Intravenous versus intracoronary streptokinase for acute transmural myocardial infarction

Analytic Review: Thrombolytic Therapy in Acute Myocardial Infarction

The salvage of myocardium in the setting of acute myocardial infarction has long been a goal of physicians involved in the care of patients with coronary artery disease. Understanding the role of thrombosis in the pathogenesis of acute myocardial infarction has led the way to an entirely new approach to the treatment of this entity. Thrombolytic therapy has now become a widely used form of treatment with encouraging results. Both intravenous and intracoronary administration of thrombolytic agents have been shown to promote recanalization of acutely occluded coronary arteries. Results of studies using the clot-specific agent, tissue plasminogen activator, intravenously have been most encouraging; successful reperfusion has been obtained in approximately 70% of patients treated. In addition, a recent large-scale trial has shown a reduction in morbidity and mortality with the early use of thrombolytic agents.

Ongoing trials should help delineate the precise role and timing of these agents as the initial form of therapy for acute myocardial infarction. Other issues that remain unresolved are the frequency of restenosis and the role of percutaneous transluminal coronary angioplasty in addition to thrombolytic therapy in the treatment of acute myocardial infarction.

Do different doses of intravenous streptokinase alter the frequency of coronary reperfusion in acute myocardial infarction?

This study assessed the relative efficacy of 3 doses of intravenous streptokinase in causing hypofibrinogenemia and coronary reperfusion in patients with acute myocardial infarction. Accordingly, 56 patients (50 men and 6 women, ages 58 +/- 10 years [mean +/- standard deviation]) with evolving acute myocardial infarction and chest pain less than or equal to 5 hours in duration were assigned to receive varying doses of streptokinase. Twenty were administered 500,000 units during 145 minutes, 18 were given 750,000 units during 30 minutes and 18 received 1.5 million units in 60 minutes of streptokinase. Serum creatine kinase was measured on admission and 6, 12, 18 and 24 hours after the initiation of streptokinase. The time intervals from onset of pain to peak creatine kinase and from streptokinase administration to peak creatine kinase were used to determine the occurrence of reperfusion. The plasma fibrinogen concentration was measured 30, 60, 90 and 120 minutes after the initiation of streptokinase. For the 3 groups, the time from onset of pain to peak creatine kinase was less than 17 hours and the time from streptokinase to peak creatine kinase was 6 or 12 hours in 15 (75%), 16 (89%) and 12 patients (67%), respectively (differences not significant). The plasma fibrinogen concentration decreased to 45 +/- 34 mg/dl, 19 +/- 14 mg/dl and 29 +/- 43 mg/dl, respectively, during the 2 hours after streptokinase was begun (p less than 0.05 for the first versus the second and third values).(ABSTRACT TRUNCATED AT 250 WORDS)

Evolving concepts in the treatment of acute myocardial infarction

Recent studies in patients with transmural acute myocardial infarction have demonstrated that intravenous thrombolytic therapy with streptokinase or tissue plasminogen activator improves left ventricular function and reduces mortality. To accomplish this, these agents must be infused early, ie, within 3 to 4 hours of the onset of chest pain; later administration of the agents exerts no significant beneficial effect. Tissue plasminogen activator appears to be the most effective and safest of the available thrombolytic agents: its intravenous administration is followed by coronary reperfusion in about 70% of patients, and its use is not associated with allergic reactions, a systemic fibrinolytic state, or a prolonged fibrinolytic effect. Once reperfusion has been established with an intravenous thrombolytic agent, intravenous heparin is given for several days, followed by oral aspirin to prevent reocclusion. Since many of these patients have a residual high-grade coronary artery stenosis in the infarct-related artery, mechanical alleviation of the residual stenosis with angioplasty or bypass surgery is an attractive therapy 2 to 4 days after reperfusion, and preliminary data indicate that elective coronary angioplasty 3 days after thrombolytic therapy is beneficial. However, further studies are needed to assess more definitively the use of such an aggressive therapeutic strategy.

Thrombolytic therapy for patients with acute myocardial infarction

Thrombolytic therapy is becoming an important addition to the care of patients with transmural (Q-wave) myocardial infarction. In this review, the authors analyze the mechanisms of effect and thrombolytic capabilities of several currently used thrombolytic interventions and review the influence of reperfusion in reducing mortality and protecting segmental ventricular function in animal models and patients. The problems related to thrombolytic therapy also are discussed and patient subgroups most likely to benefit from thrombolytic therapy identified. Finally, the authors speculate concerning future alterations in thrombolytic agents and additions to thrombolytic therapy as they might be usefully applied in the care of patients with acute transmural myocardial infarcts.

Effect of thrombolysis (streptokinase) on left ventricular function during acute myocardial infarction

One hundred ninety-two consecutive patients with acute myocardial infarction were enrolled in a prospective trial of coronary thrombolysis in which either intracoronary or intravenous streptokinase was administered. First-pass radionuclide ejection fraction (EF) was measured early (within 24 hours of admission) and late (10 to 14 days after admission) to assess changes in left ventricular (LV) function. In 68 patients in whom reperfusion was successful, mean EF increased from 39 +/- 11% early to 47 +/- 13% late. In 36 patients in whom reperfusion was not successful, the mean EF increase was significantly smaller (from 38 +/- 10% to 42 +/- 11%, p less than 0.025). Patients in whom reperfusion was successful were then grouped according to extent of LV functional change. The extent of EF change (delta EF) was not significantly influenced by time to lysis at intervals up to 7 hours (delta EF = 9.1 +/- 10% at 2 to 3 hours, 8.7 +/- 12% at 3 to 4 hours, 10 +/- 10% at 4 to 5 hours, and 7.0 +/- 10% at 5 to 7 hours; difference not significant [NS]), location of the infarct (delta EF = 8.9 +/- 11% for inferior and 5.7 +/- 8.0% for anterior, NS), or presence of Q waves on the initial electrocardiogram (delta EF = 8.8 +/- 11% in patients with and 7.8 +/- 9.9% in patients without Q waves). Only the initial EF was predictive of subsequent EF change.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Intravenous versus intracoronary streptokinase in acute myocardial infarction

Nine studies specifically dealing with the comparison of intravenous streptokinase (IVSK) and intracoronary streptokinase (ICSK) in the treatment of acute myocardial infarction (MI) were analyzed to determine if IVSK is as efficacious as ICSK in achieving thrombolysis. Pooled data from the studies yielded success rates of 73% for IVSK and 72% for ICSK. Considering that the studies which did not perform preintervention angiogram may have overestimated the thrombolytic success rate in IVSK patients, there is a possibility that ICSK may be slightly more effective in achieving acute reperfusion. Bleeding complications were similar, and a systemic lytic state was observed in both treatment groups. No definitive conclusions can be drawn regarding the differences between groups in improvements of left ventricular function and mortality rates. ICSK has the advantage of direct documentation of reperfusion and spares the patient the risk of anticoagulation should the attempt fail. On the other hand, IVSK is cheaper, easier to administer, and can logistically be given earlier (even in the emergency room or ambulance) than ICSK; it is therefore more widely available, and may be the preferred mode of treatment in community hospitals where cardiac catheterization facilities are not readily available, if streptokinase is to be given at all.