Aspirin does not improve early arterial patency after streptokinase treatment for acute myocardial infarction.
OBJECTIVE
To investigate the hypothesis that the magnitude of the life saving effect of aspirin in the second international study of infarct survival (ISIS-2) trial cannot be explained solely by prevention of late reocclusion of the infarct related artery. The aim of this study was to discover whether or not aspirin in combination with streptokinase had an adjuvant thrombolytic effect.


METHODS
Aspirin (150 mg) or placebo was given at the start of streptokinase infusion to 200 patients seen within six hours of the start of prolonged ischaemic cardiac pain and ST segment elevation. All patients received active aspirin at three hours. Patency of the infarct related artery was assessed non-invasively by the normalised rise of creatine kinase activity at three hours after starting streptokinase in these 200 patients and in a further 52 patients who had already taken aspirin within one week of the start of infarction.


METHODS
Rise in creatine kinase activity from baseline to > or = 20% or < 20% of the peak rise of activity in blood taken at three hours after starting infusion of streptokinase. This correlates with patency or occlusion of the infarct related coronary artery at about 2.5 hours after starting streptokinase.


RESULTS
Assessed in this way, patency of the infarct related artery was 60% in patients given aspirin, 63% in those given placebo, and 62% in patients who had already taken aspirin within one week of infarction.


CONCLUSIONS
The magnitude of the life saving effect of aspirin remains unexplained. Further investigation is needed into the mechanism of action of antiplatelet treatment in relation to thrombolytic treatment.
Norris
R M
RM
Coronary Care Unit, Green Lane Hospital, Auckland, New Zealand.
White
H D
HD
Cross
D B
DB
Woo
K S
KS
Maslowski
A H
AH
Caruana
M P
MP
Hart
H H
HH
Williams
B
B
D000368:Aged; D001241:Aspirin / Q000627:therapeutic use*; D004796:Clinical Enzyme Tests; D003402:Creatine Kinase; D004359:Drug Therapy, Combination; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000188:drug therapy* / Q000378:metabolism; D015425:Myocardial Reperfusion; D013300:Streptokinase / Q000627:therapeutic use*; D015912:Thrombolytic Therapy; D013997:Time Factors; D014654:Vascular Patency / Q000187:drug effects*
D003402:Creatine Kinase; D013300:Streptokinase; D001241:Aspirin