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

Achieving Optimal Reperfusion without Adjunctive Antithrombotic Therapy: Novel Thrombolytic Dosing Strategies

There is firm evidence that reperfusion therapy, to be effective must establish and maintain coronary arterial blood flow at a level sufficient to allow myocardial perfusion. However, current thrombolytic regimens have clear limitations, including a relatively low capacity to achieve TIMI Grade 3 blood flow and an unacceptable incidence of coronary reocclusion. Although it has been assumed that the key to achieving optimal reperfusion lies with adjunctive antithrombotic therapy, it may be that novel thrombolytics and dosing strategies can address the problem adequately. This possibility is attractive and requires careful consideration.

Defibrotide versus heparin in the prevention of coronary reocclusion after thrombolysis in acute myocardial infarction

A multicenter controlled study versus heparin was conducted to explore the activity of defibrotide, a polydesoxyribonucleotide drug, in preventing reocclusion after urokinase thrombolysis in patients with acute myocardial infarction (AMI). The study involved 137 consecutive patients with AMI and a time from the onset of symptoms < or = 6 hours, treated with urokinase (1,000,000 U intravenous bolus followed by 1,000,000 U slow-drip infusion over 12 hours). Immediately after thrombolysis, patients were allocated to treatment with defibrotide (group D: day 0, 3.6 g by intravenous infusion in 12 hours; days +1 to +6, 800 mg tid intravenously; days +7 to +10/+12, 400 mg tid intramuscularly), or heparin (group H: day 0, 1000 IU/hour infused over 12 hours; days +1 to +10/+12, 5000 IU tid subcutaneously). Coronary angiography was done, whenever possible, at +10/+12 days. The following parameters were assessed: (a) noninvasive estimate of myocardial reperfusion, through the analysis of CPK time-activity curves; (b) incidence of infarct-related artery (IRA) patency (TIMI scores 2-3) at coronary angiography. A total of 125 patients had a complete enzymatic curve (63 in group D and 62 in group H) and 106 had coronary angiography as well. IRA patency (the main end point) was observed in 63% of group D versus 43% of group H patients (p = 0.07). No statistically significant differences were found in the proportion of patients with indirect signs of early reperfusion (63% in group D versus 52% in group H patients).(ABSTRACT TRUNCATED AT 250 WORDS)

Advances in thrombolytic therapy

Alteplase and saruplase are more fibrin-specific thrombolytic drugs than anistreplase. These and the thrombolytic drugs of the first generation (streptokinase and urokinase) have shortcomings and limitations. The prolonged intravenous maintenance infusions have been replaced by a bolus injection, accelerated infusions, or the combined intravenous administration of thrombolytic agents. Numerous truncated alteplase or saruplase molecules have been constructed by deletion and domain substitution or hybrids made of the two molecules without gaining in thrombolytic potency. Recombinant staphylokinase and plasminogen activator from bat saliva have some interesting properties and are being investigated. Thrombus-targeted thrombolytic drugs were constructed using monoclonal antibodies against fibrin fragments or against epitopes of activated platelets. Fibrin-specific thrombolytic drugs require the concomitant use of a potent antithrombotic drug to prevent reocclusion. Whether hirudin or synthetic thrombin inhibitors are superior to heparin and whether novel antiplatelet agents, including monoclonal antibodies to platelet receptors and disintegrins, are more effective than aspirin is under clinical investigation. The place of stable analogues of prostacyclin during thrombolytic treatment is still unsettled.

A double-blind randomized multicenter dose-ranging trial of intravenous streptokinase in acute myocardial infarction

Intravenous streptokinase administration is now a widely applied therapy for patients in the early hours of acute myocardial infarction (AMI). The dosages used do not appear to be based on comparative clinical investigations. Therefore a double-blind randomized trial was carried out to establish the optimal dose of streptokinase. A total of 189 patients who had symptoms of AMI for less than 4 hours were treated with 200,000, 750,000, 1,500,000 or 3,000,000 IU streptokinase intravenously. At coronary angiography 2.8 +/- 2.7 hours (mean +/- standard deviation) after the start of streptokinase infusion, patency of the infarct-related coronary artery was observed in 38, 75, 60 and 82% of the patients, respectively, in the 4 groups. The result of the dosage of 200,000 IU was significantly poorer than that of the other dosages (p less than 0.01). The result of a dosage of 3,000,000 IU was significantly better than that of 1,500,000 IU (p less than 0.05), but the differences with 750,000 IU were not significant. Blood transfusion was required in 4 patients (2%), distributed over the 4 groups in 0, 2, 1 and 1 of the patients. One patient had major bleeding; this patient had been treated with 750,000 IU. The 3-month mortality-rate in the whole study population was 5%. Thus, of the 4 doses of streptokinase tested, 750,000 IU is the minimal therapeutic dosage, and the arguments for 1,500,000 IU as standard therapy for comparison with other fibrinolytic drugs are poor. The best results in this study were achieved with 3,000,000 IU, but further research will be needed to establish the efficacy and safety of this new regimen.