Randomized angiographic trial of recombinant tissue-type plasminogen activator (alteplase) in myocardial infarction. RAAMI Study Investigators

The recanalization after thrombolysis as surrogate for clinical outcomes in patients with ST-segment elevation acute myocardial infarction: A systematic review and meta-regression analysis of data from randomized controlled trials

AIMS

Thrombolytic therapy has been known to be effective in reducing clinical outcomes and increasing recanalization rate among patients with ST-segment elevation acute myocardial infarction (STEMI). However, whether post-thrombolysis recanalization could be used as a surrogate for clinical outcomes is unknown.

METHODS

We systematically searched PubMed, EMBASE and the Cochrane Library database to identify randomized controlled trials (RCT) that examined effects of thrombolytic agents in STEMI. Recanalization was defined as TIMI grade 2 or 3 flow. The primary outcome was in-hospital all-cause mortality. Secondary outcomes included in-hospital and 30-day recurrent myocardial infarction (re-MI), composite of death and re-MI, major bleeding and all bleeding. Random-effects meta-regression was used for analysis.

RESULTS

We identified 111 eligible study arms and 52 eligible comparisons from 58 RCTs involving 16 536 patients. Our analyses showed that among study arms recanalization rate was significantly inversely associated with the incidence of in-hospital all-cause mortality (β: -0.07, 95% confidence interval [CI]: -0.13 to -0.02), re-MI (β: -0.09, 95%CI: -0.18 to -0.01) and the composite of death and re-MI (β: -0.17, 95%CI: -0.28 to -0.05), and positively associated with in-hospital all bleeding but not with major bleeding. Among paired comparisons, the difference in recanalization rate was associated with the corresponding difference in incidence of in-hospital all-cause mortality (β: -0.15, 95%CI: -0.28 to -0.01) but the relationship was not significant for any other outcome.

CONCLUSION

Pooled evidence from RCTs suggest the potential use of recanalization as a surrogate for clinical outcomes in evaluating the efficacy of thrombolysis among patients with STEMI.

Comparative efficacy and safety of reperfusion therapy with fibrinolytic agents in patients with ST-segment elevation myocardial infarction: a systematic review and network meta-analysis

BACKGROUND

Fibrinolytic therapy offers an alternative to mechanical reperfusion for ST-segment elevation myocardial infarction (STEMI) in settings where health-care resources are scarce. Comprehensive evidence comparing different agents is still unavailable. In this study, we examined the effects of various fibrinolytic drugs on clinical outcomes.

METHODS

We did a network meta-analysis based on a systematic review of randomised controlled trials comparing fibrinolytic drugs in patients with STEMI. Several databases were searched from inception up to Feb 28, 2017. We included only randomised controlled trials that compared fibrinolytic agents as a reperfusion therapy in adult patients with STEMI, whether given alone or in combination with adjunctive antithrombotic therapy, against other fibrinolytic agents, a placebo, or no treatment. Only trials investigating agents with an approved indication of reperfusion therapy in STEMI (streptokinase, tenecteplase, alteplase, and reteplase) were included. The primary efficacy outcome was all-cause mortality within 30-35 days and the primary safety outcome was major bleeding. This study is registered with PROSPERO (CRD42016042131).

FINDINGS

A total of 40 eligible studies involving 128 071 patients treated with 12 different fibrinolytic regimens were assessed. Compared with accelerated infusion of alteplase with parenteral anticoagulants as background therapy, streptokinase and non-accelerated infusion of alteplase were significantly associated with an increased risk of all-cause mortality (risk ratio [RR] 1·14 [95% CI 1·05-1·24] for streptokinase plus parenteral anticoagulants; RR 1·26 [1·10-1·45] for non-accelerated alteplase plus parenteral anticoagulants). No significant difference in mortality risk was recorded between accelerated infusion of alteplase, tenecteplase, and reteplase with parenteral anticoagulants as background therapy. For major bleeding, a tenecteplase-based regimen tended to be associated with lower risk of bleeding compared with other regimens (RR 0·79 [95% CI 0·63-1·00]). The addition of glycoprotein IIb or IIIa inhibitors to fibrinolytic therapy increased the risk of major bleeding by 1·27-8·82-times compared with accelerated infusion alteplase plus parenteral anticoagulants (RR 1·47 [95% CI 1·10-1·98] for tenecteplase plus parenteral anticoagulants plus glycoprotein inhibitors; RR 1·88 [1·24-2·86] for reteplase plus parenteral anticoagulants plus glycoprotein inhibitors).

INTERPRETATION

Significant differences exist among various fibrinolytic regimens as reperfusion therapy in STEMI and alteplase (accelerated infusion), tenecteplase, and reteplase should be considered over streptokinase and non-accelerated infusion of alteplase. The addition of glycoprotein IIb or IIIa inhibitors to fibrinolytic therapy should be discouraged.

FUNDING

None.

Controversies in the Treatment of Women with ST-Segment Elevation Myocardial Infarction

Coronary artery disease is the leading cause of death in women. Women with ST-segment elevation myocardial infarctions continue to have worse outcomes compared with men despite advancements in therapies. Furthermore, these differences are particularly pronounced among young men and women with myocardial infarctions. Differences in the pathophysiology of coronary artery plaque development, disease presentation, and recognition likely contribute to these outcome disparities. Despite having worse outcomes compared with men, women clearly benefit from aggressive treatment and the latest therapies. This article reviews the treatment options for ST-segment elevation myocardial infarctions and the outcomes of women after treatment with reperfusion therapies.

Alteplase for acute ischemic stroke

Alteplase, an intravenously administered form of recombinant tissue plasminogen activator (rt-PA), remains the only US FDA-approved thrombolytic treatment for acute ischemic stroke within 3 h of symptom onset. Patients treated with intravenous rt-PA are at least 30% more likely to have minimal or no disability at 3 months compared with placebo. Despite an increased risk of symptomatic intracranial hemorrhage, rt-PA does not increase mortality. The benefit achieved with rt-PA is cost effective and sustained 1 year after treatment. Despite its clear benefit, rt-PA remains underutilized. Although the future of acute ischemic stroke treatment will most likely involve a multi-faceted treatment approach, the primary objective remains to establish recanalization of the involved vessel. For patients with acute ischemic stroke within the first 3 h of symptom onset, rt-PA remains the first step in accomplishing this goal.

