischemia (22% vs 20%, P = .01). Fewer bedside-monitored patients had subtherapeutic aPTT levels at 12 and 24 hours. Among patients with subtherapeutic levels at 6 and 12 hours, more bedside-monitored patients had therapeutic levels when next monitored. After adjustment for baseline differences, no significant difference in mortality rate was observed in bedside-monitored patients at 30 days (4.3% vs 4.8%, P = .27) and at 1 year (7.1% vs 7.7%, P = .38). The groups had similar rates of reinfarction, shock, heart failure, and stroke.

CONCLUSIONS

This prospective substudy supports the use of bedside monitoring of heparin anticoagulation after thrombolysis.

Intracoronary aspiration thrombectomy for acute myocardial infarction

To investigate the pathogenesis of acute myocardial infarction (AMI) and values of intracoronary aspiration thrombectomy (ICAT), we applied ICAT to reperfusion therapy using generally available intracoronary catheters to aspirate intracoronary occlusive tissues. We assigned ICAT or primary percutaneous transluminal coronary angioplasty (PTCA) to patients with evolving AMI (Thrombolysis In Myocardial Infarction (TIMI) trial grade 0), and investigated primary histopathologic, clinical, and angiographic outcomes in 43 patients treated with ICAT alone or followed by PTCA, and compared the outcomes with those in 48 patients treated with primary PTCA. No major complications (procedural death, emergent bypass graft surgery) occurred. Reconalization (TIMI grade 3 and 2) was achieved in 25 patients (58%) with ICAT alone and in 39 patients (91%) with ICAT alone or followed by PTCA. Aspirated thrombi were defined as recent thrombi in 21 cases (49%), atheroma in 6 (14%), no thrombi in 13 (30%), and organized thrombi in 1 case. In cases of recent thrombi, ICAT alone provided recanalization more frequently than in those of atheroma or no thrombi (18 of 21 [86%], 3 of 6 [50%], 4 of 13 [31%], respectively; p < 0.05; recent thrombi vs atheroma or no thrombi). There were no significant differences in primary recanalization rate (ICAT alone or followed by PTCA vs primary PTCA; 91% vs 92%) or incidence of complications between the 2 strategies. These results indicate that although the pathogenesis of AMI is heterogeneous in each individual case, intracoronary thrombus contributes little to the pathogenesis of average AMI, and therefore mechanical approaches may be feasible to maximize reperfusion therapies for AMI.

Heparin management in acute myocardial infarction (AMI)

Antithrombotic agents have been shown to be beneficial in the setting of acute coronary syndromes, and as an adjunct to thrombolysis for acute myocardial infarction (AMI). The optimal type and dosing of antithrombotic drug, however, remains elusive. Heparin, the agent most commonly used, has several limitations, the most important of which may be its inability to inhibit clot-bound thrombin. Newer, direct thrombin inhibitors (such as hirudin) provide potent and predictable thrombin inhibition and are able to inhibit clot-bound thrombin. Both heparin and hirudin can carry a substantial risk of haemorrhage, however, and thrombin activity is likely to rebound after discontinuation of either agent. Further, the relationships of antithrombotic/thrombolytic dosing, measures of anticoagulation (such as APTT), and clinical outcomes are not always clear. Nonetheless, from the data available from large, randomised trials, intravenous heparin should remain a standard adjunct to thrombolytic therapy for AMI.

Thrombin generation, inhibition and clinical outcomes in patients with acute myocardial infarction treated with thrombolytic therapy and heparin: results from the GUSTO-I Trial. GUSTO-I Hemostasis Substudy Group. Global Utilization of Streptokinase and TPA for Occluded Coronary Arteries

OBJECTIVES

We sought to assess the effects of antithrombotic therapy after thrombolysis for acute myocardial infarction on markers of thrombin generation and activity and to determine the relation of these markers with clinical outcomes.

BACKGROUND

Thrombin activation and generation often occur with thrombolysis for acute myocardial infarction. Antithrombotic regimens have been developed to reduce the resulting thrombotic complications.

METHODS

We sampled plasma markers of thrombin generation and activity after thrombolysis in 292 patients. We assessed the relations of these markers with clinical outcomes at 30 days.

