Comparison of intravenous anisoylated plasminogen streptokinase activator complex and intracoronary streptokinase in acute myocardial infarction

Thrombolytic Therapy: A Comprehensive Review of its Use in Clinical Medicine—Part I

In the first part of this comprehensive review of thrombolytic therapy in clinical medicine, we begin with a brief history of fibrinolysis, followed by a review of the components of die endogenous fibrinolytic system and the currently available plasminogen activators. An in-depth examination of thrombolysis in treatment of acute myocardial infarction follows, Including recommendations for management based on available clinical trial data. New developments in thrombolytic therapy are also discussed.

Saruplase in Myocardial Infarction

Saruplase is an unglucosylated single-chain recombinant urokinase-type plasminogen activator. Dose finding studies in patients with acute myocardial infarction indicated that a dose of 80 mg of saruplase, given as a bolus of 20 mg and iv infusion of 60 mg in one hour, led to excellent patency figures.Saruplase is most effective when combined with a bolus of 5000 IU heparin followed by an iv heparin infusion for at least 24 hours.When saruplase is compared to other thrombolytic agents (streptokinase, alteplase, urokinase), it becomes apparent that its profile is excellent. Early patency rates are at least comparable to alteplase. Further reocclusion rates of saruplase after one day are lower than those of streptokinase and alteplase. Patency rates 24-72 hours after start of medication are comparable between saruplase and urokinase.The large database in over 6000 patients shows that saruplase, in comparison to the other thrombolytic agents, is safe. Its bleeding complication rate is significantly lower than streptokinase, and a trend to lower in-hospital mortality is observed when compared to urokinase.Summarizing, when comparing to the presently available thrombolytic agents, saruplase is a fast acting, effective and safe thrombolytic agent.

Coronary revascularisation for postischaemic heart failure: how myocardial viability affects survival

OBJECTIVE

To assess the impact of revascularisation of viable myocardium on survival in patients with postischaemic heart failure.

METHODS

35 patients (mean (SD) age 58 (7) years) with severe heart failure (New York Heart Association (NYHA) functional class > or = III), mean left ventricular ejection fraction (LVEF) 24 (7)% (range 10-35%), and limited exercise capacity (peak oxygen consumption (VO(2)) 15 (4) ml/kg/min) were studied. 21/35 patients had no angina. Myocardial viability was assessed with quantitative positron emission tomography and the glucose analogue (18)F-fluorodeoxyglucose (FDG) (viable segment = FDG uptake > or = 0.25 micromol/min/g) in all patients before coronary artery bypass grafting. Patients were divided into two groups: group 1, > or = 8 viable dysfunctional segments (mean 12 (2), range 8-15); and group 2, < 8 viable dysfunctional segments (mean 3.5 (3), range 0-7). The two groups were comparable for age, sex, NYHA class, LVEF, and peak VO(2).

RESULTS

Two patients died perioperatively and seven patients died during follow up (mean 33 (14) months). All deaths were from cardiac causes. Kaplan-Meyer survival analysis showed 86% survival for group 1 patients versus 57% for group 2 (p = 0.03). Analysis by Cox proportional hazard model revealed three independent factors for cardiac event free survival: presence of > or = 8 viable segments (p = 0.006); preoperative LVEF (p = 0.002); and patient age (p = 0.01).

CONCLUSION

Revascularisation for postischaemic heart failure can be associated with good survival, which is critically dependent upon the amount of viable myocardium.

Bolus Administration of Saruplase in Europe (BASE), a Pilot Study in Patients with Acute Myocardial Infarction

To study the safety and efficacy of the thrombolytic agent saruplase as a bolus, the angiographic and clinical outcomes of three bolus regimens were investigated in a pilot study conducted in 192 patients with an acute myocardial infarction and were compared with the standard regimen. Fifty-two patients received a double bolus of 40 mg and 40 mg after 30 minutes, 51 patients a bolus of 80 mg, and 36 patients a bolus of 60 mg. Fifty-three patients received the standard regimen (a bolus of 20 mg and 60 mg IV infusion over 1 hour). At 60 minutes TIMI 2 and 3 flow were, respectively, 9.6% and 61.5% with the 40/40-mg bolus, 15.7% and 51.0% with the 80-mg bolus, 16.7% and 30.6% with the 60-mg bolus, and 7.5% and 54.7% with the standard 20/60-mg infusion. At 90 minutes TIMI 2 and 3 flow improved to 9.6% and 73.1%, 15.7% and 56.9%, 13.9% and 36.1%, and 5.7% and 71.7%, respectively. The primary endpoint, persistent patency (TIMI 2 + 3) at 24-45 hours, was seen in 69.2%, 64.7%, 44.4%, and 67.9% of patients who had no rescue PTCA, respectively. Inclusion in the 60-mg bolus group was prematurely stopped because of their low patency rates. The 40/40-mg bolus group had the highest mortality rate (13.5%), whereas the 60-mg bolus group had no deaths. Other adverse event rates were similar in the four groups. This clinical outcome is highly influenced by rescue PTCA of patients with insufficient TIMI flow. This pilot study indicates that in patients with an acute myocardial infarction, a double bolus of 40/40 mg resulted in the highest patency but also had the highest complication rate. The 80-mg single bolus is an attractive alternative for further evaluation because of its acceptable patency and event profile, and its easy form of administration.

Risk of non-fatal cardiac failure and ischaemic heart disease with long acting beta 2 agonists

BACKGROUND

The long term safety of beta agonists, particularly in patients with heart disease, has not been fully established.