Interventions for ST Elevation Myocardial Infarction in Women

The management of ST-segment elevation myocardial infarction (STEMI) has significantly advanced from supportive care to reperfusion therapies with thrombolytics and percutaneous coronary revascularization techniques. These advances have improved the outcomes of patients with STEMI. Although cardiovascular disease is the leading cause of death in both men and women, the minority of patients in trials studying the impact of these therapies on outcomes are women. Multiple studies have shown that men and women do not have equivalent outcomes after STEMI. This article reviews the treatment options for STEMI and the outcomes of women after treatment with reperfusion therapies.

Thrombolysis and Adjunctive Therapy in Acute Myocardial Infarction

This chapter about antithrombotic therapy for acute myocardial infarction (MI) 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 with ischemic symptoms characteristic of acute MI of < 12 h in duration, and ST-segment elevation or left bundle-branch block (of unknown duration) on the ECG, we recommend administration of any approved fibrinolytic agent (Grade 1A). We recommend the use of streptokinase, anistreplase, alteplase, reteplase, or tenecteplase over placebo (all Grade 1A). For patients with symptom duration < 6 h, we recommend the administration of alteplase over streptokinase (Grade 1A). For patients with known allergy or sensitivity to streptokinase, we recommend alteplase, reteplase, or tenecteplase (Grade 1A). For patients with acute posterior MI of < 12 h duration, we suggest fibrinolytic therapy (Grade 2C). In patients with any history of intracranial hemorrhage, closed head trauma, or ischemic stroke within past 3 months, we recommend against administration of fibrinolytic therapy (Grade 1C+). For patients with acute ST-segment elevation MI whether or not they receive fibrinolytic therapy, we recommend aspirin, 160 to 325 mg p.o., at initial evaluation by health-care personnel followed by indefinite therapy, 75 to 162 mg/d p.o. (both Grade 1A). In patients allergic to aspirin, we suggest use of clopidogrel as an alternative therapy to aspirin (Grade 2C). For patients receiving streptokinase, we suggest administration of either i.v. unfractionated heparin (UFH) [Grade 2C] or subcutaneous UFH (Grade 2A). For all patients at high risk of systemic or venous thromboembolism (anterior MI, pump failure, previous embolus, atrial fibrillation, or left ventricular thrombus), we recommend administration of IV UFH while receiving streptokinase (Grade 1C+).

Benefits of direct angioplasty for women and men with acute myocardial infarction: results of the Global Use of Strategies to Open Occluded Arteries in Acute Coronary Syndromes Angioplasty (GUSTO II-B) Angioplasty Substudy

BACKGROUND

Direct angioplasty (PTCA) and thrombolytic therapy are the chief therapies for treating an ST-segment elevation myocardial infarction (MI).

OBJECTIVE

This study was designed to evaluate sex differences in the relative benefit of direct PTCA versus thrombolytic therapy among patients enrolled in the Global Use of Strategies to Open Occluded Arteries in Acute Coronary Syndromes Angioplasty (GUSTO II-B PTCA) Substudy.

METHODS

Women and men presenting with an acute ST-segment elevation MI were randomized to receive either direct PTCA or accelerated tissue plasminogen activator (t-PA). Patients were then randomized to treatment with either heparin or bivalirudin. A gender analysis of outcome was performed.

RESULTS

Women were older than men (68.6 +/- 11.5 vs 59.5 +/- 12.0 years, P <.001) and were more likely to have diabetes (22.5% vs 13.5%, P <.0001) and hypertension (53.3% vs 34.8%, P =.001). After adjusting for differences in baseline variables, the odds ratio (OR) for reaching a 30-day clinical end point (death, nonfatal infarction, or nonfatal disabling stroke) was similar for women and men (1.35, 95% CI 0.88-2.08). The OR for reaching a clinical end point at 30 days for the PTCA-treated women compared with the t-PA-treated women was 0.685 (95% CI 0.36-1.32) and similar to the OR in men, 0.565 (95% CI 0.35-0.91), P for interaction =.535. Because women had a higher event rate than men, the absolute number of major events prevented when treating women with direct PTCA was higher than men (56 events/1000 women treated with PTCA vs 42 events per 1000 men treated with PTCA).

CONCLUSIONS

Although the relative benefit of direct PTCA to t-PA for the treatment of an acute MI appears to be similar in women and men, women may derive a larger absolute benefit from direct PTCA.

Noninvasive transcutaneous ultrasound augments thrombolysis in the left circumflex coronary artery--an in vivo canine study

BACKGROUND

Ultrasound has the potential to augment chemical thrombolysis.

METHODS AND RESULTS

Thrombotic occlusions in the left circumflex artery (LCx) were induced in 27 dogs. Sixty minutes later, tissue-type plasminogen activator (t-PA) was given intravenously over 90 min. Thrombotic occlusions (n = 20) were treated with concomitant transcutaneous low frequency (27 kHz), continuous wave (CW) (n = 10) or pulsed wave (PW) (n = 10) ultrasound. Tissue-type plasminogen activator plus ultrasound (n = 20) vs. tissue-type plasminogen activator alone (n=7) resulted in more frequent Thrombolysis in Myocardial Infarction (TIMI) 3 flow (90% vs. 43%, P = 0.024) and less reocclusion (11% vs. 67%, P = 0.080). At 60 min, median TIMI grade flow for tissue-type plasminogen activator alone was 2 (mean: 1.43 +/- 1.40) compared to 3 (mean: 2.70 +/- 0.95) for tissue-type plasminogen activator plus continuous as well as pulsed wave ultrasound (P = 0.035). Continuous wave and pulsed wave ultrasound were equally effective in augmenting thrombolysis. Histologically, no ultrasound-mediated injury to the myocardium or coronary arteries occurred.

CONCLUSION

Both transcutaneous low frequency continuous wave ultrasound and pulsed wave ultrasound enhance tissue-type plasminogen activator-mediated thrombolysis of the posterior circulation with higher TIMI 3 flow rates and less reocclusion than with tissue-type plasminogen activator alone. In addition, at the energy levels used, low frequency ultrasound appears safe.

Comparative fibrinolytic activity of front-loaded alteplase and the single-bolus mutants tenecteplase and lanoteplase during treatment of acute myocardial infarction

BACKGROUND

Quantification of fibrinolytic activity (FAct) in clinical practice has been abandoned because of the complexity of existing assays. The relationship between thrombolytic drug concentration and FAct is complex. FAct profiles of currently used thrombolytic drugs were not characterized.

METHODS

By use of a system that quantifies FAct by shortening of clot lysis onset time (LOT), we measured LOT in vitro with incremented concentrations of alteplase (t-PA) and tenecteplase (TNK-tPA) and ex vivo in patients with acute myocardial infarction who were receiving front-loaded t-PA (n = 31), 30 to 40 mg TNK-tPA (n = 19), and 120 kU/kg lanoteplase ([n-PA] n = 23).

