Randomized comparison of coronary thrombolysis achieved with double-bolus reteplase (recombinant plasminogen activator) and front-loaded, accelerated alteplase (recombinant tissue plasminogen activator) in patients with acute myocardial infarction. The RAPID II Investigators

Hospital transfer for primary coronary angioplasty in high risk patients with acute myocardial infarction

OBJECTIVE

To investigate the feasibility, safety, and associated time delays of interhospital transfer in patients with acute myocardial infarction for primary percutaneous transluminal coronary angioplasty (PTCA).

DESIGN AND PATIENTS

Prospective observational study with group comparison in a single centre. 68 consecutive patients with acute myocardial infarction transferred for primary PTCA from other hospitals (group A) were compared with 78 patients admitted directly to the referral centre (group B).

MAIN OUTCOME MEASURES

Patient groups were analysed with regard to baseline characteristics, time intervals from onset of chest pain to balloon angioplasty, hospital stay, and follow up outcome.

RESULTS

Patients in group A presented with a higher rate of cardiogenic shock initially than patients in group B (25% v 6%, p = 0.01) and had been resuscitated more frequently before PTCA (22% v 5%, p = 0.01). No deaths or other serious complications occurred during interhospital transfer. Median transfer time was 63 (range 40-115) minutes for helicopter transport (median 42 (28-122) km, n = 14), and 50 (18-110) minutes by ground ambulance (median 8 (5-68) km, n = 54). The median time interval from the decision to perform coronary arteriography to balloon inflation was 96 (45-243) minutes in group A and 52 (17-214) minutes in group B (p = 0.0001). In transferred patients (group A) the transportation associated delay and the longer in-hospital median decision time (50 (10-1120) minutes in group A v 15 (0-210) minutes in group B, p = 0.002) concurred with a longer total period of ischaemia (239 (114-1307) minutes in group A v 182 (75-1025) minutes in group B, p = 0.02) since the beginning of chest pain. Success of PTCA (TIMI 3 flow in 95% of all patients), in-hospital mortality (7% v 9%, mortality for patients not in cardiogenic shock 0% v 4%), and follow up after median 235 days was similarly favourable in groups A and B, respectively. Only one hospital survivor (group A) died during follow up.

CONCLUSION

Interhospital transport for primary PTCA in high risk patients with acute myocardial infarction is safe and feasible within a reasonable period of time. Short and medium term outcome is favourable. Optimising the decision process and transport logistics may further improve outcome by reducing the total time of ischaemia.

Current state of thrombolytic therapy

More than 200,000 people have been enrolled into clinical trials examining different reperfusion strategies for patients with acute myocardial infarction. Each year approximately 1 million people in the United States experience acute myocardial infarction. Thrombolytic agents, including streptokinase and tissue-type plasminogen activator, activate plasminogen. These agents are often divided into "fibrin-specific" and "non-fibrin-specific" drugs. New thrombolytic agents designed to address several of the shortcomings of existing thrombolytics are in various stages of clinical development.

Clinical trials in acute myocardial infarction

Long-term follow-up of placebo-controlled thrombolysis trials has proven that the survival benefit from thrombolysis in acute myocardial infarction (AMI) is maintained for up to 10 years. Ongoing research is being conducted with the aim to further improve early restoration of blood flow in the infarct vessel and, thus, reperfusion of the infarcted myocardium in patients with AMI, with the ultimate goal to improve survival. In two recent mega-trials, two new single-bolus fibrinolytics (lanoteplase and TNK-tissue plasminogen activator) were shown to be equivalent to front-loaded alteplase in reducing infarct mortality. The ease of application of these agents might help reduce the time from symptom onset to start of therapy. More potent thrombin inhibitors such as hirudin and hirulog seem to speed up thrombolysis with streptokinase and reduce the rate of reinfarctions. Very promising results are derived from angiographic trials combining reduced doses of thrombolytics with glycoprotein IIb/IIIa inhibitors. Advances in mechanical revascularization can be achieved with the use of stents and better conjunctive therapies. All of these developments are expected to further improve clinical outcome of patients with AMI in the near future.

Combination therapy for acute myocardial infarction: glycoprotein IIb/IIIa inhibitors plus thrombolysis

Although thrombolytic therapy has been a major advance in the treatment of acute ST-segment elevation myocardial infarction (MI), new thrombolytic agents have been unable to improve early reperfusion. Because aspirin has been shown to be a very effective adjunctive agent in patients with acute MI, it has been hypothesized that the use of platelet glycoprotein (GP) IIb/IIIa receptor inhibitors combined with thrombolytic agents would lead to more effective platelet inhibition and improved angiographic and clinical efficacy. Emerging experimental and clinical data, including the Thrombolysis in Myocardial Infarction (TIMI)-14 trial, suggest that combining GP IIb/IIIa receptor inhibition with reduced-dose thrombolytic therapy improves early infarct-related artery patency without increasing bleeding risk. Thus, given the strong clinical and physiologic rationale, clinical investigation in patients with acute ST-segment elevation MI is currently focused on combining GP IIb/IIIa receptor inhibitors with reduced-dose fibrinolytic agents in acute MI.