METHODS

This study accessed the results of three cohort studies involving: 12,294 patients receiving at least one prescription for nedocromil between November 1986 and September 1988; 15,407 patients prescribed salmeterol between December 1990 and May 1991; and 8098 patients prescribed bambuterol between February 1993 and December 1995. Details of all dispensed prescriptions for these drugs prescribed by general practitioners in England soon after their launch were provided in confidence by the Prescription Pricing Authority. Questionnaires were sent to the prescriber asking for details of events occurring after the first prescription (prescription event monitoring). Rates and relative risks of non-fatal cardiac failure and ischaemic heart disease were calculated, comparing bambuterol and salmeterol with the reference drug nedocromil.

RESULTS

The age and sex adjusted relative risk of non-fatal cardiac failure associated with bambuterol was 3.41 (95% confidence limits (CL) 1.99 to 5.86) when compared with nedocromil. When salmeterol was compared with nedocromil the adjusted relative risk of non-fatal cardiac failure was 1.10 (95% CL 0.63 to 1.91). The adjusted relative risk of non-fatal ischaemic heart disease was 1.23 (95% CL 0.73 to 2.08) and 1.07 (95% CL 0.69 to 1.66) for bambuterol and salmeterol, compared with nedocromil, respectively. However, in the first month of exposure the adjusted relative risk of non-fatal ischaemic heart disease was 3.95 (95% CL 1.38 to 11.31) when bambuterol was compared with nedocromil.

CONCLUSIONS

Caution should be exercised when prescribing long acting oral beta agonists to patients at risk of cardiac failure. More definitive evidence would come from prospective randomised trials.

Comparison of the long-term prognostic value of peak exercise oxygen pulse and peak oxygen uptake in patients with chronic heart failure

OBJECTIVE

To evaluate the ratio of peak oxygen consumption to peak heart rate (peak oxygen pulse) as a predictor of long term prognosis in chronic heart failure.

PATIENTS AND SETTING

178 consecutive heart failure patients recruited to the cardiology department of a tertiary referral centre between 1986 and 1993.

DESIGN

Bicycle ergometry with measurement of respiratory exchange. Mean (SD) follow up was 32 (25) months.

RESULTS

Patients who died had a lower peak oxygen consumption (16.0 (5.5) v 18.0 (5.5) ml/min/kg, p = 0.05), lower indexed peak oxygen consumption (52 (14) v 60 (16)%, p = 0.006) but similar peak oxygen pulse (8.4 (2.6) v 8.4 (3.0) ml/beat, NS). The following variables were associated with a good long term prognosis: New York Heart Association class II, non-ischaemic heart failure, peak oxygen consumption > or = 17 ml/min/kg, indexed peak oxygen consumption > 63%. Peak oxygen pulse did not have predictive value. Only indexed peak oxygen consumption remained an independent predictor of survival in multivariate analysis.

CONCLUSIONS

Peak oxygen pulse has lower prognostic value than peak oxygen consumption, especially when the latter is indexed to predicted values.

Left ventricular atrioventricular plane displacement: an echocardiographic technique for rapid assessment of prognosis in heart failure

OBJECTIVE

To assess the prognostic value of atrioventricular plane displacement in heart failure patients.

DESIGN

Patients were followed prospectively for one year after atrioventricular plane displacement determination.

SETTING

Malmö University Hospital, with a primary catchment area of 250,000 inhabitants.

PATIENTS

181 patients with a clinical diagnosis of heart failure; age 75.7 (SD 5.2) years, duration of heart failure 2.7 (5.7) years; 100 men, 81 women.

MAIN OUTCOME MEASURES

Mortality in relation to atrioventricular plane displacement.

RESULTS

Total mortality was 22.7% (41/181), and was highly significantly (P = 0.001) related to atrioventricular plane displacement. Mortality within prospectively defined categories of displacement was: > or = 10.0 mm, 0% (0/19); 8.2 to 9.9 mm, 10.3% (3/29); 6.4 to 8.1 mm, 19.4% (12/62); and < 6.4 mm, 36.6% (26/71). The groups were similar in age, sex, angiotensin converting enzyme inhibitor and beta blocker treatment, and cause and duration of heart failure.

CONCLUSIONS

Mortality in heart failure is strongly related to atrioventricular plane displacement.

Effects of lacidipine on peak oxygen consumption, neurohormones and invasive haemodynamics in patients with mild to moderate chronic heart failure

OBJECTIVE

To evaluate the efficacy and safety of the second generation dihydropyridine calcium channel blocker lacidipine in patients with heart failure.

DESIGN

Placebo controlled, parallel group, double blind study over 8 weeks.

SETTING

General community hospital in Breda, The Netherlands.

PATIENTS

A random sample was studied of 25 outpatients with symptoms of mild to moderate heart failure, despite treatment with diuretics, digoxin, and angiotensin converting enzyme inhibitors. Their mean age was 65 years, with mean left ventricular ejection fraction of 0.24 and a peak oxygen consumption of 14.4 ml/min/kg. Two patients dropped out on lacidipine, one patient on placebo.

INTERVENTION

Treatment with lacidipine 4 mg once daily or placebo for eight weeks.

MAIN OUTCOME MEASURE

Cardiopulmonary exercise testing, invasive haemodynamics, and plasma neurohormones.

RESULTS

Treatment with lacidipine 4 mg once daily, as compared to placebo treatment, significantly improved peak oxygen consumption (P < 0.02), cardiac index (P < 0.01), and stroke volume (P < 0.03) paralleled by a decrease in systemic vascular resistance (P < 0.03) and arteriovenous oxygen content difference (P < 0.01). Plasma noradrenaline, plasma renin activity, and aldosterone values did not differ between lacidipine and placebo.

CONCLUSIONS

This second generation dihydropyridine may be of value as an adjunct to standard treatment in congestive heart failure patients.