RESULTS

In vitro, FAct depended on drug concentration by means of a double exponential model revealing 2 distinct activity zones (weak/strong). Ex vivo, no FAct was detected before agent administration (LOT > 1200 seconds). Ten minutes after a bolus was given, FAct was sharply increased in all patients, but it increased more with TNK-tPA than with t-PA or n-PA (mean LOT of 109, 125, and 130 seconds, respectively, P <.05). At 90 minutes, accelerated infusion of t-PA resulted in FAct that remained stronger than that observed for TNK-tPA (P <.0001) or n-PA (P =.011). At 180-minutes, significant FAct (LOT <600 seconds) was only observed in patients who received n-PA.

CONCLUSION

This study provides the first direct comparison of FAct between t-PA, TNK-tPA, and n-PA by use of the LOT test, the results of which are reliably related to drug concentration. The ideal FAct profile would combine an immediate strong FAct of relatively short duration, as seen with TNK-tPA, that may contribute to its better efficacy/safety profile in the Assessment of Safety and Efficacy of a New Thrombolytic Agent-2 (ASSENT-2) trial. Prolonged FAct after n-PA may contribute to increased hemorrhagic complications, as seen in the Intravenous n-PA for Treatment of Infarcting Myocardium Early-2 (InTIME-2) trial. Thus, characterizing FAct profiles might provide insights in developing more efficient thrombolytic regimens.

Glycoprotein IIb/IIIa antagonism and fibrinolytic therapy for acute myocardial infarction

Fibrinolytic therapy for the treatment of ST-segment elevation myocardial infarction unquestionably reduces mortality when administered within 12 hours of symptom onset. By promptly restoring antegrade perfusion, infarct size is limited, ventricular function is less compromised, and mortality rates are lowered. Although fibrinolytic therapy initially restores antegrade flow in the infarct vessel in the majority of patients, sustained, tissue-level reperfusion occurs in only approximately one fourth of patients. Thrombin and platelets associated with a coronary thrombus are not specifically targeted by fibrinolytic agents, but rather have paradoxically increased activity. These components contribute to the tendency for vessel reocclusion after initially successful reperfusion. Thus, adjunctive therapy with antithrombins and antiplatelet agents are essential in the successful treatment of a coronary thrombus. Although aspirin has been shown to reduce mortality in acute myocardial infarction, it is a weak antiplatelet agent that is pathway specific. Glycoprotein IIb/IIIa inhibitors are potent antiplatelet agents that block the final common pathway for platelet aggregation. Thus, the growing evidence of platelet preeminence in the pathophysiology of failed thrombolysis has lead to the study of combination drug therapy with glycoprotein IIb/IIIa inhibition and reduced dose fibrinolytic agents in the treatment of acute ST-segment elevation myocardial infarction. This article reviews the rationale, results, and clinical implications of the major trials of combination drug therapy in acute myocardial infarction.

Exploring the issues of appropriate dosing in the treatment of acute myocardial infarction: potential benefits of bolus fibrinolytic agents

The Institute of Medicine report on the frequency and consequences of medical errors in clinical practice has stimulated physicians to evaluate current practice and means of improving medical care. In the treatment of patients with acute myocardial infarction, previous studies have found that dosing of fibrinolytic therapy is closely related to outcomes, with too low a dose associated with lower rates of infarct-related artery patency and higher doses associated with increased intracranial hemorrhage. Thus there is a narrow "therapeutic window" for fibrinolytic-antithrombotic regimens, and the potential for adverse outcomes is high if incorrect doses are administered. The first demonstration of this concept came from the GUSTO-I trial, in which 13.5% of patients treated with streptokinase and 11.5% of patients treated with tissue plasminogen activator (t-PA) had a dosing regimen that deviated from the protocol, that is, an incorrect total dose or infusion length. In patients with protocol deviations, 24-hour and 30-day mortality rates were significantly higher compared with those of patients with per-protocol dosing: for t-PA, patients who received incorrect dosing had a 30-day mortality rate of 7.7% versus 5.5% for patients who received correct t-PA dosing (P <.001), with similar findings for streptokinase. More recent data from the InTIME-II trial have shown that the use of a bolus fibrinolytic agent significantly increases the percentage of patients who receive complete and optimally dosed fibrinolysis. Thus use of the simpler bolus fibrinolytic agents may reduce medication errors and thus may optimize clinical outcomes.

Reducing medication errors: potential benefits of bolus thrombolytic agents

A recent Institute of Medicine report highlighted the high incidence of medical errors in clinical practice, and the important fact that errors are associated with increased mortality. The administration of thrombolytic therapy for acute myocardial infarction is a particularly high-risk situation for emergency physicians. The combination of extreme time pressure with a narrow "therapeutic window" increases the potential for adverse outcomes due to dosing errors. Numerous trials have found that the dose of thrombolytic therapy is closely related to outcomes, with too low a dose associated with lower rates of infarct-related artery patency and higher doses associated with increased bleeding and intracranial hemorrhage. In the GUSTO-I trial, 13.5% of patients treated with streptokinase and 11.5% of patients treated with tissue plasminogen activator (t-PA) had a medication error (i.e., incorrect dose or infusion length). Most importantly, 30-day mortality was significantly higher in patients with medication errors: for t-PA dosing errors mortality was 7.7% vs 5.5% for patients who received the correct t-PA dose (p < 0.001), with similar findings for streptokinase. More recent data from the InTIME2 trial and other studies showed that use of a bolus thrombolytic agent reduced the rate of medication errors. Thus, use of the simpler bolus thrombolytic agents may reduce emergency department medication errors, and thus improve overall clinical outcome.

Thrombolysis medication errors: benefits of bolus thrombolytic agents

A recent report has highlighted the high incidence of medical errors in clinical practice and the important fact that errors are associated with increased mortality. This issue is now being examined closely in the field of thrombolytic therapy for acute myocardial infarction. Numerous trials have found that the dose of the thrombolytic agent is closely related to outcome, with too low a dose associated with lower rates of infarct-related artery patency and higher doses associated with increased bleeding and intracranial hemorrhage. Thus, the "therapeutic window" for thrombolytic therapy is small, and the potential for adverse outcome from dosing errors is high. In the Global Use of Strategies To Open occluded arteries (GUSTO)-I trial, 13.5% of patients treated with streptokinase and 11.5% of patients treated with tissue plasminogen activator (t-PA) were subjected to a medication error (e.g., incorrect dose or infusion length). Most importantly, 30-day mortality was significantly higher in patients with medication errors: For t-PA dosing errors, mortality was 7.7% versus 5.5% for patients who received the correct t-PA dose (p<0.001); findings were similar for streptokinase. More recent data from the Intravenous n-PA for Treatment of Infarcting Myocardium Early (InTIME)-II trial and other studies showed that use of a bolus thrombolytic agent reduced the rate of medication errors. Thus, use of the simpler bolus thrombolytic agents may improve overall clinical outcome.

