Coronary thrombolysis for evolving myocardial infarction

Compartment syndrome of the arm: a complication of noninvasive blood pressure monitoring during thrombolytic therapy for myocardial infarction

We report a rare case of tricep compartment syndrome caused by a hematoma which resulted from noninvasive blood pressure monitoring (NIBPM) during thrombolytic therapy. Clinicians administering thrombolytic agents should be aware of the risk of bleeding and compartment syndrome at the site of NIBPM. Appropriate preventative measures should be instituted when using automated pneumatic cuffs. An understanding of the pathophysiology and clinical presentation of an arm compartment syndrome will allow for prompt diagnosis and surgical treatment.

Anistreplase versus alteplase in acute myocardial infarction: comparative effects on left ventricular function, morbidity and 1-day coronary artery patency. The TEAM-3 Investigators

OBJECTIVES

This double-blind, randomized, multicenter trial was designed to compare the effects of treatment with anistreplase (APSAC) and alteplase (rt-PA) on convalescent left ventricular function, morbidity and coronary artery patency at 1 day in patients with acute myocardial infarction.

BACKGROUND

Anistreplase (APSAC) is a new, easily administered thrombolytic agent recently approved for treatment of acute myocardial infarction. Alteplase (rt-PA) is a rapidly acting, relatively fibrin-specific thrombolytic agent that is currently the most widely used agent in the United States.

METHODS

Study entry requirements were age less than or equal to 75 years, symptom duration less than or equal to 4 h, ST segment elevation and no contraindications. The two study drugs, APSAC, 30 U/2 to 5 min, and rt-PA, 100 mg/3 h, were each given with aspirin (160 mg/day) and intravenous heparin. Prespecified end points were convalescent left ventricular function (rest/exercise), clinical morbidity and coronary artery patency at 1 day. A total of 325 patients were entered, stratified into groups with anterior (37%) or inferior or other (63%) acute myocardial infarction, randomized to receive APSAC or rt-PA and followed up for 1 month.

RESULTS

At entry, patient characteristics in the two groups were balanced. Convalescent ejection fraction at the predischarge study averaged 51.3% in the APSAC group and 54.2% in the rt-PA group (p less than 0.05); at 1 month, ejection fraction averaged 50.2% versus 54.8%, respectively (p less than 0.01). In contrast, ejection fraction showed similar augmentation with exercise at 1 month after APSAC (+4.3% points) and rt-PA (+4.6% points), and exercise times were comparable. Coronary artery patency at 1 day was high and similar in both groups (APSAC 89%, rt-PA 86%). Mortality (APSAC 6.2%, rt-PA 7.9%) and the incidence of other serious clinical events, including stroke, ventricular tachycardia, ventricular fibrillation, heart failure within 1 month, recurrent ischemia and reinfarction were comparable in the two groups; and mechanical interventions were applied with equal frequency. A combined clinical morbidity index was determined and showed a comparable overall outcome for the two treatments.

CONCLUSIONS

Convalescent rest ejection fraction was high after both therapies but higher after rt-PA; other clinical outcomes, including exercise function, morbidity index, and 1-day coronary artery patency, were favorable and comparable after APSAC and rt-PA.

Relative importance of emergency medical system transport and the prehospital electrocardiogram on reducing hospital time delay to therapy for acute myocardial infarction: a preliminary report from the Cincinnati Heart Project

Substantial time delays from symptom onset to diagnosis and treatment of patients with acute myocardial infarction have been demonstrated. To determine the relative importance of prehospital mode of patient transport and the relative impact of emergency medical system transport with or without a prehospital cellular electrocardiogram (ECG) on hospital time delays to initiation of thrombolytic therapy, four prospective parallel groups of patients with acute myocardial infarction were evaluated. The median hospital time delay to treatment median (twenty-fifth and seventy-fifth percentiles) was 64 minutes (46 and 87 minutes, respectively, for twenty-fifth and seventy-fifth percentiles) for patients transported by private automobile ("walk-in"); 55 minutes (45 and 68 minutes, respectively) for patients transported by local ambulance; 50 minutes (38 and 81 minutes, respectively) for patients transported by the emergency medical system without a prehospital ECG; and 30 minutes (27 and 35 minutes, respectively) for patients transported by the emergency medical system who had a 12-lead ECG transmitted from the field. Patients transported by the emergency medical system were randomized to receive cellular telephone transmission of a prehospital 12-lead ECG. Specialized emergency medical system transport alone did not facilitate in-hospital initiation of thrombolytic therapy in patients with acute myocardial infarction when compared with those brought by local ambulance or by private automobile. A significant reduction in hospital time delay to treatment was observed only in patients transported by the emergency medical system who had cellular transmission of a prehospital 12-lead ECG from the field.