RESULTS

Fibrinopeptide A (FPA), a marker of thrombin activity toward fibrinogen, was elevated at baseline (12.3 ng/ml) and increased to 18.4 ng/ml by 90 min after streptokinase and subcutaneous heparin treatment. With intravenous heparin, this increase was attenuated, but intravenous heparin did not prevent thrombin generation, as measured by prothrombin fragment 1.2 (F1.2). Heparin level, measured by anti-Xa activity, correlated with activated partial thromboplastin time (aPTT, r = 0.62 to 0.67). Thrombin activity, measured by FPA, was as closely related to aPTT as to the heparin level. Baseline levels of F1.2 were significantly related to the risk of death or reinfarction at 30 days (p = 0.008); values 12 h after enrollment also were related to 30-day mortality (p = 0.05).

CONCLUSIONS

Although intravenous heparin partly suppresses the increased thrombin activity associated with thrombolysis, it does not inhibit thrombin generation. The aPTT was as good a measure of suppression of thrombin activity as the heparin level itself. Hematologic markers of thrombin generation were found to be related to the subsequent risk of thrombotic events.

Relation of coagulation parameters to patency and recurrent ischemia in the Thrombolysis in Myocardial Infarction (TIMI) Phase II Trial

Current protocols for use of tissue-type plasminogen activator in acute myocardial infarction include heparin estimated by the activated partial thromboplastin time (aPTT). Recent reports indicate a risk of recurrent ischemic events with long aPTT values. Longer aPTT values in the Thrombolysis in Myocardial Infarction-II (TIMI II) Trial, obtained within the first 48 hours, were associated with patency at 18 to 48 hours and better left ventricular function at discharge (average 9.6 days), but also with emergency catheterizations within the first 48 hours and, weakly, with recurrent ischemia during the first 18 hours. A moderate decrease in fibrinogen, compared with a "small" decrease, was also associated with patency, but a "large" decrease was associated with hemorrhagic events. Patency was associated with higher fibrinogen values and higher plasminogen values at baseline. The aPTT results support frequent monitoring during the first 24 to 48 hours to ensure optimal clinical outcome. The coagulation factor results suggest that there may be an optimum window for fibrinogenolysis in this setting.

Comparison of saruplase and alteplase in acute myocardial infarction. SESAM Study Group. The Study in Europe with Saruplase and Alteplase in Myocardial Infarction

Four hundred seventy-three patients with acute myocardial infarction (AMI) were treated with either saruplase (80 mg/hour, n = 236) or alteplase (100 mg every 3 hours, n = 237). Comedication included heparin and acetylsalicylic acid. Angiography was performed at 45 and 60 minutes after the start of thrombolytic therapy. When flow was insufficient, angiography was repeated at 90 minutes. Coronary angioplasty was then performed if Thrombolysis In Myocardial Infarction (TIMI) trial 0 to 1 flow was seen. Control angiography was at 24 to 40 hours. Baseline characteristics were similar. Angiography showed comparable and remarkably high early patency rates (TIMI 2 or 3 flow) in both treatment groups: at 45 minutes, 74.6% versus 68.9% (p = 0.22); and at 60 minutes 79.9% versus 75.3% (p = 0.26). Patency rates at 90 minutes before additional interventions were also comparable (79.9% and 81.4%). Angiographic reocclusion rates were not significantly different: 1.2% versus 2.4% (p = 0.68). After rescue angioplasty, angiographic reocclusion rates of 22.0% and 15.0% were observed. Safety data were similar for both groups. Thus, (1) early patency rates were high for saruplase and alteplase treatment, (2) reocclusion rates for both drugs were remarkably low, and (3) complication rates were similar. Thus, saruplase seems to be as safe and effective as alteplase.

Antiplatelet and anticoagulant use after myocardial infarction

Coronary thrombosis leading to myocardial infarction is a complex process involving the interaction of the arterial wall, the coagulation cascade, and platelets. Increased understanding of the molecular biology of thrombosis has prompted an evolution in antithrombotic therapy, from the early use of warfarin following myocardial infarction to agents targeting specific receptors or modulators in the thrombotic process. The complexity of thrombosis allows for numerous sites of pharmacologic intervention; the multiple pathways leading to platelet aggregation and thrombin formation provide the opportunity for combined therapies. This review presents the current clinical data on antiplatelet, anticoagulant, and specific antithrombin therapies following myocardial infarction.

