Evidence for free radical generation after primary percutaneous transluminal coronary angioplasty recanalization in acute myocardial infarction.

In animal models, oxygen-derived free radicals have been found to be important mediators of reperfusion injury to ischemic but viable myocardium. However, in humans, there is no direct evidence of free radical production after the restoration of coronary artery patency in acute myocardial infarction. The purpose of this study was to quantitate and assess the time course of free radical production in coronary venous outflow in patients with acute myocardial infarction undergoing successful recanalization of the infarct-related artery by primary percutaneous transluminal coronary angioplasty (PTCA). Primary PTCA was performed in 17 patients with acute myocardial infarction of < 6 hours duration. Direct free radical production was assessed by coronary venous effluent blood sampling before PTCA and at timed intervals up to 24 hours (or 48 hours in 6 patients) after recanalization. All samples were added to the spin trapping agent alpha-phenyl N-tert butyl nitrone and analyzed by electron paramagnetic resonance spectroscopy. Vessel patency resulted in a sharp increase in free radical signal. Relative to the level before PTCA, the changes reached statistical significance after only 15 minutes (p < 0.05). Peak signals were observed between 1 1/2 and 3 1/2 hours (p < 0.001), then declined up to 5 hours. A second increase in signal level was detected between 18 and 24 hours despite no angiographic evidence of reocclusion. A gradual decline was observed after 24 hours. These findings provide the first direct and quantitative evidence of free radical production in the immediate postrecanalization phase after thrombotic occlusion of a major coronary artery in humans.