Optimal management of acute myocardial infarction at the dawn of the next millennium

At the dawn of the next millennium, the optimal management of acute myocardial infarction will have been defined by multiple clinical trials of acute reperfusion strategies, in conjunction with adjunctive pharmacotherapy. Reperfusion therapy with thrombolytic agents or primary angioplasty is the standard of care for many patients examined with ST-segment elevation or left bundle branch block within approximately 12 hours of symptoms. The superiority of fibrin-specific agents over streptokinase has been established, as have the advantages of primary angioplasty in selected institutions with the requisite expertise and logistical capabilities. The key to successful reperfusion lies more in the efficiency of delivery than in the choice of modality. Reocclusion remains the "Achilles' heel" of reperfusion therapy, as does the presence of reperfusion injury microvascular dysfunction and the "no-reflow" phenomenon. These entities are major targets for further investigation in the next 5 years. The wealth of adjunctive pharmacologic agents currently available presents a challenge to the optimal treatment of myocardial infarction. A major objective is to define the magnitude of the incremental benefits and risks of using the available and new drugs, both alone and in combination. Moreover, community-wide studies indicate a marked underutilization of therapies that are available and are of proven effectiveness. The key to optimal management, as we enter the new millennium, lies in the search for new therapies in concert with the most effective use of those agents already at our disposal.

Glycoprotein IIb/IIIa blockade and thrombolytics: early lessons from the SPEED and GUSTO IV trials

Reperfusion with a regimen of thrombolytic therapy, aspirin, and unfractionated heparin is limited by a number of factors. Only 50% to 60% of patients achieve early thrombolysis in myocardial infarction grade-3 flow within 90 minutes with the most effective thrombolytic regimens. Even after initial reperfusion is achieved, transient and permanent reocclusion occurs too often and is associated with high mortality rates. As more older patients are treated, intracranial hemorrhage is becoming more common. Finally, the risk of bleeding and procedural failure has been high in patients who received an acute percutaneous interventional procedure shortly after treatment with thrombolytic therapy. Given the important role of platelets in the thrombotic process and the relatively weak inhibitory effect of aspirin, it is reasonable to seek agents that will provide more profound platelet inhibition. Early studies with full-dose fibrinolytic and glycoprotein IIb/IIIa inhibitors have been promising, but concern about bleeding has hindered this strategy. Several recent trials have evaluated full-dose abciximab with reduced-dose fibrinolytic therapy and have yielded promising results.

Survival 12 years after randomization to streptokinase: the influence of thrombolysis in myocardial infarction flow at three to four weeks

OBJECTIVES

The purpose of this study was to determine whether the mortality benefit of intravenous streptokinase administered within 4 h of the onset of acute myocardial infarction is maintained at 12 years, and whether Thrombolysis in Myocardial Infarction (TIMI) flow grades independently influence late survival.

BACKGROUND

Treatment with reperfusion therapies and achievement of TIMI 3 flow are associated with increased short- and medium-term survival after infarction. Whether infarct artery flow independently influences survival more than five years after infarction is unknown.

METHODS

The late survival of patients randomized to receive either streptokinase (1,500,000 IU over 30 to 60 min) or a matching placebo within 4 h of symptom onset in 1984-1986 was determined. Angiography was performed in surviving patients at three to four weeks, and TIMI flow grades were assessed blind to randomization and outcomes. The late vital status was determined in 99% of patients.

RESULTS

Patients randomized to receive streptokinase (n = 107) had improved survival compared with those randomized to placebo (n = 112) at five years (84% vs. 70%; p = 0.023) and 12 years (66% vs. 51%; p = 0.022). At five years 94% of patients with TIMI grade 3 flow, 81% of those with TIMI grade 2 flow and 72% of those with TIMI grade 0-1 flow survived (p = 0.005). At 12 years 72% of patients with TIMI 3, 67% of those with TIMI 2 and 54% of those with TIMI 0-1 flow survived (p = 0.023). Multivariate analysis identified the ejection fraction (p = 0.014), exercise duration (p = 0.013) and TIMI 3 flow (p = 0.04 compared with TIMI 0-2 flow) as important factors for five-year survival. At 12 years multivariate predictors of late survival were the ejection fraction (p = 0.006), exercise duration (p = 0.003) and myocardial score (p = 0.013). The end-systolic volume index was similar to the ejection fraction as a predictor of survival at five and 12 years.

CONCLUSIONS

The survival benefits of streptokinase persist for 12 years after infarction. TIMI flow at three to four weeks is an independent predictor of five-year survival.

Hemodynamic effects of double bolus reteplase versus alteplase infusion in massive pulmonary embolism

BACKGROUND

Thrombolytic agents are given in massive pulmonary embolism to dissolve or reduce the clot and normalize hemodynamics. Comparative clinical studies have shown that administration of a 2-hour infusion of alteplase is more effective than urokinase over a 12-hour period. Reteplase is a new generation thrombolytic with a longer half-life that can be administered more conveniently as a double bolus. We compared efficacy and safety of reteplase with the approved regimen of alteplase in massive pulmonary embolism.