Overview of randomized trials of intravenous heparin in patients with acute myocardial infarction treated with thrombolytic therapy

Intravenous heparin is routinely given after thrombolytic therapy for patients with acute myocardial infarction in the United States and in some, but by no means all, other countries. Several trials have documented improved infarct-artery patency in patients treated with heparin; however, none was large enough individually to assess the effect of heparin on clinical outcomes. We performed a systematic overview of the 6 randomized controlled trials (1,735 patients) to summarize the available data concerning the risks and benefits of intravenous heparin versus no heparin after thrombolytic therapy. Mortality before hospital discharge was 5.1% for patients allocated to intravenous heparin compared with 5.6% for controls (relative risk reduction of 9%, odds ratio 0.91, 95% confidence interval 0.59 to 1.39). Similar rates of recurrent ischemia and reinfarction were observed among those allocated to heparin therapy or control. The rates of total stroke, intracranial hemorrhage, and severe bleeding were similar in patients allocated to heparin; however, the risk of any severity of bleeding was significantly higher (22.7% vs 16.2%; odds ratio 1.55, 95% confidence interval 1.21 to 1.98). There was no significant difference in the observed effects of heparin between patients receiving tissue-type plasminogen activator and those receiving streptokinase or anisoylated plasminogen streptokinase activator complex, or between patients who did and did not receive aspirin. The findings of this overview demonstrate that insufficient clinical outcome data are available to support or to refute the routine use of intravenous heparin therapy after thrombolysis. It is not known if these findings are due to lack of statistical power, inappropriate levels of anticoagulation, or lack of benefit of intravenous heparin. Large randomized studies of heparin (and of new antithrombotic regimens) are needed to establish the role of such therapy.

Activated partial thromboplastin time and outcome after thrombolytic therapy for acute myocardial infarction: results from the GUSTO-I trial

BACKGROUND

Although intravenous heparin is commonly used after thrombolytic therapy, few reports have addressed the relationship between the degree of anticoagulation and clinical outcomes. We examined the activated partial thromboplastin time (aPTT) in 29,656 patients in the Global Utilization of Streptokinase and t-PA for Occluded Coronary Arteries (GUSTO-I) trial and analyzed the relationship between the aPTT and both baseline patient characteristics and clinical outcomes.

METHODS AND RESULTS

Intravenous heparin was administered as a 5000-U bolus followed by an initial infusion of 1000 U/h, with dose adjustment to achieve a target aPTT of 60 to 85 seconds. aPTTs were collected 6, 12, and 24 hours after thrombolytic administration. Higher aPTT at 24 hours was strongly related to lower patient weight (P < .00001) as well as older age, female sex, and lack of cigarette smoking (all PT< .0001). At 12 hours, the aPTT associated with the lowest 30-day mortality, stroke, and bleeding rates was 50 to 70 seconds. There was an unexpected direct relationship between the aPTT and the risk of subsequent reinfarction. There was a clustering of reinfarction in the first 10 hours after discontinuation of intravenous heparin.

CONCLUSIONS

Although the relationship between aPTT and clinical outcome was confounded to some degree by the influence of baseline prognostic characteristics, aPTTs higher than 70 seconds were found to be associated with higher likelihood of mortality, stroke, bleeding, and reinfarction. These findings suggest that until proven otherwise, we should consider the aPTT range of 50 to 70 seconds as optimal with intravenous heparin after thrombolytic therapy.

Relation between systemic anticoagulation as determined by activated partial thromboplastin time and heparin measurements and in-hospital clinical events in unstable angina and non-Q wave myocardiaL infarction. Thrombolysis in Myocardial Ischemia III B Investigators

Although coronary thrombosis is thought to play a pivotal role in the pathogenesis of unstable angina and non-Q wave myocardial infarction and antithrombotic therapy is a mainstay in the early management of these patients, the relation between measures of systemic anticoagulation and clinical events has not been defined clearly. In the Thrombolysis in Myocardial Ischemia III trial, 1473 patients with ischemic chest pain at rest evaluated within 24 hours of symptom onset were randomized to (1) tissue plasminogen activator (TPA) or placebo and (2) an early invasive or an early conservative strategy. All patients received a full complement of anti-ischemic medication, aspirin, and continuous intravenous heparin titrated to an activated partial thromboplastin time (aPTT) of 1.5 to 2.0 times control for 72 to 96 hours. The median aPTT in all study groups exceeded the minimum threshold (45 seconds) by 24 hours and remained within the designated range during the protocol-directed heparin infusion. No differences in median aPTT values for the 72- to 96-hour study period were observed between groups (p=not significant). Median 12-hour heparin concentrations were >0.2 U/ml in all groups; however, values <0.2 U/ml were common thereafter, particularly in TPA-treated patients. Time-dependent covariate analyses failed to identify statistically significant differences in either aPTT or heparin levels between patients with in-hospital clinical events (spontaneous ischemia, myocardial infarction, or death) and those without events (p=0.27). Furthermore, early clinical events occurred in a similar percentage of patients with optimal anticoagulation (all aPTTs >60 seconds, all heparin levels>0.2 U/ml), and those with aPTTs or heparin levels below these thresholds. Aggressive (high-intensity) anticoagulation with heparin to achieve aPTTs >2.0 times control does not appear to offer additional clinical benefit to lower levels (1.5 to 2.0 times control) among patients with unstable angina and non-Q wave myocardial infarction receiving intravenous heparin and oral aspirin. Therefore, the optimal level of anticoagulation in this common clinical setting is between 45 and 60 seconds when heparin is included in the treatment strategy. Direct plasma heparin measurement does not offer an advantage to routine aPTT monitoring. The occurrence of spontaneous ischemia, myocardial infarction, and death in spite of antischemic therapy and optimal anticoagulation (as it is currently defined) with heparin supports ongoing efforts to develop more effective antithrombotic agents.