Baroreflex sensitivity and cardiovascular mortality in patients with mild to moderate heart failure

OBJECTIVE

To assess the influence of both sympathetic (plasma noradrenaline concentrations) and parasympathetic (baroreflex activation) tone on survival in patients with congestive heart failure.

DESIGN

Invasive study with determination of parasympathetic activity and follow up for at least 4.5 years.

SUBJECTS

35 patients with sinus rhythm and mild to moderate heart failure (New York Heart Association grades II-III) (mean age 53 (SD 3)).

RESULTS

20 patients whose hearts survived were compared with 15 patients whose hearts did not (12 died and three received transplants). The two groups differed significantly in terms of mean arterial blood pressure (98 (3) v 90 (3) mm Hg), heart rate (82 (2) v 93 (4) beats/min), and mean pulmonary artery pressure (24 (3) v 35 (2) mm Hg) (all P < 0.05), while cardiac index, stroke volume index, and right atrial pressures were not different. The survivors had significantly lower plasma renin activities (3.6 (0.8) v 9.0 (3.6) angiotensin I/ml/h; P < 0.05) and tended to have lower noradrenaline values than non-survivors (170 (23) v 286 (74) pg/ml) at baseline. Baroreflex sensitivity was significantly lower in non- survivors than in survivors (1.3 (0.2) v 2.3 (0.3) ms/mm/Hg); P < 0.02). As the time of cardiac transplantation is dependent on complex logistical factors the three patients who received a transplant were excluded from the analysis of survival time. The risk of death in relation to baroreflex sensitivity at the median sensitivity of 1.48 ms/mm Hg was calculated. Survival was significantly different (P < 0.04) between the resulting two groups; three of the 16 subjects with high baroreflex sensitivity died compared with nine of the 16 with a baroreflex sensitivity < 1.48 ms/mm Hg. When systemic blood pressure, pulmonary artery pressure, stroke volume index, plasma noradrenaline concentrations, and baroreflex sensitivity were entered into a Cox proportional hazards regression, only systolic blood pressure and plasma noradrenaline values predicted survival (P < 0.001).

CONCLUSIONS

Low vagal tone is correlated with a poor prognosis in patients with heart failure. Sympathetic tone measured as plasma noradrenaline concentration also contributed to survival. An additional contribution of vagal tone to survival could not be shown when sympathetic tone was considered simultaneously. This may be due to the inverse relation of sympathetic and parasympathetic tone and to the insensitivity of the multiple regression method to identify additional risk factors in small numbers of patients.

Frequency of achieving optimal reperfusion with thrombolysis in acute myocardial infarction (analysis of four German multicenter studies)

Patients from 4 German multicenter studies on thrombolysis in acute myocardial infarction (AMI) were retrospectively evaluated to assess the incidence of optimal reperfusion, defined as a completely perfused infarct vessel after 90 minutes, without subsequent death or reinfarction, and without reocclusion or deterioration of flow in control angiograms. Of 907 patients with a 90-minute angiogram, 75% had an open infarct vessel by conventional definition (perfusion grade 2 or 3 according to the criteria of the Thrombolysis in Myocardial Infarction [TIMI] study). However, only 62% had TIMI grade 3 complete perfusion. Of the 561 patients with such primary treatment success, 106 (19%) had secondary treatment failure by death, reinfarction, or subtotal or total reocclusion of the infarct vessel. In a subset of 668 patients with a first angiogram after 60 minutes, conventional patency was 70%, complete perfusion 51%, and an optimal perfusion result was achieved in only 42%. The efficacy of thrombolysis in AMI is substantially overestimated by conventional 90-minute patency rates.

A randomized trial of intravenous heparin in conjunction with anistreplase (anisoylated plasminogen streptokinase activator complex) in acute myocardial infarction: the Duke University Clinical Cardiology Study (DUCCS) 1

OBJECTIVES

We designed a randomized trial to evaluate the effects of heparin administration in conjunction with anistreplase (anisoylated plasminogen streptokinase activator complex [APSAC]) on arterial patency and clinical end points.

BACKGROUND

The role of conjunctive intravenous heparin therapy with APSAC has not been tested despite the recommendations that intravenous heparin should be used.

METHODS

Four hours after APSAC administration, 250 patients with acute myocardial infarction were randomly assigned to receive 325 mg of either aspirin alone or aspirin and a continuous infusion of heparin (15 IU/kg body weight per h). Clinical ischemic events and bleeding complications were monitored. On hospital day 5, coronary arteriography and left ventriculography were performed.

RESULTS

The primary end point of the trial (the combined outcome of death, reinfarction, recurrent ischemia and occlusion of the infarct-related artery) occurred in 42% of the heparin-treated group versus 43% of the group treated without heparin (p = 0.94). A patent infarct-related artery was present in 80% of the patients treated with heparin and in 73% of those treated without heparin (p = 0.26). Left ventricular function, as measured by ejection fraction, was well preserved in both groups (52% vs. 50.5%, respectively, p = 0.29). The overall bleeding rate was higher in patients with (32%) than without (17.2%) heparin (p = 0.006).

CONCLUSIONS

Weight-adjusted intravenous heparin therapy after APSAC in acute myocardial infarction does not reduce the combined incidence of death, reinfarction, recurrent ischemia and occlusion of the infarct-related artery. Furthermore, withholding intravenous heparin therapy is associated with a 46% reduction in bleeding complications. Our findings do not support the addition of intravenous heparin after APSAC therapy, as currently recommended, and suggest that a strategy of withholding heparin is simpler and safer and does not place the patient at increased risk for ischemic complications after myocardial infarction.

Culprit lesion morphology and stenosis severity in the prediction of reocclusion after coronary thrombolysis: angiographic results of the APRICOT study. Antithrombotics in the Prevention of Reocclusion in Coronary Thrombolysis

OBJECTIVES

In the APRICOT study (Antithrombotics in the Prevention of Reocclusion In Coronary Thrombolysis), we sought to determine whether angiographic characteristics of the culprit lesion could predict reocclusion after successful thrombolysis and to analyze the influence of three antithrombotic treatment regimens.

