Reperfusion Injury in Patients with Acute Myocardial Infarction

Summary

It has been shown in the clinical situation that the infarct size varies in patients with acute myocardial infarction after successful reperfusion, even if the factors determining the infarct size, i. e., area at risk, time from onset to reperfusion, or collaterals at the onset, were the same. The reasons for this variability remain unknown. In this study, we attempted to clarify one such reason. A group of 68 patients with first anterior acute myocardial infarction with successful reperfusion was divided into three subgroups according to the infarct size in proportion to time from the onset to reperfusion: the “large” group (n = 24), the “standard” group (n = 18), and the “small” group (n = 26). There were no significant differences among the three groups in patients’ characteristics, the area at risk, time from onset to reperfusion, and collateral grade at the initial angiography. The infarct size (mean ± SE) determined by thallium-201 single photon emission computed tomography (SPECT) of the large group (1479 ± 106 units) was significantly greater than that of both the small group (323 ± 74 units) and the standard group (735 ± 117). Significant difference was observed among the three groups in the plasma free-radical scavenger activity, one of the factors involved in determining the infarct size: the plasma free-radical scavenger activity in the large group (24.1 ± 0.7NU/1) was significantly lower than that of both the standard group (27.0 ± 1.0NU/1) and the small group (29.9 ± 1.3NU/1). These results suggested that the biological free-radical scavenger system prevented the myocardial reperfusion injury caused by the free-radical generation at the time of reperfusion, thereby reducing the infarct size. The variations in infarct size in the clinical situation might reflect the individual differences in the free-radical scavenger activities.