Frequency of "optimal anticoagulation" for acute myocardial infarction after thrombolysis with front-loaded recombinant tissue-type plasminogen activator and conjunctive therapy with recombinant hirudin (HBW 023). ALKK Study Group

This retrospective analysis reviewed 183 patients with acute myocardial infarction who were given front-loaded recombinant tissue-type plasminogen activator (rt-PA) and r-hirudin (HBW 023) in 1 of 4 dose groups (bolus dose of 0.07, 0.1, 0.2, or 0.4 mg/kg, followed by an infusion of 0.05, 0.06, 0.1, or 0.15 mg/kg/hour over 48 hours). Activated partial thromboplastin time (aPTT) levels were determined at baseline and at 4, 8, 12, 16, 20, 24, 32, 40, and 48 hours. Of the 178 patients with r-hirudin treatment for > or = 12 hours, anticoagulation was optimal in 55.1% (all aPTTs > 2 x baseline), suboptimal in 33.7% (lowest aPTT > 1.5 but < 2 x baseline), and inadequate in 11.2% (> or = 1 aPTT but < 1.5 x baseline). Optimal anticoagulation was observed more frequently in the higher dose groups (dose 1, 15%; dose 2, 44.4%; dose 3, 63.4%; dose 4, 73.4%; p for trend < 0.0001). Patency (according to Thrombolysis in Myocardial Infarction trial grade 2 or 3) of the infarct artery after 36 to 48 hours was higher in the group with optimal anticoagulation compared with those with suboptimal or inadequate anticoagulation: 97.9%, 88.4%, and 85%, respectively (p = 0.03 optimal vs suboptimal or inadequate anticoagulation). In conclusion, r-hirudin in a dose of 0.1 or 0.15 mg/kg/hour achieves an optimal anticoagulation in about 63% or 74% of patients, which is associated with an enhanced patency 24 to 48 hours after rt-PA. A subsequent study revealed that this effective anticoagulation may be accompanied by an increased risk of severe bleeding complications after thrombolysis.

Thrombolytic and antithrombotic treatment in myocardial infarction: main achievements and future perspectives

Several trials enrolling thousands of patients have demonstrated the beneficial effect of thrombolytic therapy on survival in patients with acute myocardial infarction. Three large trials have compared the effect of different thrombolytic agents on mortality from myocardial infarction: GISSI-2/International trial, ISIS-3, and GUSTO. In this last trial, treatment with accelerated t-PA and intravenous heparin resulted in a 14% relative reduction in mortality compared with streptokinase and intravenous or subcutaneous heparin. The results of the GUSTO trial renewed the interest toward new strategies for enhancing the speed and rate of coronary reperfusion. An improvement in coronary patency can be anticipated by adopting a variety of pharmacological approaches that include the development of more effective therapeutic regimens with the available thrombolytic agents, the development of more fibrin specific agents and the development of safer and more effective adjunctive antithrombotic agents to accelerate thrombolysis and to prevent rethrombosis.

Early reactivation of ischaemia after abrupt discontinuation of heparin in acute myocardial infarction

Intravenous heparin after thrombolytic therapy for acute myocardial infarction is an effective, widely used treatment. Six cases of acute myocardial infarction are reported with early disease reactivation following the abrupt discontinuation of heparin infusion three days after alteplase thrombolysis and concomitant aspirin therapy. Immediate reinfusion of heparin resulted in regression of symptomatic ischaemia in all six patients. The activated partial thromboplastin time values, determined four hours before the discontinuation of heparin therapy, were within the therapeutic range in five of the six patients, and no difference was found in the values obtained one hour after the reinfusion of heparin (P = 0.065).