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.

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)

Impact of field-transmitted electrocardiography on time to in-hospital thrombolytic therapy in acute myocardial infarction

To assess the impact of a field-transmitted electrocardiogram (ECG) on patients with possible acute myocardial infarction, randomized and open trials were performed with a portable electrocardiographic system coupled with a cellular phone programmed to automatically transmit ECGs to the base hospital. Consecutive patients served by the 6 units of the Salt Lake City Emergency Rescue System were studied; 71 patients were randomized to in-field ECG (n = 34) versus no ECG (n = 37). Time on scene was 16.4 +/- 9.7 minutes for the ECG group versus 16.1 +/- 7.0 minutes for the non ECG group (difference not significant). Time of transport averaged 18.2 +/- 9.9 and 17.6 +/- 13.1 minutes, respectively (difference not significant). Six of 34 patients with in-field ECG showed acute myocardial infarction, qualified for and received thrombolytic therapy at 48 +/- 12 minutes after hospital arrival (range 30 to 60) compared with 103 +/- 44 minutes (p less than 0.01) for 51 historical control patients and 68 +/- 29 minutes for 6 concurrent control patients without in-field ECG. Thus, in-field ECG causes negligible delays in paramedic time, leads to significant decreases in time to in-hospital thrombolysis and may make in-field therapy feasible. In-field ECG may be an important addition to reperfusion strategies.

Coronary reperfusion studies with pro-urokinase in acute myocardial infarction: evidence for synergism of low dose urokinase

Pro-urokinase is a single chain precursor of two chain urokinase, which has been shown to induce fibrin-selective plasminogen activation. In the present study, thrombolytic efficacy of 9 million U of glycosylated pro-urokinase administered intravenously was compared with that of a combined regimen utilizing 4.5 million U of pro-urokinase and 0.2 million U of urokinase. Seventy-five patients with a first myocardial infarction were randomized to receive high dose pro-urokinase (n = 40, group A) or the combination therapy (n = 35, group B). Reperfusion of the infarct-related artery was assessed by repeat coronary angiography. Thrombolysis in Myocardial Infarction trial (TIMI) grade II or III reperfusion was achieved in 73% of group A patients compared with 66% of group B patients (p = NS). A trend toward faster reopening of the infarct-related artery was observed in patients in group B. Coronary artery reocclusion occurred in 5 (10%) of 49 patients in whom angiography was repeated within 36 h after the start of therapy. Clot-selective thrombolysis was indicated by a minimal fibrinogen decline (15% and 13%, respectively, in groups A and B). Alpha 2-antiplasmin levels, however, decreased more rapidly in patients in group B (p less than 0.05). This finding and the equivalent reperfusion rate in the combined treatment group strongly suggest synergistic interaction between these two thrombolytic agents. In summary, the high incidence of reperfusion, the low rate of early reocclusion and the paucity of side effects, particularly with regard to bleeding complications, indicate that pro-urokinase possesses the characteristics of an ideal thrombolytic agent.

Pharmacokinetics, thrombolytic efficacy and hemorrhagic risk of different streptokinase regimens in heparin-treated acute myocardial infarction