Early, Complete Infarct Vessel Patency: Arriving at a Gold Standard for Future Clinical Investigation in Myocardial Reperfusion

Early clinical trials of thrombolytic therapy in the setting of acute myocardial infarction (AMI) demonstrated that early angiographic reperfusion correlated with improved survival. This supported the open-artery hypothesis that early reperfusion decreases infarct size, improves left ventricular function, and improves survival. Two subsequent comparative thrombolytic trials showed no difference in left ventricular function or survival between agents with different rates of reperfusion. Additionally, reduction in mortality was demonstrated without improvement in left ventricular function and with the late administration of thrombolytic therapy. Therefore, there was a real question as to the importance of infarct vessel patency, and its relation to clinical outcome. This article discusses the various markers of coronary artery patency, their relation to clinical outcome, and how they reflect perfusion at the tissue level. The coronary angiogram gives a snapshot view of the infarct-related artery (IRA) that does not reflect the dynamic process of vessel reocclusion and recanalization. The patent artery is therefore "open" at only a given time frame, and may undergo cyclic or complete reocclusion. Angiographically characterized flow has been demonstrated to be more clinically meaningful. The GUSTO-I trial was designed to test the open-artery hypothesis. This trial confirmed that improved early IRA patency and optimal (TIMI-3) flow correlated with improved survival. The presence of TIMI-3 flow in the IRA has consistently demonstrated significant improvement in patient morbidity and mortality, and conversely, less than optimal, but still "patent" (TIMI-2) flow in the IRA correlates with clinical outcomes observed in patients with occluded infarct vessels. Even TIMI-3 flow in the IRA does not always confirm perfusion of the myocardium at risk. Therefore, the "patent" IRA can be subsequently compromised by intermittent patency, reocclusion, less than TIMI-3 flow, and a "no-reflow" effect at the tissue level. The development of accurate, reliable non-invasive markers of IRA patency is crucial. This would allow a more selective application of invasive and interventional techniques to restore patency to the IRA. The merits and faults of these noninvasive markers are discussed. The ideal gold standard for establishing the adequacy of therapy in AMI is one that could detect rapid, complete, and sustained coronary reperfusion with adequate myocardial perfusion. Current technologic achievements allow an approach to this ideal; however, as of 1997, the coronary angiogram demonstrating TIMI-3 flow represents the clinically proven standard of optimal therapeutic efficacy.

Achieving Optimal Reperfusion without Adjunctive Antithrombotic Therapy: Novel Thrombolytic Dosing Strategies

There is firm evidence that reperfusion therapy, to be effective must establish and maintain coronary arterial blood flow at a level sufficient to allow myocardial perfusion. However, current thrombolytic regimens have clear limitations, including a relatively low capacity to achieve TIMI Grade 3 blood flow and an unacceptable incidence of coronary reocclusion. Although it has been assumed that the key to achieving optimal reperfusion lies with adjunctive antithrombotic therapy, it may be that novel thrombolytics and dosing strategies can address the problem adequately. This possibility is attractive and requires careful consideration.

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.

Methodologic drift in the assessment of TIMI grade 3 flow and its implications with respect to the reporting of angiographic trial results. The TIMI Study Group

BACKGROUND

The Thrombolysis in Myocardial Infarction (TIMI) Study Group originally defined TIMI grade 3 flow (complete perfusion) as antegrade flow into the bed distal to the obstruction that occurs as promptly as antegrade flow into the bed proximal to the obstruction. Recently, several groups have defined TIMI grade 3 flow as opacification of the coronary artery within 3 cardiac cycles.

METHODS AND RESULTS

On the basis of heart rate data at the time of the cardiac catheterization and the time for dye to go down the artery (TIMI frame count/30 = seconds), we estimated the number of patients who would meet the 3 cardiac cycle criterion and compared this with the number of patients with TIMI grade 3 flow by using the original definition in 1157 patients from 3 recent TIMI trials (10 A, 10B, and 14). In 74 patients without acute myocardial infarction and normal coronary arteries, the fraction of a cardiac cycle required for dye to traverse the artery was a mean of 0.93 +/- 0.34 cardiac cycles (n = 74) (median 0.80, minimum 0.44, maximum 2.1, none >3.0 cycles). The mean heart rate at 90 minutes after thrombolysis in the TIMI 14 trial was 79.6 +/- 16.8 beats/min (n = 194), and the duration of 3 cardiac cycles was a mean of 2.36 seconds, or a TIMI frame count of 70.8 frames. In all trials, the rate of TIMI grade 3 flow was 57.3% (n = 663/1157) with the original definition and 66.8% (n = 743/1113) with the <3 cardiac cycle definition (P <.001).

CONCLUSIONS

A duration of 3 cardiac cycles for dye to traverse the artery lies approximately 6 SD above that observed in normal coronary arteries. A 3 cardiac cycle definition of TIMI grade 3 flow results in rates of normal perfusion that are approximately 10% higher than if the original definition of TIMI grade 3 flow is applied. Application of this simple correction factor may help place data reported with the 3 cardiac cycle definition of TIMI grade 3 flow in context.

Primary angioplasty versus systemic thrombolysis in anterior myocardial infarction

OBJECTIVES

This study compares the efficacy of primary angioplasty and systemic thrombolysis with t-PA in reducing the in-hospital mortality of patients with anterior AMI.

BACKGROUND

Controversy still exists about the relative benefit of primary angioplasty over thrombolysis as treatment for AMI.

METHODS

Two-hundred and twenty patients with anterior AMI were randomly assigned in our institution to primary angioplasty (109 patients) or systemic thrombolysis with accelerated t-PA (111 patients) within the first five hours from the onset of symptoms.

RESULTS

Baseline characteristics were similar in both groups. Primary angioplasty was independently associated with a lower in-hospital mortality (2.8% vs. 10.8%, p = 0.02, adjusted odds ratio 0.23, 95% confidence interval 0.06 to 0.85). During hospitalization, patients treated by angioplasty had a lower frequency of postinfarction angina or positive stress test (11.9% vs. 25.2%, p = 0.01) and less frequently underwent percutaneous or surgical revascularization after the initial treatment (22.0% vs. 47.7%, p < 0.001) than did patients treated by t-PA. At six month follow-up, patients treated by angioplasty had a lower cumulative rate of death (4.6% vs. 11.7%, p = 0.05) and revascularization (31.2% vs. 55.9%, p < 0.001) than those treated by t-PA.

