ISIS-3: a randomised comparison of streptokinase vs tissue plasminogen activator vs anistreplase and of aspirin plus heparin vs aspirin alone among 41 299 cases of suspected acute myocardial infarction

41,299 patients entering 914 hospitals up to 24 h (median 4 h) after the onset of suspected acute myocardial infarction were randomised between streptokinase (SK: 1.5 MU infused over about 1 h), tissue plasminogen activator (tPA, duteplase: 0.60 MU/kg infused over about 4 h), or anisoylated plasminogen-streptokinase activator complex (APSAC), anistreplase: 30 U over about 3 min). All patients were to receive aspirin (162 mg/day enteric-coated), with the first tablet chewed for rapid and full antiplatelet effect. Half of all patients were randomly allocated subcutaneous calcium heparin (12,500 IU starting at 4 h and given twice daily for 7 days or until prior discharge) in addition to aspirin, and the other half were to receive aspirin alone. ASPIRIN PLUS HEPARIN VERSUS ASPIRIN ALONE--The addition of heparin to aspirin was associated with an excess of transfused or other major non-cerebral bleeds (1.0% aspirin plus heparin vs 0.8% aspirin alone; 2p < 0.01) and of definite or probable cerebral haemorrhage (0.56% vs 0.40%; 2p < 0.05), but with no significnat differences in total stroke (1.28% vs 1.18%). Reinfarctions were slightly less common among those allocated aspirin plus heparin (3.16% vs 3.47%; 2p = 0.09). There was no signficant difference in the pre-specified endpoint of 35-day mortality (2132 [10.3%] aspirin plus heparin vs 2189 [10.6%] aspirin alone). During the scheduled heparin treatment period there were slightly fewer deaths in the aspirin plus heparin group (days 0-7 in hospital: 1534 [7.4%] vs 1633 [7.9%]; 2 p = 0.06), with a slight convergence by day 35 (598 further deaths [3.1% of survivors] vs 556 [2.9%]). The pattern was similar to that observed in the GISSI-2 trial, so that in both trials combined there was a significant reduction in mortality during the scheduled treatment period (2071 [6.8%] vs 2239 [7.3%]; 2p < 0.01). This indicates avoidance of 5 deaths (SD 2) per 1000 patients allocated this high-dose subcutaneous heparin regimen in addition to aspirin, but some of any early benefit may be lost after heparin ceases, with no significant mortality advantage in days 0-35 (both trials: 3100 [10.0%] vs 3172 [10.2%]) or during follow-up to 6 months. SK VERSUS APSAC--APSAC was associated with significantly more reports of allergy causing persistent symptoms and of non-cerebral bleeds, but not of transfused bleeds or of reinfarctions. There was a slight excess of strokes with APSAC (1.04% SK vs 1.26% APSAC; 2p = 0.08), much of it appearing soon after treatment started (strokes during days 0-1: 0.50% SK vs 0.73% APSAC; 2p < 0.02) and being attributed to cerebral haemorrhage (0.24% SK vs 0.55% APSAC; 2p < 0.0001). No significant difference was observed in reinfarction (3.47% SK vs 3.55% APSAC). There was no significant mortality difference during days 0-35, either among all randomised patients (1455 [10.6%] SK vs 1448 [10.5%] APSAC) or among the pre-specified subset presenting within 0-6 h of pain onset and with ST elevation on the electrocardiogram in whom fibrinolytic treatment may have most to offer (861 [10.0%] SK vs 855 [9.9%] APSAC). No significant difference in 6-month survival was apparent overall or in the subset.(ABSTRACT TRUNCATED AT 400 WORDS)