901-98 Are Indirect Markers an Accurate Measure of Free Radical Activity Following Primary Angioplasty Reperfusion in Acute Myocardial Infarction?

Oxygen-derived free radicals (FR) have been found to be important mediators of myocardial reperfusion injury in animal studies. In man, most studies of FR measurement after reperfusion have relied on indirect markers alone. However, their accuracy and relationship to FR's has been controversial. We have therefore used primary PTCA for AMI as a model of acute reperfusion to compare direct FR measurement using electron paramagnetic resonance (EPR) spectroscopy and the spin trap agent α-phenyl N-tert butyl nitrone, with two of the most commonly used indirect markers. These were: [1] the percentage molar ratio (PMR) of the diene conjugate 9,11-octa-decadieneoic acid to the naturally-occurring isomer 9,12-linoleic acid, and [2] serum malonaldehyde (MDA). 16 patients (mean age: 56.9 yrs, range 47–66). undergoing successful primary PTCA (8 LAD, 1 Intermed, 1 LCx, 6 RCA) of less than 6 h duration (mean 3.55 h, range 2.25–5.0). had venous sampling from the base of the right atrium/coronary sinus before angioplasty (TIMI 0) and at timed intervals up to 24 h after recanalisation (TIMI 3). Direct FR measurement using EPR showed a biphasic time-course. Relative to the pre-PTCA level, FR's increased sharply after 15 min (P l 0.05) with peak levels at 1½ and 3½ h (P l 0.001). Following a decline to 6 h a late peak was observed at 24 h which may originate from accumulating my ocardial leukocyte infiltration. Indirect FR measurement using PMR showed a significant increase between 15 min and 1½ h (P l 0.01) only. MDA levels remained unchanged throughout the study. These results demonstrate that compared to direct FR measurement using EPR, indirect markers used in this study have limited or no usefulness in assessing FR generation in AMI. Myocardial reperfusion studies in man should ideally use direct methods.