CONCLUSIONS

In centers with an experienced and readily available interventional team, primary angioplasty is superior to t-PA for the treatment of anterior AMI.

An angiographic assessment of alteplase: double-bolus and front-loaded infusion regimens in myocardial infarction. DouBLE Study Investigators. Double Bolus Lysis Efficacy

BACKGROUND

This study was designed to investigate the efficacy of alteplase double-bolus dosing compared with the front-loaded 90-minute infusion regimen in patients with acute myocardial infarction. Recent pilot studies have suggested that bolus dosing may provide improved efficacy in establishing early, complete, and sustained patency of the infarct-related artery in the thrombolytic treatment of acute myocardial infarction.

METHODS AND RESULTS

In this multicenter, randomized, open-label trial, 461 patients with acute myocardial infarction received 100 mg alteplase as a front-loaded 90-minute infusion (15 mg bolus, then 50 mg over a 30-minute period, then 35 mg over a 60-minute period) or double bolus (two 50 mg bolus injections 30 minutes apart). All patients also received intravenous heparin and oral aspirin during and after alteplase treatment. The 90-minute angiographic patency rates were 74.5% in the double-bolus group and 81.4% in the infusion group (p = 0.08). Patency rates were also comparable for the two groups at 60 minutes (76.8% vs 77.5%) and 24 hours (95.5% vs 93.5%) after initiation of treatment. In-hospital mortality rates were 4.5% in the bolus group and 1.3% in the infusion group (p = 0.04); 30-day mortality rates were 4.5% and 1.7%, respectively (p = NS). The two-groups were comparable in frequency of all other adverse events.

CONCLUSIONS

Double-bolus alteplase administration produced reperfusion rates comparable to front-loaded infusion, but in-hospital and 30-day mortality rates were higher in the double-bolus group. These findings are in agreement with those of the COBALT megatrial, which also reported a trend to higher mortality rates with double-bolus dosing.

Fibrinogen breakdown, long-lasting systemic fibrinolysis, and procoagulant activation during alteplase double-bolus regimen in acute myocardial infarction

Recent clinical studies comparing accelerated versus bolus administration of alteplase tissue plasminogen activator (t-PA) suggest similar thrombolytic efficacy, but reveal higher bleeding complications among older patients during the double-bolus regimen. The objective of the present study was to characterize the hemostatic profile of t-PA administered as double-bolus doses of 50 mg, at intervals of 30 minutes. Among 50 patients with acute myocardial infarction treated by double-bolus t-PA thrombolysis, coagulation and fibrinolysis parameters, as well as t-PA levels, were monitored. Monitored t-PA levels peaked at 5 and 35 minutes and were detectable within the therapeutic range even after 90 minutes. Marked systemic fibrinolytic activation was indicated by 75% depletion of both plasminogen and fibrinogen, as well as by 19-fold and 300-fold increases of fibrin degradation and fibrinogen degradation products. Plasminogen-activator inhibitor activity was completely suppressed. Pronounced procoagulant activation was reflected by a 3.4-fold increase of both factor XIIa and prothrombin fragment 1+2, and by a threefold increase of thrombin-antithrombin complex. Independent of t-PA weight dosage, fibrinolytic activation was more pronounced among older patients (> or = 63 years). We conclude that t-PA after bolus administration has a long half-life. Double-bolus regimen leads to a long-lasting systemic fibrinolytic state, which is even more remarkable among older patients--a fact that may explain the higher bleeding complications reported for this age group.

Primary angioplasty for acute myocardial infarction

The use of thrombolytic therapy has been widely accepted for the treatment of acute myocardial infarction. Despite improving mortality, thrombolytic therapy may be contraindicated in many patients presenting with myocardial infarction and is associated with a small, yet significant risk of hemorrhagic sequelae. This article outlines the rationale behind reperfusion therapy, the use of pharmacological thrombolysis and the role of adjunctive angioplasty. The potential advantages of a therapeutic strategy of primary angioplasty, instead of thrombolysis, are discussed. These include anatomical definition, risk stratification, reduced recurrent ischemia, enhanced coronary perfusion and improved coronary patency. The randomized trials in which primary angioplasty and thrombolytic therapy were compared are reviewed. We conclude that angioplasty results in a reduction of short-term mortality and nonfatal reinfarction and therefore advocate the routine use of coronary angioplasty as a primary reperfusion strategy for acute myocardial infarction. The potential limitations of primary angioplasty in the community hospital setting are discussed. Finally, we examine the roles of adjunctive mechanical (e.g. stents) and pharmacological (e.g. Abciximab) means of further enhancing outcomes after primary angioplasty.

A prospective, randomized, double-blind multicenter trial of a single bolus injection of the novel modified t-PA E6010 in the treatment of acute myocardial infarction: comparison with native t-PA. E6010 Study Group

OBJECTIVES

This prospective, randomized, double-blind multicenter trial evaluated the efficacy and safety of a single bolus injection of the novel modified tissue-type plasminogen activator (t-PA) E6010 in the treatment of acute myocardial infarction compared with that of native t-PA.

BACKGROUND

E6010 is a novel modified t-PA with a prolonged half-life (t1/2 alpha > or = 23 min) compared with native t-PA (t1/2 alpha = 4 min). E6010 can be administered in patients as a single intravenous bolus injection, and early recanalization can be expected.

METHODS

The efficacy of E6010 was compared with that of native t-PA in 199 patients with acute myocardial infarction who were treated within 6 h of onset in a prospective, randomized, double-blind multicenter trial. Patients were given either 0.22 mg/kg body weight of E6010 intravenously over 2 min or native t-PA (tisokinase) 28.8 mg or 14.4 million IU (10% of the total dose over 1 to 2 min, the remainder infused over 60 min).

RESULTS

The primary end point was the recanalization rate of the infarct-related coronary artery at 60 min after the start of treatment. Time to reperfusion was shorter in the E6010 group than in the native t-PA group. Thrombolysis in Myocardial Infarction flow grade 2 or 3 recanalization at 15, 30, 45 and 60 min after administration was observed in 37%, 62%, 74% and 79% (95% confidence interval [CI] 70% to 87%) of the E6010-treated patients and in 14%, 32%, 50% and 65% (95% CI 55% to 74%) of native t-PA-treated patients, respectively (p = 0.032 at 60 min).