The systemic activator activity of 4 streptokinase (SK) regimens (250,000 IU intracoronary, group A; 500,000 IU, group B; 1.5 X 10(6) IU, group C; and 30 U anisoylated plasminogen streptokinase activator complex (APSAC) intravenously, group D) was tested with the fibrin plate technique. One hour after initiation of treatment, the activator activity was highest after APSAC (3.6 +/- 0.9 U), slightly but not significantly less after SK 1.5 X 10(6) IU (3.0 +/- 0.7), and significantly less after SK 500,000 IU (1.6 +/- 0.5) and 250,000 IU (0.6 +/- 0.5), p less than 0.001. After SK, activator activity half-lives were 184 minutes (group B) and 169 minutes (group C), and after APSAC 188 minutes (group D). These were all in agreement with greater than 12 hour duration of changes in other markers of systemic fibrinolysis (euglobulin lysis time) and substrates depletion (fibrinogen, plasminogen, alpha 2 antiplasmin). In extended pilot clinical groups given identical thrombolytic regimens during full anticoagulation with heparin, angiographic coronary patency was found in 83% (35 of 42) after intracoronary SK (group 1), in 73 and 75%, respectively, after 500,000 IU (31 of 43) and 1.5 X 10(6) IU (30 of 40) (group 2 and 3, difference not significant) and 80% (8 of 10) after the 30-U bolus of APSAC (group 4). The overall hemorrhagic risk was 24%, equally distributed among the 4 regimens and mostly (91%) related to catheters. The incidence of bleeding unrelated to vessel puncture was 4%; no deaths occurred. It is concluded that APSAC is the most fibrinolytic regimen but its potential thrombolytic superiority over SK remains to be demonstrated.(ABSTRACT TRUNCATED AT 250 WORDS)

Multicenter reperfusion trial of intravenous anisoylated plasminogen streptokinase activator complex (APSAC) in acute myocardial infarction: controlled comparison with intracoronary streptokinase

The recent establishment of a firm therapeutic role for reperfusion in acute myocardial infarction has stimulated interest in the development of more ideal thrombolytic agents. Anisoylated plasminogen streptokinase activator complex (APSAC) is a new plasminogen activator possessing properties that are promising for intravenous thrombolytic application in acute myocardial infarction. To assess the reperfusion potential of intravenous APSAC, a multi-center, angiographically controlled reperfusion trial was performed. An approved thrombolytic regimen of intracoronary streptokinase served as a control. Consenting patients with clinical and electrocardiographic signs of acute myocardial infarction were studied angiographically and 240 qualifying patients with documented coronary occlusion (flow grade 0 or 1) were randomized to treatment in less than 6 h of symptom onset (mean 3.4 h, range 0.4 to 6.0) with either intravenous APSAC (30 U in 2 to 4 min) or intracoronary streptokinase (160,000 U over 60 min). Both groups also received heparin for greater than or equal to 24 h. Reperfusion was evaluated angiographically over 90 min and success was defined as advancement of grade 0 or 1 to grade 2 or 3 flow. Rates of reperfusion for the two treatment regimens were 51% (59 of 115) at 90 min after intravenous APSAC and 60% (67 of 111) after 60 min of intracoronary streptokinase (p less than or equal to 0.18). Reperfusion at any time within the 90 min was observed in 55 and 64%, respectively (p less than or equal to 0.16). Time to reperfusion occurred at 43 +/- 23 min after intravenous and 31 +/- 17 min after intracoronary therapy. The success of intravenous therapy was dependent on the time to treatment: 60% of APSAC patients treated within 4 h exhibited reperfusion compared with 33% of those treated after 4 h (p less than or equal to 0.01). Reperfusion rates were also dependent on initial flow grade (p less than or equal to 0.0001): 48% (81 of 168) for grade 0 (APSAC = 43%, streptokinase = 54%), but 78% for grade 1 (APSAC = 78%, streptokinase = 77%). APSAC given as a rapid injection was generally well tolerated, although the median change in blood pressure at 2 to 4 min was greater after APSAC than after streptokinase (-10 versus -5 mm Hg). Mean plasma fibrogen levels fell more at 90 min after the sixfold higher dose of APSAC than after streptokinase (to 32 versus 64% of control). Reported bleeding events were more frequent after APSAC but occurred primarily at the site of catheter insertion and no event was intracranial.(ABSTRACT TRUNCATED AT 400 WORDS)

