Intravenous streptokinase in acute myocardial infarction (I.S. A.M.): assessment of left ventricular function 1 and 7 months after infarction by radionuclide ventriculography

l.S.A.M. was a prospective, placebo-controlled, double-blindmulticentre trial of high-dose short-term intravenous streptokinasein acute myocardial infarction (AMI) within 6 h of the onsetof symptoms. Determination of left ventricular ejection fraction(LVEF) by radionuclide ventriculography was performed 1 and7 months after AMI in a subset of 192 patients at rest and,in 140 of them, also during exercise. Regional myocardial functionwas analysed in all 145 patients with neither a history of aprevious myocardial infarction nor revascularization proceduresor reinfarction within the 7-month follow-up period. One month after AMI, mean LVEF was higher in the streptokinasegroup in patients with anterior AMI (50±15% vs 42 ±16%,P = 0.013). This difference was more marked in the subgrouptreated within 3 h (53 ± 14% vs 42 ± 15%, P =0.004), whereas patients treated 3–6 h after the onsetof symptoms did not differ from respective controls (41 ±16%vs 41 ±18%). In patients with inferior A MI, the differencein mean LVEF was small (57±11% vs 55 ±12%, P =0.47). After anterior AMI benefit due to streptokinase therapywas preserved up to 7 months (52 ±14% vs 44 ±17%,P = 0.013). During exercise, the increase of mean LVEF was greaterin the streptokinase group at both dates, especially 7 monthsafter AMI (41 ±61% vs l.2±6.3%, P = 0.015). Instreptokinase-treated patients with anterior AMI, regional LVEFat rest was higher at both dates compared with controls, withinthe infarct zone as well as in remote myocardium. No treatment-controldifferences were demonstrable in patients with inferior AMI.During exercise, regional contractile reserve was better inthe streptokinase group within the infarct zone as well as inremote myocardium, irrespective of the site of infarction. Thus, intravenous streptokinase within 3 h after the onset ofA MI preserves global left ventricular function m anterior AMIover a period of at least 7 months. Intravenous streptokinaseimproves regional myocardial function within the infarct zoneas well as in remote areas. In inferior AMI investigation solelyat rest may underestimate the benefit of streptokinase therapy.