BACKGROUND

After successful thrombolysis, reocclusion is a major problem. Prediction of reocclusion by angiographic data and choice of antithrombotic treatment would be important for clinical management.

METHODS

After thrombolysis, patients were treated with intravenous heparin until initial angiography was performed within 48 h. Patients with a patent infarct-related artery were eligible. Three hundred patients were randomly selected for treatment with coumadin, aspirin (300 mg once daily) or placebo. Patency on a second angiographic study after 3 months was the primary end point of the study.

RESULTS

Reocclusion rate was 25% with aspirin, 30% with coumadin and 32% with placebo (p = NS). Lesions with > 90% stenosis reoccluded more frequently (42%) than did those with < 90% stenosis (23%) (p < 0.01). Reocclusion rate of smooth lesions was higher (34%) than that of complex lesions (23%) (p < 0.05). In lesions with < 90% stenosis, the reocclusion rate was lower with aspirin (17%) than with coumadin (25%) or placebo (30%) (p < 0.01). In complex lesions, the reocclusion rate was lower with aspirin (14%) than with coumadin (32%) or placebo (25%) (p < 0.02). Multivariate analysis showed only stenosis severity > 90% to be an independent predictor of reocclusion (odds ratio 2.31, 95% confidence interval 1.28 to 4.18, p = 0.006).

CONCLUSIONS

Angiographic features of the culprit lesion after successful coronary thrombolysis significantly predict the risk of reocclusion: high grade (> 90%) stenoses reoccluded more frequently. Aspirin was effective only in complex and less severe lesions (< 90% stenosis). These findings should prompt investigation of the effects of an aggressive approach to patients with severe residual stenosis.

Impact of early perfusion status of the infarct-related artery on short-term mortality after thrombolysis for acute myocardial infarction: retrospective analysis of four German multicenter studies

OBJECTIVE

This study evaluated the impact of early patency of the infarct-related vessel on short-term mortality after thrombolysis for acute myocardial infarction.

BACKGROUND

Different thrombolytic regimens for acute myocardial infarction proved to be equally effective in large scale mortality trials despite significant differences in their efficacy with respect to early infarct-related vessel patency as shown in smaller angiographic trials.

METHODS

Patients from four German multicenter studies of thrombolysis in acute myocardial infarction were retrospectively evaluated. Of 939 patients with acute myocardial infarction (duration of symptoms < 6 h) treated with thrombolysis, 907 (96.6%) had an angiogram of the infarct-related artery 90 min after the initiation of thrombolytic therapy. The perfusion status was graded according to the Thrombolysis in Myocardial Infarction (TIMI) study criteria.

RESULTS

Complete reperfusion (TIMI grade 3) was found in 561 of 907 patients and partial reperfusion (TIMI grade 2) in 122 of 907. Overall, the in-hospital mortality rate was 4.6% (43 patients). In patients with complete reperfusion of the infarct-related vessel, the mortality rate was only 2.7% versus 7.1% in patients with an occluded vessel at the 90-min angiogram. This difference was highly significant in univariate as well as in multivariate analysis. In patients with partial perfusion of the infarct vessel, the mortality rate was 6.6%.

CONCLUSIONS

The early perfusion status of the infarct-related artery is an independent predictor of short-term survival. However, only complete early reperfusion is associated with a reduced in-hospital mortality rate whereas patients with partial perfusion (TIMI grade 2) have a short-term prognosis similar to that of patients with persistently occluded infarct vessels. Therefore, when used as a surrogate end point for mortality, only TIMI grade 3 perfusion of the infarct vessel should be interpreted as a treatment success of thrombolysis in acute myocardial infarction.

Retreatment with alteplase for early signs of reocclusion after thrombolysis. The European Cooperative Study Group

Recurrent chest pain with new ST-segment elevation was observed in 26 of 652 patients (4%) with myocardial infarction in a clinical trial of alteplase (recombinant tissue-type plasminogen activator; 100 mg) and aspirin with or without heparin. Clinical and electrocardiographic signs of reocclusion were treated with a second dose of alteplase: 50 mg in 20 patients with signs of reocclusion < or = 24 hours after initial therapy, and 100 mg in 5 patients with signs between 24 and 77 hours, and in 1 patient with early signs of reocclusion. Pain and ST changes disappeared within 100 minutes (median 50). D-dimer determinations in 15 patients were increased, indicating activation of the coagulation system. Signs of reocclusion occurred despite adequate anticoagulation with heparin in 5 of 11 patients in whom coagulation measurements were available. No excess bleeding was observed in patients who received a second dose of alteplase. Retreatment with alteplase is feasible and provides an alternative for angioplasty in patients with clinical and electrocardiographic signs of reocclusion early after thrombolytic therapy.

Comparison of results of intravenous infusion of anistreplase versus streptokinase in acute myocardial infarction

This randomized study compares the coronary perfusion rate in patients with acute myocardial infarction (AMI) treated with 2 different intravenous thrombolytic agents: streptokinase 1.5 million U given over 60 minutes and anisoylated human plasminogen streptokinase activator complex (anistreplase) administrated as a bolus of 30 U over 5 minutes. One hundred seventy-five patients (149 men and 26 women, mean age 54 years) have been included in this study. Eighty-nine patients were treated with anistreplase and 86 patients with streptokinase. AMI was inferior in 54 patients (61%) in the anistreplase group and in 54 patients (63%) in the streptokinase group. It was anterior in 35 (40%) and 32 (37%) patients, respectively. Coronary angiography and ventriculography were performed at a mean time (+/- SEM) of 207 +/- 11 minutes after the beginning of thrombolysis in 170 patients. A perfusion score grade of 2 or 3 according to the Thrombolysis in Myocardial Infarction trial was found in 63 patients (72%) in the anistreplase group and in 56 patients (68%) in the streptokinase group (p = NS). Severe bleeding occurred in 7 patients (8%) after anistreplase and in 6 patients (7%) after streptokinase. No cerebral hemorrhage occurred. Nine patients (5%) died during their hospital stay: 6 after anistreplase and 3 after streptokinase. It is concluded that intravenous administration of anistreplase or streptokinase is efficient and safe. Coronary patency 207 minutes after fibrinolysis, incidence of adverse events and mortality are similar in both groups.

