A total of 231 patients suffering from a first acute
myocardial infarction were randomly allocated within 4 hours following the onset of symptoms either to
anistreplase or
anisoylated plasminogen streptokinase activator complex (
APSAC), 30 U over 5 minutes, or to conventional
heparin therapy, 5000 IU in bolus injection.
Heparin was reintroduced in both groups 4 h after initial
therapy at a dosage of 500 IU/kg per day. A total of 112 patients received
anistreplase and 119 received
heparin within a mean period of 188 +/- 62 min following the onset of symptoms.
Infarct size was estimated from single photon emission computerized tomography and expressed in percentage of the total myocardial volume. The patency rate of the
infarct-related artery was 77% in the
anistreplase group and 36% in the
heparin group (p less than 0.001). Left ventricular ejection fraction determined from contrast angiography was significantly higher in the
anistreplase group than in the
heparin group (6 absolute percentage point difference). A significant 31% reduction in
infarct size was found in the
anistreplase group (33% for the anterior wall
infarction subgroup [p less than 0.05] and 16% for the inferior wall
infarction subgroup, NS). A close inverse relation was found between the values of left ventricular ejection fraction and
infarct size (r = -.73, p less than 0.01). In conclusion, early infusion of
anistreplase in acute
myocardial infarction produced a high early patency rate, a significant limitation of
infarct size, and a significant preservation of left ventricular systolic function, mainly in the anterior wall
infarctions.