Alteplase: a tissue plasminogen activator for acute myocardial infarction

Alteplase is a human tissue plasminogen activator (t-PA) produced by recombinant DNA technology. It is a relatively fibrin-specific thrombolytic agent, used primarily to lyse coronary artery clots. It has proven effective in the treatment of acute myocardial infarction (AMI). Despite continuous reevaluation of pharmacokinetic parameters for t-PA, limited distribution and clearance data mandate administration of t-PA as a continuous infusion. Tissue plasminogen activator is eliminated primarily by hepatic metabolism with an elimination half-life of five to ten minutes. Plasma levels show great interindividual variation but correlate with infusion rate and decrease in fibrinogen level. The current recommended dose is 100 mg administered as a 10-mg iv bolus followed by a continuous infusion over three hours. However, 40-150 mg has been used in clinical trials. The compound has undergone extensive testing, comparing it with placebo and streptokinase (SK), and combining it with angioplasty and coronary artery bypass surgery. Tissue plasminogen activator is effective at opening clotted coronary arteries in approximately 70 percent of AMI patients and has been shown to be approximately twice as effective as SK in one U.S. trial. Although there is considerable evidence of efficacy with t-PA, data evaluating the influence of t-PA on mortality are limited, but suggest a reduction to five percent. Currently, thrombolytic therapy is indicated for patients experiencing a transmural AMI with onset of symptoms within three to six hours before presenting to the emergency room. Active internal bleeding or conditions predisposing to serious hemorrhage are contraindications to thrombolytic therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Development and evaluation of anisoylated plasminogen streptokinase activator complex (APSAC) as a second generation thrombolytic agent

Anisoylated plasminogen streptokinase activator complex (APSAC) was developed as a second generation thrombolytic agent in an attempt to overcome some of the limitations to the intravenous application of streptokinase for coronary artery thrombolysis. Temporary protection of the active site on the plasminogen molecule by acylation allows APSAC to be given by rapid injection, confers semiselectivity for clot (at lower doses) and prolonged fibrinolytic action. These properties may simplify intravenous administration, improve coronary reperfusion response and reduce reocclusion potential. Clinical trials with APSAC, still ongoing, allow the following tentative conclusions: the efficacy of intravenous APSAC appears to be equivalent to that of intracoronary streptokinase, when given within 4 hours of the onset of symptoms of myocardial infarction, and superior to that of intravenous streptokinase, but it is easier to administer. Early APSAC therapy leads to reperfusion rates of 60 to 65% and patency rates of 70 to 80%. Early reocclusion rates (within 24 hours) appear to be as low as or lower than those obtained with other agents. Bleeding complications and allergic manifestations after APSAC are acceptably low and comparable with those of equivalent doses of streptokinase. The potential for mortality benefit after APSAC appears to be high and is undergoing additional study. Thus, APSAC therapy, which can be given by simple injection over 2 to 5 minutes, appears promising as a future first line approach to reperfusion therapy in acute myocardial infarction.

The search for the ideal thrombolytic agent

Since streptokinase and urokinase became available for clinical use, numerous attempts have been made to improve these useful thrombolytic agents. To decrease its antigenicity, streptokinase has been fragmented or coupled to human plasminogen or polyethylene glycols. With a plasmin B chain-streptokinase complex a more potent agent was obtained. To prolong their half-life, streptokinase and urokinase were immobilized with water-soluble carriers. Coupling urokinase with fibrin-specific antibodies increases its thrombolytic efficacy, at least in vitro. The only thrombolytic agents with a relative fibrin specificity available for clinical purposes are tissue-type plasminogen activator and single chain urokinase-type plasminogen activator. Mutants and hybrids of these molecules are being constructed and may further improve their fibrin specificity and therapeutic potential.

Appraisal of various thrombolytic agents in the treatment of acute myocardial infarction

The immediate therapeutic objective after the onset of symptoms of an evolving myocardial infarction is to stop the process from progressing. Evidence has accumulated that this can be accomplished by the early dissolution of the clot within an acutely thrombosed artery, resulting in reperfusion of the ischemic area. There are five clot-dissolving agents currently being evaluated by intravenous administration for their ability to dissolve coronary thrombi and to produce clinical benefit; all are plasminogen activators and each has distinctive properties. Streptokinase, because it has been the agent most extensively studied and its clinical benefits have been established, now serves as a standard for comparison with the others (anisoylated plasminogen-streptokinase activator complex, urokinase, recombinant tissue plasminogen activator, and recombinant pro-urokinase). It is apparent that each of the agents has advantages and disadvantages and that none has established its superiority over the others as of yet.