Thrombolysis in patients with unstable angina improves the angiographic but not the clinical outcome. Results of UNASEM, a multicenter, randomized, placebo-controlled, clinical trial with anistreplase

BACKGROUND

The value of thrombolytic therapy in unstable angina is unclear.

METHODS AND RESULTS

To study this problem, 159 patients were studied in a double-blind, placebo-controlled multicenter trial. Patients without a previous myocardial infarction, with a typical history of unstable angina, and ECG abnormalities indicative of ischemia were included. After baseline angiography, study medication (anistreplase or placebo) was given. Angiography was repeated after 12-28 hours. A significant decrease occurred in diameter stenosis between the first and second angiogram in the anistreplase group compared with the placebo group (11% versus 3%, p = 0.008). This difference was caused by reopening of occluded vessels in the thrombolytic group. However, no beneficial clinical effects of thrombolytic treatment were found. Bleeding complications were significantly higher in patients who received thrombolytic therapy (21 versus seven patients, p = 0.001).

CONCLUSIONS

Thus, angiographic but no clinical improvement after thrombolytic treatment with anistreplase was found in patients with unstable angina with an excess of bleeding complications. Therefore, thrombolytic treatment cannot be recommended in patients diagnosed as having unstable angina until proven otherwise.

Importance of the pharmacological profile of thrombolytic agents in clinical practice

Three thrombolytic agents are frequently used in the United States for treating patients with acute myocardial infarction: streptokinase, alteplase (tissue plasminogen activator [t-PA]), and anistreplase (anisoylated plasminogen-streptokinase activator complex [APSAC]). A fourth agent, urokinase, is occasionally used but clinical experience is considerably more limited with this agent. Streptokinase, alteplase, and anistreplase differ in a number of pharmacologic properties, which include half-life, enzymatic efficiency, and induction of platelet aggregation; these differences may be clinically important. For example, anistreplase and alteplase have high affinity for fibrin and bind to intravascular thrombi after intravenous administration, which may result in higher clot specificity. Anistreplase has the longest half-life of the 3 agents and, therefore, can be administered conveniently and quickly. Alteplase has a shorter half-life and heparin is generally a necessary adjunctive agent. These differences can be clinically significant in various settings and application of such theoretical advantages is just beginning.

Brief overview of the end points of thrombolytic therapy

In addition to mortality, several measurable end points of thrombolytic therapy have been studied. These include coronary arterial patency, left ventricular function, reocclusion, reinfarction, and bleeding complications. Current wisdom dictates that recanalization of occluded arteries in the early phases of acute myocardial infarction should be attempted to preserve viable cardiac muscle, with the ultimate goal of decreasing mortality. Unfortunately, the number of patients eligible for thrombolytic therapy far exceeds the number receiving it, despite the clear benefits that have been demonstrated.

Thrombolysis: the need for a critical review

The (Thrombolysis in Myocardial Infarction) TIMI-I trial led to the hypothesis that the greater reperfusion rate seen with recombinant tissue-type plasminogen activator (rt-PA) versus streptokinase would result in greater reductions in infarct size and mortality in patients with acute myocardial infarction. Despite extensive investigation, no trial comparing rt-PA with streptokinase (European Cooperative Study Group, Plasminogen Activator Italian Multicenter Study [PAIMS], Gruppo Italiano per lo Studio della Sopravvivenze nell'Infarto Miocardico [GISSI-2], International Study on Infarct Survival [ISIS-3], even TIMI-I itself) nor rt-PA and anisoylated plasminogen-streptokinase activator complex (APSAC or anistreplase) (Bassand, TEAM-3, ISIS-3), have confirmed this hypothesis. In a reversal of traditional scientific method, the studies, rather than the unconfirmed hypothesis, have been rejected. A lack of independent review of this subject may have contributed to this outcome. It is proposed that standards of review and editorial comment mandating true critical distance and independence be followed, permitting greater independence of scientific inquiry, review and debate.

Comparative effects of APSAC and rt-PA on infarct size and left ventricular function in acute myocardial infarction. A multicenter randomized study

BACKGROUND

Recombinant tissue-type plasminogen activator (rt-PA or alteplase) and anisoylated plasminogen streptokinase activator complex (APSAC or anistreplase) have been demonstrated to limit infarct size significantly and to preserve left ventricular function when injected soon after acute myocardial infarction. However, as yet, the efficacy and safety of these two thrombolytic agents have not been directly compared in one trial; this was the aim of this study.