METHODS

Thirty-six patients were enrolled and randomly assigned: 23 received reteplase and 13 received alteplase along with intravenous heparin. Reteplase was administered as 2 intravenous bolus injections of 10 U 30 minutes apart, and alteplase was administered as an intravenous infusion of a total dose of 100 mg over a 2-hour period, including an initial 10-mg bolus. Diagnosis of pulmonary embolism was confirmed by selective pulmonary angiography. Hemodynamic monitoring was conducted during the first 24 hours after administration. The primary end point was change in total pulmonary resistance. Secondary variables were pulmonary pressure, cardiac index, clinical parameters, and adverse events.

RESULTS

The primary parameter of total pulmonary resistance showed a significant decrease after just 0.5 hours in the reteplase group and after 2 hours in the alteplase group, with a further decrease persisting for up to 24 hours in both treatment groups. A similar pattern was seen in other directly measured hemodynamic parameters, especially mean pulmonary artery pressure and cardiac index; there was no significant difference between reteplase and alteplase. There was also no apparent difference between the treatment groups with respect to safety, and no stroke or intracranial hemorrhage occurred. The rate of bleedings and the incidence of nonhemorrhagic adverse events were as expected for patients with pulmonary embolism treated with a thrombolytic agent.

CONCLUSIONS

Reteplase is suitable for treatment of massive pulmonary embolism with a standard double bolus 10 + 10 U. Efficacy of reteplase appeared to be at least as good at decreasing pulmonary vascular resistance as that of the approved alteplase regimen of 100 mg infusion over a 2-hour period.

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.

New thrombolytic drugs

Thrombolytic drugs reduce mortality from myocardial infarction and research is focused on newer drugs with improved clinical efficacy. The ideal thrombolytic drug should be effective in dissolving fresh and older thrombi, be rapid in its action with complete dissolution of the thrombus, be able to be given as a bolus and be safe without hypotensive or allergic or immunogenic reactions. The types of agents being developed fall into five broad categories: * mutants or variants of single chain urokinase type plasminogen activator; * mutants or variants of tissue type plasminogen activator; * recombinant chimaeric plasminogen activators; * conjugates of plasminogen activators and anti-fibrin monoclonal antibodies; * compounds derived from haemophagous animals. Within the mutant and variant groups there may be single point mutations which increase the half life or deletion of various amino acid sequences to increase resistance to plasma protease inhibitors or cause more selective binding to fibrin. The recombinant chimaeric plasminogen activators are designer drugs where the kringle regions, the growth hormone domain region, the finger domain region and the serine protease part of the molecules are all cleaved and recombined in various ways to improve potency. The conjugates of plasminogen activators and anti-fibrin and monoclonal antibodies improve the targeting of the agent to fibrin clot. Monoclonal antibodies are commonly used against the seven aminoterminal residues of the beta chain of fibrin. These are cross linked and bound to plasminogen activators. A variety of substances from haemophageous animals are currently being studied including salivary plasminogen activator from vampire bats, venom from southern copperhead snakes and staphylokinase from bacteria. Currently available thrombolytic agents have many limitations, but the novel thrombolytic agents have yet to be tested in clinical trials. With few exceptions, they all act via the plasminogen system and it may be in the future that combinations of anti-platelet and thrombolytic agents may prove to be more efficacious than thrombolytics and aspirin alone.

Thrombolytic therapy versus primary angioplasty in the treatment of acute myocardial infarction

The quest to identify the acute interventional approach that will achieve the lowest mortality rate with the fewest adverse events has led to a continued controversy surrounding the relative merits of thrombolytic therapy compared with primary angioplasty in the setting of acute myocardial infarction. This article summarizes the benefits and limitations of each reperfusion strategy and highlights adjunctive therapies that will enhance either treatment strategy.

New plasminogen activators: a clinical review

Rapid restoration of patency of the infarct-related artery is the key to preserving myocardium and improving survival. This understanding has led to the application of genetic engineering to develop new plasminogen activators with specific clinical features. These novel activators may provide faster and more complete reperfusion in a greater number of patients, and do so with less risk of bleeding and intracranial hemorrhage. This article reviews the pharmacologic profiles and clinical performance of several novel plasminogen activators engineered from the human tissue plasminogen activator molecule or developed from animal and bacterial proteins.

Reteplase: a new thrombolytic for the treatment of acute myocardial infarction

OBJECTIVE

To summarize the published data on reteplase, the most recent thrombolytic agent approved by the Food and Drug Administration for use in the management of acute myocardial infarction in adults.

DATA SOURCES

Published data on reteplase identified by MEDLINE searches (January 1985-June 1997), as well as other pertinent literature.