Objectives of thrombolytic therapy in acute myocardial infarction

The objectives of thrombolytic therapy in acute myocardial infarction are to restore coronary artery patency, salvage myocardium, reduce infarct size, and facilitate coronary artery repair. Urokinase and streptokinase are the two most frequently used thrombolytic agents. Both dissolve thrombi by converting circulating plasminogen, an inert precursor, into plasmin. One possible advantage of urokinase and streptokinase over new clot-specific agents is that the former have systemic fibrinolytic effects. This reduces blood viscosity and prevents other thrombi from forming. Angiography is the most objective technique for assessing reestablished arterial patency, but being invasive, it present disadvantages. Noninvasive criteria for coronary reperfusion include lowering of elevated ST-segments, shifting creatine kinase isoenzyme MB curves, and the appearance of reperfusion arrhythmias. Techniques for assessing myocardial salvage include thallium uptake, assessment of wall motion and myocardial thickening, ejection fraction, and positron emission tomography to assess infarct size. The role and appropriate timing of coronary artery repair after thrombolytic therapy are being studied.

Plasminogen activators and their potential in therapy

Plasminogen activators (PAs) are proteases that convert plasminogen to plasmin. Plasmin, in turn, is a protease that can lyse a fibrin clot and, therefore, PAs have a primary role in fibrinolysis. Two PAs, urokinase (UK) and streptokinase (SK), have been available for therapeutic use for years. Unfortunately, both can cause systemic fibrinogenolysis and other side effects which have limited their use. Interest has focused on a different enzyme, tissue plasminogen activator (t-PA), which will cause specific clot lysis without systemic problems. The gene for t-PA has been cloned and many biotechnology firms are preparing to produce t-PA for therapeutic use. The properties and potential for therapy of t-PA are reviewed and compared to new forms of other activators, such as pro-urokinase. How the interactions of PAs and inhibitors may affect the use of PAs is also discussed.

Recent clinical developments in thrombolysis in acute myocardial infarction

Intracoronary streptokinase can accomplish reperfusion in 70 to 75% of patients with acute myocardial infarction (AMI), and intravenous streptokinase in approximately 50% of those with prior documented coronary occlusion. The time constraints for accomplishing significant myocardial salvage have proved to be quite restrictive, however. Studies in which treatment has begun after an average of 4 hours of symptoms have not shown significant improvement in ventricular function. In contrast, those in which intervention has been applied earlier, particularly in less than 2 to 3 hours, have consistently shown benefit. The price for applying thrombolytic therapy includes the risk of severe bleeding (about 5%) but, fortunately, mortality as a result of bleeding has been rare (less than or equal to 0.5%). Reperfusion may be only transient or incomplete (and insufficient). An early reocclusion rate of about 15 to 20% has been commonly noted, in fact. Recently, major studies have pointed to a reduction in early mortality in patients treated early (within about 3 hours) after the onset of symptoms. Much interest is now being focused on developing safer, more effective thrombolytic agents such as tissue plasminogen activator and anisoylated plasminogen streptokinase activator complex (APSAC). Adjunctive therapy with coronary angioplasty is also being applied. In the judgement of many, reperfusion therapy may represent the greatest advance in the approach to AMI of the current decade.

Coronary thrombolysis with recombinant tissue-type plasminogen activator: patency rate and regional wall motion after 3 months

In a double-blind, placebo-controlled, randomized trial the long-term (+/- 3 months) effects of intravenous administration of recombinant tissue-type plasminogen activator (rt-PA) versus placebo were compared in relation to left ventricular function, coronary patency rate and antigenicity in 28 patients with a first myocardial infarction. Patency rate of the infarct-related coronary artery at the end of the rt-PA/placebo infusion and after 3 months of medical treatment (including oral anticoagulant agents) was 86 and 71%, respectively, in the rt-PA group, and 21 and 58%, respectively, in the placebo group. Regional wall motion of the infarct-related area was quantitated with digital subtraction angiography. Intrapatient comparisons revealed significant improvement in regional wall motion after 3 months in both the rt-PA and placebo groups. The improvement in the rt-PA group was not significantly greater than that in the placebo group. Thirteen patients (10 with rt-PA and 3 with placebo) with persistent patency (both early and late) of the infarct-related coronary artery showed a significant improvement of both global and regional left ventricular function, while 8 patients (2 with rt-PA and 6 with placebo) with persistent occlusion showed no changes. Antibodies against rt-PA were not detected in serum 2 weeks after the infusion, which is indicative of the lack of antigenicity of rt-PA and allows for its repeated administration.

