Complement activation in patients with acute myocardial infarction treated with streptokinase

Twenty patients with acute myocardial infarction (AMI) treated with streptokinase (SK) and 11 patients with AMI not treated with SK were clinically and echocardiographically evaluated in the intensive coronary care unit (ICCU). Blood samples, in which complement components C4d, C5b-9, and Bb were measured, were taken immediately after arrival of the patient at the ICCU, 1 hour after SK infusion, and 24 hours later from the SK group, and similar time-matched samples were taken from the control group. The classic, alternative, and common complement pathways were found to be activated in AMI, but this activation was statistically significant only in the SK-treated group. Activation was not related to the site of the AMI nor to the extent of its damage, as assessed by Killip class and ejection fraction. However, in the SK-treated group and even more so in non-SK group, the C5b-9 increment was significantly higher in patients diagnosed with reperfusion, based on ST-segment recovery of ≥50% reduction from the peak ST-segment level. There was little change in complement levels when reperfusion did not occur. Detection of reperfusion without coronary angiography would have important practical clinical implications, and complement activation may predict its occurrence. However, more studies of this phenomenon are needed.