METHODS AND RESULTS

One hundred eighty-three patients suffering from a first acute myocardial infarction were randomly allocated to either APSAC (30 units over 5 minutes) or single-chain rt-PA (100 mg over a 3-hour period) within 4 hours of the onset of symptoms. Global and regional left ventricular function were assessed from contrast angiography an average of 5.3 +/- 2.3 days after initial therapy. Radionuclide angiography and thallium-201 single-photon emission computerized tomography were performed before hospital discharge. Infarct size was assessed by single-photon emission computerized tomography and expressed in percentage of the total myocardial volume. Ninety patients received APSAC and 93 received rt-PA within a mean period of 172 +/- 52 minutes after the onset of symptoms. The two groups were similar in age, location of the acute myocardial infarction, Killip class, and time of randomization. The patency rate of the infarct-related artery was 72% in the APSAC group and 76% in the rt-PA group (NS). Initial and predischarge left ventricular ejection fraction as well as infarct size were similar in both therapeutic groups (0.50 +/- 0.14 versus 0.52 +/- 0.12 for initial and 0.48 +/- 0.10 versus 0.47 +/- 0.10 for predischarge ejection fraction, 11 +/- 7% versus 9 +/- 7% for infarct size, respectively, for APSAC- and rt-PA-treated patients). Bleeding complications requiring blood transfusion occurred in one APSAC patient and in two rt-PA patients. One patient in the rt-PA group died of a massive intracranial hemorrhage. At the end of the 3-week follow-up period, five APSAC patients (5.5%) and seven rt-PA patients (7.5%) had died.

CONCLUSIONS

The early infusion of APSAC or rt-PA in acute myocardial infarction produced a similar patency rate, limitation of infarct size, and preservation of left ventricular systolic function with an equivalent rate of bleeding complications.

Angiographically assessed coronary arterial patency and reocclusion in patients with acute myocardial infarction treated with anistreplase: results of the anistreplase reocclusion multicenter study (ARMS)

In this open multicenter study, 156 patients with acute myocardial infarction received 30 U of anistreplase intravenously over 5 minutes within 4 hours of the onset of chest pain. The patency of the infarct-related vessel was determined by coronary angiography 90 minutes after anistreplase treatment, and also 24 hours after treatment, in patients with a patent infarct-related vessel at 90 minutes, to assess the reocclusion rate. The investigators categorized the infarct-related vessel as patent or occluded, and 2 independent cardiologists graded the infarct-related vessel according to the Thrombolysis in Myocardial Infarction (TIMI) perfusion criteria. At the 90-minute assessment, 106 of 145 evaluable patients (73%) had patent infarct-related vessels, and 39 of 145 (27%) had occluded infarct-related vessels. Of the 139 independently assessed patients, 98 (71%) had TIMI grades 2 or 3 and 41 (29%) had TIMI grades 0 or 1. At the 24-hour assessment, 98 of 102 patients (96%) had a patent infarct-related vessel, and reocclusion had occurred in 4 of 102 patients (4%). Of the 94 independently assessed patients 90 (96%) had TIMI grades 2 or 3, and 4 (4%) had TIMI grades 0 or 1. The reliability of noninvasive parameters as indicators of achieved patency of the infarct-related vessel was estimated by means of correlation with patency assessed by coronary angiography. A significant correlation of 0.62 was found. The patency rate of 71 to 73% after use of anistreplase in patients with acute myocardial infarction corresponds with findings in earlier studies. The low reocclusion rate of 4% after use of anistreplase probably reflects the prolonged action of anistreplase.

Multicenter patency trial of intravenous anistreplase compared with streptokinase in acute myocardial infarction. The TEAM-2 Study Investigators

Thrombolytic therapy has been shown to improve clinical outcome when administered early after the onset of symptoms of acute myocardial infarction; the mechanism of benefit is believed to be reestablishment and maintenance of coronary artery patency. Anistreplase is a second generation thrombolytic agent that is easily administered and has a long duration of action. To compare anistreplase (30 units/2-5 min) and therapy with the Food and Drug Administration-approved regimen of intravenous streptokinase (1.5 million units/60 min), a randomized, double-blind, multicenter patency trial was undertaken in 370 patients less than 76 years of age with electrocardiographic ST segment elevation who could be treated within 4 hours of symptom onset. Coronary patency was determined by reading, in a blinded fashion, angiograms obtained early (90-240 minutes; mean, 140 minutes) and later (18-48 hours; mean, 28 hours) after beginning therapy. Early total patency (defined as Thrombolysis in Myocardial Infarction grade 2 or 3 perfusion) was high after both anistreplase (132/183 = 72%) and streptokinase (129/176 = 73%) therapy, and overall patency patterns were similar, although patent arteries showed "complete" (grade 3) perfusion more often after anistreplase (83%) than streptokinase (72%) (p = 0.03). Similarly, residual coronary stenosis, determined quantitatively by a validated computer-assisted method, was slightly less in patent arteries early after anistreplase (mean stenosis diameter, 74.0%) than streptokinase (77.2%, p = 0.02). In patients with patent arteries without other early interventions, reocclusion risk within 1-2 days was defined angiographically and found to be very low (anistreplase = 1/96, streptokinase = 2/94). Average coronary perfusion grade was greater, and percent residual stenosis was less, at follow-up than on initial evaluation and did not differ between treatment groups. Enzymatic and electrocardiographic evolution was not significantly different in the two groups. Despite rapid injection, anistreplase was associated with only a small (4-5 mm Hg), transient (at 5-10 minutes) mean differential fall in blood pressure. In-hospital mortality rates were comparable for anistreplase and streptokinase (5.9%, 7.1%). Stroke occurred in one (0.5%) and three (1.6%) patients, respectively; one stroke was hemorrhagic. Other serious bleeding events and adverse experiences occurred uncommonly and with similar frequency in the two groups. Thus, for the end points of our study (patency, safety), anistreplase and streptokinase showed overall favorable and relatively comparable outcomes, with a few differences.(ABSTRACT TRUNCATED AT 400 WORDS)

French multicenter trial of anistreplase versus heparin in acute myocardial infarction