DATA SYNTHESIS

Reteplase is a new thrombolytic agent derived from human tissue plasminogen activator. Its mechanism of action is similar to that of alteplase, but it differs in pharmacokinetic and pharmacodynamic properties. Certain structural changes contribute to differences in pharmacokinetic properties such as a prolonged half-life (15 min), which allows it to be administered as two 10-MU bolus injections. Reteplase has been shown to have fibrin specificity similar to that of alteplase, but with a lower binding affinity for fibrin. This enables reteplase to bind to the thrombus repeatedly and increases its fibrinolytic potential. In clinical trials, reteplase demonstrated more rapid and complete coronary patency compared with alteplase, without a significant increase in clinical adverse events. However, the improvement in coronary artery patency with reteplase versus alteplase did not result in a reduction in mortality in the GUSTO III trial.

CONCLUSIONS

Despite evidence that use of reteplase results in an improved coronary artery patency rate versus accelerated infusion alteplase, an improvement in mortality rate with reteplase was not shown. Reteplase may have an advantage over alteplase due to a more rapid and simpler dosing regimen, but the significance of this difference is yet to be determined.

Intraoperative local fibrinolysis as emergency therapy after early coronary artery bypass thrombosis

OBJECTIVE

Acute graft occlusion early postoperatively after coronary artery bypass grafting (CABG) is a rare but dramatic complication, frequently making resuscitation necessary. Emergency reoperation with reanastomosing of the concerning grafts is the normal procedure to restrict the otherwise unavoidable myocardial damage. Mortality in these cases is up to 50%. Due to this unsatisfying situation, we perform since 1995 in such cases an adjuvant intraoperative intracoronary installed fibrinolysis with recombinant tissue type plasminogen activator (rt-PA; alteplase).

METHODS

Between 1/1994 and 8/1998, 4231 patients underwent CABG. In 18 of these patients, emergency reoperation within the first 12 h after CABG due to clinical signs of acute myocardial infarction was necessary. In nine of the patients (group II) additionally intraoperative rt-PA lysis of the involved vessel/s has been performed. When the peripheral anastomosis was reopened and the thrombotic material was removed, we inserted for this a left atrial-catheter (LA-catheter) of 1.2 mm in diameter, into the coronary artery. Then we administered within 3-5 min, up to 100 mg rt-PA (t1/2: 5-9 min.) locally into the vessel. All patients were treated postoperatively with acetylsalicyl acid (ASA) and heparine.

RESULTS

In group I (n = 9; seven males, two females) without thrombolytic therapy, 78% of the patients (n = 7) could not have been prevented from large myocardial infarction despite emergency reoperation. Three of these patients died during or early after reintervention. In group II with fibrinolytic therapy (n = 9) three of the patients developed Q-wave myocardial infarction following reoperation. None of the patients died. Creatinkinase maximum were in group I significantly higher than in group II (group I: CK = 1254 units/I, CK-MB = 197 units/l; group II: CK = 502 units/l, CK-MB = 61 units/l; P < 0.01). Postoperative bleeding was considerable elevated in both groups. In group I, 832 ml/24 h (375-1420 ml), in group II 1164 ml/24 h (520-1560 ml). Lysis-associated complications were not observed.

CONCLUSIONS

Reoperation of patients with acute thrombotic bypass occlusion after CABG is characterized by a high mortality and morbidity. If additionally fibrinolysis is performed, a sufficient myocardial perfusion seems to be restored. A short half-life in combination with the presented non-systemic application technique of rt-PA seem to prevent unpredictable bleeding. Rt-PA lysis apparently contributes very effectively to the restoration of the macro- and microcirculation within the infarct-related area. Thrombolytic therapy during cardiac surgery with rt-PA is feasible, its application easy and harmful complications are not seen.

New strategy of thrombolysis. Conjunctive effect of plasminogen activators with different pharmacokinetic profile

Combined actions of native and prolonged thrombolytics allow the use of lower doses and simplified schemes of administration, thus yielding significant results in experimental therapy regarding the efficacy and safety of thrombolysis. Development of prolonged forms of plasminogen activators and testing their effect in combination with the thrombolysis trigger are well founded and of current interest. Thrombolytic compositions on the basis of short- and long-term-acting plasminogen activators appear to be promising and potentially eligible for bolus administration.

Importance of time to reperfusion for 30-day and late survival and recovery of left ventricular function after primary angioplasty for acute myocardial infarction

OBJECTIVES

The purpose of this study was to evaluate the importance of time to reperfusion for outcomes after primary angioplasty for acute myocardial infarction.

BACKGROUND

Survival benefit of thrombolytic therapy for acute myocardial infarction is strongly dependent on time to treatment. Recent observations suggest that time to treatment may be less important for survival with primary angioplasty.

METHODS

Consecutive patients (n=1,352) with acute myocardial infarction treated with primary angioplasty were followed for up to 13 years. Paired acute and follow-up ejection fraction data were obtained at cardiac catheterization in 606 patients.

RESULTS

Reperfusion was achieved within 2 h in 164 patients (12%). Thirty-day mortality was lowest with early reperfusion (4.3% at <2 h vs. 9.2% at > or = 2 h, p=0.04) and was relatively independent of time to reperfusion after 2 h (9.0% at 2 to 4 h, 9.3% at 4 to 6 h, 9.5% at >6 h). Thirty-day-plus late cardiac mortality was also lowest with early reperfusion (9.1% at <2 h vs. 16.3% at > or = 2 h, p=0.02) and relatively independent at time to reperfusion after 2 h (16.4% at 2 to 4 h, 16.9% at 4 to 6 h, 15.6% at >6 h). Improvement in left ventricular ejection fraction was greatest in the early reperfusion group and relatively modest after 2 h (6.9% at <2 h vs. 3.1% at > or =2 h, p=0.007).