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.

New thrombolytic agents and strategies

Despite their widespread use in patients with acute myocardial infarction, all currently available thrombolytic agents suffer from a number of significant limitations, including resistance to reperfusion, the occurrence of acute coronary reocclusion, and bleeding complications. Several lines of research towards improvement of thrombolytic therapy are being explored, including strategies to enhance the fibrinolytic potency of plasminogen activators and to improve conjunctive antiplatelet or antithrombotic agents. Mutants and variants of plasminogen activators, chimeric plasminogen activators, and conjugates of plasminogen activators with monoclonal antibodies have been constructed, and plasminogen activators from animal or bacterial origin have been evaluated. Some of these new thrombolytic agents have shown promise in animal models of venous or arterial thrombosis and in pilot studies in patients with acute myocardial infarction. Such molecules include mutants of tissue-type plasminogen activator (t-PA) with prolonged half-life and/or resistance to protease inhibitors and staphylokinase. Antiplatelet strategies include the use of platelet glycoprotein IIb/IIIa receptor blocking agents, of thromboxane synthase inhibitors and endoperoxide receptor antagonists. Antithrombotic strategies include the use of selective inhibitors of thrombin, tissue factor or factor Xa. The efficiency and safety of these new agents in man will have to be carefully evaluated.

Hirudin: initial results in acute myocardial infarction, unstable angina and angioplasty

The central role of thrombosis in the pathogenesis of acute myocardial infarction, unstable angina and complications after angioplasty has led to intense interest in developing more effective antithrombotic agents for these disorders. Hirudin, a direct thrombin inhibitor, has undergone extensive testing in experimental models and has recently been evaluated in patients in several pilot trials. Across these three indications, hirudin has been found to achieve a more consistent level of anticoagulation than heparin, as gauged by the activated parital thromboplastin time. Similarly, as an adjunct to thrombolytic therapy in acute myocardial infarction, in the treatment of unstable angina and in support of angioplasty, hirudin appeared to improve indexes of coronary reperfusion and patency. Initial results with clinical end points, including death or myocardial infarction, appeared to favor hirudin over heparin. In several large phase III trials, hirudin is being compared with heparin for all three indications. In the first phases of these trials, the rate of hemorrhagic events, including intracranial hemorrhage, was higher than expected in both the hirudin and heparin arms, which demonstrated that a safety ceiling had been reached. The reformulated Thrombolysis in Myocardial Infarction (TIMI) 9 and Second Global Use of Strategies to Open Occluded Coronary Arteries (GUSTO II) trials are using lower doses of hirudin and heparin, which should allow testing of whether the initial favorable results observed in pilot trials will translate into improved clinical outcome, with an acceptable safety profile, for patients with acute myocardial infarction or unstable angina or those undergoing angioplasty.

Medical therapy of acute myocardial infarction: Part I. Role of thrombolytic and antithrombotic therapy

Thrombolytic therapy has been established as a safe and effective therapeutic strategy in acute myocardial infarction (MI). Its efficacy is improved with early administration, although modest benefits can be demonstrated for up to 12 hours. Tissue plasminogen activator (TPA) appears to offer benefits over streptokinase when administered to patients who present within 4 hours, those with an anterior MI, and who are less than 75 years old. Age alone is not a contraindication for thrombolysis because the risk of bleeding complications in the elderly is outweighed by a significant improvement in mortality. One of the major limitations of thrombolytic therapy in acute MI is reocclusion. Use of adjunctive antithrombotic therapy can reduce the rate of reocclusion following successful thrombolysis. The beneficial role of aspirin is well established. Use of intravenous heparin in conjunction with streptokinase offers no clinical benefit. The efficacy of heparin when administered with other thrombolytic agents remains to be established. These issues and the role of newer antiplatelet and antithrombin agents are being examined in ongoing clinical trials. The objective of this review is to provide the information needed for careful and appropriate judgment in the use of thrombolytic agents and antithrombotic therapy. General principles are emphasized, and specific recommendations are included as guidelines.

Early angiography cannot predict postthrombolytic coronary reocclusion: observations from the GUSTO angiographic study. Global Utilization of Streptokinase and t-PA for Occluded Coronary Arteries

OBJECTIVES

The purpose of this study was to determine whether early qualitative or quantitative angiographic features can predict reocclusion after initially successful coronary thrombolysis.