Eighty-four patients aged less than 71 years with less than 4-hour duration acute myocardial infarction (AMI) were randomized in a multicenter study to 30 U anistreplase or heparin (single injection of 6500 IU followed by 1000 IU/hr). Early reperfusion was assessed from ECG changes (50% of sum ST decrease 2 hours postdosing) and the CK release profile (CK peak less than 16 hours after onset of symptoms, CK slope greater than 10%/hr). Reperfusion rates in patients meeting at least two criteria of reperfusion were 62.5% on anistreplase versus 27.5% on heparin. On delayed angiogram (13.7 +/- 3.4 days), patency rates were 66% with anistreplase versus 47% (NS) with heparin in 76 patients. Global LVF was similar in both groups. With anistreplase, the mean lowest fibrinogen level was 0.43 +/- 0.55 g/l, plasminogen was 20 +/- 9%, and the highest F.D.P. was 1447 +/- 548 micrograms/ml. All values recovered by hour 48. In-hospital and 1-year follow-up mortality was 7.2% (three patients) with anistreplase versus 10.2% (four patients) with heparin. Bleeding occurred in 9.7% and 5.1% of the patients (NS), respectively. No intracranial hemorrhage occurred. Thus, with combined clinical criteria or reperfusion, anistreplase is twice as efficient as heparin, has a good tolerance, and is easy to use as a single injection.

Future directions in plasminogen activator therapy

Thrombotic disorders such as myocardial infarction and stroke are the leading causes of death and disability in industrialized nations. Timely institution of thrombolytic therapy can achieve a reduction of infarct size, a preservation of left ventricular function, and a reduction in mortality. The administration of streptokinase, urokinase, and acylated plasminogen-streptokinase activator complex (APSAC) can be associated with a complete breakdown of the hemostatic system. Tissue-type plasminogen activator (t-PA) and single-chain urokinase-type plasminogen activator (scu-PA, prourokinase) are more fibrin specific; however, at the large dosages of activator needed for therapeutic efficacy, bleeding complications are still a problem. New approaches to optimizing the risk/benefit ratio for the patient by improving efficacy without sacrificing specificity include the use of synergistic combinations of plasminogen activators, mutants of t-PA and scu-PA, chimeric molecules, and antibody-targeted thrombolytic agents. The last approach opens the possibility of targeting several different components of the clot with either fibrinolytic or antiplatelet effector functions in one optimized molecule.

Anistreplase: a novel thrombolytic agent for acute myocardial infarction

Anistreplase, a modified congener of streptokinase, is a recently approved thrombolytic agent used in the treatment of acute myocardial infarction (AMI). Clinical studies have demonstrated anistreplase to be equally efficacious as intracoronary streptokinase when given within four hours of the onset of chest pain. Thirty units, given as a single bolus intravenous injection, result in reperfusion rates of approximately 60-70 percent. The adverse-effect profile of anistreplase compares favorably with that of streptokinase, with hemorrhagic complications being the most serious. Anistreplase has two distinct advantages over both streptokinase and alteplase: (1) it can be administered as a single bolus intravenous injection and (2) it has a longer half-life which may result in decreased reocclusion rates. Anistreplase therapy is associated with reductions in both short- and long-term mortality and has been shown to preserve left ventricular function. A large, long-term, comparative clinical trial (Third International Study of Infarct Survival or ISIS-III) investigating morbidity and mortality rates with streptokinase, alteplase, and anistreplase is ongoing, as is a direct comparative study against alteplase alone (TEAM-3, Multicenter Thrombolytic Trials of Eminase in Acute Myocardial Infarction).

Pharmacology of anistreplase

Eminase (anistreplase), or anisoylated plasminogen streptokinase activator complex (APSAC), is a reversibly inactivated lys-plasminogen-streptokinase activator complex that is given rapidly over a period of 2-5 minutes, and has a half-life in the circulation of 90-105 min. Eminase represents a significant advance in drug design for therapeutic thrombolysis based on convenience in administration, high gradient (especially initially) for diffusion into thrombus, improved fibrin binding, ability to lyse fibrin rapidly, improved stability in the circulation, long duration of action, and production of an antithrombotic state.

Summary of U.S. clinical trials program for evaluation of anistreplase

Because the reestablishment of coronary blood flow is believed to be central to the benefit of thrombolytic therapy, the U.S. evaluation program of anistreplase has focused on reperfusion, patency, and reocclusion comparisons with approved thrombolytic regimens, including (1) intracoronary streptokinase (completed) (TEAM-I), (2) intravenous streptokinase (completed) (TEAM-II), and (3) intravenous tissue plasminogen activator complex or alteplase (tPA, ongoing) (TEAM-III). The TEAM trials have established that anistreplase possesses similar reperfusion efficacy to intracoronary streptokinase, if given within 4 h, but is much easier to administer; comparisons with currently approved intravenous agents, streptokinase, and tissue plasminogen activator (tPA) have been completed and are being analyzed or are underway; reocclusion and reinfarction rates are low; safety is good, and similar to that of streptokinase; and mortality rates have been low with treatment, consistent with beneficial reports from randomized trials. Based on overall efficacy, ease of administration, and safety, anistreplase has been shown to be a promising agent for treatment of acute myocardial infarction.