CONCLUSIONS

The present study indicates that, compared with native t-PA, a single bolus injection of E6010 over 2 min produces a higher rate of early recanalization of the infarct-related coronary artery without fatal bleeding complications.

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.

TIMI grade 3 flow and reocclusion after intravenous thrombolytic therapy: a pooled analysis

Early and sustained flow of grade 3 according to Thrombolysis in Myocardial infarction (TIMI) criteria and reocclusion rates are the key measures that define the physiologic efficacy of thrombolytic agents in the treatment of acute myocardial infarction. We performed a systematic overview of angiographic studies after intravenous thrombolysis with accelerated and standard-dose tissue-plasminogen activator (TPA), anisoylated plasminogen streptokinase activator complex (APSAC), and streptokinase. There were 5475 angiographic observations from 15 studies for TIMI flow analysis and 3147 angiographic observations from 27 studies for reocclusion. At 60 and 90 minutes, the rates of TIMI grade 3 flow were 57.1% and 63.2%, respectively, with accelerated TPA, 39.5% and 50.2% with standard-dose TPA, 40.2% and 50.1% with APSAC, and 31.5% at 90 minutes with streptokinase. Overall reocclusion with standard-dose TPA was 11.8% versus 6.0% for accelerated TPA, 4.2% for streptokinase, and 3.0% for APSAC. Although the incidence of TIMI grade 3 flow increased over time with all thrombolytic regimens, decreased patency was observed at 180 minutes with accelerated TPA. Still, accelerated TPA is the most effective agent to establish early (90-minute) TIMI grade 3 flow.

Effect of a mechanical vs a pharmacologic increase in aortic pressure on coronary blood flow and thrombolysis induced by IV administration of a thrombolytic agent

This study was designed to compare the effect of a mechanical vs a pharmacologic increase in BP on coronary artery blood flow and thrombolysis induced by IV administration of recombinant tissue plasminogen activator. We employed a canine model of coronary thrombosis induced by injection of radioactive blood clot in the left anterior descending coronary artery. Subsequently, all dogs underwent phlebotomy to decrease systolic BP to 75 mm Hg and this decreased coronary blood flow by 50%. BP was increased to 130 mm Hg by norepinephrine (NE) infusion or by inflation of a Fogarty catheter placed in the descending aorta. Interventions with NE or with a Fogarty balloon catheter increased coronary artery blood flow to similar values and rates of coronary thrombolysis were similar. However, cardiac output was significantly higher with NE. These results indicate coronary clot lysis is dependent on perfusion pressure and coronary blood flow, not cardiac output.

Accelerated TPA for treatment of prosthetic valve thrombosis

The first case of prosthetic valve thrombosis treated with an accelerated regimen of TPA is reported. The experience suggests that this therapeutic approach is feasible and may produce higher rates of patency for thrombosed prosthetic valves than other thrombolytic therapies currently available. This therapeutic strategy is worthy of further evaluation as a treatment for this disorder.

Optimizing coronary thrombolysis with i.v. administration of recombinant tissue plasminogen activator. Single bolus vs double bolus vs front-loading

This study was designed to compare the efficacy of coronary thrombolysis obtained with i.v. administration of three dose regimens of recombinant tissue plasminogen activator (rtPA). Although many studies have confirmed the efficacy of thrombolytic therapy in treatment of acute myocardial infarction, few prospective studies have been designed to determine which dose regimen optimizes the rate of coronary thrombolysis. A canine model was used. Coronary thrombosis was induced by injection of radioactive, autologous blood clots through a catheter placed in the left anterior descending coronary artery. Subsequently, 15 dogs were randomized into 3 groups of 5 dogs each. In group 1 dogs, 1.25 mg/kg of rtPA was administered i.v. as a bolus; in the group 2 dogs, 1.25 mg/kg of rtPA was administered over 60 min. The administration was "front loaded" so that 15% was administered as a bolus, 60% over 30 min, and 25% over 30 min; in group 3, 1.25 mg/kg of rtPA was divided into two i.v. boluses and administered 15 min apart. Coronary thrombolysis was assessed with a gamma camera. Despite differences in rate of administration of rtPA, at 15, 30, and 90 min after onset of treatment, extent of clot lysis was similar between groups. These results indicate that despite differences in dose regimens, rates of thrombolysis are similar when i.v. rtPA is relatively rapidly administered. Further, the similar rates of clot lysis over time between groups suggest both an effective upper limit to the dose-thrombolytic rate relationship and relatively high, sustained steady-state plasma concentrations of rtPA.

Emergency primary coronary angioplasty in patients with acute myocardial infarction who are unsuitable for intravenous thrombolysis

Intravenous thrombolytic therapy is now accepted as the standard method of achieving coronary reperfusion in patients with acute myocardial infarction. There are several important limitations. Primary percutaneous transluminal coronary angioplasty is an attractive method for reopening occluded coronary arteries. Between 1986 and 1993, 14 patients in whom there was an absolute contraindication to thrombolysis underwent emergency coronary angioplasty as the primary treatment for acute myocardial infarction. Coronary artery patency was restored in 13/14 (93%). One patient died in hospital. The median follow-up was one year. One patient suffered a further myocardial infarction and one patient required coronary artery bypass surgery at follow-up. Emergency coronary angioplasty services should be developed to treat those patients in whom there is a contraindication to thromboloysis.

Intravenous administration of recombinant tissue plasminogen activator. Optimizing the rate of coronary thrombolysis

Although many studies have confirmed the efficacy of thrombolytic therapy in treatment of acute myocardial infarction, few studies have been designed to determine which dose regimen optimizes the rate of coronary thrombolysis. This study was designed to compare the efficacy of coronary thrombolysis obtained with intravenous administration of three dose regimens of recombinant tissue plasminogen activator (rtPA). The same total dose was administered as a bolus, over 30 min, or over 90 min. A canine model was employed. Coronary thrombosis was induced by injection of radioactive blood clot through a catheter placed in the left anterior descending coronary artery. Subsequently, 18 dogs were randomized into 3 groups of 6 dogs each. In group 1 dogs, 0.5 mg/kg of rtPA was administered intravenously as a bolus; in the group 2 dogs, rtPA was administered intravenously over 30 min (rtPA30); in the group 3 dogs, the drug was administered over 90 min (rtPA90). Coronary thrombolysis was assessed with a gamma camera. While at 100 min, the extent of clot lysis was similar between groups, 15 and 30 min after the start of rtPA administration, coronary thrombolysis was significantly less in the rtPA90 group. These results indicate that for a given total dose of rtPA, the rate of intravenous administration may significantly affect the rate of coronary thrombolysis.