BACKGROUND

Although both the benefits of early reperfusion and the consequences of subsequent reocclusion after thrombolysis for acute myocardial infarction have been well described, efforts to describe angiographic markers of lesions at high risk for reocclusion have produced conflicting results. The Global Utilization of Streptokinase and t-PA for Occluded Coronary Arteries (GUSTO) angiographic trial provides the opportunity to examine these relations in the largest single, prospective patient cohort studied to date.

METHODS

We studied 559 patients undergoing follow-up angiography at 90 min and 5 to 7 days after thrombolysis in the GUSTO trial. Patients received one of four thrombolytic regimens: 1) streptokinase with intravenous heparin; 2) streptokinase with subcutaneous heparin; 3) accelerated-dose recombinant tissue-type plasminogen activator (rt-PA) with intravenous heparin; or 4) a combination of streptokinase and conventionally dosed rt-PA with intravenous heparin. Qualitative variables examined at 90-min angiography included Thrombolysis in Myocardial Infarction (TIMI) flow grade, visible thrombus and lesion morphology. Quantitative variables included percent diameter stenosis, percent area stenosis, minimal lumen diameter and lesion length. The study contained a power > 0.85 to detect clinically important differences in percent diameter stenosis, percent area stenosis and minimal lumen diameter between the groups with subsequent reocclusion and sustained patency at the p = 0.05 level.

RESULTS

At follow-up, 33 patients (5.9%) had reocclusion. The reocclusion rate for patients with early TIMI grade 2 flow was 6.3% versus 5.6% for TIMI grade 3 flow (p = NS). When the group with reocclusion was compared with the group with continued patency, there were no differences in presence of early visible thrombus, complex lesion morphology, percent diameter stenosis, percent area stenosis, minimal lumen diameter or lesion length.

CONCLUSIONS

Our findings demonstrate that neither qualitative nor quantitative angiographic variables at 90 min after initiation of thrombolytic therapy can be used to predict subsequent coronary reocclusion.

Bedside coagulation monitoring in heparin-treated patients with active thromboembolic disease: a coronary care unit experience

Patients with active venous and arterial thromboembolic disorders are known to benefit from systemic anticoagulation with heparin. Clinical studies have shown, however, that therapeutic anticoagulation is rarely achieved rapidly and often is not maintained over time. Prolonged laboratory turnaround time of the activated partial thromboplastin time (aPTT) may contribute directly to these common problems. A total of 272 aPTT determinations were performed on 120 heparin-treated patients admitted to the coronary care unit. The time from sample collection to data availability was 126 +/- 84 minutes with standard laboratory aPTT testing. In contrast, a bedside coagulation device provided an aPTT within 3 minutes (p < 0.001). Subtherapeutic aPTT values (< 65 seconds) were documented in 21% of all patients; in each, the heparin dose was changed and a repeat aPTT was required. In a separate study of 33 heparinized patients randomized to either bedside or central laboratory aPTT testing (264 aPTT determinations), the time to achieve a therapeutic state of systemic anticoagulation was 8.2 hours and 18.1 hours, respectively (p < 0.005). The time from aPTT determination to a decision regarding heparin titration adjustments was 14.5 minutes and 3 hours with bedside and laboratory testing, respectively (p < 0.001). Thus bedside coagulation monitoring provides a convenient, rapid, and accurate assessment of systemic anticoagulation among heparin-treated patients with active thromboembolic disease in the coronary care unit. This technology warrants further clinical investigation.

A pilot trial of recombinant desulfatohirudin compared with heparin in conjunction with tissue-type plasminogen activator and aspirin for acute myocardial infarction: results of the Thrombolysis in Myocardial Infarction (TIMI) 5 trial

OBJECTIVES

The purpose of this study was to assess the value of recombinant desulfatohirudin (hirudin) as adjunctive therapy to thrombolysis in acute myocardial infarction.

BACKGROUND

Failure to achieve initial reperfusion and reocclusion of the infarct-related artery remain major limitations of thrombolytic therapy despite aggressive regimens of heparin and aspirin. Hirudin, a direct thrombin inhibitor, has been shown in experimental models to enhance thrombolysis and reduce reocclusion.

METHODS

The Thrombolysis in Myocardial Infarction (TIMI) 5 trial was a randomized, dose-ranging, pilot trial of hirudin versus heparin, given with front-loaded tissue-type plasminogen activator and aspirin to 246 patients with acute myocardial infarction. Patients received either intravenous heparin or hirudin at one of four ascending doses for 5 days. Patients underwent coronary angiography at 90 min and at 18 to 36 h, unless rescue angioplasty was performed.