CONCLUSIONS

Time to reperfusion, up to 2 h, is important for survival and recovery of left ventricular function. After 2 h, recovery of left ventricular function is modest and survival is relatively independent of time to reperfusion. These data suggest that factors other than myocardial salvage may be responsible for survival benefit in patients treated with primary angioplasty after 2 h.

A perspective on the regulation of the evaluation of new antithrombotic drugs

We have entered a period of great possibility for improving clinical outcomes for patients with arterial thrombotic disorders using new antithrombotic agents. A variety of new therapies are now in clinical trials, while several others have just received regulatory approval for use in clinical practice. Because of the increasing complexity of the clinical environment and improvements in our ability to manipulate biology for potential therapeutic benefit, a host of new therapeutic agents will be available for testing in the next decade, and it will become increasingly difficult to determine when a true benefit has occurred. In this therapeutic field, regulatory approval requires a substantial level of evidence from randomized controlled trials. "Superiority" trials are relatively easy to understand, but placebo-controlled trials are becoming increasingly difficult to justify when at least one effective therapy already exists for a disease. Proving superiority over an active control can be difficult and may require a large sample size. Positive-control trials are aimed at equivalence or noninferiority in an effort to prove that a significant difference in clinical outcomes can be excluded. Another approach to demonstrating that the experimental therapy is superior to a putative placebo has been called "sufficiency." A review of recent regulatory decisions demonstrates the need for carefully constructed clinical trial programs that take into account previous experience, interactions, and the current therapeutic environment.

Clinical predictors of early infarct-related artery patency following thrombolytic therapy: importance of body weight, smoking history, infarct-related artery and choice of thrombolytic regimen: the GUSTO-I experience. Global Utilization of Streptokinase and t-PA for Occluded Coronary Arteries

OBJECTIVES

The purpose of this study was to determine patient characteristics that are a priori predictors of early infarct related artery patency following thrombolytic therapy, and to provide a paradigm which may identify patients who would be most likely to achieve restoration of normal (TIMI 3) coronary flow in response to thrombolytic therapy.

BACKGROUND

Restoration of infarct-related artery perfusion in acute myocardial infarction is necessary for preservation of ventricular function and mortality reduction. Clinical variables that are a priori predictors of early patency with currently available thrombolytic regimens have not been fully characterized.

METHODS

The probability of early infarct-related artery patency (TIMI 3 flow) was determined by multivariable logistic regression. We determined a reduced (parsimonious) model for predicting early (90 min) infarct-related artery patency (TIMI grade 3) based on data from 1,030 patients in the GUSTO-I Angiographic study.

RESULTS

Predictors of 90 min TIMI 3 flow are use of an accelerated t-PA regimen (vs. streptokinase containing regimens) (chi2=39.1; p < or = 0.0001), infarct related artery (RCA/Lcx vs. LAD) (chi2=12.7; p=0.0004), body weight (chi2=10.3; p=0.001) and history of smoking (chi2=7.4; p=0.007). Time from symptom onset to treatment was not significant (p=0.71).

CONCLUSIONS

The efficacy of currently available thrombolytic regimens is chiefly dependent on choice of thrombolytic regimen, body weight, infarct-related coronary artery and smoking history. Clinical variables alone correctly predict a priori TIMI 3 flow in the infarct-related artery 64% of the time. Patients with body weights greater than 85 kg are at a significant disadvantage with regard to achieving successful thrombolysis compared to those with lesser body weights.

Neutrophil adhesion and activation during systemic thrombolysis in acute myocardial infarction

In a pilot study, alterations of polymorphonuclear neutrophil function during systemic thrombolysis in acute myocardial infarction have been investigated in humans. The following parameters of neutrophil function were measured before and at 15 and 45 minutes after initiation of systemic thrombolysis with a recombinant tissue-type plasminogen activator in 20 patients with acute myocardial infarction: (1) neutrophil adhesion and (2) neutrophil activation. During systemic thrombolysis a significant decrease was observed in neutrophil adhesion (5.5+/-6.4 to 3.2+/-3.3; p<0.05), in phagocyting neutrophil activation (39+/-18 to 25+/-14%; p<0.05), and in resting neutrophil activation (9+/-7 to 3+/-4%; p<0.05). Successful reperfusion coincided with a significantly higher reduction of phagocyting neutrophil activation (40+/-14 to 20+/-12% vs. 39+/-24 to 26+/-19% in unsuccessful reperfusion; p<0.05), and of neutrophil adhesion (6.2+/-5.7 to 2.7+/-3.0 vs. 4.1+/-3.8 to 3.5+/-4.0 in unsuccessful reperfusion; p<0.05) during thrombolysis. Systemic thrombolysis in acute myocardial infarction is accompanied by a reduction in neutrophil adhesion and activation dependent on thrombolytic success.