Link between the angiographic substudy and mortality outcomes in a large randomized trial of myocardial reperfusion. Importance of early and complete infarct artery reperfusion. GUSTO-I Investigators

BACKGROUND

The Global Utilization of Streptokinase and TPA for Occluded Coronary Arteries (GUSTO-I) trial was designed to test whether thrombolytic strategies achieving more complete, early, sustained coronary artery patency would lead to further reductions in mortality in patients with acute myocardial infarction. An angiographic substudy within GUSTO-I provided a unique opportunity to examine the relation between mortality and degrees of patency among the regimens.

METHODS AND RESULTS

Four thrombolytic strategies were compared in 41,021 patients in GUSTO-I: streptokinase with subcutaneous or intravenous heparin, accelerated tissue plasminogen activator (TPA) with intravenous heparin, and combination streptokinase plus TPA with intravenous heparin. Accelerated TPA was associated with lower 30-day mortality (6.3%) than the other strategies (7.2%, 7.4%, and 7.0%, respectively). Among the 1210 patients in the angiographic substudy randomized to angiography 90 minutes after starting treatment, there was improved patency, particularly Thrombolysis in Myocardial Infarction (TIMI) grade 3 flow, with accelerated TPA over the other regimens (P < .0001). Coronary artery perfusion (TIMI grade 3) at 90 minutes was also a significant predictor of 30-day survival (P < .01). To determine whether differences in mortality among the four strategies matched differences in 90-minute patency, a model was developed for predicting mortality differences in the main trial from the angiographic substudy. The model assumed that any differences in treatment effects on 30-day mortality were mediated through differences in 90-minute patency for the four treatments. The predicted rates were then compared with observed mortality rates of the remaining patients in the main trial for each treatment group. The predicted and observed 30-day mortality rates of the four treatments were streptokinase with subcutaneous heparin, 7.46% versus 7.28%; streptokinase with intravenous heparin, 7.26% versus 7.39%; accelerated TPA, 6.31% versus 6.37%; and streptokinase plus TPA, 6.98% versus 6.96%. The correlation between predicted and observed results was .97, and the proportion of squared error explained (R2) was .92.

CONCLUSIONS

The close relation between the predicted and observed 30-day mortality rates supports the concept that an important mechanism for improved survival with thrombolytic therapy is achievement of early, complete perfusion. The close match provides a strong biological explanation for the mortality differences seen in GUSTO-I and a sound rationale for the additional survival advantage of the accelerated TPA regimen. Irrespective of which treatment is used, early and complete restoration of infarct artery perfusion represents an essential goal of myocardial reperfusion therapy.

Gusto Hawaii: A Community Hospital's Experience in an International Randomized Study

Multiple thrombolytic agents are available for treating patients with acute myocardial infarction. The recently completed Global Utilization of Streptokinase and rt-PA for Occluded coronary arteries (GUSTO) study randomized 41,000 patients to 1 of 4 thrombolytic treatment regimens. Straub Clinic and Hospital, a small community hospital in Hawaii, participated in this international clinical trial enrolling a total of 40 patients. Our patient characteristics and use of concomitant therapy were similar to the combined GUSTO, study results. Coronary angiography was performed in 93% of patients postthrombolytic therapy, with a majority of patients having single vessel coronary disease and a patent infarct-related artery. The severity of coronary artery disease at our hospital was similar to the combined GUSTO study results. Percutaneous transluminal coronary angioplasty was performed in 53% of patients and coronary artery bypass surgery in 13% of patients postthrombolytic therapy at our hospital, compared to 15% and 9% in the combined GUSTO study, respectively. The clinical events postthrombolytic therapy at Straub Clinic and Hospital were similar to the combined GUSTO study results, except for a lower incidence of ischemia/reinfarction at our hospital (7.5% v 23.2% respectively).

These data suggest that treatment of acute myocardial infarction with thrombolytic therapy can be administered in a safe and timely manner at a small community hospital.

Predictors of in-hospital and 6-month outcome after acute myocardial infarction in the reperfusion era: the Primary Angioplasty in Myocardial Infarction (PAMI) trail

OBJECTIVES

This study examined the predictors of in-hospital and 6-month outcome after different reperfusion strategies in acute myocardial infarction.

BACKGROUND

Thrombolytic therapy and primary angioplasty are both widely applied as reperfusion modalities in patients with myocardial infarction. Although it is accepted that restoration of early patency of the infarct-related artery can reduce mortality and salvage myocardium, the optimal reperfusion strategy remains controversial, and the predictors of outcome in the reperfusion era have been incompletely characterized.

METHODS

At 12 centers, 395 patients presenting within 12 h of onset of acute transmural myocardial infarction were prospectively randomized to receive tissue-type plasminogen activator (t-PA) or undergo primary angioplasty without antecedent thrombolysis. Sixteen clinical variables were examined with univariate and multiple logistic regression analysis to identify the predictors of clinical outcome.

RESULTS

By univariate analysis, in-hospital mortality was increased in the elderly, women, patients with diabetes and in patients treated with t-PA as opposed to angioplasty. Only advanced age and treatment by t-PA versus angioplasty independently correlated with increased in-hospital mortality (6.5% vs. 2.6%, respectively, p = 0.039 by multiple logistic regression analysis). Similarly, the only variables independently related to in-hospital death or nonfatal reinfarction were advanced age and treatment by t-PA versus angioplasty (12.0% vs. 5.1%, p = 0.02). The reduction in in-hospital death or reinfarction with angioplasty versus t-PA was particularly marked in patients > or = 65 years of age (8.6% vs. 20.0%, p = 0.048). Furthermore, primary management with angioplasty versus t-PA was the most powerful multivariate correlate of freedom from recurrent ischemic events (10.3% vs. 28.0%, p = 0.0001). The independent beneficial effect of angioplasty on freedom from death or reinfarction was maintained at 6-month follow-up (8.2% vs. 17.0%, p = 0.02).

CONCLUSIONS

In the reperfusion era, the two most powerful determinants of freedom from death, reinfarction and recurrent ischemia after myocardial infarction are young age and treatment by primary angioplasty.