RESULTS

The primary end point, TIMI grade 3 flow in the infarct-related artery at 90 min and 18 to 36 h without death or reinfarction before the 18- to 36-h catheterization was achieved in 97 (61.8%) of 157 evaluable hirudin-treated patients compared with 39 (49.4%) of 79 evaluable heparin-treated patients (p = 0.07). All four doses of hirudin led to similar findings in the angiographic and clinical end points. At 90 min, TIMI grade 3 flow was present in 105 (64.8%) of 162 hirudin-treated patients compared with 48 (57.1%) of 84 heparin-treated patients (p = NS). Infarct-related artery patency (TIMI grade 2 or 3 flow) was similar in the two groups (82.1% and 78.6%, respectively). At 18 to 36 h, 129 (97.8%) of 132 hirudin-treated patients had a patent infarct-related artery compared with 58 (89.2%) of 65 heparin-treated patients (p = 0.01). Reocclusion by 18 to 36 h occurred in 2 (1.6%) of 123 hirudin-treated patients versus 4 (6.7%) of 60 heparin-treated patients (p = 0.07). Death or reinfarction occurred during the hospital period in 11 (6.8%) of 162 hirudin-treated patients compared with 14 (16.7%) of 84 heparin-treated patients (p = 0.02). Major spontaneous hemorrhage occurred in 1.2% of hirudin-treated patients versus 4.7% of heparin-treated patients (p = 0.09), and major hemorrhage at an instrumented site occurred in 16.3% and 18.6%, respectively (p = NS).

CONCLUSIONS

Hirudin is a promising agent compared with heparin as adjunctive therapy with thrombolysis for acute myocardial infarction, and its evaluation in larger trials is warranted.

Thrombolytic retreatment with tissue plasminogen activator for threatened reinfarction and thrombotic coronary reocclusion

Following successful coronary arterial thrombolysis, thrombogenic substrate persists, increasing the risk of recurrent thrombosis, reocclusion, and reinfarction. The preferred treatment in this setting has not been established. Although many patients receive mechanical revascularization, it is conceivable that repeat thrombolysis, primarily with tissue plasminogen activator, represents the most readily available and effective alternative.

New strategies for enhancing the speed and rate of coronary reperfusion

Large, controlled clinical trials have conclusively demonstrated that intravenous thrombolytic therapy reduces mortality in patients with acute myocardial infarction. The recently published Global Utilization of Streptokinase and t-PA for Occluded Arteries (GUSTO) study demonstrated that patency within 90 minutes is predictive of survival. As a consequence, the interest in new strategies for enhancing the speed and rate of coronary reperfusion has been renewed. Further improvements in coronary patency can be anticipated by adopting a variety of approaches. Some of these approaches are simple and require only the application of proven principles, whereas others are more complex and require further research. The first approaches include earlier treatment after the onset of clinical symptoms, because of the strong relation between early treatment and improved clinical efficacy. Other approaches include development of more effective dosage regimens for the available thrombolytic agents, development of more fibrin-specific agents in an attempt to speed up lysis, and development of safer, more effective adjunctive antithrombotic agents to accelerate thrombolysis and prevent rethrombosis. The potential benefits from these latter approaches must not be offset by unacceptable increases in major bleeding or in the costs of treatment. The application of proven principles to improve coronary reperfusion should not be obscured by the research of more effective pharmacologic approaches. Actually, earlier and wider use of the currently available thrombolytic agents could potentially save more lives than the development of technically more exciting new approaches.

Tailored thrombolytic therapy. A perspective

BACKGROUND

In contrast with current standard regimens, it seems more appropriate to tailor thrombolytic therapy to individual patient characteristics. A proposed model for such tailored therapy is based on individual assessment of benefits and risks of thrombolytic therapy, taking into account the response of individual patients to the therapy given.

METHODS AND RESULTS

Potential benefits of thrombolysis in individual patients can be predicted by use of demographic patient characteristics (age, sex, history of previous infarction) together with indicators of the ischemic area at risk (total ST segment deviation) and treatment delay. Using these parameters, the number of "lives saved" by thrombolytic therapy for specific patient characteristics can be estimated. Similarly, the risk of intracranial hemorrhage during thrombolytic therapy can be estimated from the patient's age, blood pressure at admission, and body weight. Depending on benefit/risk estimates, a choice can be made between regimens with high, medium, or modest thrombolytic efficacy. Continuous multilead ECG ischemia monitoring and rapid assays of myocardial proteins in serum can be used to assess the occurrence or absence of reperfusion and to detect signs of reocclusion. Such data help to decide whether thrombolytic therapy should be continued or intensified or might be discontinued in individual patients before the total standard dose has been administered. Such tailored reduction of the total thrombolytic dose will reduce the risk for bleeding complications in some of the patients.