Acute interventions for myocardial reperfusion

The primary goal of treatment in acute myocardial infarction is reperfusion of the infarct-related artery in as short a time as possible. Present strategies for acute reperfusion include the use of thrombolytic agents and a variety of catheter-based interventions. This article presents a brief review of these strategies and discusses the patient subsets better served by a particular type of intervention.

Prehospital thrombolytic treatment of massive pulmonary embolism with reteplase during cardiopulmonary resuscitation

A 52-year-old previously healthy man experienced acute severe dyspnoea after suffering from gastroenteritis for 3 days. After arrival of the ambulance, cardiac arrest with an initial rhythm of electro mechanical dissociation occurred. Circulation was restored after 10 min of cardiopulmonary resuscitation but soon cardiac arrest reoccurred. Based on a strong clinical suspicion of massive pulmonary embolism, thrombolytic treatment with heparin 5000 IU and reteplase 20 U, given as single boluses and heparin was continued as an infusion 1000 IU h(-1). After 7 min of continued resuscitation, circulation was restored and after 40 min the vital functions began to stabilize, thus indicating pulmonary reperfusion. The diagnosis of pulmonary embolism was confirmed by a ventilation-perfusion scan and by spiral computerised tomography. The patient was discharged from intensive care after 2 days with a cerebral performance category I. Based on previous calculations, the annual number of patients who present with massive pulmonary embolism leading to cardiac arrest (and thus who would theoretically be candidates for thrombolytic treatment) was estimated to be 0.7/100000 inhabitants in this emergency medical services system.

Thrombolytic therapy: a review of its use in acute myocardial infarction

OBJECTIVE

To review the literature on the use of thrombolytic agents in the pharmacotherapeutic management of acute myocardial infarction (AMI).

DATA SOURCE

English-language clinical trials, reviews, and editorials derived from MEDLINE (January 1966-September 1997) and/or cross-referencing of selected articles.

STUDY SELECTION

Articles that were selected best represent the clinical trials researching the role for thrombolytics in the therapy of AMI to improve morbidity and mortality.

DATA SYNTHESIS

AMI is one of the leading causes of mortality in the US. Following supportive data that the most common cause of an AMI is an intracoronary thrombus, clinical investigation has demonstrated that intravenous thrombolytic agents improve survival rates in patients who experience an AMI. Several clinical trials have been conducted to determine whether one thrombolytic agent is superior to others with respect to improving mortality. At present, only the first Global Use of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries (GUSTO-I) trial has reported any statistically significant difference in mortality rate. In this trial, "front-loaded" alteplase induced a statistically significant (p < 0.001) 1% absolute reduction in 30-day and 1-year mortality compared with streptokinase. This has led to alteplase being the preferred thrombolytic at many US institutions. However, the results of GUSTO-I have been questioned by some on the basis of either study design or clinical significance.

CONCLUSIONS

Thrombolytic agents have secured a place in the treatment of AMI due to their well-proven reduction in mortality rates. In general, comparative trials have demonstrated minimal differences in efficacy among these agents. Probably just as important as choosing which thrombolytic agent to use is ensuring that a patient experiencing an AMI is administered thrombolytic therapy unless a contraindication to receive such therapy exists in the patient and/or the patient is a candidate to receive an emergent intracoronary procedure. Trials also indicate that the sooner thrombolytics can be administered, the greater the benefit to the patient.

Effect of reteplase on hemostasis variables: analysis of fibrin specificity, relation to bleeding complications and coronary patency

The first aim of the present study was to characterize the systemic and fibrin-specific lytic effect of reteplase in the treatment of patients with acute myocardial infarction. The second aim was to investigate the relation of hemostasis variables to risk of bleeding complications and to coronary patency. The present study is a hemostatic substudy of the German Recombinant Activator Study. Forty two patients have been treated with 10 MU of reteplase (Group A) and 100 patients with 15 MU of reteplase (Group B), given as a single bolus. Blood samples for assessment of fibrinogen, plasminogen, alpha-2-antiplasmin, fibrinogen degradation products (FDP) and D-dimers were obtained before and at 2, 4, 8, and 24 h after thrombolytic therapy. The median fibrinogen concentration was decreased from 279 to 169 mg/dl in Group A and from 254 to 92 mg/dl in Group B four hours after administration of reteplase. The decrease in fibrinogen was significantly more pronounced in Group B (P=0.0004). The median plasminogen concentration was decreased to 53% in Group A and to 33% in Group B two hours after administration of reteplase (P=0.0001). Alpha-2-antiplasmin was reduced to 27% and 17,5%, respectively (P=0.0007). D-Dimer levels were increased to 5.2 microg/ml in Group A and 11,6 microg/ml in Group B (P=0.02) and FDP levels to 3.0 microg/ml in Group A and 12,6 microg/ml in Group B (P=0.04). Patients with bleeding complications revealed significant lower nadir levels of fibrinogen than patients without bleeding complications (54 mg/dl versus 125.5 mg/dl, P=0.02). There was no significant difference in any hemostatic parameter between patients with patent and nonpatent infarct related arteries.