A pooled analysis of coronary arterial patency and left ventricular function after intravenous thrombolysis for acute myocardial infarction

Individual studies of patency rates and left ventricular (LV) function after thrombolysis have generally been limited by small numbers of observations, wide confidence intervals, and limited numbers of time points. To obtain a more reliable estimate of patterns of patency and LV ejection fraction, a systemic overview of angiographic studies was performed after intravenous thrombolytic therapy. A total of 14,124 angiographic observations from 58 studies evaluating patency after no thrombolytic agent, streptokinase, standard dose tissue-type plasminogen activator (t-PA), accelerated dose t-PA, or anistreplase (anisoylated plasminogen streptokinase activator complex [APSAC]) were included. At 60 and 90 minutes, streptokinase had the lowest patency rates of 48% and 51%, respectively, standard dose t-PA and APSAC had similar intermediate rates of approximately 60% and 70%, and accelerated t-PA had the highest patency rates of 74% and 84%. By 2 to 3 hours and longer, the patency rates were similar for the various regimens. Reocclusion rates in studies including 1,172 patients randomized to t-PA versus a nonfibrin-specific agent were higher after t-PA (13.4% vs 8.0%, p = 0.002). Ten studies enrolling 4,088 patients treated with thrombolytic therapy versus control demonstrated a modest improvement in mean LV ejection fraction in the thrombolytic group at each of the times after thrombolytic therapy: hour 4, day 1, day 4, day 7 to 10, and day 10 to 28 after thrombolysis. By 4 days, mean ejection fraction was 53% versus 47% (thrombolytic vs control therapy, p < 0.01); by 10 to 28 days it was 54.1% and 51.5%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of front-loaded recombinant tissue-type plasminogen activator, anistreplase and combination thrombolytic therapy for acute myocardial infarction: results of the Thrombolysis in Myocardial Infarction (TIMI) 4 trial

OBJECTIVES

The aim of our study was to determine a superior thrombolytic regimen from three: anistreplase (APSAC), front-loaded recombinant tissue-type plasminogen activator (rt-PA) or combination thrombolytic therapy.

BACKGROUND

Although thrombolytic therapy has been shown to reduce mortality and morbidity after acute myocardial infarction, it has not been clear whether more aggressive thrombolytic-antithrombotic regimens could improve the outcome achieved with standard regimens.

METHODS

To address this issue, 382 patients with acute myocardial infarction were randomized to receive in a double-blind fashion (along with intravenous heparin and aspirin) APSAC, front-loaded rt-PA or a combination of both agents. The primary end point "unsatisfactory outcome" was a composite clinical end point assessed through hospital discharge.

RESULTS

Patency of the infarct-related artery (Thrombolysis in Myocardial Infarction [TIMI] grade 2 or 3 flow) at 60 min after the start of thrombolysis was significantly higher in rt-PA-treated patients (77.8% vs. 59.5% for APSAC-treated patients and 59.3% for combination-treated patients [rt-PA vs. APSAC, p = 0.02; rt-PA vs. combination, p = 0.03]). At 90 min, the incidence of both infarct-related artery patency and TIMI grade 3 flow was significantly higher in rt-PA-treated patients (60.2% had TIMI grade 3 flow vs. 42.9% and 44.8% of APSAC- and combination-treated patients, respectively [rt-PA vs. APSAC, p < 0.01; rt-PA vs. combination, p = 0.02]). The incidence of unsatisfactory outcome was 41.3% for rt-PA compared with 49% for APSAC and 53.6% for the combination (rt-PA vs. APSAC, p = 0.19; rt-PA vs. combination, p = 0.06). The mortality rate at 6 weeks was lowest in the rt-PA-treated patients (2.2% vs. 8.8% for APSAC and 7.2% for combination thrombolytic therapy [rt-PA vs. APSAC, p = 0.02; rt-PA vs. combination, p = 0.06]).

CONCLUSIONS

Front-loaded rt-PA achieved significantly higher rates of early reperfusion and was associated with trends toward better overall clinical benefit and survival than those achieved with a standard thrombolytic agent or combination thrombolytic therapy. These findings support the concept that more rapid reperfusion of the infarct-related artery is associated with improved clinical outcome.

New recombinant glycosylated prourokinase for treatment of patients with acute myocardial infarction. Prourokinase Study Group

OBJECTIVES

Three dosage regimens of a new recombinant glycosylated prourokinase (A-74187) were evaluated by measuring coronary artery patency at 90 min in patients with acute myocardial infarction.

BACKGROUND

Prourokinase is a thrombolytic drug with unique pharmacologic properties that may be clinically advantageous.

METHODS

Aspirin (325 mg), intravenous heparin and prourokinase (60- or 80-mg monotherapy or 60 mg "primed" with a preceding bolus dose of 250,000 IU of recombinant urokinase) were administered to 128 patients. Coronary angiography was performed at 60 min (wherever possible), 90 min (primary end point) and 24 h to determine arterial patency and reocclusion rates. Plasma was collected serially to measure fibrinogen, plasminogen, thrombin antithrombin III and fibrinopeptide A. Clinical events until hospital discharge were recorded.

RESULTS

The coronary artery patency rate at 90 min was similar for all three regimens, averaging 73% (95% confidence interval [CI] 64% to 80%); Thrombolysis in Myocardial Infarction (TIMI) grade 3 flow rates averaged 52% (95% CI 42% to 61%). Arterial patency at 60 min was 62% (95% CI 50% to 73%), and reocclusion occurred in 1.4% (95% CI 0.1% to 4.1%). Prourokinase demonstrated relative fibrin specificity at all doses studied. Fibrinopeptide A and thrombin antithrombin III levels were elevated at baseline and declined rapidly during the 1st 12 h. There was no difference in the baseline values of these thrombin markers between patients with patent versus closed arteries at 90 min. There was one death; no strokes occurred.

CONCLUSIONS

A-74187 prourokinase is a rapid-acting, effective fibrin-specific thrombolytic agent. Reocclusion was unusual, possibly because of aggressive anticoagulation with intravenous heparin or unique features of the drug. Full definition of the clinical effectiveness of this drug merits examination in future randomized trials evaluating clinical and angiographic effectiveness.

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.

Effect of rate of administration of recombinant tissue plasminogen activator on efficacy of coronary thrombolysis

The authors employed a canine model of coronary thrombosis, induced by injection of radioactive blood clot, via a catheter placed in the left anterior descending (LAD) coronary artery, to compare effects of different rates of administration of recombinant tissue plasminogen activator (rtPA) on efficacy of coronary thrombolysis. In one group of dogs 0.75 mg/kg of rtPA was administered via the catheter placed in the LAD coronary artery over fifteen minutes. In a second group of dogs the same dose of rtPA was administered over forty-five minutes. Compared with the group in which the drug was administered over forty-five minutes, by thirty and forty-five minutes after onset of treatment, the extent of coronary thrombolysis was significantly greater (P < 0.05) in the group who received the drug over fifteen minutes. These results demonstrate that the rate of intracoronary administration of rtPA may significantly affect thrombolytic efficacy.