CONCLUSIONS

The concept of tailoring thrombolytic therapy and the models presented for benefit/risk assessment should be tested in clinical studies and may subsequently help the physician to select the optimal approach in individual patients.

The effects of tissue plasminogen activator, streptokinase, or both on coronary-artery patency, ventricular function, and survival after acute myocardial infarction

BACKGROUND

Although it is known that thrombolytic therapy improves survival after acute myocardial infarction, it has been debated whether the speed with which coronary-artery patency is restored after the initiation of therapy further affects outcome.

METHODS

To study this question, we randomly assigned 2431 patients to one of four treatment strategies for reperfusion: streptokinase with subcutaneous heparin; streptokinase with intravenous heparin; accelerated-dose tissue plasminogen activator (t-PA) with intravenous heparin; or a combination of both activators plus intravenous heparin. Patients were also randomly assigned to cardiac angiography at one of four times after the initiation of thrombolytic therapy: 90 minutes, 180 minutes, 24 hours, or 5 to 7 days. The group that underwent angiography at 90 minutes underwent it again after 5 to 7 days.

RESULTS

The rate of patency of the infarct-related artery at 90 minutes was highest in the group given accelerated-dose t-PA and heparin (81 percent), as compared with the group given streptokinase and subcutaneous heparin (54 percent, P < 0.001), the group given streptokinase and intravenous heparin (60 percent, P < 0.001), and the group given combination therapy (73 percent, P = 0.032). Flow through the infarct-related artery at 90 minutes was normal in 54 percent of the group given t-PA and heparin but in less than 40 percent in the three other groups (P < 0.001). By 180 minutes, the patency rates were the same in the four treatment groups. Reocclusion was infrequent and was similar in all four groups (range, 4.9 to 6.4 percent). Measures of left ventricular function paralleled the rate of patency at 90 minutes; ventricular function was best in the group given t-PA with heparin and in patients with normal flow through the infarct-related artery irrespective of treatment group. Mortality at 30 days was lowest (4.4 percent) among patients with normal coronary flow at 90 minutes and highest (8.9 percent) among patients with no flow (P = 0.009).

CONCLUSIONS

This study supports the hypothesis that more rapid and complete restoration of coronary flow through the infarct-related artery results in improved ventricular performance and lower mortality among patients with myocardial infarction. This would appear to be the mechanism by which accelerated t-PA therapy produced the most favorable outcome in the GUSTO trial.

Anticoagulant effects of hirulog, a novel thrombin inhibitor, in patients with coronary artery disease

Selective thrombin inhibitors are a new class of antithrombotic drugs that, unlike heparin, can effectively inhibit clot-bound thrombin and escape neutralization by activated platelets. Hirulog is a 20 amino acid hirudin-based synthetic peptide that has shown promise in experimental models of thrombosis. Little information is available about the effects of hirulog in patients with coronary artery disease. Forty-five patients undergoing cardiac catheterization, who were taking aspirin, were randomized to receive either (1) hirulog, 0.05 mg/kg intravenous bolus followed by 0.2 mg/kg/hour intravenous infusion until the end of the catheterization; (2) hirulog, 0.15 mg/kg intravenous bolus followed by 0.6 mg/kg/hour intravenous infusion; or (3) heparin; 5,000 U intravenous bolus. Serial activated partial thromboplastin time (APTT), prothrombin time, activated clotting time and fibrinopeptide A were measured. Hirulog produced a dose-dependent prolongation of all coagulation parameters; the 0.6 mg/kg/hour dose prolonged the APTT to 218 +/- 50% of baseline after 2 minutes and 248 +/- 50% of baseline after 15 minutes. The half-life of the effect on APTT was 40 minutes. The hirulog blood level correlated well with the APTT, prothrombin time and activated clotting time (r = 0.77, 0.73, and 0.82 respectively, all p < 0.001). Both doses of hirulog potently suppressed the generation of fibrinopeptide A (p < 0.05). There were no major hemorrhagic, thrombotic or allergic complications in patients treated with hirulog or heparin. Thus, hirulog, a direct thrombin inhibitor, provides a predictable level of anticoagulation and appears to have a potent yet well-tolerated anticoagulant profile in patients with coronary artery disease.