CONCLUSIONS

Reteplase causes a moderate systemic lytic effect comparable with other relative fibrin specific thrombolytic agents. An increase in the dose from 10 to 15 MU is associated with a marked increase in both fibrin specific and systemic lytic effect. Patients with bleeding complications reveal significant lower nadir levels of fibrinogen than patients without bleeding complications. Determination of any hemostatic parameter seems to be no useful method to predict efficacy of thrombolysis in terms of coronary patency in the individual patient.

Coronary and Peripheral Thrombolysis: Current Status and Recommendations

Thrombolytics are mainly indicated in acute myo cardial infarction (AMI), with limited evidence of usefulness in stroke and acute peripheral arterial occlusion (PAO). Throm bolytics can successfully dissolve thrombi in any vessel, but clinical benefit varies according to the involved vascular bed. The anticipated clinical benefit of thrombolytics in treating AMI, stroke, and PAO must be carefully balanced against the risk of bleeding (especially intracranial hemorrhage). In AMI, fibrinolytic agents reduce mortality rates by as much as 30% when started within 6 h of symptom onset and by as much as 50% if given within 1 to 2 h. Therefore, the timing of fibrino lytic therapy largely determines the magnitude of reduction in mortality after AMI. Streptokinase is a well-documented treat ment for AMI, with r-TPA plus IV heparin enabling better results, specially in anterior MI and in the elderly. Reteplase was not superior to alteplase in GUSTO-III and TNK-TPA is in the early phase of investigation. However their ease of admin istration and potential for more potent and specific clot lysis may prove advantageous. In acute stroke, the most recently reported phase III trials of streptokinase and recombinant tissue plasminogen activator (r-TPA) have stressed the importance of the clinical benefit/hemorrhage risk balance. These studies sup ported the viewpoint that the use of fibrinolytic agents for stroke must be limited to r-TPA in well-characterized patients and with a narrow time window. Finally, local administration of thrombolytic agents in acute arterial thrombosis, mainly in the limbs, is commonly used by interventional radiologists. Goods results have been reported in terms of safety and effec tiveness in the treatment of acute lower extremity ischemia. The preliminary results of the Thrombolysis or Peripheral Ar terial Surgery (TOPAS) trial suggest that recombinant uroki nase therapy (4,000 IU/min) is associated with limb salvage and patient survival rates similar to those achieved with sur gery, concurrent with a reduced need for complex surgery after thrombolytic intervention.

In summary, AMI represents the most important indication for thrombolysis, with large amounts of data supporting its use. In acute stroke, there is less evidence of efficacy and it is limited to a few well-characterized patients, whereas local ad ministration in patients with acute PAO may favorably affect patient outcome despite of the absence of evidence of improved limb salvage. Key Words: Thrombolysis—Myocardial infarc tion—Stroke—Acute peripheral arterial occlusion.

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.

Thrombolytic Therapy in Acute Myocardial Infarction Part II: 1997 Update

Thrombolytic therapy has become an established treatment for acute myocardial infarction. Streptokinase was first demonstrated in 1988 to reduce mortality rates. In 1993, tissue plasminogen activator was shown to have a slight superiority over streptokinase in reducing mortality rates (approximately 1%). Reteplase is a second generation thrombolytic agent that is given in two bolus injections intravenously over 30 minutes. Studies demonstrated slightly better and more rapid improvement in myocardial perfusion with reteplase compared to tissue plasminogen activator. However, recent studies showed 30-day mortality rates in patients treated with reteplase were similar as those treated with tissue plasminogen activator. The use of angioplasty, aspirin, beta blockers, angiotensin converting enzyme inhibitors, and lipid lowering agents also contribute to the reduction of mortality from acute myocardial infarction.

Pharmacotherapeutics of Biotechnology-Derived Products

Biotechnology has contributed to important advances in the healthcare field. Products include various hormones, enzymes, cytokines, vaccines, and monoclonal antibodies, with use in diverse therapeutic areas. The majority of approved biotechnology-derived therapeutic products are recombinant proteins. Many have orphan drug status and, therefore, are used in relatively small patient populations. Newer generation biotechnology products are likely to include small molecules, gene therapy products, and increased numbers of vaccines and monoclonal antibody products. Biotechnology provides the means to develop diverse, innovative, and effective approaches to the prevention, treatment, and cure of human disease.

Sixty-minute alteplase protocol: a new accelerated recombinant tissue-type plasminogen activator regimen for thrombolysis in acute myocardial infarction

OBJECTIVES

Our aim was to design and evaluate a new and easily administered recombinant tissue-type plasminogen activator (rt-PA) regimen for thrombolysis in acute myocardial infarction (AMI) based on established pharmacokinetic data that improve the reperfusion success rate.

BACKGROUND

Rapid restoration of Thrombolysis in Myocardial Infarction (TIMI) grade 3 flow is a primary predictor of mortality after thrombolysis in AMI. However, TIMI grade 3 patency rates 90 min into thrombolysis of only 50% to 60% indicate an obvious need for improved thrombolytic regimens.