Coronary thrombolysis during acute myocardial infarction by intravenous BRL 26921, a new anisoylated plasminogen-streptokinase activator complex

The safety and fibrinolytic efficacy of a new anisoylated plasminogen-streptokinase activator complex (APSAC) was tested in 50 patients with acute myocardial infarction (AMI) less than 4 hours in duration. APSAC (30 mg) was given intravenously as a bolus injection 151 +/- 47 minutes after clinical symptoms. Coronary angiography was then performed to assess coronary artery patency: 28 patients had an inferior AMI and 22 an anterior AMI. A patent infarct-related artery was found in 32 patients (64%) on first coronary angiography 66 +/- 21 minutes after administration of APSAC. Subsequent reperfusion was observed in 10 patients after 74 +/- 16 minutes (84%). Bleeding complications or hematomas were observed in 18 patients, of whom 3 required blood transfusions. Marked hypofibrinogenemia was observed within 24 hours in most patients. A control coronary angiogram was recorded in 37 patients (74%) after 25 +/- 19 days and showed reocclusion in 5 patients.

Intravenous fibrinolytic therapy of acute myocardial infarction: new perspectives from plasminogen activators?

The early treatment of acute myocardial infarction has changed rapidly in recent years. Given the fact that an occlusive coronary thrombus can be found in most infarct patients within 4 h after clinical symptoms, the idea of instituting medical or mechanical recanalization of the occluded vessel is intriguing. However, invasive measures are time consuming, expensive and not freely available to a great number of patients. Thus, only i.v. fibrinolytic therapy of acute myocardial infarction will gain wider application in the near future. Several concepts have been worked out, one of which uses a high-dosage streptokinase or urokinase regimen. A different therapeutic alternative has been made possible by the development of selective fibrinolytic substances, such as the tissue-type plasminogen activator (t-PA) or the anisoylated plasminogen-streptokinase activator complex (APSAC). Preliminary clinical data have shown that the coronary artery patency rate achieved after i.v. administration of t-PA or APSAC is higher than that after conventional treatment with streptokinase or urokinase. The incidence of severe bleeding complications is low and comparable in these studies. However, until myocardial salvage has been demonstrated with early i.v. fibrinolytic therapy in acute myocardial infarction in a placebo-controlled randomized trial, this therapeutic concept will still be unsettled.

Double-blind randomised trial of intravenous tissue-type plasminogen activator versus placebo in acute myocardial infarction

In a double-blind randomised trial 129 patients with first myocardial infarction of less than 6 h duration were allocated to treatment with human recombinant tissue-type plasminogen activator (rt-PA) given intravenously over 90 min, or to placebo infusion. Coronary angiography at the end of this infusion showed that the infarct-related vessel was patent in 61% of 62 assessable coronary angiograms in the rt-PA-treated group compared with 21% in the control group. Treatment with rt-PA was not accompanied by any major complications. In the rt-PA group the circulating fibrinogen level at the end of the catheterisation was 52 +/- 29% (mean +/- SD) of the starting value.

Randomised trial of intravenous recombinant tissue-type plasminogen activator versus intravenous streptokinase in acute myocardial infarction. Report from the European Cooperative Study Group for Recombinant Tissue-type Plasminogen Activator

In a single-blind randomised trial in patients with acute myocardial infarction of less than 6 h duration, the frequency of coronary patency was found to be higher after intravenous administration of recombinant human tissue-type plasminogen activator (rt-PA) than after intravenous streptokinase. 64 patients were allocated to 0.75 mg rt-PA/kg over 90 min, and the infarct-related coronary artery was patent in 70% of 61 assessable coronary angiograms taken 75-90 min after the start of infusion; 65 patients were allocated to 1 500 000 IU streptokinase over 60 min, and the infarct-related vessel was patent in 55% of 62 assessable angiograms. The 95% confidence interval of the differences ranges from +/- 30 to -2% (p = 0.054). Bleeding episodes and other complications were less common in the rt-PA patients than in the streptokinase group. Hospital mortality was identical in the 2 treatment groups. At the end of the rt-PA infusion the circulating fibrinogen level was 61 +/- 35% of the starting value, as measured by a coagulation-rate assay, and 69 +/- 25% as measured by sodium sulphite precipitation. After streptokinase infusion, corresponding fibrinogen levels were 12 +/- 18% and 20 +/- 11%. In the rt-PA group only 4.5% of the fibrinogen was measured as incoagulable fibrinogen degradation products, compared with 30% in the streptokinase group. Activation of the systemic fibrinolytic system was far less pronounced with rt-PA than with streptokinase.