DIFFERENTIAL FREE-RADICAL ACTIVITY AFTER SUCCESSFUL AND UNSUCCESSFUL THROMBOLYTIC REPERFUSION IN ACUTE MYOCARDIAL-INFARCTION

Background: Free-radical generation after successful thrombolysis in a cute myocardial infarction may jeopardise ischaemic but viable myocard ium, thus limiting the optimal benefits of reperfusion. Methods: Circu lating free-radical activity was assessed in 25 consecutive patients w ith acute myocardial infarction. Those who successfully reperfused (Gr oup A) were compared with those who did not (Group B). We also compare d patients who had or had not developed Q waves and patients with and without previous angina or myocardial infarction. All patients present ed within 6 h of the onset of chest pain and received standard intrave nous streptokinase therapy. Free-radical activity in serial serum samp les collected over 72 h was measured using the percentage molar ratio (PMR) of the concentrations of 9,11-linoleic acid to 9,12-linoleic aci d, and malonaldehyde concentration. Results: Throughout the study peri od Group A (n=11) showed significantly greater change in serum PMR and malonaldehyde levels compared with Group B (n=14) (P < 0.01). PMR dif ferences between the two groups were most pronounced at 3 and 12 h (P < 0.001). Patients with non-Q-wave myocardial infarction (n=5) showed significantly greater changes in serum PMR and malonaldehyde levels (P < 0.01) compared with those with Q-wave infarction (n=20). A history of previous infarction or angina had no apparent effects on the change s in serum free-radical activity. Conclusions: Successful early reperf usion and non-Q-wave myocardial infarction are both associated with a significantly greater increase in the levels of markers of serum free- radical activity immediately after infarction. The results support pre sent concepts of free-radical-mediated reperfusion injury. Use of thes e assays may identify those patients who may be at risk from free-radi cal-mediated reperfusion injury.