New developments in thrombolytic therapy

Thrombotic complications of cardiovascular disease are a main cause of death and disability and, consequently, thrombolysis could favorably influence the outcome of such life-threatening diseases as myocardial infarction, cerebrovascular thrombosis and venous thromboembolism. Thrombolytic agents are plasminogen activators that convert plasminogen, the inactive proenzyme of the fibrinolytic system in blood, to the proteolytic enzyme plasmin. Plasmin dissolves the fibrin of a blood clot, but may also degrade normal components of the hemostatic system and predispose to bleeding. Currently, five thrombolytic agents are either approved for clinical use or under clinical investigation in patients with acute myocardial infarction. These include streptokinase, urokinase, recombinant tissue-type plasminogen activator (rt-PA), anisoylated plasminogen streptokinase activator complex (APSAC) and single chain urokinase-type plasminogen activator (scu-PA, prourokinase). The first generation thrombolytic agents, streptokinase (and probably also urokinase), are only moderately efficacious and their administration is associated with extensive systemic fibrinogen breakdown. In comparative studies performed in patients with acute myocardial infarction, recombinant tissue-type plasminogen activator (rt-PA) is a more effective and fibrin-specific thrombolytic agent than streptokinase. The acylated plasminogen streptokinase activator complex (APSAC) has a profile of thrombolytic efficacy and fibrin-specificity that is similar or somewhat better than that of streptokinase, but has the advantage that it can be administered by bolus injection. Single chain urokinase-type plasminogen activator is more fibrin-specific than urokinase. Comparative data on the efficacy and safety of this agent are limited as it is in the early stage of clinical investigation. Reduction of infarct size, preservation of ventricular function and/or reduction in mortality has been observed with streptokinase, rt-PA and APSAC. Therefore, thrombolytic therapy will probably become routine therapy for early acute myocardial infarction. In patients with acute myocardial infarction, intravenous streptokinase recanalizes 40-45 percent of occluded coronary arteries and reduces mortality by 25 percent; it costs approximately $200 for a therapeutic dose of 1,500,000 units. Recombinant tissue-type plasminogen activator (rt-PA) is more potent for coronary arterial thrombolysis, producing both more rapid and more frequent (65-70 percent) reperfusion, but it costs over $1,000 for a therapeutic dose of 100 mg. Side effects (mainly bleeding) and the incidence of reocclusion associated with the use of streptokinase and rt-PA are not markedly different. Whether the higher efficacy of rt-PA will translate into a comparably larger reduction of mortality remains to be determined in large comparative clinical trials. Both agents are available for clinical use.(ABSTRACT TRUNCATED AT 400 WORDS)

Reperfusion, patency and reocclusion with anistreplase (APSAC) in acute myocardial infarction

Because the reestablishment of coronary blood flow is believed to be central to the benefit of thrombolytic therapy, measurements of reperfusion (i.e., angiography before and after therapy), patency (i.e., angiography after therapy) and reocclusion rates are important to the evaluation of new thrombolytic therapies. For anisoylated plasminogen streptokinase activator complex (APSAC, anistreplase), comparisons have been made with control or placebo therapies to assess absolute efficacy, and with streptokinase to assess relative efficacy. In pooled experience from reperfusion studies, APSAC (30 U over 2 to 5 minutes) led to angiographic reperfusion in 55% of patients (98 of 177) who had symptoms of acute myocardial infarction (MI) for less than 6 hours. Among 107 patients treated with APSAC in angiographic patency studies, 69% (74) showed an open infarct-related artery 1 to 4 hours after therapy. (Patency rates are generally 10 to 20% greater than reperfusion rates, because some patients with acute MI may have a patent [subtotally occluded or spontaneously reperfused] infarct-related artery when entered into patency studies.) Using early peaking (less than or equal to 15 hours) of the creatine kinase curve as an indicator, a patency rate of 63% was observed among 387 patients treated with APSAC. The initial success rate with thrombolytic therapies is diminished by the rates of reocclusion and reinfarction, which must be accounted for in determining the net success of therapy. In 6 studies, a total of 87 patients with initially patent arteries after APSAC returned for reevaluation in 1 to 3 days.(ABSTRACT TRUNCATED AT 250 WORDS)

Multicenter trial of intravenous anisoylated plasminogen streptokinase activator complex (APSAC) in acute myocardial infarction: effects on infarct size and left ventricular function

Two hundred thirty-one patients with a first acute myocardial infarction were randomly allocated within 5 h after the onset of symptoms either to treatment with anisoylated plasminogen streptokinase activator complex (APSAC), 30 U over 5 min, or to conventional heparin therapy, 5,000 IU in a bolus injection. Heparin was reintroduced in both groups 4 h after initial therapy at a dosage of 500 IU/kg per day. One hundred twelve patients received APSAC and 119 received heparin within a mean period of 188 +/- 62 min after the onset of symptoms. Both groups were similar in age, location of the acute myocardial infarction, Killip functional class and time of randomization. Elective coronary arteriography was performed on an average of 4 +/- 1.2 days after initial therapy. Follow-up radionuclide angiography and thallium-201 single photon emission computed tomography were performed before hospital discharge. Infarct size was estimated from single photon emission computed tomography and expressed as a percent of total myocardial volume. The patency rate of the infarct-related artery was 77% in the APSAC group and 36% in the heparin group (p less than 0.001). Left ventricular ejection fraction determined from contrast angiography was significantly higher in the APSAC group than in the heparin group. This was true for the entire study group (0.53 +/- 0.13 versus 0.47 +/- 0.12; p = 0.002) as well as for the subgroups of patients with anterior and inferior wall infarction (0.47 +/- 0.13 versus 0.40 +/- 0.11; p = 0.04 and 0.56 +/- 0.10 versus 0.51 +/- 0.11; p = 0.02, respectively). At 3 weeks, the difference remained significant for the anterior myocardial infarction subgroup. A significant 31% reduction in infarct size was found in the APSAC group (33% for the anterior infarction subgroup [p less than 0.05] and 16% for the inferior infarction subgroup [p = NS]). A close inverse relation was found between the values of left ventricular ejection fraction and infarct size (r = -0.73, p less than 0.01). By the end of a 3 week follow-up period, seven APSAC-treated patients and six heparin-treated patients had died. In conclusion, the early infusion of APSAC in acute myocardial infarction produced a high early patency rate, significant limitation of infarct size and significant preservation of left ventricular systolic function, mainly in anterior wall infarction.