High-dose streptokinase therapy with three million units in one hour significantly improves early coronary patency rates in acute myocardial infarction

Thrombolysis in acute myocardial infarction: analysis of studies comparing accelerated t-PA and streptokinase

OBJECTIVES

To compare outcomes from accelerated alteplase (recombinant tissue plasminogen activator, t-PA) and streptokinase use in acute myocardial infarction.

METHODS

Review of available studies identified by Medline and other literature searches that met the criteria of being a prospective, randomised clinical trial enrolling over 1000 patients with acute myocardial infarction. The studies had to contain an intervention arm comprising accelerated infusion t-PA, or an intervention arm comprising streptokinase provided accelerated t-PA that was compared in the same trial. Interventions compared were streptokinase 1.5 million units given over one hour compared with accelerated t-PA infusion, with concomitant use of aspirin and heparin, and main outcome measure of 30 day mortality.

RESULTS

Four studies met prespecified criteria, these being the GUSTO I, GUSTO IIb Angioplasty Substudy, GUSTO III, and COBALT trials. There was a total study population of 64,387 patients of whom 20,251 received streptokinase, 19,474 received t-PA, with others receiving different treatment. Pooled data show that accelerated t-PA produces a marginal 30 day mortality advantage compared with streptokinase (6.6% v 7.3%, p = 0.02, Bonferroni adjusted p = 0.12, that is borderline significance, relative risk 0.918, 95% confidence interval 0.854 to 0.986). Any benefit is attributable entirely to patients recruited in the United States in the GUSTO I study. There is an increased incidence of stroke with t-PA.

CONCLUSIONS

The data do not consistently show a 30 day mortality benefit from using t-PA compared with streptokinase in acute myocardial infarction, but do show increased risk of stroke. Streptokinase can be considered the thrombolytic agent of choice.

Coronary and Peripheral Thrombolysis: Current Status and Recommendations

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

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