METHODS

Pharmacokinetic simulations were performed to design a new rt-PA regimen. We aimed for a plateau tissue-type plasminogen activator (t-PA) plasma level similar to that of the first plateau of the Neuhaus regimen. These aims were achieved with a 20-mg rt-PA intravenous (i.v.) bolus followed by an 80-mg i.v. infusion over 60 min (regimen A). This regimen was tested in a consecutive comparative trial in 80 patients versus 2.25 10(6) IU of streptokinase/60 min (B), and 70 mg (C) or 100 mg (D) of rt-PA over 90 min. Subsequently, a confirmation trial of regimen A in 254 consecutive patients was performed with angiographic assessment by independent investigators of patency at 90 min.

RESULTS

The comparative phase of the trial yielded, respectively, TIMI grade 3 and total patency (TIMI grades 2 and 3) of 80% and 85% (regimen A), 35% and 50% (B), 50% and 55% (C) and 60% and 70% (D). In the confirmation phase of the trial, regimen A yielded 81.1% TIMI grade 3 and 87.0% total patency. At follow-up angiography 7 (4.1%) of 169 vessels had reoccluded. In-hospital mortality rate was 1.2%. Nadir levels of fibrinogen, plasminogen and alpha2-antiplasmin were 3.6 +/- 0.8 mg/ml, 60 +/- 21% and 42 +/- 16%, respectively (mean +/- SD). Fifty-seven patients (22.4%) suffered from bleeding; 3.5% needed blood transfusions.

CONCLUSIONS

The 60-min alteplase thrombolysis in AMI protocol achieved a TIMI grade 3 patency rate of 81.1% at 90 min with no indication of an increased bleeding hazard; it was associated with a 1.2% overall mortality rate. These results are substantially better than those reported from all currently utilized regimens. Head to head comparison with established thrombolytic regimens in a large-scale randomized trial is warranted.

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

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

A comparison of reteplase with alteplase for acute myocardial infarction

BACKGROUND

Reteplase (recombinant plasminogen activator), a mutant of alteplase tissue plasminogen activator, has a longer half-life than its parent molecule and produced superior angiographic results in pilot studies of acute myocardial infarction. In this large clinical trial, we compared the efficacy and safety of these two thrombolytic agents.

METHODS

A total of 15,059 patients from 807 hospitals in 20 countries who presented within 6 hours after the onset of symptoms with ST-segment elevation or bundle-branch block were randomly assigned in a 2:1 ratio to receive reteplase, in two bolus doses or 10 MU each given 30 minutes apart, or an accelerated infusion of alteplase, up to 100 mg infused over a period of 90 minutes. The primary hypothesis was that mortality at 30 days would be significantly lower with reteplase.

RESULTS

The mortality rate at 30 days was 7.47 percent for reteplase and 7.24 percent for alteplase (adjusted P=0.54; odds ratio, 1.03; 95 percent confidence interval, 0.91 to 1.18). The 95 percent confidence interval for the absolute difference in mortality rates was -1.1 to 0.66 percent. Stroke occurred in 1.64 percent of patients treated with reteplase and in 1.79 percent of those treated with alteplase (P= 0.50). The respective rates of the combined end point of death or nonfatal, disabling stroke were 7.89 percent and 7.91 percent (P=0.97; odds ratio, 1.0; 95 percent confidence interval, 0.88 to 1.13).

CONCLUSIONS

As compared with an accelerated infusion of alteplase, reteplase, although easier to administer, did not provide any additional survival benefit in the treatment of acute myocardial infarction. Other results, particularly for the combined end point of death or nonfatal, disabling stroke, were remarkably similar for the two plasminogen activators.

Acute myocardial infarction. Recommendations for medical management and primary angioplasty

Deaths from acute myocardial infarction have declined in recent years, thanks to the introduction of thrombolytic drugs and therapy with other types of medication that are beneficial when appropriately used. In this article, the authors review the mechanism of action of these agents and focus on recent clinical trials, indications and contraindications, and proper administration. They also discuss the place of primary angioplasty as an alternative to thrombolytic therapy.

Reteplase (r-PA): a new plasminogen activator

Reteplase (r-PA) is a genetically engineered deletion mutant of wild-type tissue-type plasminogen activator. The structural differences lead to different functional properties, such as a prolonged half-life. The compound demonstrated good thrombolytic efficacy in in vitro as well as in animal studies. In angiographically controlled patency studies (GRECO, GRECO-2 RAPID-1, RAPID-2), the double-bolus application scheme was established, and a superior patency profile for reteplase in comparison to alteplase was demonstrated. Mortality studies established reteplase as a safe drug with a 30-day mortality at least equivalent to streptokinase (INJECT) and very similar to alteplase (GUSTO-3). A possible advantage may be the double-bolus application without a need for weight adjustment, especially in a prehospital setting. Thus, reteplase can be regarded as an excellent alternative to streptokinase or alteplase for thrombolytic therapy in acute myocardial infarction.